Presentation type:
G – Geodesy

EGU24-4118 | Orals | MAL18-G | Vening Meinesz Medal Lecture

The Evolution of Positioning Accuracy and Linear vs. Non-linear Motions of the Earth 

Jeffrey Freymueller

The precision and accuracy of GPS/GNSS positioning has improved by considerably more than an order of magnitude over the course of my career, and the amount of data readily available (GNSS sites) has increased by several orders of magnitude. Over the last 40 years, geodesists have exploited this dramatic (and still continuing) increase in measurement capability to discover and study an ever-increasing set of phenomena. In the 1980s and early 1990s, the GPS satellite constellation was incomplete and there was only a sparse global tracking network. As a result, measurement noise limited rate accuracy to a few to several mm/yr, whereas today we are approaching accuracies of a few tenths of 1 mm/yr for long-term rates, and likely approaching the limit at which variability in surface loading makes motions fundamentally non-linear.

In this talk I will take a historical perspective, highlighting the improvement in measurement capabilities and our understanding of tectonic and other earth processes. At the beginning of my career, we focused on estimating rates of steady processes like rigid plate motions, the distribution of strain across rapidly-deforming plate boundary zones, or the displacements due to large earthquakes. We thought that over most of the Earth, motion and deformation mostly occurred linearly with time. The noise level in position solutions at that time was very high, and most non-linear variations in observed time series were considered to be noise either due to positioning error or to unstable geodetic monuments. While the deformation due to changing surface loads was recognized as a physical signal, knowledge of the changing loads was rudimentary and the signal was below the noise level in most cases. Today we recognize a wide variety of signals that produce a mix of linear and non-linear motions of the Earth, and positioning geodesy has become the essential tool for studying most of them. I have had the good fortune to work on measuring and understanding many of these processes, and I will discuss some of the highlights of the evolutionary path of positioning geodesy along with future perspectives. We have reached, or nearly reached, the point at which the approximation of linear motion breaks down because the measurement precision is now comparable to or smaller than the non-linear surface loading deformation over most of the planet. The coming years should see more exciting discoveries, but we must think broadly about the full range of geophysical signals that are contained within our data.

How to cite: Freymueller, J.: The Evolution of Positioning Accuracy and Linear vs. Non-linear Motions of the Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4118, https://doi.org/10.5194/egusphere-egu24-4118, 2024.

EGU24-11422 | ECS | Orals | MAL18-G | G Division Outstanding Early Career Scientist Award Lecture

GRACE for Earth system science: novel insights into hydrology, sea level rise, and solid Earth uplift 

Bramha Dutt Vishwakarma

The Gravity Recovery and Climate Experiment Satellite mission has provided estimates of spatiotemporal changes in the Earth’s gravity field, which represents mass transport near the surface of the Earth. This unique satellite mission has been used to study groundwater depletion, lake volume changes, sea level rise, and the viscoelastic response of solid Earth to glacial cycles; glacial isostatic adjustment. In this talk, I will share my experiences: published, unpublished, and even incomplete, in using GRACE data for Earth system science and emphasize the power and limitations of this unique satellite mission. 

How to cite: Vishwakarma, B. D.: GRACE for Earth system science: novel insights into hydrology, sea level rise, and solid Earth uplift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11422, https://doi.org/10.5194/egusphere-egu24-11422, 2024.

G1 – Geodetic Theory and Algorithms

EGU24-1903 | Orals | G1.1

Dictionary learning for downward continuation of gravity data 

Volker Michel, Naomi Schneider, and Nico Sneeuw

A multitude of basis functions is available for modelling the gravitational field based on satellite data. The Regularized Functional Matching Pursuit (RFMP) algorithm, which has been developed by the Geomathematics Group Siegen, proved to be able to combine different sets of such trial functions. For this purpose, a dictionary is built as a redundant union of different established basis systems (such as spherical harmonics, radial basis functions and Slepian functions). In an iterative scheme, a best basis is selected by minimizing a Tikhonov-Phillips functional. In a recent add-on (the LRFMP), the dictionary does not have to be discretely predefined but can be learned as part of the algorithm. This is implemented as a non-linear optimization problem. The LRFMP has several benefits, which will be demonstrated in the presentation, where we show numerical tests regarding the inversion of noisy gravity data on real satellite orbits.

References:

N. Schneider, V. Michel and N. Sneeuw, High-dimensional experiments for the downward continuation using the LRFMP algorithm, preprint available at http://arxiv.org/abs/2308.04167, 2023.

N. Schneider, V. Michel: A dictionary learning add-on for spherical downward continuation, Journal of Geodesy, 96 (2022), article 21 (22pp). 

Source Code:

N. Schneider, (L)IPMP source code for gravitational field modelling, v2-dc-2023. Zenodo. https://doi.org/10.5281/zenodo.8223771, 2023. 

 

How to cite: Michel, V., Schneider, N., and Sneeuw, N.: Dictionary learning for downward continuation of gravity data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1903, https://doi.org/10.5194/egusphere-egu24-1903, 2024.

EGU24-2824 | Posters on site | G1.1

FarZone4IT: A new software for the calculation of far–zone effects for spherical integral 

Martin Pitonak, Petr Trnka, Jiri Belinger, Pavel Novák, and Michal Sprlak

Integral transformations are a useful mathematical apparatus for modelling the gravitational field. They represent the mathematical basis for the formulation of integral estimators of gravity field values, including error propagation. The theoretical and practical aspects of integral transformations traditionally used for the calculation of geoid/quasi-geoid heights in geodesy, such as Stokes’ and Hotine’s integral transformations, have already been studied. However, theoretical and practical concepts regarding other integral transformations, including non-isotropic (azimuth-dependent) transformations, have not yet been explored. One of the basic assumptions of integral transformations is global data coverage. However, the availability of ground measurements is frequently limited. In practice, the global integral is divided into two complementary regions, namely the near and far zones. Non-negligible systematic effects of data in the far zone require accurate evaluation. For this purpose, a new software library entitled FarZone4IT is being created in the MATLAB environment to calculate far-zone effects in integral transformations for gravitational potential gradients up to the third order. The library contains scripts for the calculation of integral kernels, error kernels, truncation error coefficients, and far zone effects for a selected set of input parameters. This contribution concerns the implementation of theoretical equations defining far zone effects and the subsequent numerical testing of the library functionality. Closed-loop tests were carried out using gravitational potential functionals generated from a synthetic model of the Earth's gravity field.

How to cite: Pitonak, M., Trnka, P., Belinger, J., Novák, P., and Sprlak, M.: FarZone4IT: A new software for the calculation of far–zone effects for spherical integral, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2824, https://doi.org/10.5194/egusphere-egu24-2824, 2024.

The numerical integration method has been routinely used by major institutions worldwide (for example, NASA Goddard Space Flight Center and GFZ) to produce global gravitational models from satellite tracking measurements. Such Earth’s gravitational products have found widest possible multidisciplinary applications. The method is essentially implemented by solving the differential equations of the partial derivatives of the orbit of a satellite with respect to the unknown force parameters under the zero initial conditions. From the statistical point of view, satellite gravimetry from satellite tracking is essentially to estimate the unknown parameters in the Newton’s nonlinear differential equations from satellite tracking measurements --- the mathematical foundation for satellite gravimetry from tracking. From this perspective, it is rather trivial to prove that the numerical integration method, originating from Gronwall on Ann Math almost 100 years ago and currently implemented and used in mathematics/statistics, chemistry/physics, and satellite gravimetry, is groundless, even though, up to this moment, many researchers in the geoscientific community still have problems in understanding this side point of my research. In this talk, we focus on presenting three different methods to derive local solutions to the Newton’s nonlinear differential equations of motion of satellites, given unknown initial values and unknown force parameters. They are mathematically correct and can be used to estimate unknown differential equation parameters, with applications in gravitational modelling from satellite tracking measurements as a typical example in geodesy. These solution methods are generally applicable to any differential equations with unknown parameters. More precisely, we develop the measurement-based perturbation theory and construct global uniformly convergent solutions to the Newton’s nonlinear differential equations of motion of satellites, given unknown initial values and unknown force parameters. From the physical point of view, the global uniform convergence of the solutions implies that they are able to exploit the complete/full advantages of unprecedented high accuracy and continuity of satellite orbits of arbitrary length and thus will automatically guarantee theoretically the production of a high-precision high-resolution global standard gravitational models from satellite tracking measurements of any types. Finally, we develop an alternative method by reformulating the problem of estimating unknown differential equation parameters, or the mixed initial-boundary value problem of satellite gravimetry with unknown initial values and unknown force parameters as a standard condition adjustment model with unknown parameters.
Xu P (2018) Measurement-based perturbation theory and differential equation parameter estimation with applications to satellite gravimetry. Commun Nonlinear Sci Numer Simulat, 59, 515-543. DOI 10.1016/j.cnsns.2017.11.021
Xu P (2008) Position and velocity perturbations for the determination of geopotential from space geodetic measurements. Celest Mech Dyn Astr, 100, 231–249.
Xu P (2009) Zero initial partial derivatives of satellite orbits with respect to force parameters violate the physics of motion of celestial bodies. Sci China Ser D, 52, 562–566.
Xu P (2012) Mathematical challenges arising from earth-space observation: mixed integer linear models, measurement-based perturbation theory and data assimilation for ill-posed problems. Invited talk, joint mathematical meeting of American mathematical society, Boston, January 4–7.

How to cite: Xu, P.: Statistical estimation of differential equation parameters: the mathematical foundation for satellite gravimetry from tracking, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3550, https://doi.org/10.5194/egusphere-egu24-3550, 2024.

EGU24-4098 | ECS | Posters on site | G1.1

Estimation of the Global Root Mean Square Error of Selected Gravitational Field Functionals Calculated by Integral Transforms 

Jiri Belinger, Martin Pitonak, Petr Trnka, Pavel Novak, and Michal Sprlak

Integral transformations of the gravitational field gradients are defined over the entire solid angle on the surface of the sphere. Despite the indisputable progress in satellite gravimetry and gradiometry, gravity field focused satellite missions allow accurate determination of the gravity field with a spatial resolution of 100 km, i.e. only in its long-wavelength part. However, there is also a need for high-resolution gravity field models at regional, national or continental scales, especially concerning the determination of the quasi-geoid or geoid. On the other hand, potential weakness of ground-based data is the long-wavelength gravity field accuracy and limited availability due to several constraints (e.g. deserts, lakes and large rivers, forests, or lack of goodwill between neighboring countries to share sensitive data). The ideal scenario combines ground and satellite data that complement each other.

In this contribution, relations defining the estimation of the global root mean square errors of selected gravitational field functionals using integral transformations will be derived and presented. For practical calculation, knowledge about the accuracy of measured terrestrial data and formal errors of global satellite models of the Earth's gravity field will be utilized.

How to cite: Belinger, J., Pitonak, M., Trnka, P., Novak, P., and Sprlak, M.: Estimation of the Global Root Mean Square Error of Selected Gravitational Field Functionals Calculated by Integral Transforms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4098, https://doi.org/10.5194/egusphere-egu24-4098, 2024.

EGU24-4313 | Posters on site | G1.1

Current adjustment of the mean Earth ellipsoid parameters 

Georgios Panou and Urs Marti

The need for the determination of the parameters of an equipotential rotational ellipsoid of revolution that approximates closer and closer to the Earth requires analysis of the most currently available data. The main objective of this study is to examine such new data and to perform an adjustment technique to estimate the parameters and their standard deviations of the mean Earth ellipsoid. The parameters considered are the geocentric gravitational constant, the angular velocity, the geoidal potential, the dynamical form factor, and the major and minor semi-axes. A-priori estimates of these quantities, which may be determined independently, are treated as “observations” and their adjusted values from a weighted least-squares procedure are presented. Since a level ellipsoid of revolution and its gravity field are completely determined by four constants, we use two non-linear condition equations to relate the six parameters for performing the adjustment. Among the products of the adjustment is the correlation matrix of the adjusted values of parameters, which helps us in the selection of a consistent set of four parameters for the definition of a new Geodetic Reference System (GRS). After the selection of the four parameters, we compute by Newton’s method the two derived parameters and estimate their standard deviations by applying the law of propagation of variances. Furthermore, all the derived geometric and physical constants are computed from the defining constants of a GRS, by means of closed formulas. Finally, in order to yield numerical results of high precision, all computations are executed in computer algebra system software using variable precision floating point numbers.

How to cite: Panou, G. and Marti, U.: Current adjustment of the mean Earth ellipsoid parameters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4313, https://doi.org/10.5194/egusphere-egu24-4313, 2024.

EGU24-5214 | Orals | G1.1

On the physical meaning of geodetic networks’ over-constraints solutions 

Dimitrios Ampatzidis, Kyriakos Balidakis, and Alexandros Tsimerikas

It is widely known that the geodetic networks (both terrestrial and space) suffer from the so-called rank deficiency. This is the algebraic expression of the weakness of the observations to sense all the necessary information for the reference system definition (in terms of origin scale and orientation). For example, the SLR technique is sensitive to the origin and scale, while the orientation can be only externally defined. On the other hand, the traditional quasar-based VLBI does not sense either origin and orientation but only scale.

In general, the rank deficiency is remedied by the use of the so-called constraints. The constraints can be divided into two major categories: a. The minimum constraints, where they just treat the rank deficiency problem (as the word minimum dictates) and do not interfere with the shape of the network, and b. the over-constraints, which do not only solve the rank deficiency but alter the shape of the geodetic network.

While the minimum constraint solutions are widely discussed in the geodetic literature, regarding their nature, the over-constraints' physical meaning is not so clear (if not vague). The present study aims to provide a physical meaning of the over-constraints solution, under the prism of its stochastic interpretation.

How to cite: Ampatzidis, D., Balidakis, K., and Tsimerikas, A.: On the physical meaning of geodetic networks’ over-constraints solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5214, https://doi.org/10.5194/egusphere-egu24-5214, 2024.

The study presents along-track nonlinear diffusion filtering of the airborne gravity data. At first, the provided airborne gravity disturbances from the GRAV-D campaign are transformed into the airborne complete Bouguer disturbances (CBD). This aims to reduce a correlation of the filtered data with the topography. Then the nonlinear diffusion filtering in 1D based on the Perona-Malik model is applied. In this model, a diffusivity coefficient depends on the edge detector, which allows reducing noise while preserving important gradients in the filtered data. As a numerical method we use the finite volume method (FVM). The derived semi-implicit numerical scheme leads to a three-diagonal system matrix that is solved in every iterative step. Here the diffusivity coefficients are updated in every step by new values of the edge detector recomputed from the previous solution.

The numerical experiment presents the along-track nonlinear filtering of the airborne CBD in high mountainous area of the ‘Colorado geoid experiment’. Afterwards, the along-track filtered data are gridded into a 2D map of the airborne CBD. The obtained results show that an appropriate choice of a sensitivity parameter of the diffusivity coefficient can better detect significant structures in the airborne CBD, especially their edges that are usually smoothed by the Gaussian filtering. Finally, the filtered and gridded airborne CBD are backward transformed into the airborne gravity disturbances.

How to cite: Cunderlik, R., Zahorec, P., and Papčo, J.: Along-track nonlinear filtering of airborne gravity data from the GRAV-D campaign: case study for the ‘Colorado geoid experiment’, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5215, https://doi.org/10.5194/egusphere-egu24-5215, 2024.

EGU24-5272 | Posters on site | G1.1

Modelling gravity field of irregularly shaped bodies by numerical methods 

Marek Macak, Michal Šprlák, and Zuzana Minarechová

Gravity field modelling of irregularly shaped bodies such as the Earth's Moon is a challenging task that can reveal both the strong and weak points of each modelling technique. In our approach we will develop a numerical approach based on the finite element method (FEM) and compare the obtained solutions with the solution by the spectral approach that relies on spherical harmonics. In this way, we aim to study whether the numerical methods such as FEM can overcome the limitations of the spherical-harmonic-based approaches, namely their divergence in the vicinity of the gravitating body. We hope that the presented developed approach could form a valuable alternative to the spherical harmonics.

How to cite: Macak, M., Šprlák, M., and Minarechová, Z.: Modelling gravity field of irregularly shaped bodies by numerical methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5272, https://doi.org/10.5194/egusphere-egu24-5272, 2024.

Studying the gravitational effects of the Earth's topography and crustal layers is a fundamental topic in gravity field modeling in geodesy and geophysics. The introduction of gravitational curvatures (GC), which are the third-order derivatives of the gravitational potential (GP), has recently broadened theoretical research on gravitational effects. Using tensor analysis, this paper comes up with a general formula for the physical parts of the third-order tensor of the potential in cylindrical coordinates. Then, the expressions for the GC of a vertical cylindrical prism are accordingly derived in cylindrical coordinates. Based on the relation among the vertical cylindrical prism, cylindrical shell, and cylinder, the analytical expressions for gravitational effects up to the GC of a vertical cylindrical shell and a cylinder are derived when the computation point is located on the Z-axis no matter whether it is situated below, inside, or above the cylindrical shell and cylinder. Laplace's equation has been adopted to confirm the correctness of the newly derived formulas of the GC. In addition, a benchmark of a cylindrical shell discretized into cylindrical prisms is proposed to reveal the numerical properties of derived GC formulas with the computation point located on the Z-axis. Numerical results reveal that when the computation point's height increases, the relative and absolute errors of the GP, gravitational vector (GV), gravitational gradient tensor (GGT), and GC decrease, in which the relative errors in log10 scale of the nonzero GP, GV, GGT, and GC components are approximately less than -2 when the computation is located below, inside, and above the cylindrical shell. These newly derived formulas lay the theoretical foundation for the GC in cylindrical coordinates and help to investigate the potential applications of the GC in geodesy and geophysics. This new benchmark can become the standard for testing the correctness of the gravitational effects of the cylindrical prism using different numerical algorithms in cylindrical coordinates in practical applications.

How to cite: Deng, X.: A benchmark for gravitational potential up to its third-order derivatives of a vertical cylindrical shell discretized into cylindrical prisms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5992, https://doi.org/10.5194/egusphere-egu24-5992, 2024.

EGU24-6872 | ECS | Orals | G1.1

Developed empirical refraction model for precise trigonometric levelling of the La Valette Landslide, France 

Mansoor Sabzali, Gilbert Ferhat, Lloyd Pilgrim, Mehdi Khaki, and Jean-Philippe Malet

Atmospheric refraction is the main source of deviations for laser-based sensors. Having a profound understanding of refraction, and the knowledge of the geometry of the line of sight, assists in identifying an accurate model to correct this error. The height of the point, similar to two other planar coordinates, is also impacted as a result of the refracted beam line. The height can be obtained through numerous geodetic measurement approaches such as spirit levelling or trigonometric levelling. An empirical refraction model was proposed in 1984 to better quantify the observations of trigonometric levelling. In this research, we propose a developed empirical model for the La Valette Landslide (Southeast French Alps) to determine the height of the target benchmarks in a landslide zone. The landslide is located in the Ubaye Valley, where the thrust fault of clay-shale sediments at the bottom and sandstone and limestone competent rocks at the top, control the occurrence of landsliding in this region. The deformation is attributed to the low resistance of the slope material and the increase in pore-fluid pressure resulting from the different hydraulic conductivities of the two geological units. The landslide has been monitored over many years, with several remote sensing techniques, and the task is undertaken as a part of the French Landslide Observation Service - OMIV. Since September 2019, an automated total station Long-Range Trimble S9 has been monitoring 54 reflectors’ positions every 1 to 3 hours with respect to three reference control points. The targets have been uniformly distributed over the landslides at distance from 350m to 2300m from the monitoring station, and at elevations varying from 1300m to 2100m. The research determined the point heights using the empirical trigonometric levelling model with the addition of an improved refraction model incorporating the development refraction correction for the observed angles of the control points.

How to cite: Sabzali, M., Ferhat, G., Pilgrim, L., Khaki, M., and Malet, J.-P.: Developed empirical refraction model for precise trigonometric levelling of the La Valette Landslide, France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6872, https://doi.org/10.5194/egusphere-egu24-6872, 2024.

EGU24-7346 | Posters on site | G1.1

On solving the nonlinear geodetic boundary value problem using mapped infinite elements 

Zuzana Minarechová, Marek Macák, Róbert Čunderlík, and Karol Mikula

The numerical approach for solving the nonlinear geodetic boundary value problem based on the finite element method with mapped infinite elements and itterative procedure is developed and implemented. In this approach, the 3D semi-infinite domain outside the Earth is bounded only by the triangular discretization of the whole Earth's surface and extends to infinity. Then the BVP consists of the Laplace equation for unknown disturbing potential which holds in the domain, the nonlinear boundary condition given directly at computational nodes on the Earth's surface, and regularity of the disturbing potential at infinity. In experiments, a convergence of the proposed numerical scheme to the exact solution is tested and then the numerical study is focused on a reconstruction of the harmonic function above the Earth's topography.

How to cite: Minarechová, Z., Macák, M., Čunderlík, R., and Mikula, K.: On solving the nonlinear geodetic boundary value problem using mapped infinite elements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7346, https://doi.org/10.5194/egusphere-egu24-7346, 2024.

EGU24-7800 | ECS | Orals | G1.1

Seafloor topography recovery improved by combination of different gravity data functionals 

david fuseau, Lucia Seoane, Guillaume Ramillien, José Darrozes, Bastien Plazolles, Didier Rouxel, Thierry Schmitt, and Corinne Salaün

Tesseroid and radial columns decomposition of the undersea relief strategies have been considered to recover the seafloor topography by Kalman Filter (KF) inversion of gravity data in the case of the Great Meteor seamount located in the North Atlantic ocean. These both modeling approaches are shown to be equivalent at high grid sampling rate (<1'). Different types of gravity data functionals for geoid height anomaly, vertical gravity component and gravity gradient (or tensor) are analyzed by spectral decomposition and combined to retrieve most detailed 3-D seafloor topography solutions, as gravity gradient data provide short-wavelength information to have access to high-resolution details. Besides only the vertical gravity tensor Vzz is usually inverted in previous field-related studies, considering up to six components of the gravity gradient is tested for improving the accuracy of the KF solution. The iterative KF scheme has been optimized and parallelized using C++ Armadillo software to accelerate the determination of a very large number of juxtaposed topographic heights.

How to cite: fuseau, D., Seoane, L., Ramillien, G., Darrozes, J., Plazolles, B., Rouxel, D., Schmitt, T., and Salaün, C.: Seafloor topography recovery improved by combination of different gravity data functionals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7800, https://doi.org/10.5194/egusphere-egu24-7800, 2024.

EGU24-8993 | ECS | Posters on site | G1.1

An alternative to PCA utilizing Dynamic Time Warping 

Bernd Uebbing, Jan Höckendorff, Caroline Jungheim, Anne Driemel, Christian Sohler, and Jürgen Kusche

The Earth’s system is warming due to natural and human driven climate change. Observing, analyzing and understanding the associated geophysical processes is important in order to improve prediction of future changes and mitigate impacts on society and infrastructure. Investigating individual climate processes, such as sea level change, often requires partitioning of the total signal for identifying sub-signals and drivers; in the sea level example these could be trend and seasonal signals or impacts from the El Niño Southern Oscillation (ENSO).

A commonly applied method is the (real) Principal Component Analysis (PCA), which factorizes a given input dataset into time-invariant Empirical Orthogonal Functions (EOF), i.e. spatial patterns, and time-variable Principal Components (PC) based on the most dominant eigenvalues. However, this real-EOF analysis assumes more or less static patterns over time and, thus, lacks the ability to capture temporal variations in the patterns. This can be circumvented by the application of complex or Hermitian EOF analysis, which also enables capturing phase shifts or in other words allows for time-varying spatial patterns.

Here, we present first results from a novel approach utilizing dynamic time warping (DTW) for extracting dominant modes in the form of spatially distributed amplitudes and lags with respect to a ‘base curve’. While classic PCA methods are sensitive to outlier influence on the partitioning, our approach represents a robust alternative. Furthermore, base curves are computed that represent spatial modes via traversal matrices, which act as extensions of the base curves to capture individual lag. We introduce our new approach, compare to complex/Hermitian EOF, explain the numerical scheme, and present some first results based on gridded sea level change data.

How to cite: Uebbing, B., Höckendorff, J., Jungheim, C., Driemel, A., Sohler, C., and Kusche, J.: An alternative to PCA utilizing Dynamic Time Warping, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8993, https://doi.org/10.5194/egusphere-egu24-8993, 2024.

EGU24-9318 | Posters on site | G1.1

Fast seafloor topography mapping of large oceanic provinces by optimization/parallelization 

Lucia Seoane, David Fuseau, Guillaume Ramillien, José Darrozes, Bastien Plazolles, Didier Rouxel, Corinne Salaün, and Thierry Schmitt

During the last decades, several inversion approaches have been proposed to derive sea floor topography from satellite-based gravity data. Unfortunately, the most accurate non linear ones are based on iterative schemes that remain very time-consuming, especially if the number of topographic heights to be fitted is very important, e.g. when the oceanic domain is large and/or the gravity data is geographically dense and thus the maximum grid resolution to be accessible is high. Our strategy of computation is to decompose the total area into geographical cells that are overlapped to cancel the edge effects. The reference ocean depth given by GEBCO and the elastic thickness for regional compensation in function of the square root of the age of the oceanic crust are assumed to be constant in each cell. The initial inversion code has been translated into C++ and optimized using Armadillo software and LAPACK library to obtain a gain of speed of 1000 for a large region such as the complete North Atlantic Ocean (-54,-26,18,37). Post-fit and absolute errors are typically less than 200 m and 50 m r.m.s. respectively. These new detailed maps of bathymetry represent a precious source of information for geophysical applications. 

How to cite: Seoane, L., Fuseau, D., Ramillien, G., Darrozes, J., Plazolles, B., Rouxel, D., Salaün, C., and Schmitt, T.: Fast seafloor topography mapping of large oceanic provinces by optimization/parallelization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9318, https://doi.org/10.5194/egusphere-egu24-9318, 2024.

Although centralized coordinates are applied in geodetic coordinate transformations implicitly or explicitly, the centering strategy has not been comprehensively investigated from the theoretical perspective. We rigorously model and extend the empirically used three center strategies based on different models:

  • Original model: Based on the partition representations of the solution, we propose a modified iteration policy, which reduces the parameter number and improves numerical stability during iteration. Also, its simplified version is analyzed when the cofactor matrix has the Kronecker product structures. It can be regarded as the extension of the work of Teunissen, since we essentially follow the same idea of partitioning the transformation parameters and the translation parameters, but more general covariance matrix structures are investigated in our consideration.
  • Shifting model: With the partitioned solution forms, we prove the estimated transformation matrix and the residual vector are translational invariant. For iteration, with the classical iteration policy, the shifts should be chosen properly; with the modified iteration policy, there is no restriction since it is numerically equivalent to the original model. In addition, this model shows the feasibility of conducting the adjustment with the centralized coordinates and the original stochastic model.
  • Translation elimination model: By multiplying the transformation relation with a specific matrix from both sides, we formulate the translation elimination model with the coordinates centralized and the translation parameters eliminated. With this model reduction, the covariance matrix has also been transformed since the observation equations are comprised of coordinate combinations. In addition, Leick’s model reduction strategy is a special case of this model, which is conducted by subtracting one particular observation equation from the remaining equations. 

Test computations with different weight structures show the validity of these strategies.

How to cite: Zhan, W., Fang, X., and Zeng, W.: Center strategies for universal geodetic transformations: modified iteration policy and two alternative models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13902, https://doi.org/10.5194/egusphere-egu24-13902, 2024.

EGU24-15596 | Posters on site | G1.1

Uncertainties associated with integral-based transforms of measured potential gradients 

Pavel Novak, Mehdi Eshagh, and Martin Pitoňák

The geoid model over dry land areas is determined from data observed at or above the Earth’s surface. Observable quantities include various functional of the disturbing potential defined as the difference between the real and model (normal) gravity potential. Transformation of the measured data into the sought-after, but directly unobservable gravity potential is often carried out using mathematical tools of the potential theory. An example of such a transformation is the well-known Hotine integral transform that transforms disturbing gravity, i.e., the first-order vertical gradient of the disturbing potential (Stokes formula is applied to anomalous gravity which is still often encountered in geodesy). Higher-order gradients of the Earth's gravitational potential have been collected by sensors on board aircraft or low-orbiting satellites. This advancement in data availability has resulted in the formulation of new tools based on Green's integral transforms and equations. Associated deterministic models have been well developed, tested, and successfully implemented. However, stochastic models for estimating uncertainties in sought values have only been partially developed. These uncertainties should reflect the inevitable implementation and approximation errors, the propagation of formal errors, as well as external accuracy estimation if relevant independent reference values are available. This contribution discusses mathematical models that can be used to estimate various types of uncertainties related to integral-based transformations of the measured potential gradients into the disturbing potential.

How to cite: Novak, P., Eshagh, M., and Pitoňák, M.: Uncertainties associated with integral-based transforms of measured potential gradients, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15596, https://doi.org/10.5194/egusphere-egu24-15596, 2024.

The problem of determining the anomalous potential T on the earth's surface can be solved on the basis of various initial available data: gravity anomalies Δg and gravity disturbances δg, their vertical derivatives ∂(Δg)/∂H, ∂(δg)/∂H, gravity gradient anomalies Δ(∂g/∂H) etc. Existing methods of such BVP solution use the integral kernels, elaborated for the sphere and ellipsoid. The attempts to determine the real geoid are closely related to the direct problems of the potential theory, when the mass distribution is assumed to be approximately known (in Molodensky's theory the earth's crust density is used in topographic reductions only for better anomalies interpolation).

Using of the two tipes of related gravity data could be considered as a control, e.g., the anomalous potential T from the gravity anomalies Δg can be used to obtain the gravity disturbances δg, from which we must also get the same anomalous potential T. For the real Earth's surface more flexible is the method of integral equations.

 

(The prime sign indicates a point on the telluroid.)

Molodensky's integral equation for the simple layer density (distributed on the Earth's surface) using the gravity disturbances (1) and gravity anomalies (2) is known, but is usually solved indirectly with an introduction of the small parameter (the Molodensky's parameter k or/and ellipsoid eccentricity e), that lead to the series solution with the well-known integrals. Being the Fredholm equation, the Molodensky's integral equation itself can be solved directly by successive approximations in the ellipsoidal coordinate systems as well as in the spherical one. The integration procedure is probably longer, but any step is of the same type. Then the anomalous potential can be calculated by integration in the form (3).

Figure 1. Simple layers distributed with densities φ on the Earth’s surface S (green). Auxiliary simple layer density χ is distributed on the mean Earth’s sphere Ω  with radius R. In general case, the normal n to the surface, inclination angle α and the radius-vector ρ are slightly different in the two cases. E - reference ellipsoid (blue), the telluroid Σ (red), g - plumb-line.

Some real estimates are possible on the surface and gravity field models. In this study we use the Earth's model in the form of mascons for the surface and gravity field, see Fig. 2. We know all the elements of the anomalous field, the precise coordinates of the points with data and so we can estimate the real theoretical accuracy of the formulas and the number of iterations.

Figure 2. The scheme of the mass forming the anomalous field

In case of gravity anomalies the integration procedure can be considered as an integration over the successively refined  boundary surface. It is enough to find the density distribution of a simple layer on a smoothed surface constructed from the heights of points in the form of the sum of the normal height (from leveling) and the height anomaly from the Stokes approximation.

How to cite: Popadyev, V. and Sermiagin, R.: Control of the accuracy of the Molodensky's integral equation for the gravity anomalies and disturbances on the Earth's models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18996, https://doi.org/10.5194/egusphere-egu24-18996, 2024.

EGU24-19367 | ECS | Orals | G1.1

A novel globally convergent maximizer for the multivariate carrier-phase integer ambiguity function 

Lotfi Massarweh and Peter Teunissen

Current theory of integer inference, which is key to many carrier-phase driven observing systems, consists of a rich variety of different estimation principles, each with their own optimality and statistical properties. The various estimators can be classified into different classes of estimators, of which the integer estimation class is the smallest and the integer equivariant class the largest. Although the estimation theory for mixed integer models has matured significantly, there are still some important identifiable open unsolved problems. One of those concerns the way in which in practice the integer-equivariant baseline maximizer of the carrier-phase integer ambiguity function is resolved. Most of the methods employed in practice use rather ad hoc, brute-force grid search techniques, whereby proper considerations of the intrinsic properties of the objective function are lacking. As a result none of the available techniques have a demonstrated proven guarantee of global convergence. In this contribution we will present a novel algorithm for the numerical maximization of the multivariate carrier-phase integer ambiguity function. Our proposed method, which has finite termination with a guaranteed user-defined tolerance, is developed from combining the branch-and-bound principle with the projected-gradient-descent methodology, for which a special continuous differentiable convex-relaxation of the critical elements of the ambiguity objective function is constructed. The methodology of these three constituents is described in an integrated manner and numerical results are provided to illustrate the theory.

How to cite: Massarweh, L. and Teunissen, P.: A novel globally convergent maximizer for the multivariate carrier-phase integer ambiguity function, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19367, https://doi.org/10.5194/egusphere-egu24-19367, 2024.

EGU24-1087 | ECS | Posters on site | G1.2

Sensitivity Analysis of Digital Elevation Models in Geoid Modelling for Indian region 

Alok Kumar, Vipin maurya, and Ramji dwivedi

Digital Elevation Models (DEMs) are fundamental components in geodetic computations, serving as key inputs in geoid modelling processes. Mostly, the freely available DEMs are used for geoid modelling without considering its impact on the developed geoid. Considering the criticality of terrain and downward continuation corrections calculated from DEMs, this research work explores the sensitivity of geoid models to variations in DEMs, aiming to elucidate the impact of different DEMs on the accuracy and precision of geoid modelling. The study aims at a comprehensive sensitivity analysis framework to assess the influence of DEM resolution, terrain representation, and fitting methods on regional geoid modelling in India. The selected study area consists of three states of India (Haryana, Punjab, and Himachal Pradesh) bounding approximately 169,500 km2 of the area (73.5≤λ≤77.5 and 29≤ϕ≤33 of longitude and latitude, respectively) of vast topography including Indo-Gangetic Plain, Shivalik Hills, lofty hills, deep valleys, and verdant forests. This study employs Least Squares Modification of Stokes formula with Additive Corrections (LSMSAC) method developed by the Royal Institute of Technology, Sweden and evaluates four DEMs, Cartosat, Merit, Palsar and SRTM. For surface correction (fitting), 24 GNSS points are used with 4,5 & 7 parameter fitting models which is validated with 15 other GNSS point based on elementary statistics. This investigation offers insights into selection of an optimal DEM by obtaining RMSE between developed geoid using various DEMs and 15 GNSS points. Based on the obtained results by considering above-mentioned DEMs with various fitting models, the Cartosat DEM outperformed other DEMs by obtaining lowest RMSE (0.078603m) with 7 parameter fitting model. Surprisingly, the lowest RMSE (0.064557m) is obtained by Cartosat DEM with 4 parameter model which could be because of Cartosat DEM being an India specific DEM. While comparing the efficacy of developed geoid between globally available DEM, Merit performed best with lowest RMSE (0.078657m). Out of 90 combinations of each DEM for various sets of Degree/order of Global Geopotential model (GGM), integration cap size; the best result is obtained by 180 degree of GGM and 0.8 integration cap size for each DEM. Presented study improved our understanding in assessing the sensitivity of geoid models to various DEMs. This research aids geodesists, geophysicists, and remote sensing specialists in making informed decisions while selecting a suitable DEM for geoid computations. The findings presented in this paper contribute to the ongoing efforts to enhance the precision and reliability of geoid modelling techniques, ultimately improving our understanding of Earth's gravity field.

How to cite: Kumar, A., maurya, V., and dwivedi, R.: Sensitivity Analysis of Digital Elevation Models in Geoid Modelling for Indian region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1087, https://doi.org/10.5194/egusphere-egu24-1087, 2024.

EGU24-1346 | Posters on site | G1.2

FVM: A Good Match to Airborne Gravimetry? 

Xiaopeng Li, Robert Cunderlik, Miao Lin, Marek Macak, Pavol Zahorec, Juraj Papco, Zuzana Minarechova, Jordan Krcmaric, and Daniel Roman

Numerical methods like the Finite Element Methods (FEM) or Finite Element Methods (FVM) are widely used in many engineering applications to solve boundary value problems that are hard to find rigorous analytical solutions. These numerical methods have been also applied in geodesy in many previous studies regardless of its huge computation demands. They have arisen due to the fact that the upper boundary condition was usually set up at the satellite orbit level, hundreds of kilometers above the Earth. The relatively large distances between the bottom boundary Earth' s surface, and the upper boundary even exacerbates the computation loads because of the required discretization in between. Considering that many areas such as the US have uniformly distributed airborne gravity data that are just a few kilometers above the topography, we propose to move the upper boundary from the satellite orbit level to the mean flight level of the airborne gravimetry. The significant reduction in altitudes, dramatically saves the large computation demands in previous FEM or FVM computations. This paper demonstrates this benefit by using FVM for both simulated data and real data in the target area. In the simulated case, the FVM numerical results show that about an order of magnitude precision improvement can be obtained when moving the upper boundary from 250km to 10km, the maximum altitude of GRAV-D. For the real data sets, 2-3 cm level of accurate quasi geoid model can be obtained depending on different schemes used to model the topographic mass. The paper also demonstrates how to find the upper layer in case no airborne data is available. Last but not the least, this study provides a 3D representation of the entire local gravity field instead of a single 2D surface, the (quasi) geoid.

How to cite: Li, X., Cunderlik, R., Lin, M., Macak, M., Zahorec, P., Papco, J., Minarechova, Z., Krcmaric, J., and Roman, D.: FVM: A Good Match to Airborne Gravimetry?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1346, https://doi.org/10.5194/egusphere-egu24-1346, 2024.

EGU24-2185 | ECS | Posters on site | G1.2 | Highlight

Assessing Groundwater Sustainability in the Arabian Peninsula and its Impact on Gravity Fields through GRACE Measurements  

Hussein A. Mohasseb, Wenbin Shen, Hussein A. Abd-Elmotaal, and Jiashuang Jiao

This groundbreaking study addresses the imperative to comprehend gravity shifts resulting from Groundwater Storage (GWS) variations in the Arabian Peninsula. Despite the critical importance of water resource sustainability and its relationship with gravity, limited research emphasizes the need for expanded exploration. The investigation explores the impact of GWS extraction on the gravity field, utilizing Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) data in addition to validation using WaterGAP Global Hydrology Model (WGHM). Spanning April 2002 to June 2023, the study predicts GWS trends over the next decade using the Seasonal Autoregressive Integrated Moving Average (SARIMA) model.  The comprehensive time-series Analysis reveals a huge GRACE-derived GWS trend about -4.90±0.32 mm/year during the period of study. This significantly influences the gravity anomaly GA values, demonstrating a corresponding fluctuation in GWS time series. The projected GWS indicates a depletion rate of 14.51 km³/year over the next decade. The correlation between GWS and GA is substantial at 0.80, while GA and rainfall correlation is negligible due to low precipitation rates. Employing multiple linear regression explains 80.61% of the variance in gravity anomaly due to GWS, precipitation, and evapotranspiration. The study investigates climate change factors—precipitation, temperature, and evapotranspiration—providing a holistic understanding of forces shaping GWS variations. Precipitation and evapotranspiration exhibit nearly equal values, limiting GWS replenishment opportunities. This research holds significance in studying extensive GWS withdrawal in the Arabian Peninsula, particularly concerning crust mass stability. Integrating GRACE and hydrological models’ datasets furnishes a comprehensive understanding, contributing valuable foresight into the future trajectory of GWS. The results illuminate intricate relationships between GWS, gravity anomalies, and climate factors, presenting a robust framework for sustainable water resource management. 

How to cite: Mohasseb, H. A., Shen, W., Abd-Elmotaal, H. A., and Jiao, J.: Assessing Groundwater Sustainability in the Arabian Peninsula and its Impact on Gravity Fields through GRACE Measurements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2185, https://doi.org/10.5194/egusphere-egu24-2185, 2024.

EGU24-4068 | Posters on site | G1.2

Physics-Informed Neural Networks for geoid modeling: preliminary results in Colorado 

Tao Jiang, Zejie Tu, and Yamin Dang

Although machine learning has become increasingly important in geodesy related fields such as geophysics, seismology and remote sensing, its applications in geodesy, especially in physical geodesy, are still in its early stages. The main reason for this can be attributed to the black box nature of pure data-driven machine learning, which lacks physical interpretability and credibility, making it difficult for machine learning approaches to be used in physical geodesy that takes reliability and accuracy as its core criteria. Physics-Informed Neural Networks (PINNs) is a class of deep learning algorithms aims to seamlessly integrate data and physical prior knowledge including ordinary or partial differential equations, it can yield more physically interpretable machine learning models that provide robust and accurate predictions. We present the PINN approach for gravimetric geoid modeling from Earth gravity model, terrestrial and airborne gravity datasets. A convolutional neural network (CNN) deep learning architecture is used, gravity measurements and physical laws are integrated by embedding the Laplace’s equation of disturbing potential and the fundamental equation of gravity anomaly into the loss function of the neural network using automatic differentiation. The PINN based geoid computation approach is tested in the area of the Colorado 1-cm geoid experiment. Simulated gravity observations and GNSS leveling derived geoid heights based on EIGEN-6C4 are used to validate the theoretical correctness and validity of the proposed PINN approach, and its performance on precise geoid modeling in this challenging area is evaluated using the actual terrestrial and airborne gravity observations, GNSS leveling measured geoid heights and high resolution DEM provided by NGS/NOAA.

How to cite: Jiang, T., Tu, Z., and Dang, Y.: Physics-Informed Neural Networks for geoid modeling: preliminary results in Colorado, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4068, https://doi.org/10.5194/egusphere-egu24-4068, 2024.

EGU24-4477 | Posters on site | G1.2

Effect of Implementing Moho Depths on Gravity Interpolation at Large Data Gaps  

Hussein Abd-Elmotaal and Norbert Kühtreiber

The coverage of the gravity data plays an important role in the geoid determination process. Still some parts in the world have poor gravity data coverage, with sometimes, large data gaps, e.g., Africa. In this paper we study the effect of implementing Moho depths on the gravity interpolation at large data gaps. For this reason, and in order to qualify that effect, an artificial data gap has been made in the gravity data set of Austria (originally with perfect gravity data coverage). The outcome of the present study is essential for the IAG sub-commission on the gravity and geoid in Africa in order to determine the African geoid from the available data sets with the best possible precision. The gravity interpolation has been made at the original omitted data points at the data gap with and without the Moho information. The interpolated gravity has thus been compared to the original omitted data values for both cases to determine the effect of using Moho depths on gravity interpolation. The results are shown and comprehensively discussed.

How to cite: Abd-Elmotaal, H. and Kühtreiber, N.: Effect of Implementing Moho Depths on Gravity Interpolation at Large Data Gaps , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4477, https://doi.org/10.5194/egusphere-egu24-4477, 2024.

EGU24-5383 | ECS | Posters on site | G1.2

Methods for geoid determination in regions with challenging data quality and coverage 

Qing Liu, Michael Schmidt, and Laura Sánchez

The combination of satellite positioning techniques (e.g., GPS) and high-resolution geoid or quasi-geoid models provides an alternative to the expensive and time-consuming spirit leveling for the determination of physical heights. The reliability of the physical heights thus undergoes the same accuracy limitations of the (quasi-) geoid models. However, in many regions, especially developing or newly industrializing countries, there is no reliable regional gravity model, due to the low availability or quality of surface gravity data. This study tackles such challenges in a case study in the northwestern part of South America and provides the first up-to-date high-resolution Colombian quasi-geoid model.

This region is a challenging study area with coastlines on both the Pacific and the Atlantic Ocean and rugged topography with high elevation reaching more than 5,000 m. Available terrestrial and airborne data were collected during the last eight decades, which frequently contain systematic errors and biases and the corresponding metadata is missing. We develop approaches to validate and improve the quality of old gravity datasets. They are then combined with a global gravity model (GGM) and topography models, which play an important role in mountainous areas, within the remove-compute-restore (RCR) procedure. In the offshore area, satellite altimetry-derived gravity data are additionally incorporated, which are obtained from the latest release of the DTU (Technical University of Denmark) gravity anomaly grid, DTU21GRA.

The computed quasi-geoid model is thoroughly validated with independent GPS/leveling data. It delivers an STD of 15.76 cm in comparison to the GPS/leveling data, which is 36% smaller than that obtained from the latest South American quasi-geoid model QGEIOD2021 (24.51 cm). Five recent high-resolution GGMs, namely EGM2008, EIGEN6C4, GECO, SGG-UGM-1, and XGM2019 are also validated using the same GPS/leveling data. They deliver STD values of 28.09 cm, 21.10 cm, 20.39 cm, 20.93 cm, and 17.86 cm, respectively, which are averagely 38% larger than that of our computation.

How to cite: Liu, Q., Schmidt, M., and Sánchez, L.: Methods for geoid determination in regions with challenging data quality and coverage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5383, https://doi.org/10.5194/egusphere-egu24-5383, 2024.

EGU24-8340 | Posters on site | G1.2

A consolidated 30 Arc-second Global Digital Elevation Model for Geodesy and Geophysics 

Christoph Förste, Oleh Abrykosov, and Elmas Sinem Ince

We have analysed the digital elevation models (DEMs) published in recent years and merged them to create a new elevation grid together with complementary Earth’s relief model for bedrock, surface, bathymetry, ice surface, and ice thickness. Although each model is unique in its own, the merged grid is able to provide seamless elevation information based on a common reference surface globally with high spatial resolution as required for various geoscience applications. We present how the merging procedure was carried out, how the accuracy of the model was evaluated and for which application areas it is intended. Our aim is to disseminate the use of a homogeneous and a consistent elevation model that is particularly suitable for geodetic applications in all parts of the world, including global and regional geoid calculations. The DEMs and associated auxiliary files included in the merged product are: TanDEM-X 90m over all dry land and ice-covered regions, ETOPO2022, GEBCO-2022 and GEBCO-2023 over land and ocean, BedMachineGreenland-v5 over Greenland, BedMachineAntarctica-v3 over Antarctica, GLOBathy (the Global Lakes Bathymetry Dataset) over lakes globally. Masks for ocean, dry land, lakes, islands in the lakes, ponds on the islands, ice-covered land, ice-covered shelves, the area outside Greenland and the ice-covered lake Vostok (Antarctica) were taken into account in the merging. This complete model is anticipated to provide a standardized DEM for various applications in geodesy and geophysics.  Our future plans include high resolution topographic gravity field modelling using this consolidated 30 arc-second digital elevation model and laterally varying global density data.

How to cite: Förste, C., Abrykosov, O., and Ince, E. S.: A consolidated 30 Arc-second Global Digital Elevation Model for Geodesy and Geophysics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8340, https://doi.org/10.5194/egusphere-egu24-8340, 2024.

EGU24-14283 | Posters on site | G1.2

Observation requirements for precise determination of local (quasi)geoid 

Jinshui Huang, Guolei Zheng, Ailixiati Yushan, and Bang Qiu

Many geodetic-related observations nowadays require a precise local geoid height that is as accurate as sub-centimeters. Here, we develop a method to combine global Earth Gravitational Model (EGM), Digital Terrain Model (DTM), as well as highly accurate local gravity and Global Navigation Satellite System (GNSS) observations to achieve this goal. We carried out several observation campaigns to obtain high space resolution and high accuracy gravity and GNSS data. Firstly, we analyze the accuracy of the commonly used methods such as those that use EGM only or use EGM and DTM combined. Then we test our method with a synthetic earth that was developed with EGM, DTM, and local high-resolution topography. Our results should that, the high degree EGM-only geoid has a mean error of tens of centimeters; the geoid from combined EGM and DTM can achieve accuracy of several centimeters; and if we want to have a local geoid with deviations less than sub-centimeter, high accurate observations with space resolution as high as 1"x1" are needed.

How to cite: Huang, J., Zheng, G., Yushan, A., and Qiu, B.: Observation requirements for precise determination of local (quasi)geoid, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14283, https://doi.org/10.5194/egusphere-egu24-14283, 2024.

EGU24-17974 | Posters on site | G1.2

Refinements of regional gravimetric and hybrid geoid models in support of the GeoNetGNSS CORS network in Northern Greece 

Dimitrios A. Natsiopoulos, Georgios Vergos, Elisavet G. Mamagiannou, Eleni A. Tzanou, Anastasia I. Triantafyllou, Ilias N. Tziavos, Dimitrios Ramnalis, and Vassilios Polychronos

In the frame of the GeoNetGNSS project, funded by the European Union and National Funds through the Region of Central Macedonia (RCM) in Northern Greece, regional gravimetric and hybrid geoid models have been determined with the main goal being to support a newly established network of Continuously Operating Reference Stations (CORS). The main aim was to assist everyday surveying purposes by delivering accurate orthometric heights based on GNSS/Levelling, i.e., determining orthometric heights without the need to carry out levelling. With that in mind, a regional gravimetric geoid was determined based on historical and newly acquired high-accuracy and density gravity data, employing the Remove-Compute-Restore (RCR) technique and both stochastic and spectral evaluations of Stokes’ integral. Consequently, a hybrid deterministic and stochastic approach was used to model the residuals of the gravimetric geoid solution relative to available GNSS/Levelling geoid heights. The latter refer to 533 geodetic benchmarks in the entire study area, where accurate static GNSS observations and orthometric heights from the Hellenic Military Geographic Service (HMGS) were available. Various parametric models ranging from simple north-south bias and tilt to 2nd and 3rd order degree polynomial models were evaluated in terms of the fit residual absolute and relative differences. After the deterministic fit, a collocation approach employing exponential and 2nd order Gauss-Markov covariance functions was used to model the stochastic residuals. Finally, the hybrid deterministic and stochastic corrector surface, provided as grid corrections for the entire area under study, has been determined to accommodate user needs for orthometric height determination. From the results acquired, absolute differences of the order of 1-2 cm and relative ones at the 3-4 ppm have been achieved after validation against independent GNSS/Levelling observations.

How to cite: Natsiopoulos, D. A., Vergos, G., Mamagiannou, E. G., Tzanou, E. A., Triantafyllou, A. I., Tziavos, I. N., Ramnalis, D., and Polychronos, V.: Refinements of regional gravimetric and hybrid geoid models in support of the GeoNetGNSS CORS network in Northern Greece, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17974, https://doi.org/10.5194/egusphere-egu24-17974, 2024.

EGU24-770 | ECS | Posters on site | G1.3

Altimetry Waveform Classification and Retracking Strategy for Improved Coastal Altimetry Products 

Shubhi Kant and Balaji Devaraju

Coastal zones exhibit unique altimetry signal characteristics, primarily influenced by the presence of land artifacts. The shape of the altimetry echo serves as a distinctive marker, representing the physical parameters of the surface it originates from. Open ocean reflections for SAR (Synthetic Aperture Radar) mode yield signals with a steep leading edge and a trailing edge modeled by a negative exponential function. In contrast, land areas in coastal zones typically produce specular and quasi-specular waveforms. The presence of specific waveform classes is further influenced by seasonality and changes in land use and patterns such as coastal erosion.

This study aims to classify altimetry waveforms in coastal zones at various global sites and subsequently retrack the identified waveform classes using an optimal retracking strategy. Site selection is based on the availability of in-situ tide gauge data. Waveform classification is achieved using a Long Short-Term Memory (LSTM) auto-encoder, capturing the temporal nature of waveforms and providing an 8-dimensional feature representation. In addition, the LSTM-autoencoder  provides de-noised waveforms, which are used for subsequent retracking processes.

Different waveform shapes necessitate specific retracking strategies. While an Ocean retracker suffices for SAR waveforms over open oceans, it is inadequate for retracking specular, quasi-specular, and multi-peak waveforms. Advanced retracking algorithms such as OCOG, Threshold, ALES, Beta-5, and Beta-9 are employed based on the waveform class.

To validate the proposed strategy, the performance of the altimetry product, sea level anomalies, and retracking outcomes are compared with established coastal altimetry products like XTRACK, in-situ tide gauge data, and popular retracking algorithms like OCOG, Ocean retracker, Threshold, Beta-5 and Beta-9. Sea level anomalies are derived from sensor geophysical data records (SGDR) of altimetry missions and compared with existing coastal altimetry products and in-situ tide gauge records. Evaluation metrics such as Pearson's correlation coefficient and root mean square error assess the agreement in seasonal and yearly trends, as well as the accuracy of measurements.

This comprehensive analysis aims to validate the effectiveness of the proposed coastal waveform post-processing strategy, showcasing its ability to quantify long-term sea level trends and explore regional variations.

How to cite: Kant, S. and Devaraju, B.: Altimetry Waveform Classification and Retracking Strategy for Improved Coastal Altimetry Products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-770, https://doi.org/10.5194/egusphere-egu24-770, 2024.

EGU24-1853 | ECS | Orals | G1.3

Using Machine Learning for identifying TEC signatures related to earthquakes and tsunamis: the 2015 Illapel event case study 

Federica Fuso, Michela Ravanelli, Laura Crocetti, and Benedikt Soja

It is known that natural hazards such as volcanic eruptions, earthquakes, and tsunamis can trigger acoustic and gravity waves (AGWs) that could reach the ionosphere and generate electron density disturbances known as Travelling Ionospheric Disturbances (TIDs). These disturbances can be investigated in terms of variations in the ionospheric total electron content (TEC) measurements, collected by continuously operating ground-based Global Navigation Satellite Systems (GNSS) receivers. The VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithm is a well-known real-time tool for estimating TEC variations. It is based on single-time differences of geometry-free combinations of GNSS carrier-phase measurements.

Artificial Intelligence (AI), particularly in machine learning, offers computational efficiency and data handling, leading to its exploration in ionospheric studies. In this context, the abundance of data allows the exploration of a VARION-based machine learning classification approach to detect TEC perturbation. For this purpose, we used the VARION-TEC variations from the 2015 Illapel earthquake and tsunami, leveraging the distinct ionospheric response triggered by the event.

We employed machine learning algorithms, specifically Random Forest (RF) and XGBoost (XGB), using the VARION-core observations (i.e., dsTEC/dt) as input features. We formulated a binary classification problem using supervised machine learning algorithms and manually labelled the time frames of TEC perturbations as the target variable. We considered two elevation cut-off time series, namely 15° and 25°, to which we applied the classifier. XGBoost with a 15° elevation cut-off dsTEC/dt time series reached the best performance, achieving an F1 score of 0.77, recall of 0.74, and precision of 0.80 on the test data. More in detail, regarding the testing samples, the model accurately classified 183 out of 247 (74.09%) samples of sTEC variations related to the earthquake and tsunami (True Positives, TP). Moreover, 2975 out of 3021 (98.49%) testing samples were correctly classified as containing no sTEC variations caused by an earthquake (True Negatives, TN). However, 64 out of 247 samples (25.91%) were erroneously classified as not containing sTEC variations related to the event (False Negatives, FN), while 46 out of 3021 (1.51%) were wrongly classified as containing sTEC variations related to the earthquake and tsunami (False Positives, FP).

This model showed a 75-second average deviation in predicting perturbation time frames for testing links, equivalent to 5 steps in the 15-second time series intervals. This highlights the algorithm's potential for early detection of ionospheric perturbations from earthquakes and tsunamis, aiding in early warning purposes.

Finally, the model efficiently detects TIDs within 2-3 minutes, showing an impressive computational efficiency, crucial for effective early warning systems. It relies only on the VARION-generated real-time TEC time series (dsTEC/dt), enabling its application in an operational real-time setting using real-time GNSS data.

In conclusion, this work demonstrates high-probability TEC signature detection by machine learning for earthquakes and tsunamis, which can be used to enhance tsunami early warning systems.

How to cite: Fuso, F., Ravanelli, M., Crocetti, L., and Soja, B.: Using Machine Learning for identifying TEC signatures related to earthquakes and tsunamis: the 2015 Illapel event case study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1853, https://doi.org/10.5194/egusphere-egu24-1853, 2024.

EGU24-2619 | Posters on site | G1.3

From formal errors towards realistic uncertainties 

Leonid Petrov and Nlingi Hanaba

    Evaluation of uncertainties of geodetic parameter estimates 
is the problem that is not yet solved in a satisfactory way. 
A direct evaluation of the uncertainties derived from a least 
square solution is labeled "formal" and is usually biased, 
sometimes up to an order of magnitude. Customary, the use of 
formal errors for scientific analysis is discouraged. We claim 
that the root of the problem is neglecting off-diagonal elements 
in the variance-covariance matrix of the noise in the data. 
A careful reconstruction of the full variance-covariance matrix, 
including the off-diagonal terms greatly improves realism of 
uncertainty estimates derived from least squares. We processed 
the dataset of VLBI group delays and built the a priori 
variance-covariance of the atmosphere-driven noise based on 
analysis of the output of NASA high-resolution numerical weather 
models. We found that the uncertainties of parameter estimates 
derived from this least square solution that uses such 
variance-covariance matrices become much closer to realistic 
errors. We consider approaches for for implementation of this 
method in routine data analysis of space geodesy data.

How to cite: Petrov, L. and Hanaba, N.: From formal errors towards realistic uncertainties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2619, https://doi.org/10.5194/egusphere-egu24-2619, 2024.

EGU24-3117 | Orals | G1.3

Enhanced Real-time Global Ionospheric Maps using Machine Learning 

Marcel Iten, Shuyin Mao, and Benedikt Soja

Accurate ionospheric models are essential for single-frequency high-precision Global Navigation Satellite Systems (GNSS) applications. Global ionospheric maps (GIMs), which depicts the global distribution of vertical total electron content (VTEC), are a widely used ionospheric product provided by the International GNSS Service (IGS). To meet the increasing need for real-time applications, the IGS real-time service (RTS) has been established and offers real-time (RT) GIMs that can be used for real or near-real time applications. However, the accuracy of present RT GIMs is still significantly lower compared with the final GIMs. IGS RT GIMs show an RMSE of 3.5-5.5 TECU compared to the IGS final GIMs. In this study, we focus on enhancing the accuracy of RT GIMs through machine learning (ML) approaches, specifically a classical Convolutional Neural Network (CNN) and a Generative Adversarial Network (GAN). The objective is to bridge the gap between the RT GIMs and the final IGS GIMs. This is achieved by using RT GIMs as input and final GIMs as target. The ML approach is applied to the IGS combined RT GIMs and Universitat Politècnica de Catalunya (UPC) RT GIMs. The performance of the improved RT GIMs is evaluated in comparison to the combined IGS final GIM.

We consider over 11'000 pairs of RT GIMs and final GIMs. Over a comprehensive test period spanning 3.5 months, the proposed approach shows promising results with an enhancement of more than 30% in accuracy of RT GIMs. Especially for regions with high VTEC values, which are most critical, the results show a significant improvement. The results demonstrate the model’s great potential in generating more accurate and refined real-time maps.

The integration of ML techniques proves to be a promising avenue for refining and augmenting the precision of real-time ionospheric maps, thereby addressing critical needs in the realm of space weather monitoring and single-frequency applications.

How to cite: Iten, M., Mao, S., and Soja, B.: Enhanced Real-time Global Ionospheric Maps using Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3117, https://doi.org/10.5194/egusphere-egu24-3117, 2024.

EGU24-4609 | Posters on site | G1.3

Multi-Indicator Comprehensive Assessment for Observation Stochastic Model of PPP 

Guanwen Huang, Mengyuan Li, and Le Wang

In PPP, the stochastic model of observation determines the availability and reliability of positioning accuracy, and the observations are usually weighted according to the angle of the GNSS observation, and the smaller the angle of the observation, the more the influence of atmospheric noise and multipath on the observation data increases, and the accuracy of the observations decreases. Based on this, we proposed multi-indicator comprehensive assessment based on grey correlation analysis for observation stochastic modeling of PPP. The position dilution of precision (PDOP), carrier-to-noise density ratio (C/N0) and pseudorange multipath indicators are selected to construct a multi-indicator matrix. Firstly, the indicators are normalized, and then the entropy weight of each assessment indicator is calculated to determine the indicator weight. Meanwhile, after selecting the optimal indicator set, the matrix is constructed to find the grey correlation coefficient and finally the grey correlation degree. According to the above method, the comprehensive assessment results of the quality of satellite observation data for each epoch can be obtained, and the PPP weight array can be established. One-week observations from 243 MGEX stations are selected to conduct GPS-only, Galileo-only and BDS-3-only kinematic PPP, the stochastic model using the highest-elevation and the proposed method is applied, respectively. The results show that, compared with the traditional method, the positioning accuracies and convergence time all can be improved using the proposed method. The positioning accuracies of GPS can be improved by about 4.23%, 8.66%, 5.04% and 5.46% in the east(E), north(N), up(U) and three-dimensional(3D) directions, respectively; 15.96%, 14.25%, 14.72% and 15.01% for Galileo; and 13.53%, 8.42%, 11.65% and 11.40% for BDS-3. The average improvements of convergence time in the east, north and up directions are 5.53%, 7.80% and 5.01% for GPS, BDS-3 and Galileo, respectively.

How to cite: Huang, G., Li, M., and Wang, L.: Multi-Indicator Comprehensive Assessment for Observation Stochastic Model of PPP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4609, https://doi.org/10.5194/egusphere-egu24-4609, 2024.

EGU24-5743 | Posters on site | G1.3

Machine learning-based regional slant ionospheric delay model and its application for PPP-RTK 

Sijie Lyu, Yan Xiang, Wenxian Yu, and Benedikt Soja

The precise point positioning-real-time kinematic (PPP-RTK) method achieves fast convergence in global navigation satellite system (GNSS) positioning and navigation. Correcting slant ionospheric delays is crucial for this purpose. The conventional way of obtaining slant ionospheric corrections at the user end involves generating an ionospheric map using a first-order polynomial function or interpolating using methods such as IDW and Kriging. However, with these approaches is challenging to obtain precise and stable ionospheric corrections especially during ionospheric disturbances, potentially degrading the positioning solution even with augmentation. Fortunately, machine learning has the capability to capture complex and non-linear characteristics of diverse data, offering a potential solution to this issue.

In this study, we aim to improve the accuracy of slant ionospheric delay models using machine learning and evaluate them in PPP-RTK. Initially, we extract highly precise slant ionospheric delays from carrier-phase measurements after ambiguity resolution for two regional GNSS networks in Switzerland and the South of China. Then, we employ the Gaussian Process Regressor to interpolate epoch-specific and satellite-specific slant ionospheric delays, utilizing latitude and longitude as features. Two different approaches are tested: the direct interpolation from reference stations and the indirect interpolation from a gridded map. Our results indicate that the accuracy of interpolated ionospheric delays using machine learning is higher than with conventional methods, including IDW and Kriging. Finally, we evaluate PPP-RTK positioning results with ionospheric corrections from the different interpolation methods, revealing that the machine learning method exhibits superiority in both positioning accuracy and convergence time over conventional methods.

How to cite: Lyu, S., Xiang, Y., Yu, W., and Soja, B.: Machine learning-based regional slant ionospheric delay model and its application for PPP-RTK, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5743, https://doi.org/10.5194/egusphere-egu24-5743, 2024.

EGU24-9203 | ECS | Posters on site | G1.3

Deep Learning spatio-temporal analysis of anthropogenic ground deformation recorded by GNSS time series in the North Adriatic coasts of Italy  

Dung Thi Vu, Adriano Gualandi, Francesco Pintori, Enrico Serpelloni, and Giuseppe Pezzo

Automatic detection and characterization of spatial and temporal features of surface deformation signals associated with anthropogenic activities is a challenging task, with important implications for the evaluation of multi-hazard related to human activities (e.g. earthquakes, subsidence, sea-level rise and flooding), particularly in coastal areas. In this work, we use synthetic Global Navigation Satellite System (GNSS) displacement time-series and apply Deep Learning algorithms (i.e. Convolutional Neural Network (CNN) and Autoencoder) in extracting the time and space features of ground deformation due to natural and anthropogenic processes. We focus on improving three fundamental aspects such as the spatial coverage, the temporal coverage and the accuracy of measurement that come from GNSS technique. The study area is Northern Italy, and particularly the North Adriatic coasts, where gas and oil production sites as well as gas storage sites are present. If in production sites hydrocarbon is constantly extracted during the year, in storage sites the gas/oil is usually injected from April to October and extracted between November and March. Our goals are to understand the effect of hydrocarbon production and extraction/injection process on surface deformation as precisely measured by the dense network of continuous GNSS stations operating in the study area and the ability of CNN-Autoencoder to characterize ground displacements caused by anthropogenic processes. Aims of this work are to identify temporal and spatial patterns in ground deformation time series caused by oil and gas extraction/or gas storage (i.e. extraction and injection); and estimate reservoir parameters (i.e. volumes, depths and extensions). We realize the training dataset by setting up 202 GNSS stations, randomly locating gas/oil reservoirs, which are described by a simple Mogi model, characterized by different depths and temporal evolution of volume changes. The Mogi model, as an approximate spherical shape of a reservoir, displays the ratio of horizontal displacement to vertical displacement due to volume change (i.e. inflating or deflating) and pressure varying with time. The temporal evolution of the volumes of the Mogi sources is simulated by using different parameters associated with several functions namely seasonal, exponential, multi-linear and bell shape. Weighted Principal Component Analysis (WPCA) is used to deal with missing data, which is a common feature in GNSS time series, under an assumption that the weights of missing data are zero. Furthermore, since the CNN-Autoencoder works by analyzing images, the synthetic GNSS time series are interpolated by leveraging the Kriging Interpolation method, which is a Gaussian Process Regression, to obtain the ground displacement in 2D physical space. After calibrating the CNN-Autoencoder model with the synthetic GNSS time series, the model is applied to real data. The code is written in Python and runs on a High-performance computing (HPC) cluster with Graphic Process Unit (GPU) at National Institute of Geophysics and Volcanology (INGV) in Bologna, Italy. 

How to cite: Vu, D. T., Gualandi, A., Pintori, F., Serpelloni, E., and Pezzo, G.: Deep Learning spatio-temporal analysis of anthropogenic ground deformation recorded by GNSS time series in the North Adriatic coasts of Italy , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9203, https://doi.org/10.5194/egusphere-egu24-9203, 2024.

EGU24-9543 | ECS | Posters on site | G1.3

Machine learning for atmospheric delay correction in geodesy 

Duo Wang, Lingke Wang, and Hansjörg Kutterer

In recent years, geodesy based on spaceborne microwave remote sensing has gained significant advances. However, whether the observations from the Global Navigation Satellite System (GNSS) or Interferometric Synthetic Aperture Radar (InSAR), the results are inevitably influenced by atmospheric tropospheric delay. Although the tropospheric zenith total delay (ZTD) can be estimated through the gridded meteorological data products and empirical models provided by the ERA5 reanalysis product, its accuracy is still insufficient to meet the needs of modern geodesy. To overcome this challenge, we propose leveraging machine learning techniques to learn local spatio-temporal patterns of tropospheric delay for inferring total zenith delay (ZTD) and zenith wet delay (ZWD) at any location within the learning area.

Our findings indicate that artificial neural networks can establish a robust mapping between ZTD estimated by empirical models and GNSS-measured ZTD. Then employing the ensemble learning strategy and the time series dynamics model, the ZTD at any location within the sample area can be inferred. To evaluate our approach, we conducted tests during the active water vapor season in the Tübingen region of Baden-Württemberg, Germany, from June 25 to July 9, 2022. In comparative experiments with the root mean square error (RMSE) of Zenith Total Delay (ZTD) derived from ERA5, our proposed method yielded a significant reduction in RMSE, decreasing it from 16.4292mm to 7.2108mm. This reflects a remarkable accuracy improvement of 56.11%.

The proposed approach holds promise for enhancing the precision of GNSS positioning, InSAR earth observation, and generating more dependable water vapor products.

How to cite: Wang, D., Wang, L., and Kutterer, H.: Machine learning for atmospheric delay correction in geodesy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9543, https://doi.org/10.5194/egusphere-egu24-9543, 2024.

EGU24-10154 | Posters on site | G1.3

Neural network-based hydrology corrections for borehole strainmeters 

Jessica Hawthorne

Borehole strainmeters are remarkably precise instruments.  They are often installed to record deformation produced by earthquakes, postseismic slip, and slow earthquakes.  Strainmeters can record such tectonic deformation on timescales of minutes to months with a precision of 0.1 to 1 nanostrain; they record sub-Angstrom changes in borehole width.  

However, the instruments’ high precision also extends to non-tectonic signals.  The borehole width often changes by more than 1 Angstrom when it rains, when atmospheric pressure increases, and when snow loads the ground.  Thus if we want to take full advantage of the instruments and investigate tectonic deformation with high precision, we need to understand and remove the deformation produced by non-tectonic signals like water loading.

So in this study, I present several neural network-based models of hydrologic deformation.  Neural networks are ideal for this modelling as they can accommodate the nonlinearity of the system; 1 cm of rain will cause different deformation if it falls on saturated, winter soil than if it falls on dry, summer soil.  Further, neural networks can take advantage of the abundance of local weather data, including at short timescales.  In my initial modelling, I attempt to reproduce and predict strain as a function of current and past precipitation, atmospheric pressure, wind speed, and temperature.  For simplicity and ease of use, all these parameters are taken from the ECMWF reanalysis models.

I design two neural networks to model the observed strain, using physical intuition to limit the number of free parameters and thus improve the training.  The first network is simple; it creates 10 linear combinations of past rainfall, with exclusively positive weights, and then combines those linear combinations to predict the strain.  The second network also creates 10 linear combinations of past rainfall with positive weights.  But it multiplies those linear combinations of rain by nonlinear functions that could represent the state of the Earth and aquifers.  These nonlinear functions include dependencies on past rainfall, atmospheric pressure, wind speed, and temperature.

These networks train quickly, within a few minutes, and they do a reasonable job of producing the first-order features of the strain.  Both models accommodate more than 50% of the hydrologic signal on timescales of days.  Such modelling may or may not be interesting to hydrologists, but for those interested in tectonic deformation, reproducing and removing 50% of the hydrologic signal means removing 50% of the noise.

It is likely that a better developed and regularised model could remove much more of the noise, and we are continuing to add constraints, initial weights, and training schemes to improve the hydrologic modelling.

How to cite: Hawthorne, J.: Neural network-based hydrology corrections for borehole strainmeters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10154, https://doi.org/10.5194/egusphere-egu24-10154, 2024.

EGU24-10290 | ECS | Orals | G1.3

A Globally Trained Deep Learning Model for Estimation of Seasonal Residual Signals in GNSS displacement time series 

Kaan Çökerim, Jonathan Bedford, and Henryk Dobslaw

Displacement time series from Global Navigation Satellite System (GNSS) at daily rates are used commonly to investigate and understand the processes controlling Earth's surface deformation originating from tectonic processes such as postseismic slip, slow slip events and viscoelastic relaxation, but also non-tectonic processes such as reflectometry, atmospheric sensing and remote sensing. For each individual research field, different parts of the total recorded GNSS displacement time series are of intrest. A major difficulty is the modeling and isolation of non-tectonic seasonal signals that are established to be related with non-tidal surface loading.

In the past, many methods were developed with some success based on Kalman filters, matrix factorization and various approaches using curve fitting to separate the tectonic and non-tectonic contributions. However, these methods still have some difficulties in  isolating the seasonal loading signals especially in the presence of interannual variations in the seasonal loading pattern and steps in the time series.

We present here a deep learning model trained on a globally distributed, continuous 8-10 years long dataset of ~8000 stations PPP-GNSS displacement time series from NGL to estimate the seasonal loading signals using a global non-tidal surface loading model developed at ESM-GFZ. We compare our model to other statistical methods for isolation of the seasonal with the established method of subtraction of the non-tidal surface loading signals (hydrological loading, and non-tidal atmospheric and oceanic loading) as our baseline. We also present the evaluation of our model and its capabilities in reducing the seasonal loading signal as well as parts of the high-frequency scattering in the original GNSS time series.

 

How to cite: Çökerim, K., Bedford, J., and Dobslaw, H.: A Globally Trained Deep Learning Model for Estimation of Seasonal Residual Signals in GNSS displacement time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10290, https://doi.org/10.5194/egusphere-egu24-10290, 2024.

EGU24-10467 | Orals | G1.3

Improving ground deformation prediction in satellite InSAR using ICA-assisted RNN model  

Mimi Peng, Mahdi Motagh, Zhong Lu, Zhuge Xia, Zelong Guo, Chaoying Zhao, and Yinghui Quan

Geological hazards caused by both natural forces and human-induced disturbances, such as land subsidence, earthquakes, tectonic motion, mining activities, coastal erosion, volcanic activities, and permafrost alterations, cause great adverse effects to earth’s surface. The preservation of a comprehensive record detailing past, present, and future surface movements is imperative for effective disaster risk mitigation and property protection. Interferometric Synthetic Aperture Radar (InSAR) is widely recognized as a highly effective and extensively employed geodetic technique for comprehending the spatiotemporal evolution of historical ground surface deformation. However, it only reveals the past deformation evolution process and the deformation update is slowly considering the long revisit cycle of satellites. Deformation evolution in the future is also crucial for preventing and mitigating geological hazards. Unlike traditional mathematical-statistical models and physical models, machine learning methods provide a new perspective and possibility to efficiently and automatically mine the time series information over a large-scale area. In the context of InSAR time series prediction over large areas, the previous researches do not consider the spatiotemporal heterogeneity caused by various factors over a large-scale area and mainly focus on one typical deformation point.

Therefore, in this study, we present a framework designed to predict large-scale spatiotemporal InSAR time series by integrating independent component analysis (ICA) and a Long Short-Term Memory (LSTM) machine learning model. This framework is developed with a specific focus on addressing spatiotemporal heterogeneity within the dataset. The utilization of the ICA method is employed to identify and capture the displacement signals of interest within the InSAR data, enabling the characterization of independent time series signals associated with various natural or anthropogenic processes. Additionally, a K-means clustering approach is incorporated to partition the study area into spatiotemporal homogeneity subregions across a large-scale region, aiming to mitigate potential decreases in model accuracy caused by data heterogeneity. Subsequently, LSTM models are constructed for each cluster, and optimal parameters are determined. The proposed framework is rigorously tested using simulated datasets and validated against two real-world cases—land subsidence in the Willcox Basin and post-seismic deformation following the Sarpol-e Zahab earthquake. Comparative analysis demonstrates that the proposed model surpasses the original LSTM, resulting in a 34% and 17% improvement in average prediction accuracy, respectively. The spatial prediction results in 60 days over the two cases are mapped with high accuracy.

This study introduces an integrated framework that seamlessly integrates InSAR data processing with machine learning techniques such as LSTM to enhance our ability to predict deformation over large-scale geographical areas. The adaptability of the proposed model has made it an alternative to numerical or empirical models, especially when detailed on-site data is scarce or challenging to obtain. While our immediate applications have focused on scenarios on land subsidence and post-seismic deformation, the broader implications of our methodology are evident. We anticipate the proposed framework will be expanded to various application domains, including mining, infrastructure stability, and other situations involving sustained motions. The proposed framework will ultimately contribute to more informed decision-making and risk assessment in complex dynamic systems.

How to cite: Peng, M., Motagh, M., Lu, Z., Xia, Z., Guo, Z., Zhao, C., and Quan, Y.: Improving ground deformation prediction in satellite InSAR using ICA-assisted RNN model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10467, https://doi.org/10.5194/egusphere-egu24-10467, 2024.

EGU24-10575 | ECS | Orals | G1.3

 Feature Selection and Deep Learning for Simultaneous Forecasting of Celestial Pole Offset (CPO) and Polar Motion (PM) 

Sonia Guessoum, Santiago Belda, José Manuel Ferrándiz, Ahmed Begga, Maria Karbon, Harald Schuh, Sadegh Modiri, and Robert Heinkelmann

Accurate prediction of Earth orientation parameters (EOPs) is critical for astro-geodynamics, high-precision space navigation, and positioning, and deep space exploration. However, the current models' prediction accuracy for EOPs is significantly lower than that of geodetic technical solutions, which can adversely affect certain high-precision real-time users. In this study, we introduce a simultaneous prediction approach for Polar Motion (PM) and Celestial Pole Offsets (CPO) employing deep neural networks, aiming to deliver precise predictions for both parameters.
The methodology comprises three components, with the first being feature interaction and selection. The process of feature selection within the context of deep learning differs from traditional methods for machine learning, and may not be directly applicable to theme since they are designed to automatically learn relevant features. Consequently, we propose in this step a solution based on feature engineering to select the best set of variables that can keep the model as simple as possible but with enough precision and accuracy using recursive feature elimination and the SHAP value algorithm, aiming to investigate the influence of FCN (Free Core Nutation) with its amplitude and phase on the CPO forecasting. This investigation is crucial since FCN is the main source of variance of the CPO series. Considering the role represented by the effective Angular Momentum functions (EAM), and their direct influence on the Earth's rotation, it is logical to assess numerically the impact of EAM on the Polar motion and FCN excitations. SHAP value aids in comprehending how each feature contributes to final predictions, highlighting the significance of each feature relative to others,  and revealing the model's dependency on feature interactions.
During the second phase, we formulate two deep-learning methods for each parameter. The first Neural Network incorporates all features, while the second focuses on the subset of features identified in the initial step. This stage primarily involves exploring feature and hyperparameter tuning to enhance model performance. The SHAP value algorithm is also used in this stage for interpretation. 
In the final phase, we construct a multi-task deep learning model designed to simultaneously predict ( CPO ) and ( PM ).  This model is built using the optimal set of features and hyperparameters identified in the preceding steps. To validate the methodology, we employ the most recent version of the time series from the International Earth Rotation and Reference Systems Service (IERS), namely IERS 20 C04 and EAM provided by the German Research Center for Geosciences (GFZ). We focus on a forecasting horizon of 90 days, the practical forecasting horizon needed in space-geodetic applications.
In the end, we conclude that the developed model is proficient in simultaneously predicting ( CPO ) and ( PM ). The incorporation of ( EAM ), sheds light on its role in CPO excitations and Polar Motion predictions.

How to cite: Guessoum, S., Belda, S., Ferrándiz, J. M., Begga, A., Karbon, M., Schuh, H., Modiri, S., and Heinkelmann, R.:  Feature Selection and Deep Learning for Simultaneous Forecasting of Celestial Pole Offset (CPO) and Polar Motion (PM), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10575, https://doi.org/10.5194/egusphere-egu24-10575, 2024.

EGU24-10706 | ECS | Orals | G1.3

Explaining GNSS station movements based on Earth observation data 

Laura Crocetti, Rochelle Schneider, and Benedikt Soja

Global Navigation Satellite Systems (GNSS) are best known for their accurate positioning, navigation and timing capabilities. In total, over 20.000 permanent high-grade GNSS stations are available worldwide, the positions of which are monitored with millimeter accuracy. Thanks to the high accuracy and the fact that these stations are mounted on the ground, subtle movements due to hydrological changes and crustal deformation can be observed. Thus, the GNSS observations contain valuable geophysical information. Although many geodetic applications require these movements to be properly understood and potentially corrected, this is not trivial due to the complexity of the interactions within the Earth’s system. Therefore, there is a severe lack of available models explaining residual GNSS station movements beyond conventionally modeled effects. On the opposite, if these movements are properly understood, GNSS observations might contribute to the correct interpretation of emerging environmental changes.

This study exploits the wealth of satellite-derived Earth observation (EO) data to derive suitable models to explain GNSS station movements. We combine GNSS station coordinate time series and EO variables with the help of machine learning techniques to benefit from various types of information. While the target vector consists of concatenated GNSS station coordinate time series over Europe, EO variables such as precipitation, soil water, snow water equivalent, and land cover data are used as input features. Different machine learning models, including Random Forest, XGBoost, and Multilayer Perceptron, are investigated and compared. Additionally, a sensitivity analysis is performed to determine the individual impact of EO variables to quantify what drives GNSS movements, which in turn, might allow monitoring the corresponding Earth system processes based on GNSS observations.

How to cite: Crocetti, L., Schneider, R., and Soja, B.: Explaining GNSS station movements based on Earth observation data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10706, https://doi.org/10.5194/egusphere-egu24-10706, 2024.

EGU24-11029 | ECS | Orals | G1.3

Quantum Machine Learning for Deformation Detection: Application for InSAR Point Clouds 

Nhung Le, Benjamin Männel, Mahdi Motagh, Andreas Brack, and Harald Schuh

Abstract:

Machine Learning (ML) is emerging as a powerful tool for data analysis. Anomaly detection based on classical approaches is sometimes limited in processing speed on big data, especially for massive datasets. Meanwhile, quantum algorithms have been shown to have the potential for optimization, scenario simulation, and artificial intelligence. Thus, this study combines quantum algorithms and ML to improve the binary classification performance of ML models for better sensitivity of surface deformation detection. We experimented with GNSS-InSAR combination data to identify significant deformation regions in Northern Germany. We classify the movement characteristics based on four main features: vertical movement velocities, root mean square errors, standard deviations, and outliers in the GNSS-InSAR time series. Our primary results reveal that the classification accuracy based on Quantum Machine Learning (QML) is outstanding compared to the pure ML technique. Specifically, on the same sample dataset, the classification performance of the neural network based on pure ML is only around 50 to 70%, while that of the QML technique can reach ~90%. The significant deformation regions are concentrated in the river basins of Elbe, Weser, Ems, and Rhine, where the average surface subsidence speed varies around -4.5 mm/yr. Also, we suggest dividing the surface movement features in Northern Germany into five classes to reduce the effect of the data quality variety and algorithm uncertainty. Our findings will advocate the development of quantum computing applications as well as promote the potential of the QML for deformation analyses. 

Keywords:

Quantum Machine Learning, Binary Classification, GNSS-InSAR Data, Deformation Detection.

How to cite: Le, N., Männel, B., Motagh, M., Brack, A., and Schuh, H.: Quantum Machine Learning for Deformation Detection: Application for InSAR Point Clouds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11029, https://doi.org/10.5194/egusphere-egu24-11029, 2024.

EGU24-11427 | ECS | Posters on site | G1.3

Non-line-of-sight GNSS Signal Classification for Urban Navigation Using Machine Learning  

Yuanxin Pan, Lucy Icking, Fabian Ruwisch, Steffen Schön, and Benedikt Soja

The reception of non-line-of-sight (NLOS) signals is a prevalent issue for Global Navigation Satellite System (GNSS) applications in urban environments. Such signals can significantly degrade the positioning and navigation accuracy for pedestrians and vehicles. While various methods, such as dual-polarization antennas and 3D building models, have been proposed to identify NLOS signals, they often require additional equipment or impose computational burdens, which limits their practicality. In this study, we introduce a machine learning (ML)-based classifier designed to detect NLOS signals based solely on quality indicators extracted from raw GNSS observations. We examined several input features, including carrier-to-noise density and elevation, and analyzed their relative importance. The effectiveness of our approach was validated using multi-GNSS data collected statically in the city of Hannover. To establish ground truth (i.e., a target) for training and testing the model, we used ray tracing in combination with a 3D building model of Hannover. The developed ML-based classifier achieved an accuracy of approximately 90% for NLOS signal classification. Furthermore, a vehicle-borne data set was used to test the utility of the ML-based signal classifier for kinematic positioning. The performance of the ML-aided positioning solution was compared against a solution without NLOS classification (raw solution) and with the ray-tracing-based classification results (reference solution). It was found that the ML-based solution demonstrated positioning precisions of 0.47 m, 0.55 m and 1.02 in the east, north and up components, respectively. This represents improvements of 64.6%, 33.4% and 36.6% over the raw solution. Additionally, we examined the performance of the ML-based classifier across various urban environments along the vehicle trajectory to gain deeper insights.

How to cite: Pan, Y., Icking, L., Ruwisch, F., Schön, S., and Soja, B.: Non-line-of-sight GNSS Signal Classification for Urban Navigation Using Machine Learning , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11427, https://doi.org/10.5194/egusphere-egu24-11427, 2024.

EGU24-12487 | ECS | Orals | G1.3

Signal separation in global, temporal gravity data using a multi-channel U-Net 

Betty Heller-Kaikov, Roland Pail, and Martin Werner

One big challenge in the analysis and interpretation of geodetic data is the separation of the individual signal and noise components contained in the data. Specifically, the global, temporal gravity data obtained by the GRACE and GRACE Follow-On satellite missions contain spatial-temporal gravity signals caused by all kinds of mass variations in the Earth’s system. While only the sum of all signals can be measured, for geophysical interpretation, an extraction of individual signal contributions is necessary.

Therefore, our aim is to develop an algorithm solving the signal separation task in global, temporal gravity data. Since the individual signal components are characterized by specific patterns in space and time, the algorithm to be found needs to be able to extract patterns in the 3-dimensional latitude-longitude-time space.

We propose to exploit the pattern recognition abilities of deep neural networks for solving the signal separation task. Our method uses a multi-channel U-Net architecture which is able to translate the sum of various signals as single-channel input to the individual signal components as multi-channel output. The loss function is a weighted sum of the L2 losses of the individual signals.

We perform a supervised training using synthetic data derived from the updated Earth System Model of ESA. The latter consists of separate datasets for temporal gravity variations caused by mass redistribution processes in the atmosphere, the oceans, the continental hydrosphere, the cryosphere and the solid Earth.

In our study, we use different parts of this dataset to form training and test datasets. In this fully-synthetic framework, the ground truth of the individual signal components is also known in the testing stage, allowing a direct computation of the separation errors of the trained separation model.

In our contribution, we present results on optimizing our algorithm by tuning various hyperparameters of the neural network. Moreover, we demonstrate the impact of the number of superimposed signals and the definition of the loss function on the signal separation performance of our algorithm.

How to cite: Heller-Kaikov, B., Pail, R., and Werner, M.: Signal separation in global, temporal gravity data using a multi-channel U-Net, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12487, https://doi.org/10.5194/egusphere-egu24-12487, 2024.

EGU24-12556 | ECS | Posters on site | G1.3

An Ionospheric Forecasting Model Based on Transfer Learning Using High-Resolution Global Ionospheric Maps 

Shuyin Mao, Junyang Gou, and Benedikt Soja

High-precision ionospheric prediction is essential for real-time applications of the Global Navigation Satellite System (GNSS), especially for single-frequency receivers. Various machine learning (ML) algorithms have been utilized for ionospheric forecasting and shown great potential. However, previous studies have primarily relied on IGS global ionospheric maps (GIMs) as training data to develop models for global vertical total electron content (VTEC) forecasting. The forecasting accuracy is thereby limited by the input IGS GIMs due to their low spatio-temporal resolution.

Our previous work proposed a neural network-based (NN-based) global ionospheric model. GIMs generated with this approach showcased enhanced accuracy compared with conventional IGS GIMs as we can finely resolve VTEC irregularities. In this study, we benefit from these ML-based GIMs by employing the transfer learning principle to improve the quality of GIM forecasts. The ML-based model for 1-day ahead global VTEC forecasting is first trained based on a series of IGS GIMs from 2004 to 2022. Then, it is fine-tuned using the recent NN-based GIMs from 2020 to 2022. In this context, the model can gain good generalizability from the large dataset of IGS GIMs while having comparable accuracy with NN-based GIMs. Different machine learning approaches, including convolution long short-term memory (ConvLSTM) network and transformer, are implemented and compared. To validate their performance, we perform hindcast studies to compare the 1-day ahead forecasts of our model with satellite altimetry VTEC and conducted single-frequency precise point positioning tests based on the forecast maps.

How to cite: Mao, S., Gou, J., and Soja, B.: An Ionospheric Forecasting Model Based on Transfer Learning Using High-Resolution Global Ionospheric Maps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12556, https://doi.org/10.5194/egusphere-egu24-12556, 2024.

EGU24-12715 | ECS | Orals | G1.3

Explainable AI for GNSS Reflectometry: Investigating Feature Importance for Ocean Wind Speed Estimation 

Tianqi Xiao, Milad Asgarimehr, Caroline Arnold, Daixin Zhao, Lichao Mou, and Jens Wickert

Spaceborne GNSS Reflectometry (GNSS-R) is a novel remote sensing technique providing accumulating data volume with global coverage and enhanced temporal resolution. The reflected pre-existing L-Band signal of opportunity transmitted by the Global Navigation Satellite System contains information about the reflection surface properties which can be quantified and converted into data products for further studies. To retrieve such information, Artificial intelligence (AI) models are implemented to estimate geophysical parameters based on the GNSS-R observations. With more and more complex deep learning models being proposed and more and more input features being considered, understanding the decision-making process of the models and the contributions of the input features becomes as important as enhancing the model output accuracy.

This study explores the potential of the Explainable AI (XAI) to decode complex deep learning models for ocean surface wind speed estimation trained by the Cyclone GNSS (CYGNSS) observations. The input feature importance is evaluated by applying the SHAP (SHapley Additive exPlanations) Gradient Explainer to the model on an unseen dataset. By analyzing the SHAP value of each input feature, we find that in addition to the two known parameters that are used in the operational wind speed retrieval algorithm, other scientific and technical ancillary parameters, such as the orientation of the satellite and the signal power information are also useful for the model.

We seek to offer a better understanding of the deep learning models for estimating ocean wind speed using GNSS-R data and explore the potential features for more accurate retrieval. In addition to building an efficient model with effective inputs, XAI also helps us to discover the important factors found by models which can enhance the physical understanding of the GNSS-R mechanism.

How to cite: Xiao, T., Asgarimehr, M., Arnold, C., Zhao, D., Mou, L., and Wickert, J.: Explainable AI for GNSS Reflectometry: Investigating Feature Importance for Ocean Wind Speed Estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12715, https://doi.org/10.5194/egusphere-egu24-12715, 2024.

EGU24-14724 | ECS | Orals | G1.3

Exploring the performance of machine learning models for the GNSS-IR retrieval of seasonal snow height 

Matthias Aichinger-Rosenberger and Benedikt Soja

Snow is a key variable of the global climate system and the hydrological cycle, as well as one of the most critical sources of freshwater. Therefore, measurements of snow-related parameters such as seasonal snow height (SSH) or snow-water-equivalent (SWE) are of great importance for science, economy and society. Traditionally, these parameters are either measured manually or with automated ground-based sensors, which are accurate, but expensive and suffer from low temporal and spatial resolution.

A new alternative for such systems is the use of GNSS observations, by application of the GNSS interferometric reflectometry (GNSS-IR) method. The technique enables users to infer information about soil moisture, snow depth, or vegetation water content. Signal-to-Noise Ratio (SNR) observations collected by GNSS receivers are sensitive to the interference between the direct signal and the reflected signal (often referred to as “multipath”). The interference pattern changes with the elevation angle of the satellite, the signal wavelength, and the height of the GNSS antenna above the reflecting surface. By comparing this reflector heights estimated for snow surfaces with those from bare soil conditions, snow height can be determined.

The estimation of reflector heights, and respectively SSH, is typically carried out using Lomb-Scargle Periodogram (LSP) spectrum analysis. This study investigates the potential of machine learning methods for this task, using similar input parameters as the standard GNSS-IR retrieval. Results from different supervised algorithms such as Random Forest (RF) or Gradient Boosting (GB) are shown for different GNSS sites and experimental setups. First investigations indicate that snow heights can be successfully obtained with machine learning, with results less noisy than with classical approaches.

How to cite: Aichinger-Rosenberger, M. and Soja, B.: Exploring the performance of machine learning models for the GNSS-IR retrieval of seasonal snow height, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14724, https://doi.org/10.5194/egusphere-egu24-14724, 2024.

EGU24-16740 | ECS | Posters on site | G1.3

Signal decomposition of multi-source displacement fields with component analysis methods, applied to InSAR time series of the Epe gas storage cavern field (Germany) 

Alison Seidel, Markus Even, Malte Westerhaus, and Hansjörg Kutterer

Time series of interferometric SAR (InSAR) images offer the potential to detect and monitor surface displacements with high spatial and temporal resolution, even for small and slow deformation processes. Yet, due to the nature of InSAR, the interferometric signal can contain a multitude of contributions. Different displacement source mechanisms could superpose each other, signals that are residuals of atmospheric and topographic effects could not be completely removed during processing of the time series or non-coherent noise could exist. Therefore, the criteria for the selection of temporally stable pixels are often rather strict, leading to significant reduction of the spatial resolution density.

However, to understand the underlying processes of a deformation field, it is important to extract the displacement signals from the data at the best resolution possible and differentiate signals from different source mechanisms. Furthermore, being able to describe the displacement field as superposition of several simple mechanisms is a possible answer to the general question how the information content from tens of thousands of points each coming with a time series over hundreds of acquisitions can be extracted and comprehended.

We address these issues, by determining the dominant displacement signals of different sources in a subset of reliable pixels of InSAR time series datasets with data driven component analysis methods. Subsequently we use models of these signals to identify their displacement patterns in previously not regarded pixels. We utilize the statistical principal component analysis for removing uncorrelated signal contributions and compare different blind source separation methods, such as independent component analysis and independent vector analysis for differentiating between displacements of different origin.

We apply our method to a dataset of multiple orbits of Sentinel-1 InSAR time series from 2015 to 2022 above the gas storage cavern field Epe in NRW, Germany.  Epe displays a complex surface displacement field, consisting of trends caused by cavern convergence, cyclic gas pressure dependent contributions, as well as ground water dependent seasonal displacements. With our approach, we can successfully distinguish the signals of the different source mechanisms and obtain a dense spatial sampling of these signals. Our results show good agreement with geodetic measurements from GNSS and levelling and show a strong correlation to cavern filling levels and groundwater levels, suggesting causal relations.

How to cite: Seidel, A., Even, M., Westerhaus, M., and Kutterer, H.: Signal decomposition of multi-source displacement fields with component analysis methods, applied to InSAR time series of the Epe gas storage cavern field (Germany), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16740, https://doi.org/10.5194/egusphere-egu24-16740, 2024.

In geological characterization, the traditional methods that rely on the covariance matrix for continuous variable estimation often either neglect or oversimplify the challenge posed by subsurface non-stationarity. This study presents an innovative methodology using ancillary data such as geological insights and geophysical exploration to address this challenge directly, with the goal of accurately delineating the spatial distribution of subsurface petrophysical properties, especially, in large geological fields where non-stationarity is prevalent. This methodology is based on the geodesic distance on an embedded manifold and is complemented by the level-set curve as a key tool for relating the observed geological structures to intrinsic geological non-stationarity. During validation, parameters ρ and β were revealed to be the critical parameters that influenced the strength and dependence of the estimated spatial variables on secondary data, respectively. Comparative evaluations showed that our approach performed better than a traditional method (i.e., kriging), particularly, in accurately representing the complex and realistic subsurface structures. The proposed method offers improved accuracy, which is essential for high-stakes applications such as contaminant remediation and underground repository design. This study focused primarily on two-dimensional models. There is a need for three-dimensional advancements and evaluations across diverse geological structures. Overall, this research presents novel strategies for estimating non-stationary geologic media, setting the stage for improved exploration of subsurface characterization in the future.

How to cite: Park, E.: Manifold Embedding Based on Geodesic Distance for Non-stationary Subsurface Characterization Using Secondary Information, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16940, https://doi.org/10.5194/egusphere-egu24-16940, 2024.

EGU24-24 | Orals | NP4.1

The fractional Sinusoidal wavefront Model (fSwp) for time series displaying persistent stationary cycles 

Gael Kermarrec, Federico Maddanu, Anna Klos, and Tommaso Proietti

In the analysis of sub-annual climatological or geodetic time series such as tide gauges, precipitable water vapor, or GNSS vertical displacements time series but also temperatures or gases concentrations, seasonal cycles are often found to have a time-varying amplitude and phase.

These time series are usually modelled with a deterministic approach that includes trend, annual, and semi-annual periodic components having constant amplitude and phase-lag. This approach can potentially lead to inadequate interpretations, such as an overestimation of Global Navigation Satellite System (GNSS) station velocity, up to masking important geophysical phenomena that are related to the amplitude variability and are important for deriving trustworthy interpretation for climate change assessment.

We address that challenge by proposing a novel linear additive model called the fractional Sinusoidal Waveform process (fSWp), accounting for possible nonstationary cyclical long memory, a stochastic trend that can evolve over time and an additional serially correlated noise capturing the short-term variability. The model has a state space representation and makes use of the Kalman filter (KF). Suitable enhancements of the basic methodology enable handling data gaps, outliers, and offsets. We demonstrate our method using various climatological and geodetic time series to illustrate its potential to capture the time-varying stochastic seasonal signals.

How to cite: Kermarrec, G., Maddanu, F., Klos, A., and Proietti, T.: The fractional Sinusoidal wavefront Model (fSwp) for time series displaying persistent stationary cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-24, https://doi.org/10.5194/egusphere-egu24-24, 2024.

On some maps of the first military survey of the Habsburg Empire, the upper direction of the sections does not face the cartographic north, but makes an angle of about 15° with it. This may be due to the fact that the sections were subsequently rotated to the magnetic north of the time. Basically, neither their projection nor their projection origin is known yet.

In my research, I am dealing with maps of Inner Austria, the Principality of Transylvania and Galicia (nowadays Poland and Ukraine), and I am trying to determine their projection origin. For this purpose, it is assumed, based on the archival documentation of the survey, that these are Cassini projection maps. My hypothesis is that they are Graz, Cluj Napoca or Alba Julia and Lviv. I also consider the position of Vienna in each case, since it was the main centre of the survey.

The angle of rotation was taken in part from the gufm1 historical magnetic model back to 1590 for the assumed starting points and year of mapping. In addition, as a theoretical case, I calculated the rotation angle of the map sections using coordinate geometry. I then calculated the longitude of the projection starting point for each case using univariate minimization. Since the method is invariant to latitude, it can only be determined from archival data.

Based on these, the starting point for Inner Austria from the rotation of the map was Vienna, which is not excluded by the archival sources, and since the baseline through Graz also started from there, it is partly logical. The map rotation for Galicia and Transylvania also confirmed the starting point of the hypothesis.  Since both Alba Julia and Cluj Napoca lie at about the same longitude, the method cannot make a difference there; and the archival data did not provide enough evidence. In comparison, the magnetic declination rotations yielded differences of about 1°, which may be due to an error in the magnetic model.

On this basis, I have given the assumed projections of the three maps with projection starting points, and developed a method for determining the projection starting points of the other rotated grid maps. The results suggest that there is a very high probability that the section network was rotated in the magnetic north direction, and thus provide a way to refine the magnetic declination data at that time.

With this method I managed to give new indirekt magnetic declinations data from Central-East Europe, which can help to improve the historical magnetic field models. The main reason for this is that we don’t have any measurement from that region.

Furthermore the difference beetwen the angle of the section north and the declination data from gufm1 always 0.8-1°. Maybe there are systematical data error at that region.

Supported by the ÚNKP-23-6 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund.

How to cite: Koszta, B. and Timár, G.: A possible cartographical data source for historical magnetic field improvement: The direction of the section north of the Habsburg first military survey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-582, https://doi.org/10.5194/egusphere-egu24-582, 2024.

EGU24-1988 | ECS | Posters on site | NP4.1

Predictive ability assessment of Bayesian Causal Reasoning (BCR) on runoff temporal series 

Santiago Zazo, José Luis Molina, Carmen Patino-Alonso, and Fernando Espejo

The alteration of traditional hydrological patterns due to global warming is leading to a modification of the hydrological cycle. This situation draws a complex scenario for the sustainable management of water resources. However, this issue offers a challenge for the development of innovative approaches that allow an in-depth capturing the logical temporal-dependence structure of these modifications to advance sustainable management of water resources, mainly through the reliable predictive models. In this context, Bayesian Causality (BC), addressed through Causal Reasoning (CR) and supported by a Bayesian Networks (BNs), called Bayesian Causal Reasoning (BCR) is a novel hydrological research area that can help identify those temporal interactions efficiently.

This contribution aims to assesses the BCR ability to discover the logical and non-trivial temporal-dependence structure of the hydrological series, as well as its predictability. For this, a BN that conceptually synthesizes the time series is defined, and where the conditional probability is propagated over the time throughout the BN through an innovative Dependence Mitigation Graph. This is done by coupling among an autoregressive parametric approach and causal model. The analytical ability of the BCR highlighted the logical temporal structure, latent in the time series, which defines the general behavior of the runoff. This logical structure allowed to quantify, through a dependence matrix which summarizes the strength of the temporal dependencies, the two temporal fractions that compose the runoff: one due to time (Temporally Conditioned Runoff) and one not (Temporally Non-conditioned Runoff). Based on this temporal conditionality, a predictive model is implemented for each temporal fraction, and its reliability is assessed from a double probabilistic and metrological perspective.

This methodological framework is applied to two Spanish unregulated sub-basins; Voltoya river belongs to Duero River Basin, and Mijares river, in the Jucar River Basin. Both cases with a clearly opposite temporal behavior, Voltoya independent and Mijares dependent, and with increasingly more problems associated with droughts.

The findings of this study may have important implications over the knowledge of temporal behavior of water resources of river basin and their adaptation. In addition, TCR and TNCR predictive models would allow advances in the optimal dimensioning of storage infrastructures (reservoirs), with relevant substantial economic/environmental savings. Also, a more sustainable management of river basins through more reliable control reservoirs’ operation is expected to be achieved. Finally, these results open new possibilities for developing predictive hydrological models within a BCR framework.

How to cite: Zazo, S., Molina, J. L., Patino-Alonso, C., and Espejo, F.: Predictive ability assessment of Bayesian Causal Reasoning (BCR) on runoff temporal series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1988, https://doi.org/10.5194/egusphere-egu24-1988, 2024.

EGU24-3857 | ECS | Posters on site | NP4.1 | Highlight

Spatial-Temporal Analysis of Forest Mortality 

Sara Alibakhshi

Climate-induced forest mortality poses an increasing threat worldwide, which calls for developing robust approaches to generate early warning signals of upcoming forest state change. This research explores the potential of satellite imagery, utilizing advanced spatio-temporal indicators and methodologies, to assess the state of forests preceding mortality events. Traditional approaches, such as techniques based on temporal analyses, are impacted by limitations related to window size selection and detrending methods, potentially leading to false alarms. To tackle these challenges, our study introduces two new approaches, namely the Spatial-Temporal Moran (STM) and Spatial-Temporal Geary (STG) approaches, both focusing on local spatial autocorrelation measures. These approaches can effectively address the shortcomings inherent in traditional methods. The research findings were assessed across three study sites within California national parks, and Kendall's tau was employed to quantify the significance of false and positive alarms. To facilitate the measurement of ecosystem state change, trend estimation, and identification of early warning signals, this study also provides "stew" R package. The implications of this research extend to various groups, such as ecologists, conservation practitioners, and policymakers, providing them with the means to address emerging environmental challenges in global forest ecosystems.

How to cite: Alibakhshi, S.: Spatial-Temporal Analysis of Forest Mortality, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3857, https://doi.org/10.5194/egusphere-egu24-3857, 2024.

Iram Parvez1, Massimiliano Cannata2, Giorgio Boni1, Rossella Bovolenta1 ,Eva Riccomagno3 , Bianca Federici1

1 Department of Civil, Chemical and Environmental Engineering (DICCA), Università degli Studi di Genova, Via Montallegro 1, 16145 Genoa, Italy (iram.parvez@edu.unige.it,bianca.federici@unige.it, giorgio.boni@unige.it, rossella.bovolenta@unige.it).

2 Institute of Earth Sciences (IST), Department for Environment Constructions and Design (DACD), University of Applied Sciences and Arts of Southern Switzerland (SUPSI), CH-6952 Canobbio, Switzerland(massimiliano.cannata@supsi.ch).

3 Department of Mathematics, Università degli Studi di Genova, Via Dodecaneso 35, 16146 Genova, Italy(riccomag@dima.unige.it).

The deployment of hydrometeorological sensors significantly contributes to generating real-time big data. The quality and reliability of large datasets pose considerable challenges, as flawed analyses and decision-making processes can result. This research aims to address the issue of anomaly detection in real-time data by exploring machine learning models. Time-series data is collected from IstSOS - Sensor Observation Service, an open-source software that stores, collects and disseminates sensor data. The methodology consists of Gated Recurrent Units based on recurrent neural networks, along with corresponding prediction intervals, applied both to individual sensors and collectively across all temperature sensors within the Ticino region of Switzerland. Additionally, non-parametric methods like Bootstrap and Mean absolute deviation are employed instead of standard prediction intervals to tackle the non-normality of the data. The results indicate that Gated Recurrent Units based on recurrent neural networks, coupled with non-parametric forecast intervals, perform well in identifying erroneous data points. The application of the model on multivariate time series-sensor data establishes a pattern or baseline of normal behavior for the area (Ticino). When a new sensor is installed in the same region, the recognized pattern is used as a reference to identify outliers in the data gathered from the new sensor.

How to cite: Parvez, I.: Exploring Machine Learning Models to Detect Outliers in HydroMet Sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4280, https://doi.org/10.5194/egusphere-egu24-4280, 2024.

EGU24-5268 | ECS | Orals | NP4.1

Unveiling Geological Patterns: Bayesian Exploration of Zircon-Derived Time Series Data 

Hang Qian, Meng Tian, and Nan Zhang

For its immunity to post-formation geological modifications, zircon is widely utilized as chronological time capsule and provides critical time series data potential to unravel key events in Earth’s geological history, such as supercontinent cycles. Fourier analysis, which assumes stationary periodicity, has been applied to zircon-derived time series data to find the cyclicity of supercontinents, and wavelet analysis, which assumes non-stationary periodicity, corroborates the results of Fourier Analysis in addition to detecting finer-scale signals. Nonetheless, both methods still prognostically assume periodicity in the zircon-derived time-domain data. To stay away from the periodicity assumption and extract more objective information from zircon data, we opt for a Bayesian approach and treat zircon preservation as a composite stochastic process where the number of preserved zircon grains per magmatic event obeys logarithmic series distribution and the number of magmatic events during a geological time interval obeys Poisson distribution. An analytical solution was found to allow us to efficiently invert for the number and distribution(s) of changepoints hidden in the globally compiled zircon data, as well as for the zircon preservation potential (encoded as a model parameter) between two neighboring changepoints. If the distributions of changepoints temporally overlap with those of known supercontinents, then our results serve as an independent, mathematically robust test of the cyclicity of supercontinents. Moreover, our statistical approach inherently provides a sensitivity parameter the tuning of which allows to probe changepoints at various temporal resolution. The constructed Bayesian framework is thus of significant potential to detect other types of trend swings in Earth’s history, such as shift of geodynamic regimes, moving beyond cyclicity detection which limits the application of conventional Fourier/Wavelet analysis.

How to cite: Qian, H., Tian, M., and Zhang, N.: Unveiling Geological Patterns: Bayesian Exploration of Zircon-Derived Time Series Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5268, https://doi.org/10.5194/egusphere-egu24-5268, 2024.

Semi-enclosed freshwater and brackish ecosystems, characterised by restricted water outflow and prolonged residence times, often accumulate nutrients, influencing their productivity and ecological dynamics. These ecosystems exhibit significant variations in bio-physical-chemical attributes, ecological importance, and susceptibility to human impacts. Untangling the complexities of their interactions remains challenging, necessitating a deeper understanding of effective management strategies adapted to their vulnerabilities. This research focuses on the bio-physical aspects, investigating the differential effects of spring and summer light on phytoplankton communities in semi-enclosed freshwater and brackish aquatic ecosystems.

Through extensive field sampling and comprehensive environmental parameter analysis, we explore how phytoplankton respond to varying light conditions in these distinct environments. Sampling campaigns were conducted at Müggelsee, a freshwater lake on Berlin's eastern edge, and Barther Bodden, a coastal lagoon northeast of Rostock on the German Baltic Sea coast, during the springs and summers of 2022 and 2023, respectively. Our analysis integrates environmental factors such as surface light intensity, diffuse attenuation coefficients, nutrient availability, water column dynamics, meteorological data, Chlorophyll-a concentration, and phytoplankton communities. Sampling encompassed multiple depths at continuous intervals lasting three days.

Preliminary findings underscore significant differences in seasonal light availability, with summer exhibiting extended periods of substantial light penetration. These variations seem to impact phytoplankton abundance and diversity uniquely in each ecosystem. While ongoing analyses are underway, early indications suggest distinct phytoplankton responses in terms of species composition and community structure, influenced by the changing light levels. In 2022 the clear water phase during spring indicated that bloom events have occurred under ice cover much earlier than spring, while in the summer there were weak and short-lived blooms of cyanobacteria. The relationship between nutrient availability and phytoplankton dynamics, however, remains uncertain according to our data.

This ongoing study contributes to understanding the role of light as a primary driver shaping phytoplankton community structures and dynamics in these environments.  Our research findings offer insights for refining predictive models, aiding in ecosystem-specific eutrophication management strategies, and supporting monitoring efforts of Harmful Algal Blooms.

How to cite: Kaharuddin, A. and Kaligatla, R.: Comparative Study of Spring and Summer Light Effects on Phytoplankton Communities in Semi-Enclosed Fresh- and Brackish Aquatic Ecosystems., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5733, https://doi.org/10.5194/egusphere-egu24-5733, 2024.

EGU24-6065 | ECS | Orals | NP4.1

Magnetospheric time history:  How much do we need for forecasting? 

Kendra R. Gilmore, Sarah N. Bentley, and Andy W. Smith

Forecasting the aurora and its location accurately is important to mitigate any potential harm to vital infrastructure like communications and electricity grid networks. Current auroral prediction models rely on our understanding of the interaction between the magnetosphere and the solar wind or geomagnetic indices. Both approaches do well in predicting but have limitations concerning forecasting (geomagnetic indices-based model) or because of the underlying assumptions driving the model (due to a simplification of the complex interaction). By applying machine learning algorithms to this problem, gaps in our understanding can be identified, investigated, and closed. Finding the important time scales for driving empirical models provides the necessary basis for our long-term goal of predicting the aurora using machine learning.

Periodicities of the Earth’s magnetic field have been extensively studied on a global scale or in regional case studies. Using a suite of different time series analysis techniques including frequency analysis and investigation of long-scale changes of the median/ mean, we examine the dominant periodicities of ground magnetic field measurements at selected locations. A selected number of stations from the SuperMAG network (Gjerloev, 2012), which is a global network of magnetometer stations across the world, are the focus of this investigation.

The periodicities retrieved from the different magnetic field components are compared to each other as well as to other locations. In the context of auroral predictions, an analysis of the dominating periodicities in the auroral boundary data derived from the IMAGE satellite (Chisham et al., 2022) provides a counterpart to the magnetic field periodicities.

Ultimately, we can constrain the length of time history sensible for forecasting.

How to cite: Gilmore, K. R., Bentley, S. N., and Smith, A. W.: Magnetospheric time history:  How much do we need for forecasting?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6065, https://doi.org/10.5194/egusphere-egu24-6065, 2024.

EGU24-6151 | Posters on site | NP4.1

Using information-theory metrics to detect regime changes in dynamical systems 

Javier Amezcua and Nachiketa Chakraborty

Dynamical systems can display a range of dynamical regimes (e.g. attraction to, fixed points, limit cycles, intermittency, chaotic behaviour) depending on the values of parameters in the system. In this work we demonstrate how non-parametric entropy estimation codes (in particular NPEET) based on the Kraskov method can be applied to find regime transitions in a 3D chaotic model (the Lorenz 1963 system) when varying the values of the parameters. These infromation-theory-based methods are simpler and cheaper to apply than more traditional metrics from dynamical systems (e.g. computation of Lyapunov exponents). The non-parametric nature of the method allows for handling long time series without a prohibitive computational burden. 

How to cite: Amezcua, J. and Chakraborty, N.: Using information-theory metrics to detect regime changes in dynamical systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6151, https://doi.org/10.5194/egusphere-egu24-6151, 2024.

EGU24-9367 | ECS | Orals | NP4.1

Fractal complexity evaluation of meteorological droughts over three Indian subdivisions using visibility Graphs 

Susan Mariam Rajesh, Muraleekrishnan Bahuleyan, Arathy Nair GR, and Adarsh Sankaran

Evaluation of scaling properties and fractal formalisms is one of the potential approaches for modelling complex series. Understanding the complexity and fractal characterization of drought index time series is essential for better preparedness against drought disasters. This study presents a novel visibility graph-based evaluation of fractal characterization of droughts of three meteorological subdivisions of India. In this method, the horizontal visibility graph (HVG) and Upside-down visibility graph (UDVG) are used for evaluating the network properties for different standardized precipitation index (SPI) series of 3, 6 and 12 month time scales representing short, medium and long term droughts. The relative magnitude of fractal estimates is controlled by the drought characteristics of wet-dry transitions. The estimates of degree distribution clearly deciphered the self-similar properties of droughts of all the subdivisions. For an insightful depiction of drought dynamics, the fractal exponents and spectrum are evaluated by the concurrent application of Sand Box Method (SBM) and Chhabra and Jenson Method (CJM). The analysis was performed for overall series along with the pre- and post-1976-77 Global climate shift scenarios. The complexity is more evident in short term drought series and UDVG formulations implied higher fractal exponents for different moment orders irrespective of drought type and locations considered in this study. Useful insights on the relationship between complex network and fractality are evolved from the study, which may help in improved drought forecasting. The visibility graph based fractality estimation evaluation is efficient in capturing drought and it has vast potential in the drought predictions in a changing environment.

Keywords:  Drought, Fractal, SPI, Visibility Graph

How to cite: Rajesh, S. M., Bahuleyan, M., Nair GR, A., and Sankaran, A.: Fractal complexity evaluation of meteorological droughts over three Indian subdivisions using visibility Graphs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9367, https://doi.org/10.5194/egusphere-egu24-9367, 2024.

EGU24-9537 | Posters on site | NP4.1

Wavelet-Induced Mode Extraction procedure: Application to climatic data 

Elise Faulx, Xavier Fettweis, Georges Mabille, and Samuel Nicolay

The Wavelet-Induced Mode Extraction procedure (WIME) [2] was developed drawing inspiration from Empirical Mode Decomposition. The concept involves decomposing the signal into modes, each presenting a characteristic frequency, using continuous wavelet transform. This method has yielded intriguing results in climatology [3,4]. However, the initial algorithm did not account for the potential existence of slight frequency fluctuations within a mode, which could impact the reconstruction of the original signal [4]. The new version (https://atoms.scilab.org/toolboxes/toolbox_WIME/0.1.0) now allows for the evolution of a mode in the space-frequency half-plane, thus considering the frequency evolution of a mode [2]. A natural application of this tool is in the analysis of Milankovitch cycles, where subtle changes have been observed throughout history. The method also refines the study of solar activity, highlighting the role of the "Solar Flip-Flop." Additionally, the examination of temperature time series confirms the existence of cycles around 2.5 years. It is now possible to attempt to correlate solar activity with this observed temperature cycle, as seen in speleothem records [1].

[1] Allan, M., Deliège, A., Verheyden, S., Nicolay S. and Fagel, N. Evidence for solar influence in a Holocene speleothem record, Quaternary Science Reviews, 2018.
[2] Deliège, A. and Nicolay, S., Extracting oscillating components from nonstationary time series: A wavelet-induced method, Physical Review. E, 2017.
[3] Nicolay, S., Mabille, G., Fettweis, X. and Erpicum, M., A statistical validation for the cycles found in air temperature data using a Morlet wavelet-based method, Nonlinear Processes in Geophysics, 2010.
[4] Nicolay, S., Mabille, G., Fettweis, X. and Erpicum, M., 30 and 43 months period cycles found in air temperature time series using the Morlet wavelet, Climate Dynamics, 2009.

How to cite: Faulx, E., Fettweis, X., Mabille, G., and Nicolay, S.: Wavelet-Induced Mode Extraction procedure: Application to climatic data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9537, https://doi.org/10.5194/egusphere-egu24-9537, 2024.

EGU24-10258 | Orals | NP4.1

New concepts on quantifying event data 

Norbert Marwan and Tobias Braun

A wide range of geoprocesses manifest as observable events in a variety of contexts, including shifts in palaeoclimate regimes, evolutionary milestones, tectonic activities, and more. Many prominent research questions, such as synchronisation analysis or power spectrum estimation of discrete data, pose considerable challenges to linear tools. We present recent advances using a specific similarity measure for discrete data and the method of recurrence plots for different applications in the field of highly discrete event data. We illustrate their potential for palaeoclimate studies, particularly in detecting synchronisation between signals of discrete extreme events and continuous signals, estimating power spectra of spiky signals, and analysing data with irregular sampling.

How to cite: Marwan, N. and Braun, T.: New concepts on quantifying event data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10258, https://doi.org/10.5194/egusphere-egu24-10258, 2024.

EGU24-10415 | ECS | Orals | NP4.1

Application of Transfer Learning techniques in one day ahead PV production prediction 

Marek Lóderer, Michal Sandanus, Peter Pavlík, and Viera Rozinajová

Nowadays photovoltaic panels are becoming more affordable, efficient, and popular due to their low carbon footprint. PV panels can be installed in many places providing green energy to the local grid reducing energy cost and transmission losses. Since the PV production is highly dependent on the weather conditions, it is extremely important to estimate expected output in advance in order to maintain energy balance in the grid and provide enough time to schedule load distribution. The PV production output can be calculated by various statistical and machine learning prediction methods. In general, the more data available, the more precise predictions can be produced. This poses a problem for recently installed PV panels for which not enough data has been collected or the collected data are incomplete. 

A possible solution to the problem can be the application of an approach called Transfer Learning which has the inherent ability to effectively deal with missing or insufficient amounts of data. Basically, Transfer Learning is a machine learning approach which offers the capability of transferring knowledge acquired from the source domain (in our case a PV panel with a large amount of historical data) to different target domains (PV panels with very little collected historical data) to resolve related problems (provide reliable PV production predictions). 

In our study, we investigate the application, benefits and drawbacks of Transfer Learning for one day ahead PV production prediction. The model used in the study is based on complex neural network architecture, feature engineering and data selection. Moreover, we focus on the exploration of multiple approaches of adjusting weights in the target model retraining process which affect the minimum amount of training data required, final prediction accuracy and model’s overall robustness. Our models use historical meteorological forecasts from Deutscher Wetterdienst (DWD) and photovoltaic measurements from the project PVOutput which collects data from installed solar systems across the globe. Evaluation is performed on more than 100 installed PV panels in Central Europe.

How to cite: Lóderer, M., Sandanus, M., Pavlík, P., and Rozinajová, V.: Application of Transfer Learning techniques in one day ahead PV production prediction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10415, https://doi.org/10.5194/egusphere-egu24-10415, 2024.

EGU24-11897 | Posters on site | NP4.1

Results of joint processing of magnetic observatory data of international Intermagnet network in a unified coordinate system 

Beibit Zhumabayev, Ivan Vassilyev, Zhasulan Mendakulov, Inna Fedulina, and Vitaliy Kapytin

In each magnetic observatory, the magnetic field is registered in local Cartesian coordinate systems associated with the geographic coordinates of the locations of these observatories. To observe extraterrestrial magnetic field sources, such as the interplanetary magnetic field or magnetic clouds, a method of joint processing of data from magnetic observatories of the international Intermagnet network was implemented. In this method, the constant component is removed from the observation results of individual observatories, their measurement data is converted into the ecliptic coordinate system, and the results obtained from all observatories are averaged after the coordinate transformation.

The first data on joint processing of measurement results from the international network of Intermagnet magnetic observatories in the period before the onset of magnetic storms of various types, during these storms and after their end are presented. There is a significant improvement in the signal-to-noise ratio after combining the measurement results from all observatories, which makes it possible to isolate weaker external magnetic fields. A change in the shape of magnetic field variations is shown, which can provide new knowledge about the mechanism of development of magnetic storms.

How to cite: Zhumabayev, B., Vassilyev, I., Mendakulov, Z., Fedulina, I., and Kapytin, V.: Results of joint processing of magnetic observatory data of international Intermagnet network in a unified coordinate system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11897, https://doi.org/10.5194/egusphere-egu24-11897, 2024.

We introduce the CLEAN algorithm to identify narrowband Ultra Low Frequency (ULF) Pc5 plasma waves in Earth’s magnetosphere. The CLEAN method was first used for constructing 2D images in astronomical radio interferometry but has since been applied to a huge range of areas including adaptation for time series analysis. The algorithm performs a nonlinear deconvolution in the frequency domain (equivalent to a least-squares in the time domain) allowing for identification of multiple individual wave spectral peaks within the same power spectral density. The CLEAN method also produces real amplitudes instead of model fits to the peaks and retains phase information. We applied the method to GOES magnetometer data spanning 30 years to study the distribution of narrowband Pc5 ULF waves at geosynchronous orbit. We found close to 30,0000 wave events in each of the vector magnetic field components in field-aligned coordinates. We discuss wave occurrence and amplitudes distributed in local time and frequency. The distribution of the waves under different solar wind conditions are also presented. With some precautions, which are applicable to other event identification methods, the CLEAN technique can be utilized to detect wave events and its harmonics in the magnetosphere and beyond. We also discuss limitations of the method mainly the detection of unrealistic peaks due to aliasing and Gibbs phenomena.

How to cite: Inceoglu, F. and Loto'aniu, P.: Using the CLEAN Algorithm to Determine the Distribution of Ultra Low Frequency Waves at Geostationary Orbit, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12928, https://doi.org/10.5194/egusphere-egu24-12928, 2024.

EGU24-12938 | Posters on site | NP4.1

Applying Multifractal Theory and Statistical Techniques for High Energy Volcanic Explosion Detection and Seismic Activity Monitoring in Volcanic Time Series 

Marisol Monterrubio-Velasco, Xavier Lana, Raúl Arámbula-Mendoza, and Ramón Zúñiga

Understanding volcanic activity through time series data analysis is crucial for uncovering the fundamental physical mechanisms governing this natural phenomenon.

In this study, we show the application of multifractal and fractal methodologies, along with statistical analysis, to investigate time series associated with volcanic activity. We aim to make use of these approaches to identify significant variations within the physical processes related to changes in volcanic activity. These methodologies offer the potential to identify pertinent changes preceding a high-energy explosion or a significant volcanic eruption.

In particular, we apply it to analyze two study cases. First, the evolution of the multifractal structure of volcanic emissions of low, moderate, and high energy explosions applied to Volcán de Colima (México years 2013-2015). The results contribute to obtaining quite evident signs of the immediacy of possible dangerous emissions of high energy, close to 8.0x10^8 J. Additionally, the evolution of the adapted Gutenberg-Richter seismic law to volcanic energy emissions contributes to confirm the results obtained using multifractal analysis. Secondly, we also studied the time series of the Gutenberg-Richter b-parameter of seismic activities associated with volcanic emissions in Iceland, Hawaii, and the Canary Islands, through the concept of Disparity (degree of irregularity), the fractal Hurst exponent, H, and several multifractal parameters. The results obtained should facilitate a better knowledge of the relationships between the activity of volcanic emissions and the corresponding related seismic activities.  

How to cite: Monterrubio-Velasco, M., Lana, X., Arámbula-Mendoza, R., and Zúñiga, R.: Applying Multifractal Theory and Statistical Techniques for High Energy Volcanic Explosion Detection and Seismic Activity Monitoring in Volcanic Time Series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12938, https://doi.org/10.5194/egusphere-egu24-12938, 2024.

EGU24-13593 | ECS | Posters on site | NP4.1

Characterizing Uncertainty in Spatially Interpolated Time Series of Near-Surface Air Temperature 

Conor Doherty and Weile Wang

Spatially interpolated meteorological data products are widely used in the geosciences as well as disciplines like epidemiology, economics, and others. Recent work has examined methods for quantifying uncertainty in gridded estimates of near-surface air temperature that produce distributions rather than simply point estimates at each location. However, meteorological variables are correlated not only in space but in time, and sampling without accounting for temporal autocorrelation produces unrealistic time series and potentially underestimates cumulative errors. This work first examines how uncertainty in air temperature estimates varies in time, both seasonally and at shorter timescales. It then uses data-driven, spectral, and statistical methods to better characterize uncertainty in time series of estimated air temperature values. Methods for sampling that reproduce spatial and temporal autocorrelation are presented and evaluated. The results of this work are particularly relevant to domains like agricultural and ecology. Physical processes including evapotranspiration and primary production are sensitive to variables like near-surface air temperature, and errors in these important meteorological inputs accumulate in model outputs over time.

How to cite: Doherty, C. and Wang, W.: Characterizing Uncertainty in Spatially Interpolated Time Series of Near-Surface Air Temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13593, https://doi.org/10.5194/egusphere-egu24-13593, 2024.

EGU24-13879 | ECS | Posters on site | NP4.1

Understanding the role of vegetation responses to drought in regulating autumn senescence 

Eunhye Choi and Josh Gray

Vegetation phenology is the recurring of plant growth, including the cessation and resumption of growth, and plays a significant role in shaping terrestrial water, nutrient, and carbon cycles. Changes in temperature and precipitation have already induced phenological changes around the globe, and these trends are likely to continue or even accelerate. While warming has advanced spring arrival in many places, the effects on autumn phenology are less clear-cut, with evidence for earlier, delayed, or even unchanged end of the growing season (EOS). Meteorological droughts are intensifying in duration and frequency because of climate change. Droughts intricately impact changes in vegetation, contingent upon whether the ecosystem is limited by water or energy. These droughts have the potential to influence EOS changes. Despite this, the influence of drought on EOS remains largely unexplored. This study examined moisture’s role in controlling EOS by understanding the relationship between precipitation anomalies, vegetation’s sensitivity to precipitation (SPPT), and EOS. We also assess regional variations in responses to the impact of SPPT on EOS.

The study utilized multiple vegetation and water satellite products to examine the patterns of SPPT in drought and its impact on EOS across aridity gradients and vegetation types. By collectively evaluating diverse SPPTs from various satellite datasets, this work offers a comprehensive understanding and critical basis for assessing the impact of drought on EOS. We focused on the Northern Hemisphere from 2000 to 2020, employing robust statistical methods. This work found that, in many places, there was a stronger relationship between EOS and drought in areas with higher SPPT. Additionally, a non-linear negative relationship was identified between EOS and SPPT in drier regions, contracting with a non-linear positive relationship observed in wetter regions. These findings were consistent across a range of satellite-derived vegetation products. Our findings provide valuable insights into the effects of SPPT on EOS during drought, enhancing our understanding of vegetation responses to drought and its consequences on EOS and aiding in identifying drought-vulnerable areas.

How to cite: Choi, E. and Gray, J.: Understanding the role of vegetation responses to drought in regulating autumn senescence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13879, https://doi.org/10.5194/egusphere-egu24-13879, 2024.

EGU24-16981 | ECS | Orals | NP4.1

A machine-learning-based approach for predicting the geomagnetic secular variation 

Sho Sato and Hiroaki Toh

We present a machine-learning-based approach for predicting the geomagnetic main field changes, known as secular variation (SV), in a 5-year range for use for the 14th generation of International Geomagnetic Reference Field (IGRF-14). The training and test datasets of the machine learning (ML) models are geomagnetic field snapshots derived from magnetic observatory hourly means, and CHAMP and Swarm-A satellite data (MCM Model; Ropp et al., 2020). The geomagnetic field data are not used as-is in the original time series but were differenced twice before training. Because SV is strongly influenced by the geodynamo process occurring in the Earth's outer core, challenges still persist despite efforts to model and forecast the realistic nonlinear behaviors (such as the geomagnetic jerks) of the geodynamo through data assimilation. We compare three physics-uninformed ML models, namely, the Autoregressive (AR) model, Vector Autoregressive (VAR) model, and Recurrent Neural Network (RNN) model, to represent the short-term temporal evolution of the geomagnetic main field on the Earth’s surface. The quality of 5-year predictions is tested by the hindcast results for the learning window from 2004.50 to 2014.25. These tests show that the forecast performance of our ML model is comparable with that of candidate models of IGRF-13 in terms of data misfits after the release epoch (Year 2014.75). It is found that all three ML models give 5-year prediction errors of less than 100nT, among which the RNN model shows a slightly better accuracy. They also suggest that Overfitting to the training data used is an undesirable machine learning behavior that occurs when the RNN model gives accurate reproduction of training data but not for forecasting targets.

How to cite: Sato, S. and Toh, H.: A machine-learning-based approach for predicting the geomagnetic secular variation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16981, https://doi.org/10.5194/egusphere-egu24-16981, 2024.

EGU24-17344 | Posters on site | NP4.1

Introducing a new statistical theory to quantify the Gaussianity of the continuous seismic signal 

Éric Beucler, Mickaël Bonnin, and Arthur Cuvier

The quality of the seismic signal recorded at permanent and temporary stations is sometimes degraded, either abruptly or over time. The most likely cause is a high level of humidity, leading to corrosion of the connectors but environmental changes can also alter recording conditions in various frequency ranges and not necessarily for all three components in the same way. Assuming that the continuous seismic signal can be described by a normal distribution, we present a new approach to quantify the seismogram quality and to point out any time sample that deviates from this Gaussian assumption. To this end the notion of background Gaussian signal (BGS) to statistically describe a set of samples that follows a normal distribution. The discrete function obtained by sorting the samples in ascending order of amplitudes is compared to a modified probit function to retrieve the elements composing the BGS, and its statistical properties, mostly the Gaussian standard deviation, which can then differ from the classical standard deviation. Hence the ratio of both standard deviations directly quantifies the dominant gaussianity of the continuous signal and any variation reflects a statistical modification of the signal quality. We present examples showing daily variations in this ratio for stations known to have been affected by humidity, resulting in signal degradation. The theory developed can be used to detect subtle variations in the Gaussianity of the signal, but also to point out any samples that don't match the Gaussianity assumption, which can then be used for other seismological purposes, such as coda determination.

How to cite: Beucler, É., Bonnin, M., and Cuvier, A.: Introducing a new statistical theory to quantify the Gaussianity of the continuous seismic signal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17344, https://doi.org/10.5194/egusphere-egu24-17344, 2024.

EGU24-17566 | ECS | Posters on site | NP4.1

Unveiling Climate-Induced Ocean Wave Activities Using Seismic Array Data in the North Sea Region 

Yichen Zhong, Chen Gu, Michael Fehler, German Prieto, Peng Wu, Zhi Yuan, Zhuoyu Chen, and Borui Kang

Climate events may induce abnormal ocean wave activities, that can be detected by seismic array on nearby coastlines. We collected long-term continuous array seismic data in the Groningen area and the coastal areas of the North Sea, conducted a comprehensive analysis to extract valuable climate information hidden within the ambient noise. Through long-term spectral analysis, we identified the frequency band ranging from approximately 0.2Hz, which appears to be associated with swell waves within the region, exhibiting a strong correlation with the significant wave height (SWH). Additionally, the wind waves with a frequency of approximately 0.4 Hz and gravity waves with periods exceeding 100 seconds were detected from the seismic ambient noise. We performed a correlation analysis between the ambient noise and various climatic indexes across different frequency bands. The results revealed a significant correlation between the North Atlantic Oscillation (NAO) Index and the ambient noise around 0.17Hz.

Subsequently, we extracted the annual variation curves of SWH frequency from ambient noise at each station around the North Sea and assembled them into a sparse spatial grid time series (SGTS). An empirical orthogonal function (EOF) analysis was conducted, and the Principal Component (PC) time series derived from the EOF analysis were subjected to a correlation analysis with the WAVEWATCH III (WW3) model simulation data, thereby confirming the wave patterns. Moreover, we conducted the spatial distribution study of SGTS. The spatial features revealed that the southern regions of the North Sea exhibit higher wind-wave energy components influenced by the Icelandic Low pressure system and topography, which explains the correlation between ambient noise in the region and the NAO index. Furthermore, spatial features disclosed a correlation between the first EOF mode of the North Sea ocean waves and the third mode of sea surface temperature anomalies. This research shows the potential of utilizing existing off-shore seismic monitoring systems to study global climate variation and physical oceanography.

How to cite: Zhong, Y., Gu, C., Fehler, M., Prieto, G., Wu, P., Yuan, Z., Chen, Z., and Kang, B.: Unveiling Climate-Induced Ocean Wave Activities Using Seismic Array Data in the North Sea Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17566, https://doi.org/10.5194/egusphere-egu24-17566, 2024.

EGU24-18061 | ECS | Orals | NP4.1

A new methodology for time-series reconstruction of global scale historical Earth observation data 

Davide Consoli, Leandro Parente, and Martijn Witjes

Several machine learning algorithms and analytical techniques do not allow gaps or non-values in input data. Unfortunately, earth observation (EO) datasets, such as satellite images, are gravely affected by cloud contamination and sensor artifacts that create gaps in the time series of collected images. This limits the usage of several powerful techniques for modeling and analysis. To overcome these limitations, several works in literature propose different imputation methods to reconstruct the gappy time series of images, providing complete time-space datasets and enabling their usage as input for many techniques.

However, among the time-series reconstruction methods available in literature, only a few of them are publicly available (open source code), applicable without any external source of data, and suitable for application to petabyte (PB) sized dataset like the full Landsat archive. The few methods that match all these characteristics are usually quite trivial (e.g. linear interpolation) and, as a consequence, they often show poor performance in reconstructing the images. 

For this reason, we propose a new methodology for time series reconstruction designed to match all these requirements. Like some other methods in literature, the new method, named seasonally weighted average generalization (SWAG), works purely on the time dimension, reconstructing the images working on each time series of each pixel separately. In particular, the method uses a weighted average of the samples available in the original time series to reconstruct the missing values. Enforcing the annual seasonality of each band as a prior, for the reconstruction of each missing sample in the time series a higher weight is given to images that are collected exactly on integer multiples of a year. To avoid propagation of land cover changes in future or past images, higher weights are given to more recent images. Finally, to have a method that respects causality, only images from the past of each sample in the time series are used.

To have computational performance suitable for PB sized datasets the method has been implemented in C++ using a sequence of fast convolution methods and Hadamard products and divisions. The method has been applied to a bimonthly aggregated version of the global GLAD Landsat ARD-2 collection from 1997 to 2022, producing a 400 terabyte output dataset. The produced dataset will be used to generate maps for several biophysical parameters, such as Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), normalized difference water index (NDWI) and bare soil fraction (BSF). The code is available as open source, and the result is fully reproducible.

References:

Potapov, Hansen, Kommareddy, Kommareddy, Turubanova, Pickens, ... & Ying  (2020). Landsat analysis ready data for global land cover and land cover change mapping. Remote Sensing, 12(3), 426.

Julien, & Sobrino (2019). Optimizing and comparing gap-filling techniques using simulated NDVI time series from remotely sensed global data. International Journal of Applied Earth Observation and Geoinformation, 76, 93-111.

Radeloff, Roy, Wulder, Anderson, Cook, Crawford, ... & Zhu (2024). Need and vision for global medium-resolution Landsat and Sentinel-2 data products. Remote Sensing of Environment, 300, 113918.

How to cite: Consoli, D., Parente, L., and Witjes, M.: A new methodology for time-series reconstruction of global scale historical Earth observation data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18061, https://doi.org/10.5194/egusphere-egu24-18061, 2024.

EGU24-18197 | ECS | Orals | NP4.1 | Highlight

The regularity of climate-related extreme events under global warming 

Karim Zantout, Katja Frieler, and Jacob Schewe and the ISIMIP team

Climate variability gives rise to many different kinds of extreme impact events, including heat waves, crop failures, or wildfires. The frequency and magnitude of such events are changing under global warming. However, it is less known to what extent such events occur with some regularity, and whether this regularity is also changing as a result of climate change. Here, we present a novel method to systematically study the time-autocorrelation of these extreme impact events, that is, whether they occur with a certain regularity. In studies of climate change impacts, different types of events are often studied in isolation, but in reality they interact. We use ensembles of global biophysical impact simulations from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) driven with climate models to assess current conditions and projections. The time series analysis is based on a discrete Fourier transformation that accounts for the stochastic fluctuations from the climate model. Our results show that some climate impacts, such as crop failure, indeed exhibit a dominant frequency of recurrence; and also, that these regularity patterns change over time due to anthropogenic climate forcing.

How to cite: Zantout, K., Frieler, K., and Schewe, J. and the ISIMIP team: The regularity of climate-related extreme events under global warming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18197, https://doi.org/10.5194/egusphere-egu24-18197, 2024.

EGU24-18210 | ECS | Posters on site | NP4.1

Long-term vegetation development in context of morphodynamic processes since mid-19th century 

Katharina Ramskogler, Moritz Altmann, Sebastian Mikolka-Flöry, and Erich Tasser

The availability of comprehensive aerial photography is limited to the mid-20th century, posing a challenge for quantitatively analyzing long-term surface changes in proglacial areas. This creates a gap of approximately 100 years, spanning the end of the Little Ice Age (LIA). Employing digital monoplotting and historical terrestrial images, our study reveals quantitative surface changes in a LIA lateral moraine section dating back to the second half of the 19th century, encompassing a total study period of 130 years (1890 to 2020). With the long-term analysis at the steep lateral moraines of Gepatschferner (Kauner Valley, Tyrol, Austria) we aimed to identify changes in vegetation development in context with morphodynamic processes and the changing climate.

In 1953, there was an expansion in the area covered by vegetation, notably encompassing scree communities, alpine grassland, and dwarf shrubs. However, the destabilization of the system after 1980, triggered by rising temperatures and the resulting thawing of permafrost, led to a decline in vegetation cover by 2020. Notably, our observations indicated that, in addition to morphodynamic processes, the overarching trends in temperature and precipitation exerted a substantial influence on vegetation development. Furthermore, areas with robust vegetation cover, once stabilised, were reactivated and subjected to erosion, possibly attributed to rising temperatures post-1980.

This study demonstrates the capability of historical terrestrial images to enhance the reconstruction of vegetation development in context with morphodynamics in high alpine environments within the context of climate change. However, it is important to note that long-term mapping of vegetation development through digital monoplotting has limitations, contingent on the accessibility and quality of historical terrestrial images, as well as the challenges posed by shadows in high alpine regions. Despite these limitations, this long-term approach offers fundamental data on vegetation development for future modelling efforts.

How to cite: Ramskogler, K., Altmann, M., Mikolka-Flöry, S., and Tasser, E.: Long-term vegetation development in context of morphodynamic processes since mid-19th century, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18210, https://doi.org/10.5194/egusphere-egu24-18210, 2024.

EGU24-19601 | ECS | Posters on site | NP4.1

Discrimination of  geomagnetic quasi-periodic signals by using SSA Transform 

Palangio Paolo Giovanni and Santarelli Lucia

Discrimination of  geomagnetic quasi-periodic signals by using SSA Transform

  • Palangio1, L. Santarelli 1

1Istituto Nazionale di Geofisica e Vulcanologia L’Aquila

3Istituto Nazionale di Geofisica e Vulcanologia Roma

 

Correspondence to:  lucia.santarelli@ingv.it

 

Abstract

In this paper we present an application of  the SSA Transform to the detection and reconstruction of  very weak geomagnetic signals hidden in noise. In the SSA Transform  multiple subspaces are used for representing and reconstructing   signals and noise.  This analysis allows us to reconstruct, in the time domain, the different harmonic components contained in the original signal by using  ortogonal functions. The objective is to identificate the dominant  subspaces that can be attributed to the  signals and the subspaces that can be attributed to the noise,  assuming that all these  subspaces are orthogonal to each other, which implies that the  signals and noise  are independent of one another. The subspace of the signals is mapped simultaneously on several spaces with a lower dimension, favoring the dimensions that best discriminate the patterns. Each subspace of the signal space is used to encode different subsets of functions having common characteristics, such as  the same periodicities. The subspaces  identification was performed by using singular value decomposition (SVD) techniques,  known as  SVD-based identification methods  classified in a subspace-oriented scheme.The  quasi-periodic variations of geomagnetic field  has been investigated in the range of scale which span from 22 years to 8.9 days such as the  Sun’s polarity reversal cycle (22 years), sun-spot cycle (11 years), equinoctial effect (6 months), synodic rotation of the Sun (27 days) and its harmonics. The strength of these signals vary from fractions of a nT to tens of nT. Phase and frequency variability of these cycles has been evaluated from the range of variations in the geomagnetic field recorded at middle latitude place (covering roughly 4.5 sunspot cycles). Magnetic data recorded at L'Aquila Geomagnetic observatory (geographic coordinates: 42° 23’ N, 13° 19’E, geomagnetic coordinates: 36.3° N,87°.2 E, L-shell=1.6) are used from 1960 to 2009.

 

 

How to cite: Paolo Giovanni, P. and Lucia, S.: Discrimination of  geomagnetic quasi-periodic signals by using SSA Transform, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19601, https://doi.org/10.5194/egusphere-egu24-19601, 2024.

EGU24-22262 | ECS | Posters on site | NP4.1

Temporal Interpolation of Sentinel-2 Multispectral Time Series in Context of Land Cover Classification with Machine Learning Algorithms 

Mate Simon, Mátyás Richter-Cserey, Vivien Pacskó, and Dániel Kristóf

Over the past decades, especially since 2014, large quantities of Earth Observation (EO) data became available in high spatial and temporal resolution, thanks to ever-developing constellations (e.g.: Sentinel, Landsat) and open data policy. However, in the case of optical images, affected by cloud coverage and the spatially changing overlap of relative satellite orbits, creating temporally generalized and dense time series by using only measured data is challenging, especially when studying larger areas.

Several papers investigate the question of spatio-temporal gap filling and show different interpolation methods to calculate missing values corresponding to the measurements. In the past years more products and technologies have been constructed and published in this field, for example Copernicus HR-VPP Seasonal Trajectories (ST) product.  These generalized data structures are essential to the comparative analysis of different time periods or areas and improve the reliability of data analyzing methods such as Fourier transform or correlation. Temporally harmonized input data is also necessary in order to improve the results of Machine Learning classification algorithms such as Random Forest or Convolutional Neural Networks (CNN). These are among the most efficient methods to separate land cover categories like arable lands, forests, grasslands and built-up areas, or crop types within the arable category.

This study analyzes the efficiency of different interpolation methods on Sentinel-2 multispectral time series in the context of land cover classification with Machine Learning. We compare several types of interpolation e.g. linear, cubic and cubic-spline and also examine and optimize more advanced methods like Inverse Distance Weighted (IDW) and Radial Basis Function (RBF). We quantify the accuracy of each method by calculating mean square error between measured and interpolated data points. The role of interpolation of the input dataset in Deep Learning (CNN) is investigated by comparing Overall, Kappa and categorical accuracies of land cover maps created from only measured and interpolated time series. First results show that interpolation has a relevant positive effect on accuracy statistics. This method is also essential in taking a step towards constructing robust pretrained Deep Learning models, transferable between different time intervals and agro-ecological regions.

The research has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the KDP-2021 funding scheme.

 

Keywords: time series analysis, Machine Learning, interpolation, Sentinel

How to cite: Simon, M., Richter-Cserey, M., Pacskó, V., and Kristóf, D.: Temporal Interpolation of Sentinel-2 Multispectral Time Series in Context of Land Cover Classification with Machine Learning Algorithms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22262, https://doi.org/10.5194/egusphere-egu24-22262, 2024.

G2 – Reference Frames and Geodetic Observing Systems

EGU24-827 | ECS | Orals | G2.1

Improving Orbit Propagation of LEO Satellites Using Atmospheric Drag Analysis    

Soumyajit Dey, Phillip Anderson, and Aaron Bukowski

The variability of the atmospheric drag force on satellites is influenced by several factors, which include neutral density and gas composition, solar activity, and the orientation and shape of the satellite. During periods of geomagnetic activity, changes in these properties contribute to significant variations in the drag force, impacting the satellite trajectory. Therefore, the atmospheric drag force is considered as one of the largest sources of error in the orbit estimation for Low Earth Orbit (LEO) satellites. The methods presently used for satellite orbit determination define a constant term to represent the drag force, which can result in significant errors in long-term propagation and prediction of satellite positions. This work aims to improve SGP4 orbit propagation method by updating the drag term at regular intervals. The estimation of the drag term implements atmospheric drag analysis, which involves calculating the satellite drag coefficients using different Gas-Surface Interaction (GSI) models and neutral density data from Global Ionosphere Thermosphere Model (GITM) to estimate the mean motion derivative. The results demonstrate improved orbit propagation and estimation of orbital decay for the Gravity Recovery and Climate Experiment (GRACE) and Communication/Navigation Outage Forecasting System (C/NOFS) satellites during selected periods containing quiet and storm times.

How to cite: Dey, S., Anderson, P., and Bukowski, A.: Improving Orbit Propagation of LEO Satellites Using Atmospheric Drag Analysis   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-827, https://doi.org/10.5194/egusphere-egu24-827, 2024.

EGU24-876 | ECS | Orals | G2.1

Optimizing Multi-GNSS Orbit Combination: A Comprehensive Study on Weighting Strategies and Outlier Detection ; 

Radosław Zajdel, Gustavo Mansur, Andreas Brack, Pierre Sakic, and Benjamin Männel

Combined precise satellite orbits and clocks stand as core contributions from the International GNSS Service (IGS), integrating the individual inputs of various Analysis Centers (AC). The availability and quality of multi-GNSS products developed by ACs within the IGS multi-GNSS Pilot Project propel IGS towards replacing combined GPS and GLONASS products with homogeneous combined products encompassing all GPS, GLONASS, Galileo, BeiDou, and QZSS systems. A primary challenge faced by the IGS lies in refining the combination algorithm for multi-GNSS orbits and clocks to provide users with the utmost quality products.

This study delves into concepts aimed at enhancing the orbit combination algorithm, with a specific focus on adjusting the weighting scheme and detecting outlier observations. The core of the combination methodology adheres to the concept proposed by GFZ, employing a least-squares framework wherein weights used for combining AC orbits are determined through least-squares variance component estimation (VCE).

Four distinct weighting strategies are introduced and compared in this study. These strategies involve utilizing either the constellation, satellite type, satellite type on the same orbital plane, or each satellite individually to form datasets used in determining weights for each AC. Furthermore, a novel approach is developed to correct the weights for individual ACs based on the results of Satellite Laser Ranging orbit validation. This serves as an additional factor in the combination, mitigating the impact of systematic AC-dependent orbit mismodeling issues. All proposed strategies underwent testing using multi-GNSS orbit solutions over a 10-month period in 2023.

Firstly, the combination results show an agreement between the different AC’s input orbits around 15, 20, 30, 50, and 100 mm for GPS, GLONASS, Galileo, BeiDou, and QZSS, respectively. Regarding the AC weighting strategy, the constellation-specific weighting approach provides the most robust solution and allows for handling differences between AC-specific issues in the orbit modeling of individual constellations. The satellite-specific weighting approach offers better resilience against the adverse effects caused by the inhomogeneous quality of satellite blocks/types/generations within a constellation, especially for BeiDou. However, the satellite-specific weighting encounters problems related to the appearance of invalid negative variances/weights for individual satellites as the output of VCE, mainly for BDS-3 and QZSS. The negative variance component can be an important indication of defects in our variance component model. Grouping satellites of similar characteristics in a satellite-type-specific weighting approach increases redundancy and reduces the issue but not entirely. Ultimately, we demonstrate potential solutions to address this issue. This involves simplifying the iterated VCE or resorting to the legacy inverse mean square differences between the mean orbit and the AC’s orbits as weights, particularly in cases where the classic VCE proves ineffective.

How to cite: Zajdel, R., Mansur, G., Brack, A., Sakic, P., and Männel, B.: Optimizing Multi-GNSS Orbit Combination: A Comprehensive Study on Weighting Strategies and Outlier Detection ;, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-876, https://doi.org/10.5194/egusphere-egu24-876, 2024.

EGU24-2806 | ECS | Orals | G2.1

Potential of VLBI observations to satellites to estimate orbital elements  

Helene Wolf, Johannes Böhm, and Urs Hugentobler

Orbital elements define the shape, size, and orientation of a satellite’s orbit, as well as the position of the orbiting satellite along the ellipse at a specific time. Currently, precise orbit determination relies solely on satellite observations. However, future plans involve equipping Genesis and Galileo satellites with Very Long Baseline Interferometry (VLBI) transmitters. This would enable to observe satellites with VLBI radio telescopes and allow to determine orbital elements from VLBI observations to satellites.

This study investigates the potential of VLBI observations to satellites to contribute to the determination of orbital elements. In a first step, schedules, including satellite and quasar observations, are created using VieSched++.  The Vienna VLBI and Satellite Software (VieVS) is used to simulate and analyze these schedules.  To introduce the orbital elements in the Least Squares Adjustment, the partial derivatives of the position vector with respect to the orbital elements are needed. There are different approaches available for computing these partials, including numerical, analytical, or using partials obtained from the ORBGEN module in the Bernese GNSS software.  Next, the partials of the position vector are utilized to determine the partial derivative of the time delay tau with respect to the orbital elements.

This enables the estimation of orbital elements from simulated VLBI observations to satellites. The estimated parameters' quality is evaluated based on the mean formal errors and repeatabilities. Furthermore, the correlations between all orbital elements are examined.

How to cite: Wolf, H., Böhm, J., and Hugentobler, U.: Potential of VLBI observations to satellites to estimate orbital elements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2806, https://doi.org/10.5194/egusphere-egu24-2806, 2024.

EGU24-3521 | ECS | Orals | G2.1

In-flight GNSS phase map calibration modelling with Zernike polynomials 

Adrian Baños Garcia

GNSS processing for POD suffers from systematic errors when the location of the instantaneous phase center is not known
with a few millimeter accuracy. The traditional approach to model the GNSS phase center origin and variations is to
determine antenna phase maps iteratively from the residuals. A more direct approach consists in modeling the antenna
phase map through an expansion in well-chosen Zernike polynomials, in order to reduce potential correlations with dynamic
modeling errors. This strategy has been applied to derive the GNSS antenna phase maps of several altimetry missions such
as Sentinel-3A, Jason-3, Sentinel-6 MF and SWOT. The derived phase corrections were tested on CNES POE-G GNSS-only
reduced-dynamic orbit solutions to assess their impact and validate their benefits owing to independent SLR observations. 

How to cite: Baños Garcia, A.: In-flight GNSS phase map calibration modelling with Zernike polynomials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3521, https://doi.org/10.5194/egusphere-egu24-3521, 2024.

EGU24-5366 | ECS | Orals | G2.1

Contribution of SLR to satellite-only global gravity field model 

Barbara Suesser- Rechberger, Torsten Mayer-Guerr, Sandro Krauss, Patrick Dumitraschkewitz, Felix Oehlinger, and Cornelia Tieber-Hubmann

Combined satellite-only global gravity field models represent a combined solution of gravity field observations from multiple geodetic measurement principles and satellite missions. The advantage of such a combination is that it compensates for the weaknesses of individual observing techniques. However, when combining solutions estimated by different institutions, inconsistencies may arise due to the different algorithms and models used in the actually available software, leading to a deterioration in performance. To mitigate such performance degradation, it is advantageous to perform all evaluations with a uniform software package. Since our in-house Gravity Recovery Object Oriented Programming System (GROOPS) software tool has become a widely accepted tool in the scientific community, we have now also incorporated the Satellite Laser Ranging (SLR) functionality to ensure the continued development of the software. On this basis, the opportunity arises to uniformly determine all the contributions to the combined gravity field using a single software package. This contribution is intended as a preliminary study for the next Gravity Observation Combination (GOCO) model. In this regard, we present low-degree solutions based on SLR observations using GROOPS and compare them with findings from other research groups (e.g., Cheng et al. 2013, Krauss et al. 2019) as well as solutions based on the satellite mission GRACE and GRACE-FO.

How to cite: Suesser- Rechberger, B., Mayer-Guerr, T., Krauss, S., Dumitraschkewitz, P., Oehlinger, F., and Tieber-Hubmann, C.: Contribution of SLR to satellite-only global gravity field model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5366, https://doi.org/10.5194/egusphere-egu24-5366, 2024.

EGU24-5385 | Orals | G2.1

Application of ITRS 2020 realizations for the SLR-based POD of selected geodetic and Earth-observing satellites 

Mathis Bloßfeld, Julian Zeitlhöfler, Sergei Rudenko, and Manuela Seitz

Since 2023, three different solutions for the latest (2020) realization of the International Terrestrial Reference System (ITRS) are publicly available, namely the ITRF2020, the JTRF2020 and the DTRF2020. All solutions are based on the same input data but were derived using different combination approaches and data correction strategies. Since the ITRS realizations are used as a priori reference frames for precise orbit determination (POD) of Earth orbiting satellites, it is important to investigate the impact of the different frames on the POD results.

In this study, we briefly introduce the different features of the ITRS realizations and elaborate how the data correction models (e.g., periodic variations vs. non-tidal loading corrections) of the different xTRF2020 solutions can be optimally applied for the POD of selected satellites tracked by Satellite Laser Ranging (SLR) stations. We conclude the study with results obtained for various orbital parameters, such as the scaling factor of the non-gravitational (non-conservative) accelerations as well as the estimated empirical accelerations. Finally, we summarize the optimal settings of each ITRS realization for the satellite PODs discussed in this paper (i.e., LAGEOS-1, LARES-2, Jason-1/2/3).

How to cite: Bloßfeld, M., Zeitlhöfler, J., Rudenko, S., and Seitz, M.: Application of ITRS 2020 realizations for the SLR-based POD of selected geodetic and Earth-observing satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5385, https://doi.org/10.5194/egusphere-egu24-5385, 2024.

EGU24-5427 | Posters on site | G2.1

Orbit parameterization aspects in global solutions of spherical Laser Ranging Satellites 

Ulrich Meyer, Linda Geisser, Daniel König, Rolf Dach, Daniela Thaller, and Adrian Jäggi

Laser ranging to spherical satellites is a major source for the determination of geophysical and geometric parameters like the scale of the reference system and the lowest degree (1-2) gravity field coefficients, i.e. geocenter motion, dynamic oblateness and the orientation of the rotation axis of the Earth. The International Laser Ranging Service (ILRS) is collecting Satellite Laser Ranging (SLR) observations of a global station network, providing the range data as normal points to its analysis centers, which perform precise orbit determination (POD) and network solutions based on 7 day orbital arcs. Currently, efforts are undertaken to extend the classical ILRS processing of the LAGEOS and ETALON satellites by LARES 2, as well as lower-flying satellites, i.e. LARES, Stella and Starlette, necessitating an adaption of the SLR-POD model and parametrization due to the increased sensitivity to orbit perturbations at low orbit altitudes.

We present the status of the SLR-POD at AIUB, where in support of the ILRS analysis center at BKG the incorporation of the low-flying SLR satellites into the 7 day POD and network solution of LAGEOS/ETALON/LARES-2 is beeing tested, making use of long-arc stacking techniques of daily arcs to continuous 7 day arcs. All orbit and geophysical parametes are estimated in one common estimation process to avoid implicit regularization by apriori information. Special attention is paid to the co-estimation of the low-degree gravity field coefficients and the correlations with the empirical dynamic parameters deployed in the classical LAGEOS/ETALON POD model.

How to cite: Meyer, U., Geisser, L., König, D., Dach, R., Thaller, D., and Jäggi, A.: Orbit parameterization aspects in global solutions of spherical Laser Ranging Satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5427, https://doi.org/10.5194/egusphere-egu24-5427, 2024.

EGU24-5649 | ECS | Orals | G2.1

Stochastic Modeling of SLR Observations and its Impact on the Parameter Estimation 

Linda Geisser, Ulrich Meyer, Daniel Arnold, and Adrian Jäggi

Satellite Laser Ranging (SLR) observations are provided by a global station network of the International Laser Ranging Service (ILRS). Since almost all SLR stations are unique in terms of utilized equipment, e.g., laser system, photo-detector or timing devices, their measurement performances may slightly differ. Furthermore, the tracked satellites have various properties, e.g., material composition (number and type of retro-reflectors or mantel material), diameter, area-to-mass ratio, altitude or inclination, which have an impact on the measurement precision and the requirements on the background force modeling. A reliable estimation of geodetic parameters solely based on SLR can only be performed by combining SLR observations to several spherical satellites provided by the entire ILRS network. To take the quality of each individual SLR measurement into account, several stochastic models, e.g., static or time-variable station- and/or satellitespecific weights, are introduced and their impact on the parameter estimation is studied.

How to cite: Geisser, L., Meyer, U., Arnold, D., and Jäggi, A.: Stochastic Modeling of SLR Observations and its Impact on the Parameter Estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5649, https://doi.org/10.5194/egusphere-egu24-5649, 2024.

EGU24-6359 | ECS | Orals | G2.1

Sensitivity of different variants of GENESIS orbit to global geodetic parameters 

Tomasz Kur and Krzysztof Sośnica

The GENESIS mission plays a pivotal role in the FutureNAV program envisioned by the European Space Agency. This groundbreaking venture aims to co-locate four space geodetic techniques on a single platform in space. One of the primary mission objectives is accurately determining geodetic parameters, including geocenter motion, low-degree gravity field, Earth rotation parameters, and the positions of ground stations in tracking networks. Although preliminary satellite inclination and altitude were provided, there is untapped potential for studying ways to enhance the efficiency of incorporating GENESIS into geodetic products.

This research focuses on the preliminary optimization of GENESIS orbital parameters – semi-major axis, inclination, and eccentricity- to assess the benefits arising from diverse observation geometries on geodetic products. The analysis is based on simulations of different variants of GENESIS orbital parameters tracked by a network of 20 satellite laser ranging (SLR) stations. We provide GENESIS-only solutions as well as the combined solution with a selected subset of geodetic satellites that are used today or in the future for the realization of the terrestrial reference frames: LAGEOS-1, LAGEOS-2, LARES-1, and LARES-2. GENESIS will be equipped with two GNSS receivers contributing to high-accuracy orbit determination, serving as a priori parameters for SLR-based solutions. Therefore, we check the GENESIS sensitivity to global geodetic parameters, assuming that the precise orbits are not derived from SLR but can be well-defined from other techniques.

We study the impact of different GENESIS orbits on the gravity potential parameters, especially the zonal terms, Earth rotation parameters, and geocenter coordinates. Our findings underscore that, through meticulous processing, GENESIS has the potential to significantly contribute to achieving the goals of the Global Geodetic Observing System (GGOS), particularly in terms of refining the Z component of the geocenter coordinates.

How to cite: Kur, T. and Sośnica, K.: Sensitivity of different variants of GENESIS orbit to global geodetic parameters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6359, https://doi.org/10.5194/egusphere-egu24-6359, 2024.

EGU24-7776 | ECS | Orals | G2.1

Enhanced orbit determination for BDS-3 satellites with LEO onboard GNSS and inter-satellite link data 

Hanlin Chen, Tao Geng, Xin Xie, Qiang Li, Xing Su, and Qile Zhao

All BeiDou global navigation satellite system (BDS-3) satellites are equipped with Ka-band inter-satellite link (ISL) payloads to achieve the inter-satellite ranging and communication. With the rapid development of low earth orbit (LEO) satellites, the LEO onboard BDS-3 observations also become available. The LEO onboard and ISL data can be an effective supplement for precise orbit determination (POD) of the BDS-3 satellite. In this research, we processed the integrated POD of BDS-3 and LEO satellites with the real ground station, LEO onboard GNSS, and ISL observations. To analyze the contribution of different data to BDS-3 POD accuracy, four POD schemes are present: ground stations only, ground stations + 1 LEO, ground stations + ISL, and ground stations + 1 LEO + ISL. The ground tracking data are from about 40 globally distributed ground stations and 10 stations in Asia-Pacific region, respectively. The LEO onboard GNSS observations are from a dual-constellation GNSS receiver of the LUTAN-01A satellite, which is a Chinese LEO synthetic-aperture-radar (SAR) satellite for geological observation. The Ka-band observations from more than 400 ISL established between BDS-3 satellites are also used in the integrated POD. The obtained orbits are evaluated by orbit overlaps comparison, the comparison with IGS analysis center precise orbits, and SLR (satellite laser ranging) validation. Compared to the POD using the observation of only 10 ground stations, the addition of 1 LEO onboard GNSS or ISL observations can improve the orbit accuracy of BDS-3 by more than 60%. Furthermore, adding both LEO onboard GNSS and ISL observations simultaneously can lead to further improvements in BDS-3 orbit accuracy.

How to cite: Chen, H., Geng, T., Xie, X., Li, Q., Su, X., and Zhao, Q.: Enhanced orbit determination for BDS-3 satellites with LEO onboard GNSS and inter-satellite link data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7776, https://doi.org/10.5194/egusphere-egu24-7776, 2024.

EGU24-7841 | ECS | Orals | G2.1

Tuning thermal reradiation pressure accelerations for Sentinel-6 

Kristin Vielberg, Jürgen Kusche, and Heike Peter

For radar altimetry missions such as Sentinel-6, a precise orbit is mandatory for deriving reliable sea surface heights. In addition to accurate tracking measurements, precise orbit determination relies on high-fidelity non-gravitational force models. At 1300km the solar radiation pressure (SRP), which varies mainly with the satellite’s orientation towards the Sun, is the dominating non-gravitational force. Additionally, the acceleration due to the Earth radiation pressure (ERP) acts on the satellite and decreases with increasing satellite altitude. As the radiation of Sun and Earth is partly absorbed at the satellite’s surface, the satellite experiences an additional force due to the thermal reradiation of heat (thermal reradiation pressure, TRP). Aerodynamic forces are in constrast negligible at around 1300km altitude.

In previous investigations, we extended the conventional radiation pressure force models with a focus on a GRACE-like satellite. Our SRP and ERP model extensions can be easily applied to other satellites with available geometry and thermo-optical material properties. However, transferring the heat-conductive TRP model to other satellites is more challenging, as assumptions on the materials’ thermal diffusivity and thickness as well as inner heat sources need to be made to adequately model the satellite’s surface temperature.

In this study, we attempt to develop a TRP force model for Sentinel-6. We depart from GRACE settings and refine our model stepwise. Boundary conditions are updated and the material properties are replaced with available information or assumptions. Then, a stepwise tuning is necessary to match the modelled surface temperatures with thermistor measurements. We choose one beta cycle during the year 2023 for our experiments. Preliminary investigations reveal that the tuning of the satellite’s thermal properties varies strongly with the beta angle.

How to cite: Vielberg, K., Kusche, J., and Peter, H.: Tuning thermal reradiation pressure accelerations for Sentinel-6, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7841, https://doi.org/10.5194/egusphere-egu24-7841, 2024.

EGU24-8395 | Posters on site | G2.1

Assessment of GPS-based accelerometry performance with adaptive filter settings 

Jose van den IJssel, Christian Siemes, and Pieter Visser

High-quality GPS observations from low Earth orbiting (LEO) satellites can be used to derive thermosphere densities along the satellite orbit. Such GPS-derived densities are currently computed operationally for all three Swarm satellites, in the framework of the Swarm Data, Innovation, and Science Cluster. Considering the increasing number of LEO satellites equipped with GPS receivers, this so-called GPS-based accelerometry approach offers great potential for improving thermosphere models and for studying the influence of solar and geomagnetic activity on the thermosphere.

To better quantify the accuracy that can be obtained with this approach, we assess the performance using the GRACE mission as a test case. For this mission high quality accelerometer data are available, which we can use to validate our GPS-based results. In addition, the GRACE mission has experienced a large variation in density signals, which allows us to assess the performance under a large range of conditions.

We present our GPS-based accelerometry processing strategy, which is based on a Kalman filter approach. The radiation pressure accelerations are accurately modelled and empirical accelerations capture the remaining aerodynamic signal. The empirical accelerations are modeled as Gauss-Markov processes defined by a steady-state variance, process noise and correlation time, which require careful tuning. This applies in particular to the setting of the process noise in the along-track direction, due to the large variations in the encountered aerodynamic signal. Best performance is obtained when the process noise setting is adapted to these variations. Using these adaptive filter settings, results are shown for periods with low, moderate, and high density. In a next step, we will implement the improved filter settings into our regular Swarm GPS-derived density processing chain.

How to cite: van den IJssel, J., Siemes, C., and Visser, P.: Assessment of GPS-based accelerometry performance with adaptive filter settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8395, https://doi.org/10.5194/egusphere-egu24-8395, 2024.

EGU24-8672 | Posters on site | G2.1

Copernicus POD Service – POD RESULTS BASED ON DORIS 

Marc Fernández, Carlos Fernández, Heike Peter, Pierre Féménias, and Carolina Nogueira Loddo

The Copernicus Precise Orbit Determination (CPOD) Service delivers, as part of the Ground Segment of the Copernicus Sentinel-1, -2, -3, and -6 missions, orbital products and auxiliary data files for their use in the corresponding Payload Data Ground Segment (PDGS) processing chains at ESA and EUMETSAT, and to external users through the newly available Copernicus Data Space Ecosystem (https://dataspace.copernicus.eu/).

The CPOD Service is based on FocusPOD, a suite of tools for POD and geodesy powered by GMV MAORI, a new GMV in-house Flight Dynamics & Geodesy library, written from scratch in modern C++ and python. The CPOD Service makes use of GNSS measurements to generate the orbital products, and of Satellite Laser Ranging (SLR) measurements for validation purposes. Recently, DORIS-processing capabilities have been added to FocusPOD to generate orbit solutions based on this geodetic technique, which is available on-board Sentinel-3 and -6 missions.

The purpose of this work is to present the DORIS processing capabilities recently developed, including DORIS RINEX data parsing, observation preprocessing steps, and precise orbit determination results. The highlight will be the achievable accuracy based on DORIS and an analysis of the obtained residuals depending on the chosen parametrisation, including validation against GNSS-based solutions and SLR.

How to cite: Fernández, M., Fernández, C., Peter, H., Féménias, P., and Nogueira Loddo, C.: Copernicus POD Service – POD RESULTS BASED ON DORIS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8672, https://doi.org/10.5194/egusphere-egu24-8672, 2024.

EGU24-8756 | Orals | G2.1

Copernicus POD Service – Impact of High Solar activity on POD 

Sonia Lara Espinosa, Carlos Fernández, Marc Fernández, Heike Peter, and Pierre Féménias

The Copernicus Precise Orbit Determination (CPOD) Service delivers, as part of the Ground Segment of the Copernicus Sentinel-1, -2, -3, and -6 missions, orbital products and auxiliary data files for their use in the corresponding Payload Data Ground Segment (PDGS) processing chains at ESA and EUMETSAT, and to external users through the newly available Copernicus Data Space Ecosystem (https://dataspace.copernicus.eu/).

For the last few years, a progressive degradation of the accuracy of some of the CPOD orbital products has been observed, caused by the increasing solar activity. Solar activity follows an 11-year cycle, and since the minimum in 2020, overall solar activity has been higher and geomagnetic storms have been happening more often. This has two impacts on POD: a more “turbulent” atmosphere which brings higher frequency density changes, making the modelling of the satellite´s drag more challenging, and an increase of ionospheric scintillation, particularly over the polar regions, that causes an increase of the GNSS carrier phase noise.

This study aims at characterising better the impact of the solar activity on the different POD products, with a focus on the degradation of orbit determination and predictions required by the Sentinel-1 mission. Overall tendencies since the solar minimum in 2020 are analysed, including a detailed look on strong geomagnetic storms. Mitigation strategies to overcome this situation are evaluated, namely adapting the POD processing dynamic parametrisation, and updating the solar activity proxies (particularly the geomagnetic indexes) more frequently.

How to cite: Lara Espinosa, S., Fernández, C., Fernández, M., Peter, H., and Féménias, P.: Copernicus POD Service – Impact of High Solar activity on POD, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8756, https://doi.org/10.5194/egusphere-egu24-8756, 2024.

EGU24-10249 | ECS | Posters on site | G2.1

SPOCC - a GFZ Software Tool for a Multi-GNSS Orbit and Clock Combination 

Andreas Brack, Gustavo Mansur, Pierre Sakic, Radosław Zajdel, and Benjamin Männel

Among the core products of the International GNSS Service (IGS) are precise satellite orbits and clocks, which are generated by the Analysis Center Coordinator (ACC) as a combination of the solutions provided by different Analysis Centers (AC). A strategic goal of the IGS is to facilitate multi-GNSS solutions, implying that the currently operational system-wise GPS and GLONASS combinations should be replaced by a consistent set of multi-GNSS products, eventually containing at least GPS, GLONASS, Galileo, BeiDou, and QZSS.

Over the past years, the Satellite Precise Orbit and Clock Combination (SPOCC) software tool has been developed at GFZ. It provides a fully consistent multi-GNSS orbit and clock combination that covers all available and possible future constellations and is based on a well-defined unified least-squares framework. The resulting combined orbit and clock products are a weighted average of the individual AC solutions with weights determined through least-squares variance component estimation (VCE). A main objective is to support multi-GNSS precise point positioning (PPP) users.

We will introduce the combination workflow, which essentially consists of alignments harmonizing the AC products followed by the VCE and the weighted averaging, and is complemented by quality checks such as outlier detection. For the orbit combination, the alignment consists of Helmert transformations applied to the AC orbits, which is iterated with the VCE-based weighted averaging until convergence. The clock alignments consist of a radial correction from the orbit differences between the AC solutions, a removal of the impact of different reference clocks in the AC solutions, as well as an adjustment of all non-GPS satellite clocks for different inter-system bias (ISB) references at the ACs. The combination can be configured for different weighting schemes, including AC specific weights, AC+constellation specific weights, up to satellite type or even satellite specific weights, and the Helmert transformations can be based on different sets of satellite orbits.

The SPOCC software has been extensively tested with the operational IGS products, the IGS Multi-GNSS Experiment (MGEX) products, and the IGS repro3 products. Performance evaluations by means of a comparison of the combination with the input products and the official IGS combination, through a satellite laser ranging (SLR) validation, and with PPP results will be used to show that the software achieves reliable results that are suitable for the users’ high precision GNSS applications.

SPOCC is implemented in Python and will be provided as open source software.

How to cite: Brack, A., Mansur, G., Sakic, P., Zajdel, R., and Männel, B.: SPOCC - a GFZ Software Tool for a Multi-GNSS Orbit and Clock Combination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10249, https://doi.org/10.5194/egusphere-egu24-10249, 2024.

EGU24-10344 | Posters on site | G2.1

Towards a GEodesy and Time Reference In Space (GETRIS): A simulation study 

Stefan Marz, Anja Schlicht, and Urs Hugentobler

Progress in precise satellite orbit determination (POD) and navigation depends on the future ranging and time transfer capabilities. This leads to the need for high-precision links as well as high-precision clocks. However, not only a higher accuracy is required, but also the use of combination of complementary observation techniques to reduce systematic errors within an observation network. In a simulation study, we show our first concept of a GEodesy and Time Reference In Space (GETRIS). The initial GETRIS concept is based on the idea to have the reference in space build on geosynchronous orbit (GSO) satellites, but using Medium Earth Orbit (MEO) satellites is also possible. The goal is to achieve orbit accuracies of the GETRIS satellites at the same level as for ground stations – a few millimeters. Using high-precision optical links, the GETRIS shall establish connections to satellites in the near Earth environment and in deep space. When creating our GETRIS concept, we focus on three key pillars of a simulation study: Instrumentation, geometry and modelling. In terms of instrumentation, we performed scenarios using the synergy between L-band observations as well as high-precision dual one-way Optical Inter-Satellite Links (OISL) and ground-space based dual one-way links, called Optical Two-Way Links (OTWL), in different combinations. The geometry changes depending on the used observations network and the satellite constellation. Thereby, we analyze scenarios using a MEO-only and MEO+GSO constellations. To finally achieve mm-level orbit accuracies, an advanced modelling of non-gravitational forces is essential. A GETRIS can not only help with the connection of near Earth and deep space satellites, but also support the Global Geodetic Observing System (GGOS) and satellite missions such as GENESIS, which aim to realize a precise terrestrial reference frame with 1 mm accuracy and a stability of 0.1 mm/year.

How to cite: Marz, S., Schlicht, A., and Hugentobler, U.: Towards a GEodesy and Time Reference In Space (GETRIS): A simulation study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10344, https://doi.org/10.5194/egusphere-egu24-10344, 2024.

EGU24-12683 | Orals | G2.1

GNSS-based orbit and geodetic parameter estimation by means of simulated GENESIS data 

Daniel Arnold, Alexandra Miller, Cyril Kobel, Oliver Montenbruck, Peter Steigenberger, and Adrian Jäggi

The ESA GENESIS mission, which obtained green light at ESA's Council Meeting at Ministerial Level in November 2022 and which is expected to be launched in 2027, aims to significantly enhance the accuracy and stability of the Terrestrial Reference Frame (TRF). This shall be achieved by equipping one satellite at approximately 6000 km altitude with well-calibrated instruments for all four space-geodetic techniques contributing to TRF realizations, i.e., Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and by exploiting the such realized very precise space collocations.

The GENESIS satellite is foreseen to carry a zenith- and nadir-pointing GNSS antenna to track (at least) GPS and Galileo signals. Because of its very high altitude, GENESIS will cover much larger nadir angles as seen from the GNSS transmitting antennas, compared to receivers at ground or in low Earth orbit. This will partly result in GNSS observations with lower signal-to-noise ratios. Furthermore, to date, only little reliable information is available on the GNSS transmit antenna gain and carrier phase patterns at very large nadir angles. These problems lead to questions with respect to the best possible exploitation of GNSS data by GENESIS, e.g., whether phase pattern calibrations will need to be performed by means of tracked GNSS data (which would weaken the GNSS contribution to GENESIS).

The aim of this study is to assess the impact of GNSS transmit antenna phase pattern errors on the GNSS-based POD of GENESIS, as well as global GNSS network solutions for GNSS orbits and clock corrections, Earth rotation and geocenter parameters and station coordinates based on GNSS observations from GENESIS and terrestrial stations. To accomplish this, we employ simulated GNSS pseudo-range and carrier phase data for GENESIS and ground stations, which have been generated based on detailed link-budget computations and a comprehensive set of transmit antenna gain patterns. The data are used for closed-loop simulation investigations, which allow to compare the reconstructed orbit and geodetic parameter solutions to the simulation truth and offer a quantification of the impact of transmit antenna phase pattern uncertainties on the estimated parameters.

How to cite: Arnold, D., Miller, A., Kobel, C., Montenbruck, O., Steigenberger, P., and Jäggi, A.: GNSS-based orbit and geodetic parameter estimation by means of simulated GENESIS data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12683, https://doi.org/10.5194/egusphere-egu24-12683, 2024.

The Event Horizon Telescope (EHT) is a ground-based array of Very Long Baseline Interferometry (VLBI) telescopes designed to image the event horizon of black holes. To overcome its limitations, this work explores a mission concept involving a two-satellite constellation of VLBI telescopes deployed in circular and polar Medium Earth Orbit (MEO) at more than 8000 km altitude.  The attainment of high-resolution black hole images requires extremely precise baseline determination at the few millimetre level. To address this challenge, each satellite within the constellation is equipped with two Global Navigation Satellite System (GNSS) receivers and an optical Intersatellite Link (ISL) for relative navigation. This work assesses the feasibility of achieving highly accurate relative positioning within the constellation, particularly considering the large intersatellite distances involved.

The methodology employed in this simulation study encompasses several steps. Initially, the satellite orbits are estimated independently for each satellite using GNSS observations. Following this, the orbit of one of the satellites is held fixed as a reference, while the orbit of the other satellite is re-estimated by incorporating the ISL observations. To enhance the accuracy of the orbit estimation, integer GNSS ambiguity resolution is implemented in the precise orbit determination process. The simulated data incorporates an extensive set of realistic error sources, including thermal noise, instrumental delays, clock biases, errors in the GNSS ephemerides and clocks, uncertainties in the geopotential and solar radiation pressure models, and white noise in the ISL observations.

The results highlight the importance of integer ambiguity resolution in meeting the stringent relative navigation requirements of the mission. The analysis also reveals that the ISL observations primarily improve the baseline estimation along the direction of the link itself. However, in the direction of the black hole, the impact of ISL observations is minimal, indicating that the ISL does not significantly contribute to meeting the specific relative navigation requirements. Furthermore, the study identifies that large intersatellite distances lead to degraded relative orbit accuracy due to fewer shared errors between the two satellites. The work will show the accuracy obtained with the simulations, the assumptions considered, and the next steps needed.

How to cite: Salas, M., Fernández, J., and van den IJssel, J.: Precise Relative Navigation in Medium Earth Orbits with Global Navigation Satellite Systems and Intersatellite Links for Black Hole Imaging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13048, https://doi.org/10.5194/egusphere-egu24-13048, 2024.

EGU24-16139 | ECS | Orals | G2.1

On the potential of highly accurate clocks and inter-satellite clock synchronization for GNSS satellite precise orbit and geocenter determination 

Patrick Schreiner, Susanne Glaser, Rolf König, Karl Hans Neumayer, Shrishail Raut, and Harald Schuh

Improving the concepts of Global Navigation Satellite Systems (GNSS) has become a vital task for subsequent GNSS applications like the determination of the Terrestrial Reference Frame (TRF). A promising goal is the reduction of uncertainties in non-conservative force modeling such as Solar Radiation Pressure (SRP) modelling in Precise Orbit Determination (POD) and the effect on the estimated orbits and geocenter coordinates. In previous simulation studies, accelerometers on next-generation GNSS satellites have proven to be a promising opportunity. In this way, the periodic signals in the estimated geocenter coordinates induced by SRP mismodeling can be eliminated regardless of the angle of the Sun to the satellite and its orbital plane. At the same time, the satellite clock can be effectively decoupled from the satellite position estimates. In this study, we focus on the impact of highly accurate clocks and the synchronization of clocks between satellites, which would make it possible to estimate common clock parameters for the synchronized satellites. In doing so, we start with Galileo-type POD using prior simulated observations with the assumption of perfectly known clocks. Then, we simulate various scenarios assuming different clock models and compare the results with the perfect case scenario. This procedure will explore the potential of various ground reference and satellite clock accuracies. Additionally, we use inter-satellite links to synchronize the satellite clocks over one and over multiple orbital planes. Finally, we strive to assess the potential of improved clock modeling on the TRF, focusing on the estimation of geocenter coordinates.

How to cite: Schreiner, P., Glaser, S., König, R., Neumayer, K. H., Raut, S., and Schuh, H.: On the potential of highly accurate clocks and inter-satellite clock synchronization for GNSS satellite precise orbit and geocenter determination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16139, https://doi.org/10.5194/egusphere-egu24-16139, 2024.

EGU24-16732 | Posters on site | G2.1

Precise orbit determination for the maneuvering satellites 

Maciej Kalarus, Daniel Arnold, Sebastiano Padovan, Rolf Dach, and Adrian Jäggi

Routine and occasional/emergency orbital maneuvers are essential for many satellites to maintain their optimal trajectory and to achieve a wide range of operational objectives in a continuous way. However, incorrectly modelled highly dynamic changes of the orbit during maneuvers can significantly reduce the accuracy of precise orbit determination (POD) to an extent that is unacceptable for scientific requirements.

The aim of this study is to investigate strategies for maneuver handling of Low Earth Orbiting (LEO) satellites based on observations from on-board GNSS receivers complemented by a priori knowledge of thrust intensity and maneuver epochs that are provided by telemetry measurements. Assuming that the initial information is subject to instrumental biases, corrections for the maneuver accelerations are estimated together with nominal deterministic and pseudo-stochastic orbit parameters such as instantaneous velocity changes and piecewise constant accelerations.

Several estimation strategies are tested using recent developments in the Bernese GNSS software, which is continuously maintained and further developed at the Astronomical Institute of the University of Bern (AIUB). In particular, the test cases cover single long/short maneuvers as well as two consecutive maneuvers within one orbital arc. Depending on the length of the maneuver and the number of available observations, different polynomial functions (up to degree 2) are used to model the thrust acceleration. Finally, the quality of the solution is evaluated internally by comparing it to the days without maneuvers and by checking the consistency between the reduced dynamic and kinematic orbit. External validation is also performed with respect to the official independent products.

How to cite: Kalarus, M., Arnold, D., Padovan, S., Dach, R., and Jäggi, A.: Precise orbit determination for the maneuvering satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16732, https://doi.org/10.5194/egusphere-egu24-16732, 2024.

EGU24-16819 | Orals | G2.1

The Galileo for Science project: Non-Conservative Forces modeling for the Galileo FOC satellites 

Carlo Lefevre, Massimo Visco, David Lucchesi, Feliciana Sapio, Roberto Peron, Marco Cinelli, Alessandro Di Marco, Emiliano Fiorenza, Pasqualino Loffredo, Marco Lucente, Carmelo Magnafico, Francesco Santoli, and Francesco Vespe

The Galileo for Science Project (G4S_2.0) is funded by the Italian Space Agency and has several goals in the field of Fundamental Physics to be achieved by exploiting the satellites of the Galileo-FOC Constellation. In this regard, a key point is to obtain a suitable satellite orbit solution by performing an accurate Precise Orbit Determination (POD). To this purpose modeling in a reliable way the complex effects of the Non-Conservative Forces, i.e. of Non-Gravitational Perturbations (NGPs), is essential. The activities undertaken in the construction of a Box-Wing model and of a Finite Element Model of the satellite will be presented with the preliminary results obtained by including these models into the POD of the Galileo satellites. In particular, using the orbital element residuals obtained from a POD we can test our new models and the improvements in POD quality.

How to cite: Lefevre, C., Visco, M., Lucchesi, D., Sapio, F., Peron, R., Cinelli, M., Di Marco, A., Fiorenza, E., Loffredo, P., Lucente, M., Magnafico, C., Santoli, F., and Vespe, F.: The Galileo for Science project: Non-Conservative Forces modeling for the Galileo FOC satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16819, https://doi.org/10.5194/egusphere-egu24-16819, 2024.

EGU24-16831 | Posters on site | G2.1

Assessment of Jason-3 and Sentinel-6 MF radiation pressure model 

Eléonore Saquet, Marie Cherrier, Alexandre Couhert, and Flavien Mercier

Since the launch of Seasat (1978), the first satellite to study ocean topography, our knowledge of the rise of 
mean sea level has evolved. Since then, 18 additional satellites were launched, with more and more satellite 
missions (up to 10 satellites are now simultaneously flying) dedicated to the measurement of the global and 
regional sea-surface height, carrying on board state of the art precision orbit determination tracking techniques 
and instruments. 


Jason-3 (2016) and Sentinel-6 MF (2020) are part and parcel of these ocean topography missions. The two 
reference satellites were operated in tandem (with Sentinel-6 MF flying 30 seconds behind its predecessor) 
between mid-December 2020 to April 2022 for calibration purposes. The main difference between these two 
satellites has to do with their respective platform design. Indeed, Sentinel-6 MF solar panels are fixed on the 
satellite and has an almost fixed attitude, unlike Jason-3 which has some yaw steering periods. 


In this study, we focus on the solar radiation pressure modeling errors of both Sentinel-6 MF and Jason-3 
during their tandem phase (4.5 beta cycles). The idea is to analyze the estimated empirical accelerations of 
these two satellites as a function of their beta angle. The Solar Radiation Pressure (SRP) depends only on two 
parameters: the orbital angle with respect to the sub-solar point and the beta angle. We will then propose 
updates of the SRP models. The effect of the terrestrial radiative perturbations will also be assessed.

How to cite: Saquet, E., Cherrier, M., Couhert, A., and Mercier, F.: Assessment of Jason-3 and Sentinel-6 MF radiation pressure model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16831, https://doi.org/10.5194/egusphere-egu24-16831, 2024.

EGU24-16959 | Orals | G2.1

Review the IGS Strategy for Precise Point Positioning Applications 

Rolf Dach, Daniel Arnold, Elmar Brockmann, Maciej Kalarus, Lars Prange, Stefan Schaer, Pascal Stebler, and Adrian Jäggi

Within the IGS, it was agreed that Precise Point Positioning (PPP) based on satellite orbit and clock corrections of the IGS analysis centers allow a direct access to the IGS realization of the International Terrestrial Reference Frame (ITRF). This convention is considered convenient for all PPP users and should not be changed in future.

On the other hand, the groups determining the GNSS satellite orbits do prefer an origin of the frame that is related to the Earth instantaneous center of mass since this is the reference of the gravitational orbit force model. With this background, some discussions take place to change the convention related to the origin of the terrestrial frame because it is convenient for the orbit determination. This convention is, however, in contradiction to the expected needs of the PPP users that do prefer a stable coordinate origin in time.

We will introduce a strategy to serve both needs by applying the center of mass corrections for the orbit determination only.

How to cite: Dach, R., Arnold, D., Brockmann, E., Kalarus, M., Prange, L., Schaer, S., Stebler, P., and Jäggi, A.: Review the IGS Strategy for Precise Point Positioning Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16959, https://doi.org/10.5194/egusphere-egu24-16959, 2024.

EGU24-18289 | ECS | Orals | G2.1

The Galileo for Science project: Constraints on Dark Matter with the Galileo-FOC Constellation 

Alessandro Di Marco, Feliciana Sapio, Massimo Visco, David Lucchesi, Marco Cinelli, Emiliano Fiorenza, Carlo Lefevre, Pasqualino Loffredo, Marco Lucente, Carmelo Magnafico, Roberto Peron, Francesco Santoli, and Francesco Vespe

The Galileo for Science Project (G4S_2.0) is funded by the Italian Space Agency and has
several goals in the field of Fundamental Physics to be achieved by exploiting the satellites
of the Galileo-FOC Constellation and the accuracy of their onboard atomic clocks. In
particular, the clock-bias, estimated in the data reduction of the tracking observations
allows to place constraints on the possible presence of Dark Matter in our galaxy in the
form of Domain Walls (DW) eventually produced in the very early Universe by ultralight
scalar field(s). The impact of the DW on an atomic clock would provide a delta-like
transient shift on the pseudo-derivative of the clock-bias. Such signal depends both on the
nature of the clock and the characteristics of the ultralight scalar comprising the DW.
Ongoing work on the clock-bias will be introduced as regards to data pre-processing and
simulations on false alarm and detection efficiency.

How to cite: Di Marco, A., Sapio, F., Visco, M., Lucchesi, D., Cinelli, M., Fiorenza, E., Lefevre, C., Loffredo, P., Lucente, M., Magnafico, C., Peron, R., Santoli, F., and Vespe, F.: The Galileo for Science project: Constraints on Dark Matter with the Galileo-FOC Constellation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18289, https://doi.org/10.5194/egusphere-egu24-18289, 2024.

EGU24-18467 | Posters on site | G2.1

On multi technique precise orbit determination for SWOT with respect to altimetry applications. 

Anton Reinhold, Patrick Schreiner, and Tilo Schöne

SWOT (Surface Water and Ocean Topography) is a recently launched international satellite mission developed in close collaboration between CNES and NASA space agencies aimed to reach a new level of accuracy in observing global water systems of the Earth. In order to meet the high accuracy requirements of the mission most precise determined orbits are crucial. Therefore we generate orbits using dynamic Precise Orbit Determination (POD) with multiple techniques, i.e. DORIS, GPS and SLR with the aim of generating a highly precise orbit with minimal residual error. For this purpose, single technique orbits are generated based on DORIS and GPS only, using SLR for validation only. For quality analysis we evaluate the estimated parameters of the dynamic POD and perform orbit comparisons to external orbit solutions. Subsequently, to reduce technique-specific effects of the dynamic modeling, we generate a combined orbit solution based on DORIS and GPS, and estimate the reference points of the observation techniques on the satellite to examine the calibration by the manufacturer. Based on the generated orbit solutions altimetry evaluation such as cross-over point analysis is made and discussed.

How to cite: Reinhold, A., Schreiner, P., and Schöne, T.: On multi technique precise orbit determination for SWOT with respect to altimetry applications., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18467, https://doi.org/10.5194/egusphere-egu24-18467, 2024.

EGU24-19842 | Posters on site | G2.1

Treatment of Modern Global Ocean and Atmospheric Tide Atlases in Precise Orbit Determination 

Volker Klemann, Roman Sulzbach, Alexander Kehm, Mathis Blossfeld, Michael Hart-Davis, Henryk Dobslaw, and Torsten Mayer-Guerr

Tidal variability originating from the orbital dynamics of the Sun and the Moon can be observed in virtually all subsystems of the Earth. The evoked tidal phenomena in the atmosphere, the solid Earth, and the world oceans cause a large-scale redistribution of masses, primarily on daily and sub-daily time scales. The implied tidal variability impacts geodetic measurements. For example, the induced mass transport induces temporal changes in the Earth's gravity field which impact the orbits of artificial satellites. However, observations of a single satellite are generally insufficient to precisely estimate tidal signatures, resulting in a decreased accuracy of the Precise Orbit Determination (POD) of near-Earth satellites. Therefore, a priori prediction of tidal signals, especially ocean tidal signatures, by tidal atlases is necessary to exploit the full potential of geodetic data sets.

The most accurate ocean tide atlases are produced by incorporating satellite altimetry observations into the modeling process. However, limitations arising from the ambient signal-to-noise level have hindered their ability to accurately estimate small signals associated with minor tidal constituents. For those minor constituents, data-unconstrained ocean tide models can yield valuable constraints. For processing satellite altimetry data, initial experiments have been undertaken to integrate empirical and numerical models, aiming to deliver comprehensive tidal corrections (Hart-Davis et al., 2021, doi: 10.3390/rs13163310). It has been proposed that experimentation is necessary across all geodetic applications to determine the preferred model for specific tidal constituents and the optimal approach for merging models. This also includes the possibility of including minor ocean tides only implicitly, by deriving their admittance function from suitable neighboring tidal constituents.

How to cite: Klemann, V., Sulzbach, R., Kehm, A., Blossfeld, M., Hart-Davis, M., Dobslaw, H., and Mayer-Guerr, T.: Treatment of Modern Global Ocean and Atmospheric Tide Atlases in Precise Orbit Determination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19842, https://doi.org/10.5194/egusphere-egu24-19842, 2024.

EGU24-20733 | Orals | G2.1

Tailored accelerometer calibration by POD for thermospheric density computation with GRACE and GRACE-FO 

Florian Wöske, Benny Rievers, and Moritz Huckfeldt

The density of the upper atmosphere can be determined by orbit and accelerometer data from low Earth orbit satellites. Especially the accelerometers of geodetic satellites, measuring the non-gravitational accelerations acting on them are a very viable observation.

The density estimation is mainly based on three separate disciplines, which are: (1) Precise radiative non-gravitational force modelling, (3) Modelling of the interaction between the rarefied atmospheric gases and the satellite, i.e. modelling of drag coefficients, and (3) the calibration of the accelerometer data by dynamic Precise Orbit Determination (POD). This contribution focuses mainly on the last point. Nevertheless, we also validate the modelled radiative accelerations and use them as reference for the calibration results.

The accelerometers of all geodetic satellites are affected by a drifting bias and scale factors unequal to one. Therefore a calibration of the data is indispensable. Usually time dependent bias and scale factors are estimated. For standard POD or Gravity Field Recovery (GFR) these parameters are estimated together with empiric and other model parameters. In both cases, the estimated accelerometer calibration parameters are not of major interest, but improve the orbit fit or gravitational field coefficients. The used parametrizations and weighting strategies of the observation data, do not give realistic or physical accelerometer calibration results because parameters are not sensitive and effects are absorbed or smeared into other parameters and models. This is unsatisfying, especially for the anticipated use for the density determination.

In this contribution we use dynamic POD and investigate different parametrization strategies tailored for a physical accelerometer calibration. We investigated the effect of constraining the accelerometer calibration parameters in that way, that a continuous calibration over all arcs is achieved, where normally each arc is treated locally separated from all other arcs. The scale factor is concurrently estimated, but over a longer batch of arcs. We varied the length between one day and years. Furthermore, different calibration equations, different observation data and combinations (kinematic positions, science orbit data, inter-satellite ranging), weighting strategies, initial parameters and pre-processing of the accelerometer data is investigated. The validation of the results is not easy, because usual metrics like post-fit residuals do not reflect the quality of the accelerometer calibration. We introduce a validation approach using the modelled non-gravitational forces and also show the influence of the different calibration options on the resulting density or drag acceleration.

All results and data for the whole GRACE and GRACE-FO missions are available on our data server (link in presentation/ uploaded material). 

How to cite: Wöske, F., Rievers, B., and Huckfeldt, M.: Tailored accelerometer calibration by POD for thermospheric density computation with GRACE and GRACE-FO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20733, https://doi.org/10.5194/egusphere-egu24-20733, 2024.

EGU24-897 | ECS | Orals | G2.2

Improved geodetic datum realization based on simulation studies for co-located SLR-VLBI stations 

Joanna Najder, Alexander Kehm, Mathis Bloßfeld, Krzysztof Sośnica, and Matthias Glomsda

The International Terrestrial Reference System is realised in the form of multi-year reference frames such as the International Terrestrial Reference Frame (ITRF) or in the form of epoch reference frames relying on short observation time spans up to several weeks. The realisation is based on the combination of space-geodetic techniques, namely the global navigation satellite systems (GNSS), satellite laser ranging (SLR), very long baseline interferometry (VLBI) and Doppler orbitography and radiopositioning integrated by satellite (DORIS). In some ITRF and epoch reference frame solutions, SLR and VLBI are responsible for realising the datum parameters origin (only by SLR) and the scale, while the orientation of the network with respect to the Earth’s body is maintained by a mathematical constraint. The integration of the techniques is achieved by introduction of local ties (LTs) at co-located sites, i.e., by ground-based measurements of difference vectors between the technique-specific reference points. High accuracy of current LTs between techniques and the establishment of new co-location sites are necessary to provide (and further improve) a reliable realisation of the geodetic datum. Co-location sites with the SLR technique are of particular significance as this is the only technique that enables the realisation of a terrestrial reference frame origin with a high level of accuracy. As previous studies demonstrate, the performance of the observational networks has a significant impact on the accuracy and stability of the corresponding datum realisation, especially for epoch reference frames.

This study aims to examine how improving the performance of the existing network of co-located SLR stations could affect the quality of determined datum parameters. The considered simulation scenarios study the performance of SLR stations co-located with the VLBI technique and improve the performance of those that do not meet the standards set by the International Laser Ranging Service (ILRS). Moreover, it is examined how significant the improvement of the datum parameters is in the case of extending the SLR network with stations located nearby existing VLBI telescopes (due to a ‘better’ datum transfer via a higher number of local ties).

How to cite: Najder, J., Kehm, A., Bloßfeld, M., Sośnica, K., and Glomsda, M.: Improved geodetic datum realization based on simulation studies for co-located SLR-VLBI stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-897, https://doi.org/10.5194/egusphere-egu24-897, 2024.

The growing demand for Earth science applications poses challenges in improving geodetic reference frames. Systematic errors currently restrict the accuracy of these frames because the classical geometric ties between multiple geodetic techniques fall short of sufficiency. Our objective is to identify and analyze the impact of variable GNSS receiver hardware delays (incl. antenna-hardware delays) on carrier-phase time transfer with an accuracy of picoseconds/millimeters. We propose using a ground-based GNSS pseudolite system synchronized to an optical timing system (clock tie) developed at the Geodetic Observatory Wettzell to calibrate the variable hardware delays and facilitate a closure in time between multiple geodetic techniques.

This study analyzes the requirements for developing a GNSS pseudolite and its transmission chain. We reformulate the classic iono-free Precise Point Positioning (PPP) mathematical theory to incorporate pseudolite data, separating the known receiver clock error from unknown transceiver hardware delays. The analysis suggests a preference for highly directive and mechanically stable Right Hand Circularly Polarized (RHCP) log periodic or helix transmission antennae. Calibration for Phase Center Offset (PCO), Phase Center Variations (PCVs) and careful installation to minimize multipath are crucial. This results in a carrier-phase observation model with three unknowns: transceiver hardware delays (our focus), frequency-dependent ambiguity terms, and low tropospheric delay influence.

Utilizing a USRP-based transmission procedure, we successfully tracked an E1B Galileo signal replica with an in-house developed GNSS software-defined receiver (SDR). The transmission was implemented using two approaches: over-the-air and loopback. The over-the-air transmission was carefully planned using a link budget calculation to ensure that it did not exceed the allowed free-air transmission constraints. Empirical validation ensured a carrier-to-noise ratio (C/N0) below 30dB/Hz near critical public areas. In the loopback approach, the transmitted GNSS signal was fed into the local SDR within the pseudolite, sharing the same Analog-Digital-Converter (ADC)/ Digital-Analog-Converter (DAC)ADC/DAC, clock and local oscillators. In a future stage, this signal is supposed to be compared to a reference signal derived from the optical timing system. 

In our analysis, we also assessed the stability of the USRP frequency synthesizer, known as Phase Lock Loop (PLL), in the context of high-precision applications, such as real-time kinematic (RTK) positioning. We found that tuning the synthesizer in integer-n mode is crucial in maintaining a stable carrier frequency and achieving a 100% real-time kinematic positioning fixing rate. 

How to cite: Lăpădat, A. M., Kodet, J., and Pany, T.: Towards calibration of GNSS receiver hardware delays for improving geodetic reference systems through clock ties. A requirements analysis for developing a GNSS pseudolite transmission chain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1600, https://doi.org/10.5194/egusphere-egu24-1600, 2024.

EGU24-3821 | Orals | G2.2

Benefits for the terrestrial reference frame with VLBI observations to Genesis 

Johannes Böhm, Helene Wolf, and Lisa Kern

Mission Genesis of the European Space Agency (ESA) has been approved for launch in 2027. Genesis will be the first satellite in orbit to have a dedicated Very Long Baseline Interferometry (VLBI) transmitter on board, next to Global Navigation Satellite System (GNSS) and Doppler Orbitography and Radiopositioning Integrated on Satellite (DORIS) receivers as well as a Satellite Laser Ranging (SLR) reflector; consequently, Genesis will realize a space tie combining all geometric space geodetic techniques. If perfectly calibrated, the space tie will enhance and improve local ties measured on the ground. The following scenario is possible: If the orbit of Genesis is determined from the satellite techniques alone, the station coordinates of the VLBI radio telescopes in the "satellite frame" can be derived by VLBI observations to Genesis, thereby assessing the tie with the "VLBI frame", realized with decades of VLBI observations to quasars.

We present our plans to devise observing strategies for VLBI to reach accuracies as defined in the Genesis white paper. We start with our findings for VLBI transmitters on Galileo satellites, before we show the simulation results for the VLBI transmitter on Genesis. We illustrate the advantages of the Genesis satellite at 6000 km altitude compared to Galileo satellites in terms of sky coverage and accuracy of station coordinates, but also in terms of orbit estimation. Furthermore, we provide an outlook on geodetic parameters, which could not be determined with VLBI so far but will be possible with Genesis.

How to cite: Böhm, J., Wolf, H., and Kern, L.: Benefits for the terrestrial reference frame with VLBI observations to Genesis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3821, https://doi.org/10.5194/egusphere-egu24-3821, 2024.

EGU24-4333 | ECS | Posters on site | G2.2

Impact of terrestrial reference frame on the SLR validation results of GNSS and LEO orbits 

Dariusz Strugarek and Radosław Zajdel

The Satellite Laser Ranging (SLR) technique is used to independently validate the microwave-based satellite orbit products. In the so-called SLR validation, the orbit quality is assessed based on the analysis of the SLR residuals, which are the discrepancies between the direct SLR range measurements and the station-satellite vector calculated based on the SLR station positions and the evaluated orbits in Earth-fixed reference frame. Therefore the results of SLR validation are strongly related to the SLR station coordinates. In 2022, the new realization of the International Terrestrial Reference Frame – ITRF2020 – has been released, which considers a few innovations, mainly, an extended model of post-seismic deformations, and the seasonal station coordinate variations in form of annual and semi-annual terms.  In this study, we investigate the impact of recent advancements in ITRF into the SLR-based orbit validation of LEO and GNSS satellites.      

We perform the SLR validation of LEO orbit (Swarm-ABC, Sentinel-3A/B, Jason-3) products provided by European Space Agency (ESA) Copernicus Service and Technical University of Graz for one year. Also, we validate Galileo and BeiDou-3 orbit products delivered by ESA and Center for Orbit Determination in Europe in 2023. 

We incorporate the latest ITRF2020 realization into the SLR validation processing, contrasting the outcomes with solutions that involve the previous ITRF2014 release to illustrate the impact of TRF aging on validation results. Additionally, we examine the influence of including seasonal station motions on SLR validation outcomes. Furthermore, a comparison is made between SLR validation results when utilizing the most recent alternative TRF realizations, namely DTRF2020 and JTRF2020. We discuss the dependency of residuals on different measurement conditions, such as elevation angle and azimuth angle, and their time variability.

How to cite: Strugarek, D. and Zajdel, R.: Impact of terrestrial reference frame on the SLR validation results of GNSS and LEO orbits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4333, https://doi.org/10.5194/egusphere-egu24-4333, 2024.

EGU24-5732 | Orals | G2.2

First results of the analysis of the input data series provided by the IAG technique services for the extension of xTRF2020 

Manuela Seitz, Mathis Bloßfeld, Matthias Glomsda, Detlef Angermann, Sergei Rudenko, and Julian Zeitlhöfler

The latest realizations of the ITRS, specifically the ITRF2020, the JTRF2020 and the DTRF2020, have been computed using input data series provided by the IAG technique services IVS, ILRS, IGS and IDS. They cover the entire observation period of the individual techniques until the end of 2020. Since 1996, recalculations of the ITRF have been performed approximately every 3 to 6 years. The main reason for recalculation is to ensure a high accuracy of the ITRF for current applications. In particular, seismic events that occure after an ITRF release as well as the general increase of the ITRF extrapolation error with time are key factors that cause the increase of the ITRF uncertainty.

 

To enhance the frequency of ITRS realizations and consequently improve the accuracy of the ITRF, the ITRS Product Center plans to calculate annual updates of the ITRF2020 starting in 2024. The IAG technique services will provide three additional years of analyzed observations (2021-2023) collected after the end of the ITRF2020 observation period in February 2024. As an ITRS Combination Center, at DGFI-TUM, we will analyze the data series w.r.t. discontinuities, post-seismic deformations and their consistency with the input data series provided for the ITRS 2020 realizations. Model changes performed in between by the individual technique services, e.g. new PCO (phase center offsets) for GNSS satellites, updated mean long-term range biases for SLR satellites or gravitational deformation models for some more VLBI antennas, are expected to have an impact on the relevant ITRF parameters (station coordinates, EOP and datum parameters). Its order of magnitude and the effect of possible inconsistencies on the DTRF solution need to be investigated. We will present the first results of our analyses and draw preliminary conclusions regarding the accuracy of a possible DTRF2020 extension.

How to cite: Seitz, M., Bloßfeld, M., Glomsda, M., Angermann, D., Rudenko, S., and Zeitlhöfler, J.: First results of the analysis of the input data series provided by the IAG technique services for the extension of xTRF2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5732, https://doi.org/10.5194/egusphere-egu24-5732, 2024.

EGU24-6189 | Orals | G2.2

Contribution of LARES-2 to the realization of reference frames, deriving Earth rotation and gravity field parameters 

Krzysztof Sośnica, Filip Gałdyn, Joanna Najder, Radosław Zajdel, and Dariusz Strugarek

LAser RElativity Satellite 2 (LARES-2) successfully joined the constellation of geodetic satellites tracked by Satellite Laser Ranging (SLR) stations on July 13, 2022. LARES-2 has a spherical shape and a very favorable area-to-mass ratio that minimizes the non-gravitational orbit perturbations. Due to very small retroreflectors, the spread of center-of-mass corrections for different detectors installed at SLR sites is much smaller than for LAGEOS satellites. LARES-2 orbits at a similar height as LAGEOS-1, however, with a complementary inclination angle of 70° forming a butterfly configuration together with LAGEOS-1.

Although the primary objective of LARES-2 is verification of the Lense-Thirring effect emerging from general relativity, the satellite also has a substantial impact on the geodetic parameters derived from SLR observations. We process 18 months of LARES-2 data and compare the LAGEOS-1/2 solutions with the combined LAGEOS-1/2+LARES-2 solutions. We show the impact of LARES-2 on the (1) SLR station coordinates, (2) pole coordinates, (3) length-of-day excess, (4) low-degree gravity field parameters focusing on C20 and C30 coefficients, (5) scale of the reference frame, (6) geocenter motion. We show that LARES-2 can especially improve the Z component of the geocenter coordinates and de-correlate C20 from the length-of-day parameter. The secular drifts of the ascending nodes for LARES-1 and LAGEOS-1 caused by C20 are the same in terms of absolute values but with opposite signs. This allows us to successfully separate the measurements of length-of-day excess (or the UT rate) from the C20-induced changes. We also analyze the empirical accelerations acting on LARES-2 which result from unmodeled non-gravitational orbit perturbations, such as thermal effects, and compare them to those observed for LAGEOS satellites. The observation geometry of LARES-2 is especially beneficial for stations located at high and medium latitudes, which allows it to improve the estimation of station coordinates provided by LAGEOS-1/2. Therefore, LARES-2 substantially contributes not only to general relativity and fundamental physics but also to space geodesy improving the future realizations of the international terrestrial reference frames.

How to cite: Sośnica, K., Gałdyn, F., Najder, J., Zajdel, R., and Strugarek, D.: Contribution of LARES-2 to the realization of reference frames, deriving Earth rotation and gravity field parameters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6189, https://doi.org/10.5194/egusphere-egu24-6189, 2024.

EGU24-6472 | ECS | Orals | G2.2

Investigations into GNSS clock biases in a global network of IGS H-Maser stations 

Jari Simon Widczisk, Benjamin Männel, and Jens Wickert

Global Navigation Satellite Systems (GNSS) are based on measuring the time that elapses between the signal’s transmission at the satellite and its reception on the ground. Therefore, clock information is required on both sides. While the GNSS satellites are equipped with atomic clocks, ground stations usually use the time information from the internal oscillator of their GNSS receiver, which has a much lower time-keeping performance compared to the satellite clocks. Nevertheless, some continuously operated tracking stations obtain their time information from an external atomic clock, as it is the case with many stations of the International GNSS Service (IGS).

To compensate for synchronization errors, current GNSS analysis models generally introduce clock biases for satellites and receivers into the observation equations. The often-made assumption of a pure white noise behavior for the estimated clocks may lead to high correlations with other geodetic parameters, such as the radial orbit error for the satellite clock, or the station height coordinate and tropospheric delay parameters for the station clock. A general solution to this problem is to reduce the amount of unknown clock parameters by modeling them in the adjustment process. In order to be modeled adequately, the corresponding clock must have a high degree of stability, which is particularly crucial for the ground stations.

In this contribution, we investigate the clock stability of globally distributed IGS tracking stations. Those IGS stations, that are steered by an external Hydrogen-Maser (H-Maser) clock, are considered in a global network analysis over a period of several weeks. The generated clock products are used to compare the frequency stabilities within the station network, as well as with the mean behavior of GPS and Galileo satellite blocks. After some further research on stations with significantly higher deviations, the final result of this contribution will be a set of reliable ground stations, that will serve as a basis for future clock modeling approaches at GFZ.

How to cite: Widczisk, J. S., Männel, B., and Wickert, J.: Investigations into GNSS clock biases in a global network of IGS H-Maser stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6472, https://doi.org/10.5194/egusphere-egu24-6472, 2024.

EGU24-6698 | Posters on site | G2.2

Updating JTRF2020 

Claudio Abbondanza, Toshio M Chin, Richard S Gross, and Michael B Heflin

In recent years, new determinations of the ITRF based on full-blown reanalyses of frame inputs from the four space-geodetic techniques have been produced at intervals of 3-6 years. Between frame determinations, ITRF users must rely on predictions of station positions of the reference stations included in the frame whose accuracy rapidly degrades over time, thus causing errors in the products derived from such predictions.    
JTRF2020 is the most recent TRF solution computed at JPL by assimilating the frame input data submitted by  IGS, IVS, ILRS, and IDS for ITRF2020. Determined with a square-root information filter and Dyer-McReynolds smoother algorithm, JPL frame products lend themselves to being updated rather easily as long as frame inputs from the four technique centers consistent with the frame-defining data set are readily available. 
In this presentation, we will discuss and test SREF (Square-root Reference frame Estimation Filter) updating capabilities in relation to JTRF2020. We will upload state estimate and its covariance computed at the last step of JTRF2020, and update them by assimilating at daily intervals the extended frame inputs made available by IGS (Repro3 extension), IVS (BKG operational combined series with loading effects restored using loading information from the NASA GSFC solution), ILRS (v170 and v171), and IDS (wd20) from 2021 through the end of 2022.   
Discussions will focus on the peculiarities of the extended frame inputs in relation to the data submitted for the ITRF2020 computation, and in particular on the data pre-processing and transformations we’ve applied to the extended frame inputs in order to ensure consistency with JTRF2020. We’ll also assess the quality of the JTRF2020 updates in terms of frame-defining parameters.     

How to cite: Abbondanza, C., Chin, T. M., Gross, R. S., and Heflin, M. B.: Updating JTRF2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6698, https://doi.org/10.5194/egusphere-egu24-6698, 2024.

EGU24-8143 | Posters on site | G2.2

Effect of network geometry on determination of VLBI-GNSS frame orientation using a VLBI transmitter onboard Galileo satellites 

Hakan Sert, Urs Hugentobler, Ozgur Karatekin, and Veronique Dehant

Having a Very Long Baseline Interferometry (VLBI) transmitter (VT) onboard Galileo satellite allows us to determine the misorientation between GNSS and VLBI frames. To exploit the maximum performance, we study the operational strategies for VLBI ground segment. We simulate VLBI observations of a VT onboard a Galileo satellite to evaluate the rotation transformation between the VLBI and GNSS frames. The contribution of a VT as space tie is assessed by the evaluation of the formal precision of the orientation parameters between the VLBI and GNSS frames using different ground stations/baselines, aiming to find the optimal observation geometry for the best precision on the rotation transformation.

How to cite: Sert, H., Hugentobler, U., Karatekin, O., and Dehant, V.: Effect of network geometry on determination of VLBI-GNSS frame orientation using a VLBI transmitter onboard Galileo satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8143, https://doi.org/10.5194/egusphere-egu24-8143, 2024.

EGU24-8188 | Posters on site | G2.2

Changes in the multipath value at ASG-EUPOS GNSS reference network stations in 2010-2021 

Dariusz Tomaszewski, Renata Pelc-Mieczkowska, and Jacek Rapiński

The multipath phenomenon is one of the factors affecting the accuracy of GNSS positioning. It results from reflections of the satellite signal from objects in the vicinity of the GNSS antenna. There are groups of techniques that allow minimizing the impact of this error on positioning results. These include: antenna placement, the use of the appropriate type of antenna, the use of a professional receiver as well as proper post-processing of observations. However, it is impossible to completely eliminate the influence of multipath on the measurement results. In the case of carrier phase differential positioning, this error has two main effects. First of all, the multipath increases the initial search space for correct ambiguities. Consequently, the accuracy of the vector solution between the reference station and the rover receiver is affected. The authors of this article examined how the characteristics of the multipath error changed at the stations of the Polish network of ASG-EUPOS reference stations in 2010-2021. Two computational strategies were adopted to determine the multipath: Code Minus Carrier linear combination (CMC) and pseudorange multipath observable (MP). Based on the research, it was found how the multipath values changed depending on the change of the receiver and the terrain around the reference stations. It was determined which stations had high multipath values in 2010 and what changes occurred over the 11 years. Based on the carried out analyses, it was also recommended to perform periodic tests that would allow it to detect incorrect configuration or incorrect operation of receivers.

How to cite: Tomaszewski, D., Pelc-Mieczkowska, R., and Rapiński, J.: Changes in the multipath value at ASG-EUPOS GNSS reference network stations in 2010-2021, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8188, https://doi.org/10.5194/egusphere-egu24-8188, 2024.

Highly accurate Terrestrial Reference Frames (TRF) – based on the combination of the four space-geodetic techniques Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) – are the fundamental backbone for a broad range of applications like land surveying, the geodetic monitoring of geophysical processes within the Earth system or navigation on and near the Earth’s surface. Recent efforts at the Geodetic Observatory Wettzell (GOW), Germany, aim at a transition from the purely geometric link between space-geodetic techniques via local ties as the current standard to an innovative quasi-error-free combination based on a common clock (CC) and a common target (CT).

Once the CC/CT-based infrastructure at GOW is fully developed and operational, it will be possible to uncover systematics between the space-geodetic techniques as well as individual instruments. However, to guarantee the long-term accuracy and stability of the TRF, it is indispensable to know and, if possible, to eliminate the systematics over the entire observation period of the techniques. A prerequisite for this is to compile an inventory of the existing discrepancies between the techniques and their possible causes.

The DFG research unit ‘Clock Metrology: Time as a New Variable in Geodesy’ features a joint project by DGFI-TUM and Uni Bonn with focus on developing a new CC-/CT-based approach to combine the space-geodetic techniques. As a basis, we develop an approach to analyse and cross-compare station position time series from different instruments/techniques observed over several decades. Based on the example of GOW co-locating all four space-geodetic techniques, we investigate absolute station position time series consistently aligned to the datum of the DTRF2020, DGFI-TUM’s most-recent realisation of the International Terrestrial Reference System (ITRS), as well as differential time series eliminating datum-realisation-related variations in the time series of one technique. Finally, we prepare a pool of metadata (log files, data time series from meteorological sensors and weather models, estimated clock and tropospheric parameters, etc.) and include these data in the analysis to identify causes of systematics. 

From the analyses, discontinuities, time-variable drifts and the spectra of intra- and inter-technique position difference time series between individual instruments at GOW can be identified and interpreted. The result of the work is an inventory which lists both, known and previously unmodelled systematics, and, as far as possible, their causes, thus providing the basis for the consistent combination of techniques in a common space-time.

How to cite: Kehm, A., Seitz, M., and Glaser, S.: Analysis of long time series of space-geodetic techniques at co-location sites to identify technique- and instrument-specific systematics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8612, https://doi.org/10.5194/egusphere-egu24-8612, 2024.

EGU24-8737 | Posters on site | G2.2

A critical look at the reported errors of geodetic products 

Maria Karbon, Santiago Belda, Esther Acuze, Mariana Moreira, Alberto Escapa, and Jose Manuel Ferrándiz

Geodesy provides the highest precision and accuracy International Terrestrial Reference Frame, International Celestial Reference Frame and Earth Orientation Parameters. However, in our processing chain, we take mathematical shortcuts, drop higher order polynomials, assume linearity where it is no longer valid, omit correlations and colored noise, and use outdated models. If intra- or inter-technique combinations are done, they happen at different stages, and different methods are employed. The datums applied to the reference frames are inherited over decades, accumulating all uncertainties of their predecessors. Dependencies between the reference frames and the EOP are largely ignored. Finally we inflate our errors by a predefined factor, to somehow account for all of that.
This is just a short list of the inconsistencies within our main products. Even for a specialist it will be almost impossible to list them all, for a mere end-user its an insurmountable task. In this work we will investigate these central products of geodesy, focusing mainly on the errors, their derivation, and significance from a user perspective. We look exemplarily at various official IVS and IAG products, and their reported errors. We investigate how transparent their nature and derivation is for the final user, if the parameters in question follow our physical understanding of the matter, and what insight we might gain from them.

How to cite: Karbon, M., Belda, S., Acuze, E., Moreira, M., Escapa, A., and Ferrándiz, J. M.: A critical look at the reported errors of geodetic products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8737, https://doi.org/10.5194/egusphere-egu24-8737, 2024.

EGU24-9298 | Orals | G2.2

Clock Ties: A novel approach for the reduction of systematic errors 

Karl Ulrich Schreiber

The techniques of space geodesy, comprising the four techniques, Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Doppler Orbitography and Ranging Integrated by Satellite (DORIS) are currently reaching a measurement resolution in the range of 1 part per billion for the terrestrial reference frame. However, a small set of discrepancies remain evident within each of the techniques as well as in the combination of different techniques. Systematic measurement errors are causing this and problems in the local ties between the reference points of the various measurement systems and biases in the atmospheric refraction correction have long been suspected as the main contributors. 

However, it turns out that errors in the internal delay compensation of the measurement systems are also a significant contributor. They are extremely hard to detect, since they are small and come with different characteristics. It is understood that the experienced delay variation is related to a complex pattern of ambient temperature variation inside of the electronic devices. These changes relate to the micro-climate of the electronic signal path and can both be slow and highly variable. With the advent of high bandwidth mode-locked lasers and active delay compensation in the optical domain, it is now possible to utilize coherent time as an independent probe for instrumental signal delays. 

The research unit FOR5456 of the German National Science Foundation (DFG) has been formed in 2022 in order to apply and investigate active delay compensation to the techniques of space geodesy. This talk introduces the application of coherent time in space geodesy and its potential to act as a novel tie in fundamental stations.

How to cite: Schreiber, K. U.: Clock Ties: A novel approach for the reduction of systematic errors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9298, https://doi.org/10.5194/egusphere-egu24-9298, 2024.

Arctic areas are heavily affected by climate change. The temperature is increasing, the permafrost is melting, the sea ice is disappearing, and the glaciers are retreating. The elastic response of the changes in the glacier affects the earth crust. Locally on Greenland or Svalbard the uplift can reach several centimetres per year. The ice melting in Greenland is so large that it affects the land uplift in large parts of the Northern hemisphere.

The geodetic observatory in Ny-Ålesund is a key station in the global geodetic network. It is the northern most fundamental station, containing all the main geodetic techniques and important for the realisation of the ITRF. However, its stability has been questioned. The observatory experience variations in the uplift on seasonal, inter-annual, decadal and longer timescales. The uplift for a moving window of 5-years periods has increased from below 6 mm/yr in the 1990 to more than 12 mm/yr today. This has challenged the realisation and stability of global and regional reference frames. 

We have modelled the elastic response of glacier changes based on various glaciological sources. These results will be presented. We will in particular compare the elastic uplift with geodetic time-series from Ny-Ålesund and other GNSS in Svalbard and discuss how this could affect reference frames. Could for instance the VLBI scale issue in ITRF2020 be related to glacial changes? 

We found that the variations in the uplift can be explained by the glacier changes and close to 50% of the VLBI scale drift can be explained by glacier related accelerating uplift. 

How to cite: Kierulf, H. P.: Glacial induced variations in the uplift – a challenge for the reference frame , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9527, https://doi.org/10.5194/egusphere-egu24-9527, 2024.

EGU24-10560 | Orals | G2.2

ITRF2020 Updates : motivation and expectation 

Zuheir Altamimi, Paul Rebischung, Xavier Collilieux, Laurent Métivier, and Kristel Chanard

The ITRF2020 marked considerable innovations compared with previous versions of the ITRF, by modeling nonlinear station motions (seasonal signals and Post-Seismic Deformation –PSD– for sites subject to major earthquakes). It also confirmed the stability of the CM-based frame origin, as sensed by SLR, at the level of or better than 5 mm and 0.5 mm/yr. For the first time in the ITRF history, the scale agreement between SLR and VLBI solutions submitted to ITRF2020 is at the level of 0.15 ppb (1 mm at the equator) at epoch 2015.0, with no drift. Motivated by these results, and for a number of reasons that will be exposed in this paper, the ITRS Center decided to regularly (yearly) update the ITRF2020, with a first update expected to be released around mid-2024. Depending on the input data availability that will be submitted by the four technique services, we expect some preliminary results that will be discussed in this presentation. Emphasis will be given to answer some critical questions, such as: how does the VLBI scale drift evolve after 2021.0? Do the SLR and VLBI scales remain in agreement? Does the SLR origin drift or not from the ITRF2020 origin after 2021.0?

How to cite: Altamimi, Z., Rebischung, P., Collilieux, X., Métivier, L., and Chanard, K.: ITRF2020 Updates : motivation and expectation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10560, https://doi.org/10.5194/egusphere-egu24-10560, 2024.

EGU24-10691 | ECS | Orals | G2.2

Identification of system-specific observation errors for SLR and VLBI telescopes at GOW 

Julian Zeitlhöfler, Mathis Bloßfeld, Alexander Neidhardt, and Johann Eckl

The observations of the four space-geodetic techniques (GNSS, SLR, VLBI, DORIS) are used for the computation of the International Terrestrial Reference Frame (ITRF) and for the realisation of its geodetic datum as well as (except VLBI) for the precise orbit determination of Earth-observing satellites. The ITRF itself is fundamental for a broad variety of scientific and societal applications such as Earth monitoring and positioning, relevant for satellite companies, logistics, and finally new techniques like autonomous driving. However, all four techniques still suffer from unknown systematic measurement or modelling errors which makes the estimation of bias parameters inevitable.

The Geodetic Observatory Wettzell (GOW), Germany, with its unique and ideal test environment comprising multiple GNSS antennas, three VLBI antennas, two SLR telescopes, a DORIS beacon, and numerous other sensor systems provides the opportunity to systematically identify, quantify, understand, and compensate system-specific measurement errors. The installation of a so-called common target (CT) in 2017 and the realisation of a common clock (CC) enables a profound analysis of space-geodetic measurements. The CT is connected to the clocks of the space-geodetic techniques via delay-compensated fibre links which allows so-called ‘closure in time’ experiments.

Within the recently established DFG research unit ‘Clock Metrology: Time as a New Variable in Geodesy’, one project at DGFI-TUM focuses on the investigation of time-related and technique-specific errors using ‘closure in time’ experiments at the GOW. Therefore, completed experiments involving the CT are analysed and enhanced experiments will be planned and conducted. With the aid of the CC, the source of present measurement discrepancies will be investigated and resolved. We present the current state of our work with the main focus on the analysis of VLBI and SLR observations of the two SLR and three VLBI systems at GOW.

How to cite: Zeitlhöfler, J., Bloßfeld, M., Neidhardt, A., and Eckl, J.: Identification of system-specific observation errors for SLR and VLBI telescopes at GOW, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10691, https://doi.org/10.5194/egusphere-egu24-10691, 2024.

EGU24-11287 | Orals | G2.2

Accurate Long Term Height Determination at SLR Stations 

Peter Dunn, Van Husson, and Christopher Szwec

Recent advances in SLR data analysis are described in ‘The ILRS contribution to ITRF2020’, Pavlis and Luceri (2022). Improved vertical resolution can now complement the more easily resolved horizontal motion.
We examine the emerging results from ITRF2020 and prioritize the most accurate geodetic products.
Height variations at SLR stations in tectonically stable regions of Australia and North America exhibit steady and consistent height rates. 
Robust long-term vertical motion models also enable precise monitoring of behavior at higher frequencies: annual, tidal, and diurnal. Tracking operation procedures have been implemented to reduce and monitor ranging measurement accuracy. Comparisons of the vertical signals in SLR, VLBI, DORIS and GNSS systems allow robust accuracy monitoring at co-located stations.
Data handling techniques are outlined to enhance the isolation of the geodetic signals and enable their application to Earth and Ocean Model development 

How to cite: Dunn, P., Husson, V., and Szwec, C.: Accurate Long Term Height Determination at SLR Stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11287, https://doi.org/10.5194/egusphere-egu24-11287, 2024.

The future Atomic Clock Ensemble in Space (ACES) mission of the European Space Agency (ESA) will address the development of a time transfer concepts for tomorrow's technologies. The ACES configuration includes a new generation of high-precision atomic clocks, a microwave link terminal (MWL) on the ground and on the satellite, and an optical detector and reflector also on the satellite. Due to the fact, that the official launch date is in 2025, there is a lack of real observation data. For that, a full-scale simulation software has been implemented. The simulator produces MWL code and phase observations in downlink and uplink, as well as one- and two-way laser observations. To analyse the efficiency of a time transfer concept before launch, we used the simulator to generate a data set of 100 passes during July 2021.
Investigations based on this data set showed that the colocation of the high-precision geodetic observation techniques of the ACES mission could better separate the individual error contributions of a measurement. Due to the colocation of optical and microwave-based geodetic observation techniques, also error parameters like orbit and troposphere correction can be estimated together. Estimation of a common troposphere for all observation techniques, improves the accuracy of the determination of the offset between ground and ACES clocks. Our further investigations focus on the common troposphere estimation of multi-color optical observations, together with microwave-based observations and the effects of different weighting methods. An extension to a network of ground stations will demonstrate the advantages of the ACES mission for synchronizing multiple ground clocks. The colocation of different high-precision geodetic observation techniques and estimation of common parameters will benefit timing and ranging applications and fundamental physics studies.

How to cite: Vollmair, P., Schlicht, A., and Hugentobler, U.: Simulating the Colocation of High-Precision Microwave and Optical Techniques for Tropospheric Parameter Determination in Context of the ACES Mission., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11608, https://doi.org/10.5194/egusphere-egu24-11608, 2024.

EGU24-13398 | Orals | G2.2

Estimating Euler pole parameters for NATRF2022 

Mohammad Ali Goudarzi and Michael Craymer

Canada and the US are collaboratively implementing a new dynamic, geometric reference frame for North America (NA) known as the North American Terrestrial Reference Frame of 2022 (NATRF2022). It will be a plate-fixed reference frame based on ITRF2020/IGS20 that is kept aligned to the NA tectonic plate using an Euler pole rotation. We have estimated Euler pole parameters (EPP) for NA based on the spherical model of Earth using different sets of stations and compared our results to other sources, including those recently obtained by Kreemer (2023) under contract to the U.S. National Geodetic Survey. The velocity field used for our analyses are those from Kreemer (2023) that were obtained for 4274 stations using GipsyX precise point positioning in the IGb14 reference frame and corrected for non-tidal and atmospheric loading as well as hydrological loading obtained from GRACE. A challenge for our analyses is the impact of ongoing glacial isostatic adjustment (GIA) on the horizontal velocities which can bias the EPP estimation. To mitigate such biases, we have used the horizontal component of the ICE-6G model to remove the GIA effect from the velocity field. Following Kreemer (2023),  we have determined a small set of homogeneously distributed stations that closely reproduce Kreemer’s EPP estimates. We also considered that users of the new reference frame would prefer that the intra-plate motions be minimized across the entire continent for conventional use and have therefore computed the best fitting EPP that minimizes the overall intra-plate motions across the entire continent.  In addition, we chose only good stations that met certain statistical criteria for the residuals and had stable monumentation, preferably anchored to bedrock. Finally, we compare the EPP estimates for all these sets of stations with and without GIA removed using statistical tests and descriptive statistics. The differences in resulting intra-plate velocities across the continent are also discussed for each test.

How to cite: Goudarzi, M. A. and Craymer, M.: Estimating Euler pole parameters for NATRF2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13398, https://doi.org/10.5194/egusphere-egu24-13398, 2024.

EGU24-13524 | Orals | G2.2

A New Realization of the Terrestrial Reference Frame: Combining GPS, SLR and VLBI at the Observation Level from 2010–2022 

Bruce Haines, Willy Bertiger, Shailen Desai, Matthias Elmer, Michael Heflin, Da Kuang, Gabor Lanyi, Mark Miller, Chuck Naudet, Athina Peidou, Paul Ries, Alex Tolstov, Xiaoping Wu, and Nikki Zivkov

We describe the development and assessment of a new terrestrial reference frame (TRF) based on combining GPS, SLR and VLBI at the observation level over the period 2010–2022. Included in the solution, in addition to station coordinates and precise orbit solutions for all participating satellites, are Earth orientation parameters (EOP) and low-degree zonal coefficients (J2 and J3) of the geopotential. The overall solution concept grew from earlier efforts to realize a TRF using GPS data alone, capitalizing on GPS receivers on the ground and in low-Earth orbit (LEO). Here we add observations from both the SLR and VLBI techniques, which provide the foundation for traditional realizations of the TRF.

In linking the GPS and SLR techniques, our approach dispenses with traditional ground survey ties, relying exclusively on space ties from the GRACE and Jason LEO missions. In addition to SLR from these satellites, we include observations from the dedicated LAGEOS satellites, which prove particularly important for recovering low-degree gravity. A major evolution of our approach is the addition of VLBI at the observation level. Lacking a robust tie in Earth orbit for VLBI observations, we apply as constraints the published ground survey ties to nearby GPS stations, enforcing inclusion of the corresponding tracking data in the solutions. The VLBI effort is in the exploratory phase, and further tuning of the strategy is needed to better exploit collocations with both GPS and SLR. About 40% of the participating solution arcs (spanning 2010–2022) now include VLBI and support accurate recovery of UT1 as part of the EOP solution.

Though the resulting TRF solution is based on only 12.6 years of data, it is competitive with ITRF2020 in terms of fundamental frame parameters (origin and scale) and their temporal evolution, both linear and seasonal. The relative rates of origin (3D) and scale (at Earth's surface) are 0.2 mm yr-1 and 0.1 mm yr-1 respectively. Absolute scale (at epoch 2015.0) and 3D origin both differ by 2 mm. One advantage of our technique is that precise orbit solutions for both GRACE and Jason missions, defined in the realized TRF, are byproducts of the overall solution. We use the Jason orbit solutions to characterize the impact of contemporary TRF errors on sea level variations (both global and regional) and discuss the implications of these results.

How to cite: Haines, B., Bertiger, W., Desai, S., Elmer, M., Heflin, M., Kuang, D., Lanyi, G., Miller, M., Naudet, C., Peidou, A., Ries, P., Tolstov, A., Wu, X., and Zivkov, N.: A New Realization of the Terrestrial Reference Frame: Combining GPS, SLR and VLBI at the Observation Level from 2010–2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13524, https://doi.org/10.5194/egusphere-egu24-13524, 2024.

Multi-station (or time series) stacking is a fundamental task in the realization of a terrestrial reference frame (TRF), which is, however, rank-deficient in nature due to the arbitrarily selected target frame. In practice, such a model is approximated as a linear form and the classical free network theory is applied. It is known that the one-step adjustment only works in cases where the nonlinearity (measured by curvature) is moderate, and the initial point is very good; for TRF, it requires the deformable networks with a small enough time span for the network shape to be nearly unaltered. However, these assumptions can be nullified for the cases such as large time span and the integration of some local survey results. To address these limitations, we propose to solve the geodetically meaningful and numerically exact least-squares (LS) solution for the multi-station stacking model. The contributions are summarized as follows:

  • The original nonlinear LS objective for the multi-station stacking model is investigated and its characteristics are analyzed;
  • The nonlinear Baarda’s S-transformation is formulated for such a problem, which transforms different LS solutions that share the same network configuration;
  • Two ways to obtain the geodetically meaningful solution are proposed, i.e., the minimally-constrained solution and the nearest-solution, where the latter originates from the inner-constraint solution in the linear case.
  • The iterative schemes to obtain the two types of solutions are derived, which are shown to be essentially the truncated Gauss-Newton method. In addition, some techniques such as finite differences are employed to enhance numerical stability.

The developed theory is verified by the real examples.

How to cite: Hu, Y., Fang, X., and Zeng, W.: Nonlinear least-squares solution for the multi-station stacking problem in realizing a terrestrial reference frame, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14503, https://doi.org/10.5194/egusphere-egu24-14503, 2024.

EGU24-14591 | Orals | G2.2

IDS contribution to the first update of the ITRF2020 

Guilhem Moreaux, Frank Lemoine, Hugues Capdeville, Petr Štěpánek, Michiel Otten, Samuel Nahmani, Arnaud Pollet, and Patrick Schreiner

In anticipation of the first update of the 2020 realization of the International Terrestrial Reference Frame (ITRF2020), the International DORIS Service (IDS) Combination Center is participating in the estimation of DORIS stations positions/velocities as well as Earth Orientation Parameters (EOPs), using DORIS data. These computations are based on the latest weekly multi-satellite series from all four IDS Analysis Centers and two IDS Associated Analysis Centers, from January 2021 to December 2023.

The primary objectives of this study are to analyze the DORIS contribution to this first update of the ITRF2020 in terms of: (1) geocenter and scale solutions, (2) station positions and week-to-week repeatability, and (3) Earth Orientation Parameters (EOPs).

Comparisons with the IDS 19 series time extension (contributing to ITRF2020) will highlight the benefits of the new models, including the latest DORIS missions (e.g. HY-2C, HY-2D, Sentinel-6A MF), and the addition of two new IDS contributors. Additionally, this study will assess the impact of new strategies designed to mitigate perturbations caused by the South Atlantic Anomaly (SAA) on certain DORIS missions.

How to cite: Moreaux, G., Lemoine, F., Capdeville, H., Štěpánek, P., Otten, M., Nahmani, S., Pollet, A., and Schreiner, P.: IDS contribution to the first update of the ITRF2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14591, https://doi.org/10.5194/egusphere-egu24-14591, 2024.

EGU24-16188 | Orals | G2.2

Copernicus POD Service – Impact of ITRF2020 Modelling Changes on Orbit and Validation Results 

Miguel Angel Muñoz de la Torre, Carlos Fernández, Marc Fernández, Heike Peter, Pierre Féménias, and Carolina Nogueira Lodd

The new ITRF20 includes a geocenter motion (GCM) model and seasonal station corrections, both with annual and semi-annual periods. The GCM model is recommended to be applied when processing space-geodetic observation data and the seasonal station corrections should be applied if no non-tidal modelling is applied for the station coordinates. In the case of the Copernicus Precise Orbit Determination (CPOD) Service this applies to the processing of GNSS data of the Sentinel satellites for precise orbit determination (POD) and to the processing of Satellite Laser Ranging (SLR) tracking data for validation of the estimated Sentinel orbits.

The CPOD Service delivers, as part of the Ground Segment of the Copernicus Sentinel-1, -2, -3, and -6 missions, orbital products and auxiliary data files for their use in the corresponding Payload Data Ground Segment (PDGS) processing chains at ESA and EUMETSAT, and to external users through the newly available Copernicus Data Space Ecosystem (https://dataspace.copernicus.eu/). It generates routinely several types of orbital products for Sentinel-1, -2, -3 and -6: predictions, near-real time (< 10 min), short-time critical (< 1.5 days) and non-time critical (< 25 days).

The POD quality control within the service is based on comparing the CPOD orbit products to orbit solutions provided by members of the accompanying Copernicus POD Quality Working Group (QWG). A combined orbit generated by CPOD from all available orbit solutions serves as reference for the comparisons. The new ITRF20 modelling opens the door to different Centre-of-Network (CoN) or Centre-of-Mass (CoM) frame realisations, so in order to avoid inconsistencies between the solutions when doing the combination and comparisons, special care must be taken.

This study aims to analyse the impact of the new ITRF20 GCM model and the seasonal station corrections on the CPOD Service products. Sentinel orbit comparisons and the corresponding processing metrics are analysed when applying the GCM model or not, with a focus on the geocenter motion modelling used by the different CPOD QWG centres.

In the SLR validation, station range biases are routinely estimated as part of the residuals analysis. Preliminary results reveal that the estimates of these range biases show smaller seasonal variations when applying the seasonal station corrections. Detailed analyses will be shown and discussed.

How to cite: Muñoz de la Torre, M. A., Fernández, C., Fernández, M., Peter, H., Féménias, P., and Nogueira Lodd, C.: Copernicus POD Service – Impact of ITRF2020 Modelling Changes on Orbit and Validation Results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16188, https://doi.org/10.5194/egusphere-egu24-16188, 2024.

EGU24-16881 | Posters on site | G2.2

ITRF2020 usage and maintenance in a global dense network for commercial applications 

Francesco Matonti, Adam Miller, and Joanna Wnuk

Absolute positioning is a requirement for public and private GNSS networks with a global coverage due to integrations of positioning solutions into mid-tier and mass-market solutions, such as autonomous driving systems, together with an ever-increasing demand for global positioning applications. 
Global correction service providers need to support and deliver the service in a global reference frame whilst still maintaining the local (regional) reference frames. 

A quality check of the RINEX data from the HxGN SmartNet GNSS Network is performed before a computation of a daily solution, which is calculated using precise orbits and following the guidelines of the EPN Analysis Centres and Bernese GNSS Software (Dach, 2015). 

The non-linear station movements are checked to assess the stability of each station of the network. In case of a position change, a coordinate update is evaluated and applied. A periodic computation in ITRF2020 is also performed to update the coordinates in the GNSS network. A regular update and maintenance of the coordinates of the stations in the network is crucial to maintain the high precision of the correction service. The HxGN SmartNet GNSS network consists of more than 5300 GNSS reference stations and is used to provide RTK corrections at global and regional scale. Additionally, it provides support for PPP and SSR based solutions. The ITRF2020 coordinates of some sites are presented and discussed to evaluate examples of non-linear motion and what solution has been adopted to keep a homogeneous set of coordinates, whilst also considering the increasing impact of ionospheric activity. 

KEYWORDS: GNSS reference station network, Bernese GNSS 5.2, Leica CrossCheck, Leica GNSS Spider, HxGN SmartNet 

References: 
Dach, R., S. Lutz, P. Walser, P. Fridez (Eds); 2015: Bernese GNSS Software Version 5.4. User manual, 
Astronomical Institute, University of Bern, Bern Open Publishing. DOI: 10.7892/boris.72297; ISBN: 978-3-906813-05-9. 

 

How to cite: Matonti, F., Miller, A., and Wnuk, J.: ITRF2020 usage and maintenance in a global dense network for commercial applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16881, https://doi.org/10.5194/egusphere-egu24-16881, 2024.

EGU24-16905 | ECS | Posters on site | G2.2

Verifying the impact of additional breaks in station coordinates on VLBI scale drift 

Lisa Kern, Hana Krasna, Johannes Böhm, and Axel Nothnagel

With the establishment of the International Terrestrial Reference Frame 2020 (ITRF2020), investigations revealed an unexpected positive VLBI scale drift after about 2014.0. Given the crucial role of Very Long Baseline Interferometry (VLBI) in determining the ITRF scale, this peculiar behavior raises concerns. Within the VLBI community, several studies have been conducted to decipher the cause behind this pattern. A recent study by the Onsala Space Observatory (OSO) explored the introduction of additional discontinuities in the station positions of NYALES20 and/or in the positions of MATERA, WETTZELL, and ONSALA60 due to repairs or replacements. They found that the introduction significantly mitigated the scale drift with respect to ITRF2020.

Utilizing our newest state-of-the-art combination software, VieCompy, developed at the Vienna Center for VLBI, we independently assess the impact of these additional breaks on session-wise estimated scale through a combination of VLBI sessions at the normal equation level.

How to cite: Kern, L., Krasna, H., Böhm, J., and Nothnagel, A.: Verifying the impact of additional breaks in station coordinates on VLBI scale drift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16905, https://doi.org/10.5194/egusphere-egu24-16905, 2024.

EGU24-17616 | ECS | Posters on site | G2.2

Determination of physical heights via time transfer  

Klarissa Emma Lachmann and Jürgen Müller

We present a project of the research unit (RU) 'TIME' (Clock Metrology: A Novel Approach to TIME in Geodesy) which aims to determine gravity potential or height differences between remote sites by comparing optical clocks. A strontium optical lattice clock at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig will be connected with the German Research Centre for Geosciences (GFZ) in Potsdam through a delay-compensated optical fiber. Then, optical time transfer is carried out between the geodetic observatories in Potsdam and Wettzell (where a second optical clock will be operated) via the Atomic Clock Ensemble in Space (ACES) using the Satellite Laser Ranging (SLR) telescopes. The key innovation is using time transfer, not frequency and optical free-space links over an extended period to determine physical height differences. Challenges include clock/link variations, atmospheric effects, visibility constraints and data gaps, etc. We investigate the major error sources and apply corrections like tidal effects. This approach showcases accurately transferring physical heights via time transfer and demonstrates the RU’s time concept for integrating geometric and physical heights in future height systems, especially for Global Geodetic Observing System (GGOS) core stations like the Geodetic Observatory Wettzell (GOW).

In this presentation, we introduce the principles, special properties and challenges of this specific measurement scenario. We also provide preliminary numbers for the expected accuracies of the various components and the resulting height difference based on simulations.

We acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 490990195 – FOR 5456.

How to cite: Lachmann, K. E. and Müller, J.: Determination of physical heights via time transfer , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17616, https://doi.org/10.5194/egusphere-egu24-17616, 2024.

EGU24-17665 | Orals | G2.2

A Global Collaboration to Enhance GNSS Receiver Antenna Calibration: The IGS Antenna Ring Campaign 

Tobias Kersten, Andria Bilich, Igor Sutyagin, and Steffen Schön

Achieving a high-precision geodetic spatial reference depends on a thorough understanding of the equipment-specific sources of error of phase centre corrections (PCCs) of Global Navigation Satellite System (GNSS) receiver antennas. GNSS station operators and network analysers are constantly challenged regarding consistent PCCs, such as in the latest IGS Repo3 project. The challenges are, on the one hand, that not for all antennas in the network multi-GNSS calibrations are available. On the other hand, not all antennas are individually calibrated, so that type mean combinations with individual PCCs have to be used.

Even small differences between PCCs can significantly affect position accuracy, troposphere modelling, and GNSS time and frequency transfer. Such deviations manifest differently depending on used hardware, software, and data processing approach. A generalised and easily accessible benchmark for assessing the quality of PCCs remains difficult to find. There is a lack of easy-to-apply and common quality assessments of PCCs when comparing individual calibrations versus a type mean and results from the various calibration facilities and calibration methods among each other.

In response to this challenge, a global initiative involving nine calibration organisations has launched a comprehensive ring calibration campaign. By sharing six constructionally different antenna samples for calibration and presenting the subsequent results, this collaborative effort aims to enhance (1) the consistency of calibration methods and facilities, (2) develop a validation strategy, and (3) provide insights into the stability of receiver antenna calibrations.

This contribution provides an overview of the current status of this campaign, initiated one and a half years ago, outlines the calibration and evaluation concept for carrier phase patterns. First initial results from consulting contributors are presented and the roadmap towards a standardised, robust quality assessment framework for PCCs will be covered.

How to cite: Kersten, T., Bilich, A., Sutyagin, I., and Schön, S.: A Global Collaboration to Enhance GNSS Receiver Antenna Calibration: The IGS Antenna Ring Campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17665, https://doi.org/10.5194/egusphere-egu24-17665, 2024.

EGU24-19608 | ECS | Orals | G2.2

GNSS for geodynamics in Antarctica: Sensitivity to reference frame realizations 

Karl Heidrich-Meisner, Eric Buchta, and Mirko Scheinert

Determining time series of bedrock motion from global navigation satellite systems (GNSS) in Antarctica is one method to investigate geodynamical processes (e. g. glacial isostatic adjustment (GIA)). To achieve coordinate time series with the highest possible precision, a stable realization of the International Terrestrial Reference Frame (ITRF) is a crucial precondition. Regional networks of GNSS stations have the advantage of exhibiting small common mode errors and allowing to infer accurate velocity estimates. However, to achieve high consistency, it is necessary to base the analysis on a global network of International GNSS Service (IGS) stations, constraining them to their ITRF positions. Various approaches can be found in the literature on how the global solution is constrained to the ITRF and how the regional solution is transformed to the global solution. These approaches have different effects on the resulting time series and inferred parameters, e. g. absolute coordinates, linear trends, and noise properties. In this study, approximately 30 Antarctic GNSS stations are processed together with a global GNSS network of overall 200 IGS stations. We investigate different approaches to realize the ITRF and discuss the inferred results. To be consistent w. r. t. the general processing, we use a consistent set of GNSS observation data, GNSS products (e. g. orbit corrections), and apply the Bernese GNSS Software v5.4. In this way, the residuals between the different coordinate time series can be assumed to be due to the differences in reference frame realization. In our time series analysis, we put particular emphasis on linear trends because these are most important for GIA studies.

How to cite: Heidrich-Meisner, K., Buchta, E., and Scheinert, M.: GNSS for geodynamics in Antarctica: Sensitivity to reference frame realizations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19608, https://doi.org/10.5194/egusphere-egu24-19608, 2024.

EGU24-19991 | Orals | G2.2

ILRS analysis activities after the adoption of ITRF2020 

David Sarrocco, Cinzia Luceri, Antonio Basoni, Mathis Bloßfeld, Keith Evans, Magda Kuzmicz-Cieslak, Frank Lemoine, and Giuseppe Bianco

The contribution of the International Laser Ranging Service (ILRS) to the most recent realization of the International Terrestrial Reference System (ITRS) was the result of an analysis strategy with two major modifications compared to the operational products: a modeling for stations long-term systematic errors (biases reported in the ILRS Data Handling File) and an updated model of the target signature error (satellite Centre of Mass model). Both refined models were used as input information for the ILRS contribution to the ITRF2020 (International Terrestrial Reference Frame 2020).

Thereafter, the ILRS Analysis Standing Committee (ASC) focused its effort on implementing the new reference frame in its operational products, define a strategy to improve the ongoing monitoring of the systematic errors, compute the ILRS contribution to the planned ITRF2020 update, and to include LARES-2 among the considered satellites for the operational products.

The ILRS ASC implemented the ITRF2020/SLRF2020 into all its official operational products (TRF, Earth Orientation Parameters, predicted and combined satellite orbits) and its impact was evaluated. The operational products benefit from the continuous monitoring of the station systematic errors and the frequent updates of the Data Handling File whenever a significant change in the station systematic error is observed. In the future, a change-point detection algorithm, jointly estimating the times and the number of discontinuities, will be implemented to detect potential new discontinuities in the range bias series.

The inclusion of LARES-2 among the satellites whose data are operationally analyzed will furtherly increase the robustness of the estimated parameters. Finally, the ILRS ASC activities include the benchmarking of a new analysis center (CNES) which will formally begin its own contribution in 2024.

How to cite: Sarrocco, D., Luceri, C., Basoni, A., Bloßfeld, M., Evans, K., Kuzmicz-Cieslak, M., Lemoine, F., and Bianco, G.: ILRS analysis activities after the adoption of ITRF2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19991, https://doi.org/10.5194/egusphere-egu24-19991, 2024.

EGU24-20115 | ECS | Posters on site | G2.2

Gauging the Sensitivity of GNSS for Resolving Vertical Land Motion Over Europe 

Roland Hohensinn and Yehuda Bock

Through a parametric fit to daily vertical displacement time series from European Permanent GNSS stations, we conducted a statistical sensitivity analysis focusing on Vertical Land Motion (VLM) – specifically, station velocity (linear trend). We compared two independent corrections to raw observed displacements: non-tidal atmospheric, oceanic, and hydrological loading displacements, as well as a correction for common mode errors (CME). Our methodology involved selecting the most realistic stochastic models based on information criteria, analyzing GNSS-observed displacements and identifying discrepancies with loading model predictions. We also employed restricted maximum likelihood estimation (RMLE) to mitigate low-frequency noise biases, enhancing the reliability of velocity uncertainty estimates.

Our results demonstrate that 1) an autoregressive, power-law, and white noise model combination is preferred for uncorrected GNSS VLM data, 2) when compared to the corrected cases, this model choice yields lower improvement rates in trend sensitivity than previously reported, and 3) RMLE reveals that for many stations, noise is optimally modeled by a combination of random-walk, flicker-noise, and white noise. We report median trend sensitivity and detection rates of about 0.5 mm/year (with best results for the CME-corrected case), approaching the GGOS goal of a 0.1 mm/year precision, crucial for sea level studies and other applications.

How to cite: Hohensinn, R. and Bock, Y.: Gauging the Sensitivity of GNSS for Resolving Vertical Land Motion Over Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20115, https://doi.org/10.5194/egusphere-egu24-20115, 2024.

Based on approximately 15,000 global station coordinates and velocity values, the plate model PB2002_CASM was constructed using actual measured velocity field analysis and supervised clustering analysis based on global PB2002 plate boundary divisions. For plates with more stations, mathematical interpolation algorithms were applied to calculate grid velocity values, including inverse distance weighting, Euler vector method, finite element interpolation method, least squares configuration method, kriging interpolation method, and linear interpolation based on triangulation. For plates with sparse or missing stations, such as in the ocean, singular spectrum analysis was used to extract trend components and obtain station motion speeds, and the PB2002_CASM plate motion model was used to calculate grid velocity values. There are a total of 61,560 1°×1° grids within the global longitude range of -179° to 180° and latitude range of -85° to 85°, which were mathematically interpolated to form 20,071 grid points. The PB2002_CASM plate motion model was used to calculate the velocity of 40,624 1°×1° grid points. The accuracy of the calculated velocity was validated, with a deviation within 1mm, achieving 82% and 89% accuracy in the E and N directions, respectively.

How to cite: Xu, Y.: Global digital plate model PB2002_CASM and 1°×1° grid velocity field construction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20392, https://doi.org/10.5194/egusphere-egu24-20392, 2024.

EGU24-584 | ECS | Posters on site | G2.3

Estimation of the potential value of given sea segments for certain time periods 

Kamilla Cziraki and Gábor Timár

Since Gauss (1828), the theoretical shape of the Earth has been defined as a distinct potential surface of the gravity field that best fits the sea level at rest. The gravity field is described as a sum of spherical function series whose coefficients are calculated from satellite and in situ gravity measurements. Sea levels have been measured in harbours since the 18th century using mareographs, and are now often supplemented by data from nearby GNSS stations.

In our work, we developed a program to determine the potential value for a given height from mareograph data. This allows us to use the data available from the stations to determine what this value was in an earlier period as well. Furthermore, if more than one dataset is available for a particular sea segment, the average value for that sea over a certain period can be given.

We tested the method in the Japanese Sea, where we had data from 9 stations. These were averaged every 5 years and the resulting data were used to calculate the potential values, as well as the average value for the sea segment for the latest period 2016-2020. In the future, we plan to use this method to perform such calculations for more sites, which would also provide information on the effects of tectonics and global sea level change.

Gauss, C. F. (1828) Bestimmung des Breitenunterschiedes zwischen den Sternwarten von Göttingen und Altona. Vandenhoeck und Ruprecht, Göttingen, 84 p.

Supported by the ÚNKP-23-1 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund.

How to cite: Cziraki, K. and Timár, G.: Estimation of the potential value of given sea segments for certain time periods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-584, https://doi.org/10.5194/egusphere-egu24-584, 2024.

EGU24-1314 | Posters on site | G2.3 | Highlight

GGOS Portal - The future Metadata Platform for Geodetic Data - Feasibility Study and Perspectives 

Martin Sehnal and Lena Steiner

The services of the International Association of Geodesy (IAG) provide very important and valuable geodetic data, information, and data products that are increasingly relevant for Earth system research, including monitoring of global change phenomena and a wide range of diverse applications such as satellite navigation, surveying, mapping, engineering, geospatial information systems, and so on.

Currently, it is difficult for many people to obtain an overview of all available geodetic products and data. The Global Geodetic Observing System (GGOS) of the IAG aims to fill this gap by developing the GGOS-Portal (ggos.org/portal), which will serve as a unique search and access point (one-stop shop) for geodetic data and products. Data and products will be described by rich metadata and remain physically located at their originating data centers of each contributing IAG service and other data providers. With this future platform, GGOS will contribute to increase the visibility of geodetic data for scientific research and to make other disciplines and the society aware of geodesy and its beneficial products.

Several software packages are available for the realization of such a metadata platform. Two of them are particularly suitable for this purpose: GeoNetwork and CKAN. Based on the community survey conducted in spring 2023, a requirements profile for the GGOS portal was drawn up as part of a feasibility study and compared with the tested functionalities of the two software packages. A particular focus was on testing the metadata harvesting function.

How to cite: Sehnal, M. and Steiner, L.: GGOS Portal - The future Metadata Platform for Geodetic Data - Feasibility Study and Perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1314, https://doi.org/10.5194/egusphere-egu24-1314, 2024.

The accuracy and robustness of the International Terrestrial Reference Frame lies in the combination of the four space-geodetic techniques. Network imbalances, partly caused by geography and land coverage strongly favour the northern hemisphere in the number of observations and, to a less clear extent, in accuracies. This is evident in large tie discrepancies, for example in Katherine and Yarragadee in Australia, where results from the various techniques differ to a significant degree.

In this contribution we investigate the hypothesis that those discrepancies stem from deficiencies in the global combination of the various techniques, rather than from the individual observations. Specifically, we show that a regionally processed VLBI dataset is superior in its local station coordinate repeatabilities than when processed as part of the global network.

The Australian AuScope VLBI network has been operating for over 10 years, delivering higher cadence and partly more precise observations than the regular global IVS observations. It is our aim here to investigate whether a local comparison between VLBI and GNSS data in Australia can shed light into the mystery of significant tie discrepancies that are currently present in the ITRF for this region.

How to cite: McCallum, L.: High-cadence VLBI in Australia for an improved TRF in the southern hemisphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2949, https://doi.org/10.5194/egusphere-egu24-2949, 2024.

EGU24-3287 | ECS | Orals | G2.3

Optimal observing strategy of GENESIS in geodetic VLBI experiments  

David Schunck, Lucia McCallum, and Guifré Molera Calvés

One of the major deficiencies in the realization of the International Terrestrial Reference Frame (ITRF) stems from the combination of the four space-geodetic techniques, that are contributing: Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), and Doppler Orbitography and Radiopositioning Integrated by Satellites (DORIS). The GENESIS satellite mission, a component of the European Space Agency’s (ESA) FutureNAV program, will address this problem. Scheduled for launch in 2027, the GENESIS satellite embodies a dynamic space-geodetic observatory, equipped with instruments encompassing all four space-geodetic techniques. The mission’s objective is to facilitate the in-orbit combination and co-location of these techniques in space, known as space ties. It is not yet known how GENESIS will be implemented in geodetic VLBI operations. In this talk, we will present a dedicated simulation study of VLBI observations to the GENESIS satellite. We look at the realistic observability given current and foreseeable antenna networks and session cadence. We schedule and simulate VLBI observations to the GENESIS satellite to investigate the accuracy with which VLBI antenna positions of a global network can be derived. In addition to the most common VLBI error sources, troposperic delays, clock inaccuracies, and white noise, we simulate satellite orbital errors. The observations to the GENESIS satellite are scheduled within regular, geodetic experiments. We compare different schedules varying the amount of time that is dedicated to observe the satellite. We analyse how incorporating these observations reduces the amount of time quasar sources are observed and, consequently, how fundamental geodetic VLBI observables, i.e. Earth Orientation Parameters (EOPs), are affected. We try to answer the question whether it would be necessary to include observations to the GENESIS satellite outside of regular geodetic experiments in the form of dedicated GENESIS sessions. The fact that VLBI is organized in sessions instead of continuous observing further raises the question to assess a minimal mission lifetime to achieve desired accuracies.

How to cite: Schunck, D., McCallum, L., and Molera Calvés, G.: Optimal observing strategy of GENESIS in geodetic VLBI experiments , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3287, https://doi.org/10.5194/egusphere-egu24-3287, 2024.

EGU24-5776 | Orals | G2.3

The Absolute Gravity Reference Network of Italy 

Riccardo Barzaghi, Federica Riguzzi, Filippo Greco, Giovanna Berrino, Alessandro Germak, and Augusto Mazzoni

The project for realizing the reference network for absolute gravity in the Italian area is presented. This fundamental infrastructure is the general frame for all the scientific and technological activities related to the gravity field in Italy. The project is in line with the actions promoted by the International Association of Geodesy that during its 2015 General Assembly approved a resolution on the establishment of the new global gravity network the so-called International Terrestrial Gravity Reference System/Frame that will replace IGSN71.

The selection of the absolute gravity station sites in Italy has been performed either taking into account the existing absolute gravity stations and to have a homogeneous distribution of points. An initial set of 30 stations has been defined over the peninsular part of Italy and the two islands of Sicily and Sardinia. Particularly, the GGOS core station of Matera (the Agenzia Spaziale Italiana Center for Space Geodesy “Bepi” Colombo) is one of the network points as required in the documents of the GGOS-Bureau of Networks and Observations. Thus, this station will provide one link between the Italian national absolute gravity network and the GGOS observation system of IAG.

The project is now ongoing and will close at the beginning of 2025.

As required by the international standards on gravity measurements (https://www.bipm.org/documents/20126/41442296/CCM++IAG+Strategy+for+Metrology+in+Absolute+Gravimetry/7f9bc651-a2b6-08cc-7bba-f63b0a7e9765), the absolute gravimeters used in the measurements have been compared with absolute gravimeters that participated into international comparison campaigns in order to ensure the measurements traceability.

Furthermore, absolute gravity measurements have been supplemented with direct measurements of the local value of the vertical gravity gradient, in order to reduce to the ground reference level the absolute values measured by different instruments at different heights. The gravity field campaigns will be assisted by topographic survey campaigns. This will allow a precise georeferencing (of the order of 12 cm) of the gravity stations that will be so framed to the current ITRF.

The collected data will be then validated and reduced following the internationally accepted standards and finally published through a dedicate web page of the project. These data will also be sent for storage to the absolute gravity database maintained by the Bureau Gravimétrique International/Bundesamt fuer Kartographie und Geodaesie where the absolute gravity data that will contribute to the new global absolute gravity reference system are collected.

How to cite: Barzaghi, R., Riguzzi, F., Greco, F., Berrino, G., Germak, A., and Mazzoni, A.: The Absolute Gravity Reference Network of Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5776, https://doi.org/10.5194/egusphere-egu24-5776, 2024.

EGU24-6267 | ECS | Posters on site | G2.3

Investigating the independently derived tropospheric parameters at GNSS-VLBI co-located sites 

Anastasiia Walenta, Claudia Flohrer, Rolf Dach, Daniela Thaller, and Gerald Engelhardt

This paper presents the next step of the recently undertaken comparison of the tropospheric parameters independently derived from the analysis of Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite Systems (GNSS) data. We established a concept of cross-validation of the tropospheric parameters which allows us to focus now on the investigation of the discrepancies detected in the cross-validation. In particular, the dataset and its parameterization are examined in view of their impact on the obtained biases. The most recent 5 years of observations are considered, during which the sufficiently dense time series of observations are available for the legacy VLBI stations as well as for the new generation antennas following the VLBI Global Observing System (VGOS) specifications. In our study the co-location sites are limited to those observatories, where the legacy VLBI antenna, VGOS antenna and GNSS receiver are present. Furthermore, the tropospheric parameters are compared only at the common epochs, which are chosen to include the independently conducted observations of the legacy VLBI antenna, VGOS antenna and GNSS receiver during a defined time span. The corresponding solution parametrization is varied between intervals of VGOS, legacy and GNSS solution parametrizations in order to identify the most optimal duration. While the parameterization of the GNSS solution considers the tropospheric variations stable over 2 hours, the parameterization of VLBI solutions for legacy antennas is known to be reliable over a shorter 1-hour interval. The highly dense VGOS observations allow us to reach up to 20-minute duration without losing performance.

How to cite: Walenta, A., Flohrer, C., Dach, R., Thaller, D., and Engelhardt, G.: Investigating the independently derived tropospheric parameters at GNSS-VLBI co-located sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6267, https://doi.org/10.5194/egusphere-egu24-6267, 2024.

EGU24-6362 | ECS | Posters virtual | G2.3

Estimation of the Length of Day (LOD) from DORIS observations 

Vikash Kumar, Petr Stepanek, Vratislav Filler, Onkar Dikshit, and Nagarajan Balasubramanian

We estimated the true Length of Day (LOD) from DORIS observations. The DORIS RINEX data has been processed by the DORIS development version of the Bernese GPS Software 5.2. We performed single satellite and multisatellite (Sentinel-6A, Sentinel-3A, Sentinel-3B, Jason-3, HY-2C, HY-2D, SARAL, and Cryosat-2), and pre-eliminated solutions. The DORIS data has been processed separately for each satellite on the basis of daily arcs. The troposphere, frequency offset, and orbit parameters were pre-eliminated from the normal equation systems and the finalized matrices were combined on a weekly basis. Hence, individual satellite solutions as well as multi-satellite combined solutions were created. From this solution, we calculated the transformation parameters w.r.t. ITRF 2020 (more precisely w.r.t. the DORIS extension DPOD 2020,) and after applying the 7-parameter Helmert transformation we calculated the RMS w.r.t. DPOD 2020.

We performed solutions with different settings, in particular with different handling of cross-track once-per-revolution harmonic parameters (adjusted with different constraints or not adjusted), since the amplitude of the sine term correlates with LOD. For a comparison of our results, we used the IERS 20 C04 model as a reference.

How to cite: Kumar, V., Stepanek, P., Filler, V., Dikshit, O., and Balasubramanian, N.: Estimation of the Length of Day (LOD) from DORIS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6362, https://doi.org/10.5194/egusphere-egu24-6362, 2024.

EGU24-7362 | Orals | G2.3

VGOS – current status, challenges, and prospects 

Rüdiger Haas

During the last decade, the next generation VLBI system, called the VLBI Global Observing System (VGOS), has been developed. It involves new, fast moving radio telescopes, that are equipped with dual-polarization broad-band receivers covering a broad frequency range from upper S-band to lower Ku-band. VGOS is planned to become the major VLBI contribution to the Global Geodetic Observing System (GGOS), surpassing the legacy S/X VLBI contribution by about one order of magnitude in terms of precision and accuracy of the geodetic products. While still being in its roll-out phase, VGOS started to become operational in 2020. The International VLBI Service for Geodesy and Astrometry (IVS) is now operating two VLBI networks in parallel, the legacy S/X VLBI network, and the new VGOS network. In early 2024, up to 13 VGOS stations are observing together in 24 h network sessions three times per month. These sessions are meant for the determination of the terrestrial reference frame (TRF), the earth orientation parameters (EOP), and the celestial reference frame (CRF). Additionally, several short (1 h) VGOS sessions are performed on several days each week, involving two or three VGOS stations only and focussing on the determination on earth rotation, i.e. the UT1-UTC parameter. There are several ongoing projects worldwide to establish further VGOS stations. It is expected that several of these will become operational in the near future, some even already in 2024, thus improving the geographical distribution of the VGOS network. In conjunction to an improved and densified VGOS network it is also planned to intensify the observation plan. In this presentation, the current status, challenges, and prospects of VGOS are reviewed and discussed. This includes a review of the expectations and obtained results of the geodetic parameters derived from the analysis of VGOS sessions.

How to cite: Haas, R.: VGOS – current status, challenges, and prospects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7362, https://doi.org/10.5194/egusphere-egu24-7362, 2024.

EGU24-7935 | Posters on site | G2.3

VLBI processing in FocusPOD 

Carlos Fernández, Marc Fernández, and Jaime Fernández

GMV is developing FocusPOD, a suite of tools for POD and geodesy, powered by GMV MAORI, a new GMV in-house Flight Dynamics & Geodesy library, written from scratch in modern C++ and python. FocusPOD supports several projects led by GMV, including the operational provision of Precise Orbit Determination (POD) products of the Copernicus Sentinel satellites in the frame of the CPOD Service, the simulation of tracking data for Galileo 2nd Generation (G2G) System Test Bed, and other space debris and flight dynamics activities.

FocusPOD is currently capable of processing GNSS data, with a focus on on-board receivers to support POD, and Satellite Laser Ranging (SLR), mostly used in CPOD as an external orbit validation source. Capabilities to process DORIS have been recently added, also targeting POD applications as a first step. GMV’s roadmap for FocusPOD include processing VLBI in addition to these 3 techniques, with the target of becoming a reference software for the geodesy community.

This contribution intends to present FocusPOD roadmap to incorporate VLBI processing capabilities, describing the modelling challenges that have been identified and the various steps that will be taken to finally be able to process VLBI and provide VLBI-based ITRF products. As part of this roadmap, other parallel activities to tie together the rest of the techniques will also be undertaken and described, mostly related to the ground-based processing of GNSS, SLR and DORIS data.

How to cite: Fernández, C., Fernández, M., and Fernández, J.: VLBI processing in FocusPOD, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7935, https://doi.org/10.5194/egusphere-egu24-7935, 2024.

EGU24-8196 | ECS | Posters on site | G2.3 | Highlight

20 years of the ICGEM Service and the new developments   

E. Sinem Ince, Sven Reißland, Christoph Förste, and Frank Flechtner

ICGEM is one of the five services coordinated by the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). The service has been actively responding to the needs of the scientific community for the last two decades with an archive of static, temporal, and topographic global gravity field models of the Earth in a standardized format with the possibility to assign DOIs. Furthermore, ICGEM provides interactive calculation and visualisation services of gravity field functionals. Maintenance of such a service and development of new “demand-based” tools are of utmost importance to provide state-of-the-art products.

In 2016, the ICGEM portal has been renewed to guarantee a smooth transition to future needs. Since then, the last remaining component of the previous ICGEM portal, the G3 Browser, has been upgraded and integrated into the present ICGEM portal. The G3 Browser (http://icgem.gfz-potsdam.de/g3) aims to compute time series of equivalent water height interactively and gives users the opportunity to compare different gravity model time series as well as impacts of corrections (e.g., GIA, C20) or filters. The G3 Browser is complementary to existing services such as GFZ’s GravIS portal which provides ready-to-use products based on GFZ and COST-G solutions with already applied corrections and filters. On the other hand, the ICGEM G3 Browser includes time series from further processing centres and institutions and different filtering options.

Recently, ICGEM has included simulated models (http://icgem.gfz-potsdam.de/sl/simulated) in its archive that are relevant to future gravity mission studies. Currently available simulated Level 2a models are from the ESA’s MAGIC simulation studies and they are the first of their kind on the ICGEM Service. Monthly and weekly series of different scenarios have been made available on the relevant pages together with the links to the publications provided by the authors.

As demanded by the users, ICGEM plans to include some practical tools in the service, such as comparison of the functionals computed based on two different models and interactive evaluation tools n spatial and spectral domains. Finally, a new project called SAMDAT (Service and Archive for Mass Distribution And mass Transport data) that is funded by the German Research Foundation will be realized during the next three years which aims to expand the ICGEM service based on FAIR (Findable, Accessible, Interoperable, Reusable) data and a sustainable data archive principles.

How to cite: Ince, E. S., Reißland, S., Förste, C., and Flechtner, F.: 20 years of the ICGEM Service and the new developments  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8196, https://doi.org/10.5194/egusphere-egu24-8196, 2024.

EGU24-9519 | ECS | Orals | G2.3

Rethinking operational VGOS observations 

Matthias Schartner, Bill Petrachenko, Patrick Charlot, Minghui Xu, Arnaud Collioud, Hana Krasna, and Soja Benedikt

The VLBI Global Observing System (VGOS) was created to meet the ambitious requirements set by the Global Geodetic Observing System (GGOS). Its primary objective is achieving millimeter-level precision while maintaining continuous 24/7 observations. Currently, both aims remain unfulfilled. Simultaneously, new requirements, such as the development of a dedicated VGOS Celestial Reference Frame (CRF), have emerged. Thus, a reevaluation of our current VGOS observational framework is necessary to reach the VGOS goals.

This study addresses three pivotal challenges within VGOS: attaining millimeter precision, providing observations for a CRF, and achieving uninterrupted 24/7 observations. Each of these topics demand a readjustment of our current observation scheduling methodology.

Based on insight from VGOS R&D sessions, this work discusses potential approaches to meet the requisite precision through shorter, signal-to-noise-driven observations. Additionally, it explores the combination of this methodology with source-based scheduling to facilitate the creation of essential observations for establishing a dedicated VGOS CRF. Finally, it addresses the issue of reaching 24/7 observations, currently limited by data transfer and correlation capacities. To overcome this, a potential solution involves a significant reduction in the recorded data volume per session by temporarily thinning out the schedule. Thus, it comes with a trade-off in precision. This concept might be seen as a paradigm shift in VLBI observations, traditionally striving for the highest precision possible, which we believe is worth being discussed. Based on observation statistics and Monte-Carlo simulations, we will elaborate on the expected impact of this approach. 

How to cite: Schartner, M., Petrachenko, B., Charlot, P., Xu, M., Collioud, A., Krasna, H., and Benedikt, S.: Rethinking operational VGOS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9519, https://doi.org/10.5194/egusphere-egu24-9519, 2024.

EGU24-10228 | Posters on site | G2.3

GGOS Bureau of Products and Standards: Recent activities and future plans 

Detlef Angermann, Thomas Gruber, Gerstl Michael, Heinkelmann Robert, Hugentobler Urs, Sanchez Laura, and Steigenberger Peter

The GGOS Bureau of Products and Standards (BPS) supports the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) in its goal to provide highly accurate, consistent, and long-term stable geodetic products needed to monitor, map, and understand changes in the Earth’s shape, rotation, and gravity field. A key objective of the BPS is to keep track and to foster homogenization of adopted geodetic standards and conventions across all IAG components for the generation of geodetic products. This includes the interaction with the IAG Services and other entities that deal with standards and conventions, such as the Conventions Center of the IERS (International Earth Rotation and Reference Systems Service), the Commission A3 ”Fundamental Standards” of the International Astronomical Union (IAU) and the Technical Committee 211 of the International Organization for Standardization (ISO/TC 211).

This contribution presents the structure and role of the BPS. It highlights some of the recent activities, which are focused on the updating the BPS inventory of standards and conventions used for the generation of IAG products, the revision of the IERS Conventions, mainly related to Chapter 1 ”General definitions and numerical standards” as well as the description and promotion of geodetic products published at the GGOS website (www.ggos.org). The BPS also contributes to the generation of GGOS outreach material, such as videos, brochures, social media posts, etc. to make other disciplines and society aware of geodesy and its beneficial products. Finally, planned activities of the BPS according to the new GGOS Strategic Plan 2024-2034 are provided.

How to cite: Angermann, D., Gruber, T., Michael, G., Robert, H., Urs, H., Laura, S., and Peter, S.: GGOS Bureau of Products and Standards: Recent activities and future plans, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10228, https://doi.org/10.5194/egusphere-egu24-10228, 2024.

EGU24-10339 | Posters on site | G2.3

The International Association of Geodesy 

Richard Gross

2024 marks the 162nd anniversary of the founding of the International Association of Geodesy. In 1862, 15 States agreed to cooperate in a "Central European Arc Measurement" project to observe the shape of the Earth. Besides leading to an improved knowledge of the shape of the Earth, the measurements taken during this project also led to an improved reference frame and geoid for Central Europe. In the course of taking these measurements scientific issues were encountered that also had to be addressed. The spirit of cooperation in both taking operational measurements and conducting scientific research that exists today within the IAG has been a hallmark of the IAG ever since it was founded in 1862.

 

The dual nature of the IAG, in advancing both observations and science, is reflected in the organizational structure of the IAG. Services are responsible for advancing geodetic observations in their area of expertise; Commissions and Inter-commission Committees are responsible for advancing geodetic science; Projects are incubators for new initiatives; the Communications and Outreach Branch, together with GGOS, is responsible for promoting geodesy to the other sciences and to society at large; and GGOS, the Global Geodetic Observing System, is meant to integrate the diverse geodetic observations into a coherent geodetic imaging system of the Earth as a whole.

 

One of the strengths of geodesy is its interdisciplinary nature. Geodetic observations contribute to improving our understanding of many different Earth processes, from space weather to core dynamics. This affords the opportunity for geodesists to collaborate with scientists from many different disciplines. Besides the value to science, geodetic data and products are also of great value to society. The International Terrestrial Reference Frame (ITRF) provided by the International Earth Rotation and Reference Systems Service (IERS), one of the 12 Services of the IAG, underpins location-based services like navigation aids on cell phones. By forging collaborations with other organizations, the IAG can ensure that its data and products continue to meet the needs of both its scientific and societal customers.

How to cite: Gross, R.: The International Association of Geodesy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10339, https://doi.org/10.5194/egusphere-egu24-10339, 2024.

EGU24-10584 | Orals | G2.3

Modelling Global Crustal Deformations Induced by Geophysical Fluid Loading for Space-Geodetic Applications 

Henryk Dobslaw, Jungang Wang, Robert Dill, and Kyriakos Balidakis

With planet Earth being a deformable body, any geodetic marker attached to its crust exhibts slight motions in response to various geophysical forces. Prominent examples are the diurnal and semi-diurnal tides of the solid Earth, but also other periodic and non-periodic forces induced by mass transport divergence in atmosphere, oceans and the terrestrially stored water are deforming the Earth's surface and therefore displace any geodetic instrument attached to it. Based on a suite of different numerical model data-sets, the Earth System Modelling group at GFZ is routinely calculating both tidal and non-tidal surface deformations that can be readily applied as a priori information for the processing of space geodetic data. The model data-sets are publicly available as global grids with 3-hourly temporal sampling covering almost five decades from 1975 until present time.

We present results from dedicated geodetic analysis experiments in order to demonstrate potential impact of such prior information on the GNSS-based coordinate estimates. We utilize data from 220 globally distributed IGS stations from 2005 until 2019 and apply the IGS repro3 strategies for the GPS daily precise orbit determination strategy. We apply non-tidal atmospheric and oceanic loading corrections from the ESMGFZ products on the (i) observation, (ii) normal equation, and (iii) parameter levels, and study the impact of such background models on the coordinate time-series of GNSS permanent stations and other associated parameters. 

How to cite: Dobslaw, H., Wang, J., Dill, R., and Balidakis, K.: Modelling Global Crustal Deformations Induced by Geophysical Fluid Loading for Space-Geodetic Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10584, https://doi.org/10.5194/egusphere-egu24-10584, 2024.

EGU24-10637 | Posters on site | G2.3

VLBI signal transmitter onboard Earth orbiting satellites 

Özgür Karatekin, Hakan Sert, Hugues Vasseur, Veronique Dehant, Birgit Ritter, Urs Hugentobler, Jan Kodet, Željko Jelić, Karel Paternoster, Gerhard Kronschnabl, Christian Ploetz, Akhil Gunessee, Graciela Lopez Rosson, and Ananya Krishnan

Creating an absolute space-tie where all the geodetic methods are onboard is the key for an improved and stable terrestrial reference frame as well as with various scientific applications. Such satellite concepts  have already been proposed to achieve an accurate and stable terrestrial reference frame. Next generation  Galileo satellites can provide a single well-calibrated platform for the colocation of the space-based geodetic techniques establishing precise and stable ties between the key geodetic techniques.  One of the most crucial and novel aspect of such concepts is the VLBI transmitter (VT) which will emit quasar-like signals from the space to be observed by the VLBI ground stations. VT can directly link the terrestrial and celestial reference frames and bring the unique features of VLBI technique to an Earth orbiting satellite. In the context of call for future Galileo payloads a novel VT has been under development.  VT shall be compatible both with the legacy and VGOS antennas.  Here, we present the progress on ongoing ESA study for VT for Galileo as well as for other future  missions. 

How to cite: Karatekin, Ö., Sert, H., Vasseur, H., Dehant, V., Ritter, B., Hugentobler, U., Kodet, J., Jelić, Ž., Paternoster, K., Kronschnabl, G., Ploetz, C., Gunessee, A., Lopez Rosson, G., and Krishnan, A.: VLBI signal transmitter onboard Earth orbiting satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10637, https://doi.org/10.5194/egusphere-egu24-10637, 2024.

EGU24-11678 | Orals | G2.3

GGOS: Ensuring a Coherent Earth Observation System 

Laura Sanchez, Michael Pearlman, Detlef Angermann, Martin Sehnal, Thomas Gruber, Benedikt Soja, Anna Riddell, Kirsten Elger, Richard Gross, Kosuke Heki, Jose M. Ferrandiz, Michael Schmidt, Timothy Melbourne, Allison Craddock, and Basara Miyahara

The Global Geodetic Observing System (GGOS) is the response of the international geodetic community, organised under the umbrella of the International Association of Geodesy (IAG), to the need to monitor changes in the Earth system continuously. GGOS is Geodesy’s contribution to the Global Earth Observation System of Systems (GEOSS) by providing the reference frames needed for all position-dependent observations, thus the foundation for most Earth observations, and measuring changes in the Earth's shape, size, gravity field and rotation over time and space. GGOS is built on the Scientific Services of the IAG (IGS, IVS, ILRS, IDS, IERS, IGFS, ISG, PSMSL, IGETS, IDEMS, ICGEM, BGI) and the products they derive on an operational basis for Earth monitoring using space- and ground-based geodetic techniques. A key objective of GGOS is to realise an integrating framework that moves from the provision of technique-specific products to a level of combined, integrated products as the basis for a consistent modelling and interpretation of Earth system processes and interactions. This is necessary to ensure a coherent Earth monitoring system that contributes significantly to a better understanding of global change and its impacts on the environment and society. This is being achieved through strong international and multidisciplinary cooperation, focusing on (1) bringing together different geodetic observing techniques, services and analysis methods to guarantee that the same standards, conventions, models and parameters are used in all data analysis and modelling of Earth system processes; (2) combining geometric, gravimetric, and Earth rotation observations in data analysis and data assimilation to jointly estimate and model all necessary parameters representing the different elements of the Earth system; (3) identifying science and societal needs that can be addressed by (new) geodetic products and define the requirements for accuracy, time resolution, and consistency of these products; (4) identifying service gaps and developing strategies to fill them; and (5) promoting and enhancing the visibility of Geodesy by improving the accessibility of geodetic observations, information and products to the widest range of users and their attribution. This contribution summarises recent achievements, ongoing activities, and main challenges for the near future.

How to cite: Sanchez, L., Pearlman, M., Angermann, D., Sehnal, M., Gruber, T., Soja, B., Riddell, A., Elger, K., Gross, R., Heki, K., Ferrandiz, J. M., Schmidt, M., Melbourne, T., Craddock, A., and Miyahara, B.: GGOS: Ensuring a Coherent Earth Observation System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11678, https://doi.org/10.5194/egusphere-egu24-11678, 2024.

EGU24-12665 | ECS | Posters on site | G2.3

Investigation of sea level variations and trends in the Baltic Sea from geometric and gravimetric observations 

Fenghe Qiu, Thomas Gruber, and Roland Pail

Geometric and gravimetric measurements both have proven to be robust approaches to analyzing sea level changes. The relationship between them is also worth exploring. In this research, the geometric signal and gravimetric signal as well as volume variations in Baltic Sea are compared during the period from 2002.4 to 2016.12. Ideally, the geometric signal should be the sum of gravimetric signal and volume variations, which is so-called sea-level budget. Here, the geometric signal is selected as altimetric data from multi missions combined with in-situ observations from tide gauges. The Mascon solutions are used as gravimetric signals while the volume variations are represented by steric height derived from Baltic Sea Physics Reanalysis model. The Baltic Sea is divided into four regions and the sea level budget equation is applied in each region. The results reveal the gravimetric and volume components exhibit satisfying correlations with geometric signals, which are larger than 0.85 in all four regions. The north region has the least correlation due to the sea ice problem. Furthermore, the comparison underscores the dominance of the gravimetric signal, contributing to approximately 90% of the total sea level change. On the other hand, the sea level trend is estimated by both geometric signal and the sum of gravimetric and volume components. The difference between the two trends in each region is mainly caused by ocean bottom deformation, primarily influenced by glacier isostatic adjustment (GIA). In the processing of mason, the GIA effect is already removed but the geometric signal contains ocean bottom deformation. Therefore, it is necessary to consider the land deformation during the trend comparison. However, because of the sea level equation, the sea level does not change as much as ocean bottom changes, but much smaller. Here we employ the geoid change from NKG2016LU as a trend correction in ocean bottom deformation. The findings contribute valuable insights for predicting sea level changes in the Baltic Sea, emphasizing the significance of accounting for gravitational and volumetric factors along with ocean bottom deformation in sea-level research.

How to cite: Qiu, F., Gruber, T., and Pail, R.: Investigation of sea level variations and trends in the Baltic Sea from geometric and gravimetric observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12665, https://doi.org/10.5194/egusphere-egu24-12665, 2024.

EGU24-13228 | ECS | Posters virtual | G2.3

Device and angle dependent waveform and a new representation of ocean sound speed structure in GNSS-A 

Koya Nagae, Tadashi Ishikawa, Shun-ichi Watanabe, Yuto Nakamura, and Yusuke Yokota

For more than 20 years, Japan Coast Guard has been developing various technologies to improve the observation accuracy of GNSS-Acoustic ranging. In this presentation, I will introduce two topics that we have been paying attention to in recent years in GNSS-A observations.

 

The first is about instrument errors and angular characteristics that depend on the shape of the transducer (sea surface station) or transponder (seafloor station). In the long-term observations conducted by JCG, multiple types of oscillators are used on both transducers and transponders. It has become clear that this instrumental error has a non-negligible effect on the positioning accuracy of GNSS-A, so we develop a new method to read a received signal considering the instrumental and angle dependence.

 

The second is about a representation method of ocean structure. When we estimate positioning of seafloor station, it is very important to consider sound speed structure (SSS). We use the open-source software GARPOS which can estimate transponder position with SSS. Yokota et al., (in prep) introduce a new representation method of SSS with G-ellipse in GNSS-A analysis. I will talk about the meaning of G-ellipse and some applications of this method.

How to cite: Nagae, K., Ishikawa, T., Watanabe, S., Nakamura, Y., and Yokota, Y.: Device and angle dependent waveform and a new representation of ocean sound speed structure in GNSS-A, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13228, https://doi.org/10.5194/egusphere-egu24-13228, 2024.

EGU24-14602 | Orals | G2.3 | Highlight

IHRF Coordination Center, a newly established IAG/IGFS component to ensure the sustainability of the IHRS/IHRF 

Georgios S. Vergos, Laura Sánchez, and Riccardo Barzaghi

The International Association of Geodesy (IAG) introduced the International Height Reference System (IHRS) in 2015 as the international standard for the accurate determination of physical heights worldwide. The primary vertical coordinates are geopotential numbers referenced to a conventional Wo value. The realization of the IHRS is the International Height Reference Frame (IHRF), which corresponds to a global network of reference stations with precise reference coordinates, geopotential numbers specified in the IHRS and (X, Y, Z) coordinates in the International Terrestrial Reference Frame (ITRF). In the framework of the IAG and after a strong international collaboration the scientific foundations of the IHRS have been outlined and a first realization of the IHRF has been computed. In that frame, it has been deemed necessary to ensure the long-term sustainability of the IHRF by establishing a new dedicated component within the IAG gravity field related services. Recently (December 2023), the IAG has accepted the establishment of the IHRF Computation Center (IHRF-CC) as a central coordinating body under the responsibility of the International Gravity Field Service (IGFS) with direct adherence to the IGFS Central Bureau (IGFS CB), composed of individual modules taking care of the main components of the IHRF. These modules are the IHRF Reference Network Coordination, the IHRF Conventions’ Coordination, the IHRF Associate Analysis Centers, and the IHRF Combination Coordination. In this work we outline the main components of the IHRF-CC, the objectives and goals foreseen, the main responsibilities of its component as well as their planned interrelation, complementarity and synergies in order to deliver its main products. The latter refer to the IHRS standards and conventions and their update; the update of the IHRF network and status; the IHRF computation cookbook; computation of offsets to national and regional vertical datums; and finally, IHRF station coordinates for the global core network and contributions to regional and national densifications. Finaly, we outline the first steps taken to formulate the IHRF-CC components and initiatives to begin normal operation.

How to cite: Vergos, G. S., Sánchez, L., and Barzaghi, R.: IHRF Coordination Center, a newly established IAG/IGFS component to ensure the sustainability of the IHRS/IHRF, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14602, https://doi.org/10.5194/egusphere-egu24-14602, 2024.

EGU24-15350 | ECS | Orals | G2.3

Long-term geodetic product assessment derived from a VLBI transmitter on Next-Generation GNSS 

Shrishail Raut, Susanne Glaser, Patrick Schreiner, Karl Hans Neumayer, Nijat Mammadaliyev, and Harald Schuh

Classical Very Long Baseline Interferometry (VLBI) observations are unique for the estimation of UT1-UTC and Celestial Intermediate Poles (CIPs). The innovative feature of placing a VLBI transmitter on a satellite provides additional information about Earth’s origin, the geocenter. It also enables the VLBI technique to be combined with other satellite-based techniques such as GNSS via a space tie on the common satellite. This research aims to evaluate the long-term geodetic products estimated by VLBI observations to a next-generation Global Navigation Satellite System (NextGNSS) satellite. We simulate a VLBI network comprising 20 stations including 18 current and future VLBI Global Observing System (VGOS) stations that simultaneously observed a single VLBI transmitter on a Galileo-like satellite, in conjunction with extra-galactic radio sources. Terrestrial Reference Frame (TRF) including station positions and velocities, geocenter coordinates, and the full set of Earth Orientation Parameters (EOPs) are estimated for a long-term period of three years. Subsequently, we impose no-net rotation (NNR) and no-net translation (NNT) conditions, resulting in a minimum constraint solution. Satellite observations were assumed at a ratio of 30% of the total observations. The results show that the estimated corrections in the X and Y geocenter coordinates are on the mm-level and the Z coordinate on the cm-level. 

How to cite: Raut, S., Glaser, S., Schreiner, P., Neumayer, K. H., Mammadaliyev, N., and Schuh, H.: Long-term geodetic product assessment derived from a VLBI transmitter on Next-Generation GNSS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15350, https://doi.org/10.5194/egusphere-egu24-15350, 2024.

EGU24-15420 | ECS | Posters virtual | G2.3

Overview of Japan Coast Guard’s GNSS-A seafloor geodetic observation and data management 

Yuto Nakamura, Tadashi Ishikawa, Shun-ichi Watanabe, Koya Nagae, and Yusuke Yokota

The Japanese Archipelago lies along subduction zones, where megathrust earthquakes are known to occur repeatedly (e.g., Mw 9.0 2011 Tohoku-oki Earthquake). The source regions of such megathrust earthquakes mainly lie beneath the seafloor, making it necessary to monitor the crustal deformation not only on land but also on the seafloor. The Japan Coast Guard (JCG) has been conducting seafloor geodetic observation using the GNSS-Acoustic ranging combination technique (GNSS-A) since the early 2000s. By combining GNSS and underwater acoustic ranging, GNSS-A measures the absolute position of a seafloor benchmark in the precision of centimeters, which provides us fruitful information on the crustal deformation under ocean. JCG currently deploys 27 seafloor sites along the Japan Trench and the Nankai Trough named the Seafloor Geodetic Observation Array (SGO-A).

JCG and the Univ. Tokyo group has been working on open data of GNSS-A. In the past, we have published the position time series data (Yokota et al. 2018), and the GARPOS software (Watanabe et al. 2020) which is used in our current routine analysis. Recently, we have been discussing on a standardized data format for GNSS-A in the task force of the Inter-Commission Committee on Marine Geodesy (ICCM) in the International Association of Geodesy. Currently, we are releasing the latest position time series data of each SGO-A site, and the GNSS-A observation dataset in the GARPOS data format (https://www1.kaiho.mlit.go.jp/chikaku/kaitei/sgs/datalist_e.html).

How to cite: Nakamura, Y., Ishikawa, T., Watanabe, S., Nagae, K., and Yokota, Y.: Overview of Japan Coast Guard’s GNSS-A seafloor geodetic observation and data management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15420, https://doi.org/10.5194/egusphere-egu24-15420, 2024.

EGU24-15590 | Orals | G2.3

The International DORIS Service: new challenges 

Laurent Soudarin, Frank Lemoine, Claude Boniface, Guilhem Moreaux, and Jérôme Saunier

The International DORIS Service (IDS) had its 20th anniversary in 2023 and is now looking forward to new challenges.

Over a 30-year period, between 1990 and 2020, the DORIS constellation contributing to the IDS has totaled nine satellites with lifetimes ranging from 3 to 19 years (with the lifetime of SPOT-2, at 19 years, being a record). Since the launch of the SWOT mission in December 2022, nine satellites have been in simultaneous operation and are supplying DORIS data to the IDS. This large number of missions is a challenge for the Analysis Centers, which must integrate them into their processing, taking into account each mission’s special characteristics (w.r.t shape, altitude, attitude law). New missions are expected from 2025 including Sentinel-3C & 3D, Sentinel-6B & 6C, HY-2E & 2F, GENESIS. In addition, the DORIS system continues to evolve. The ground network is growing while providing a high level of service, 4G beacons are gradually replacing those of the previous generation, and a new more powerful DORIS instrument is under study.

New groups have approached IDS in recent years, bringing new processing capabilities, or wishing to become involved in DORIS processing in the medium term. These new strengths are also opening up new applications. Since 2021, DORIS data from the Jason-3 mission have been made available to IDS with a delay of less than three hours. This has enabled the IDS Working Group “NRT data” to demonstrate the value of these data for validating existing GNSS-based ionosphere models. In 2024, NRT DORIS data will be made available for additional missions (Sentinel-3A, Sentinel-3B, Sentinel-6A, Saral…). A new established IDS Working Group will focus on using these data for further ionospheric modelling applications.

In this presentation, we provide information on DORIS system developments and upcoming missions. We also present the recent achievements made by IDS and its components, and the future plans for the service.

How to cite: Soudarin, L., Lemoine, F., Boniface, C., Moreaux, G., and Saunier, J.: The International DORIS Service: new challenges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15590, https://doi.org/10.5194/egusphere-egu24-15590, 2024.

EGU24-17390 | Posters on site | G2.3

Velocity field estimated from HEPOS permanent GNSS network in Greece, preliminary results. 

Dimitrios Anastasiou, Xanthos Papanikolaou, Georgios Serelis, and Maria Tsakiri

The analysis of data from permanent Global Navigation Satellite System (GNSS) stations plays a pivotal role in the assessment of ground motion within a given region. Greece, situated at the convergence zone of various tectonic plates, experiences heightened seismic activity and other geotectonic phenomena. The Hellenic Positioning System (HEPOS) constitutes a network of 98 permanent GNSS sites strategically installed across the entire Greek territory, serving as a critical infrastructure for data provision within the country. In the framework of this study, daily data collected at a sampling rate of 30 seconds for four individual years, ranging from 2011 to 2022, were analyzed. The data was processed via the Bernese GNSS Software v5.2. For the realization of IGb14 reference frame, 19 permanent stations of the IGS network were used, additionally incorporating final products (satellite orbits, clocks, and antenna calibration parameters). Comprehensive analysis was conducted on position time series for all stations, resulting in the estimation of tectonic velocities, harmonic signals, and permanent displacements attributed to seismic events in proximity to each site. Subsequently, preliminary results of the deformation field for the entire Greek region are presented, employing diverse algorithms for the estimation of strain and rotational rates.  

This study was funded by the "Hellenic Cadastre", which also provided access to the data of the HEPOS network. 

How to cite: Anastasiou, D., Papanikolaou, X., Serelis, G., and Tsakiri, M.: Velocity field estimated from HEPOS permanent GNSS network in Greece, preliminary results., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17390, https://doi.org/10.5194/egusphere-egu24-17390, 2024.

EGU24-19106 | Orals | G2.3 | Highlight

Metadata recommendations for geodetic data 

Kirsten Elger and the GGOS Committee on DOIs for Geodetic Data Sets

The geodetic services of the International Association for Geodesy (IAG) are international key players in the provision and distribution of geodetic data. Their operating institutions and funding agencies increasingly require the provision of tangible statistics on data use and access. In addition to the classical provision of data download statistics, data use can also be provided through citations in scholarly literature. Credit through citations, together with the desire for a coordinated approach across the geodetic services, was the motivation for the IAG’s Global Geodetic Observing System (GGOS) to establish a “Working Group on using DOI (digital object identifier) for Geodetic Data Sets” in 2019. The “GGOS Committee on DOIs for Geodetic Data Sets” is continuing the work since 2023 for the longer term.

Challenges for applying DOIs to geodetic data and products include the fact that they are mostly dynamic, often provided as real-time data streams (with hundreds of files per day) where the “classical” assignment (and citation) of DOIs to individual (daily) files provided in different product levels is not a practicable solution. In addition, many geodetic data products are based on contributions from hundreds of researchers and institutions that need to be acknowledged following “rules for good scientific practice”. Today, DOI-referenced research outputs are fully citable in scholarly literature and scientific journals are increasingly demanding that all sources underlying scientific results (data, code, models, samples) are made available/ published along with the article. Initial data citation metrics allows data providers to demonstrate the value of the data collected by institutes and individual scientists. 

An additional benefit of using DOIs for geodetic data is the associated standardised (e.g. DataCite) and machine-readable metadata for data discovery. DataCite is a DOI registration agency specialised for data, code and other publications beyond scholarly literature. Their constantly further-developed metadata schema is supporting the implementation of the FAIR Principles (to make data findable, accessible, interoperable and reusable for humans and machines) and complements discipline-specific metadata standards, like GeodesyML for GNSS station information.

Here we present the first version of our metadata recommendations for geodetic data, developed for the GNSS data use case. The recommendations guide through the DataCite metadata schema, identify recommended and optional properties and how they can be used for geodetic data supporting data discovery. Initial guidelines were: (1) to include persistent identifier, like ORCID, ROR, DOI for uniquely identifying persons, institutions in the DOI metadata and cross reference with related data/articles/code whenever possible. (2) to have a maximum alignment with existing metadata, like GeodesyML or Sitelogs for GNSS station data with automated processes for mapping DOI metadata generation from existing GNSS metadata bases to DataCite metadata.

How to cite: Elger, K. and the GGOS Committee on DOIs for Geodetic Data Sets: Metadata recommendations for geodetic data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19106, https://doi.org/10.5194/egusphere-egu24-19106, 2024.

EGU24-19907 | Posters on site | G2.3

Crust deformation in the Northern Adria plate from twenty years of geodetic monitoring 

Lavinia Tunini, Andrea Magrin, Giuliana Rossi, and David Zuliani

In the complex geodynamic context of the central Mediterranean, squeezed between the two major tectonic plates of Africa and Eurasia, the Adria microplate plays a key role in modulating the deformation and seismicity of the region. The northern sector of Adria is of particular interest as it exhibits moderate seismicity despite low deformation rates.

The crustal deformation is monitored thanks to the various geodetic networks in the area, which can provide continuous and highly accurate daily data. The geodetic network with the most stations is the Friuli Regional Deformation Network - FReDNet (https://frednet.crs.ogs.it), set up by the National Institute of Oceanography and Applied Geophysics – OGS, to monitor the distribution of crustal deformation and provide complementary information for regional seismic hazard assessment (Zuliani et al., 2018). FReDNet currently counts 22 permanent GNSS stations homogeneously covering the Eastern Alps, the alluvial plain, and the coastal areas of northeastern Italy. Most of the time series are longer than 15 years. In addition to FReDNet, another geodetic network in northeastern Italy, the Marussi GNSS network, comprises ten stations and is managed by the Friuli Venezia Giulia (FVG) region. The geodetic network of the Veneto region in the west and the permanent GNSS networks of Austria and Slovenia in the North and East respectively, complete the puzzling northern border of the Adria microplate opposite the southern front of Eurasia.

We processed daily GNSS data from the different permanent geodetic networks using the GAMIT/GLOBK software package version 10.71 (Herring et al., 2018). Data processing was performed on the HPC cluster GALILEO100 of CINECA, which uses the SLURM system for job scheduling and workload management (Tunini et al., 2023).

This study shows the processing results, in the form of time-series and velocity field, as well as the different aspects taken into account to check the reliability of the processing procedure applied and the results obtained, such as the consideration or avoidance of tidal or non-tidal loads or the change of the reference stations, the influence of the type of GNSS monuments, or the location of the geodetic antenna on a roof or in an open field.

OGS and CINECA supported this research under the HPC-TRES program. We acknowledge the CINECA award under the ISCRA initiative for the availability of high performance computing resources and support (IscraC IsC96_GPSIT-2 and IsCa7_GPS-MAST).

 

References

Herring, T.A. and King, R., Floyd, M.A. and McClusky, S. C.; 2018: GAMIT Reference Manual: GPS Analysis at MIT, Release 10.7. Department of Earth. Tech. rep., Massachusetts Institute of Technology, Cambridge, Mass. URL: <http://geoweb.mit.edu/gg/Intro_GG.pdf>

Tunini, L., Magrin, A., Rossi, G., and Zuliani, D.;  2023: GNSS time series and velocities about a slow convergent margin processed on HPC clusters: products and robustness evaluation, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2023-131, in review.

Zuliani, D., Fabris, P., Rossi, G.; 2018: FReDNet: Evolution of permanent GNSS receiver system. In: New Advanced GNSS and 3D Spatial Techniques Applications to Civil and Environmental Engineering, Geophysics, Architecture, Archeology and Cultural Heritage, Lecture Notes in Geoinformation and Cartography; Cefalo, R., Zielinski, J., Barbarella, M., Eds.; Springer: Cham, Switzerland, pp.123–137.

How to cite: Tunini, L., Magrin, A., Rossi, G., and Zuliani, D.: Crust deformation in the Northern Adria plate from twenty years of geodetic monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19907, https://doi.org/10.5194/egusphere-egu24-19907, 2024.

EGU24-22454 | Posters on site | G2.3

The CDDIS – Updates and Future Developments 

Justine Woo and Taylor Yates

As earth observing services and techniques have flourished, data and products have exponentially grown, like the proliferation of GNSS stations capable of providing real-time data, SLR stations shifting to kHz lasers, and VLBI’s implementation of VGOS telescopes.  The CDDIS is continually evolving to fulfill the new storage, quality check, and latency requirements that these changes bring, as well as meet new standards such as the shift toward FAIR and open science.  These have shaped how the CDDIS develops new software and resources.  Beginning next year, the CDDIS will begin to transition their data and products to the AWS cloud, beginning with DORIS data.  This poster will highlight the CDDIS’s recently updated processing system, new data and products available, and future work.

How to cite: Woo, J. and Yates, T.: The CDDIS – Updates and Future Developments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22454, https://doi.org/10.5194/egusphere-egu24-22454, 2024.

EGU24-23 | ECS | Orals | G2.6

Improving ambiguity resolution success rate in GNSS-based relative positioning with moving-baseline length constraint 

Shaoshi Wu, Bo Fan, Yishan Ding, Zhijie Jiang, Yuzhou Ran, and Kaicheng Cao

Reliable integer ambiguity resolution is the key to the global navigation satellite system (GNSS)-based precise positioning applications. In many scenarios, it is a common setup that more than one antenna is mounted on the moving platform. The integer ambiguity resolution can therefore be improved if the constant baseline information between the antennas is used reasonably. In this contribution, the baseline information, which can be measured a prior  as the constraint and has been successfully used to improve the GNSS-based attitude determination, is now extended to relative positioning. The baseline length is fully integrated into the ambiguity objective function of the relative positioning model, thus improving the reliability of relative positioning resolution. In experimental validation, both simulated and real datasets are tested to demonstrate the benefits brought by the baseline length constraint. The results show that the constraint ensures a higher ambiguity resolution success rate, and the improvement is more obvious when the observable condition is weaker.

How to cite: Wu, S., Fan, B., Ding, Y., Jiang, Z., Ran, Y., and Cao, K.: Improving ambiguity resolution success rate in GNSS-based relative positioning with moving-baseline length constraint, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-23, https://doi.org/10.5194/egusphere-egu24-23, 2024.

We present a neural network optimized for producing GNSS displacements to explore machine learning capabilities in forecasting ground motions for earthquake early warning and to improve our understanding of ground motion in real-time. For earthquake early warning, displacements at GNSS receivers are currently being incorporated into the ShakeAlert system, but displacements in real-time are problematic due to issues with phase ambiguity fixing, cycle slips, and loss of satellite lock as well as dilution of precision from satellite network geometry. These errors can lead to anomalous motions of up to a meter. Raw GNSS observations for velocities can utilize orbits (relative positions) and remove uncertainties caused by path errors, leading to a higher precision observation than the displacements. In general, peak ground velocity is diagnostic of earthquake damage and displacement is diagnostic of total moment release, so obtaining these observations at the highest fidelity is crucial for rapid earthquake source estimation. Since processing raw GNSS velocities gives a higher precision observation, we aim to derive displacements from velocities using a machine learning approach. We use a Long Short-Term Memory (LSTM) network, a recurrent neural network (RNN) with the ability to remember values for an arbitrary amount of time, for time series prediction of the GNSS displacements. The input variables for the model are three-component GNSS velocities derived from the SNIVEL software package, with the possibility of including signal to noise and phase observables, and the output variable is the GNSS displacement time series. The GNSS displacement is validated against the displacements computed with the precise point positioning code GipsyX. With over 2250 1-Hz observations from 82 different events ranging from M4.9 to M9, we have ample data to train, validate, and test the network on. We train several neural network instances on random selection of train/validation/test split for redundancy and shuffle data input order for each instance. By computing the GNSS displacement from GNSS velocities, we produce a higher precision observation, a low-cost method for monitoring deformation without the traditionally high overhead associated with real-time GNSS processing, and the possibility of direct onboard receiver transmission of displacements.

How to cite: DeGrande, J. and Crowell, B.: Evaluating a Long Short-Term Memory(LSTM) network for real-time high-rate GNSS time series analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-309, https://doi.org/10.5194/egusphere-egu24-309, 2024.

EGU24-334 | ECS | Posters on site | G2.6

Impact of stochastic modeling applied to the receiver clock parameter for Galileo-only and multi-GNSS solutions      

Marcin Mikoś, Krzysztof Sośnica, Kamil Kazmierski, and Tomasz Hadas

In Precise Point Positioning (PPP), independently estimating the receiver clock parameters at each observation epoch introduces heightened noise in the estimated station coordinates and troposphere parameters due to correlations. To address this issue, stochastic modeling is applied to the receiver clock parameter, thereby enhancing the stability of PPP solutions and minimizing clock noise for precise time transfer. Importantly, the feasibility of receiver clock modeling relies on GNSS receivers being connected to exceptionally stable atomic clocks, such as hydrogen maser clocks (HM), which exhibit significantly lower noise compared to other clock types.

The strategy proposed by our team involves introducing Markov stochastic process modeling for the receiver clock parameters through a random walk. We opted for this stochastic process because of its simplicity in both comprehension and implementation. We conducted tests with different levels of random walk constraints for GNSS stations equipped with various clock types, exploring both Galileo-only and multi-GNSS solutions in kinematic and static PPP modes. We compare the results against a reference solution without any additional constraints. In multi-GNSS solutions, a common clock parameter is determined alongside inter-system biases (ISBs), with the common clock parameter identified as the GPS clock.

Research outcomes demonstrate that comparable results can be achieved by imposing constraints solely on the common clock parameter while treating ISBs as constant parameters. Similarly, constraints on both the common clock parameter and ISBs, with a ratio of 1:100, yield the most favorable results. However, adopting other clock-to-ISB constraint ratios, such as 1:1 and 1:10, leads to suboptimal performance. In the static PPP, the introduced clock modeling significantly enhances the precision of time transfer by effectively reducing clock noise. In the kinematic PPP, stochastic clock modeling has a marginal impact on the North and East coordinate components, whereas the Up component exhibits substantial improvement, mainly for GNSS receivers equipped with HM. An examination of Zenith Total Delay (ZTD) in both Galileo-only kinematic and static PPP modes reveals the discernible impact of clock constraints, as evidenced by observed offsets in the respective outcomes. In the case of multi-GNSS solutions, this influence is less prominent, attributed to weaker correlations between ZTD and clock parameters in multi-GNSS solutions compared to Galileo-only.

How to cite: Mikoś, M., Sośnica, K., Kazmierski, K., and Hadas, T.: Impact of stochastic modeling applied to the receiver clock parameter for Galileo-only and multi-GNSS solutions     , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-334, https://doi.org/10.5194/egusphere-egu24-334, 2024.

GNSS real-time PPP have been demonstrated to be applicable to PWV retrieval effectively. The GNSS real-time satellite clock error is one of the essential factors that affects the accuracy of PPP, and its estimation method is usually considered to be white noise random processes which ignore the stable periodic variation characteristics of GNSS atomic clocks. In addition, the GNSS satellite clock offsets real-time service have low timeliness due to the time consumption of clock offsets series estimation and fitting of quadratic polynomial coefficients, even when communication is interrupted for a short period of time, RTS cannot be obtained. Thus, we developed a method that directly estimate satellite clock model coefficients simultaneously with tropospheric wet delay, receiver clock error, and phase ambiguity parameters from global GNSS code and phase measurements. The difference from traditional RTS is that the satellite clock model coefficients can be delivered to PPP users once estimated process is completed without the step of fitting. Several satellite clock models composed of polynomial and harmonic-based functions are applied to the parameter estimation of real-time satellite clock error, we compared the accuracy of estimated model parameters to IGS real-time satellite clock offsets, and discussed its performance of PPP positioning and PWV retrieval. Finally, we simulated the performance of proposed parameter estimation scheme of satellite clock error and PWV retrieval for different update interval in case of communication interruption for several minutes.

How to cite: Li, X. and Li, H.: Parameter estimation of GNSS real-time satellite clock error and its application in PWV retrieval, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1303, https://doi.org/10.5194/egusphere-egu24-1303, 2024.

EGU24-3486 | ECS | Posters on site | G2.6

IGS GNSS satellite phase bias products: quality assessment and applications 

Bingbing Duan, Urs Hugentobler, Camille Parra, Yichen Liu, and Oliver Montenbruck

As part of the International GNSS Service (IGS), several analysis centers (i.e., CODE, CNES/CLS, GFZ, WUHN) provide GNSS (GPS, Galileo, BeiDou) satellite phase bias products to support precise point positioning with ambiguity resolution (PPP-AR). Due to the high correlation with satellite orbits and clock offsets, it is difficult to assess directly the precision of satellite phase bias products. The commonly used approach is to check the positioning performance in PPP-AR applications. However, errors or outliers in phase bias of a specific satellite are not directly visible in this process but lumped into the overall observation residuals. This contribution presents a method independent of ground measurements to detect outliers in satellite phase biases by computing the total Difference of satellite Orbits, Clock offsets and narrow-lane Biases (DOCB) at the midnight epoch between two consecutive days. This method can be also used to assess the consistency of satellite products between two different analysis centers. It is convincing that after removing the detected outliers in individual analysis centers the number of large differences of satellite phase biases between two analysis centers is notably reduced. To show the impact on PPP-AR, we generate a list marking all the outliers in the phase bias products from individual analysis centers, and evaluate the performance in ground-station kinematic positioning and Sentinel-6 satellite orbit determination.

How to cite: Duan, B., Hugentobler, U., Parra, C., Liu, Y., and Montenbruck, O.: IGS GNSS satellite phase bias products: quality assessment and applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3486, https://doi.org/10.5194/egusphere-egu24-3486, 2024.

EGU24-3695 | Posters on site | G2.6

High precision positioning and navigation technology for unmanned aerial vehicles in high-risk environments 

Junli Wu, xiaoqing Wang, and qinglan Zhang

Abstract:In high-risk and complex mountainous environmental conditions, geological hazard bodies are often located in high mountain and canyon areas, with problems such as poor observation environment, large altitude differences, frequent extreme weather, and poor data communication. When deploying GNSS monitoring equipment using drones, they face difficulties in safe flight and precise navigation and positioning.This article studies the performance enhancement technology of multi-sensor integrated navigation. Based on the low-cost MEMS and GNSS tight combination algorithm, a comprehensive filtering technology integrating unscented Kalman filtering (UKF) and particle filtering (PF) is proposed. Two parallel running UKF and PF predictors are used to alternately use the information received by the fusion filter through input interaction, model filtering, and adaptive filtering optimization, in order to improve the reliability and accuracy of filtering, Simultaneously combining the advantages of Fuzzy Inference System (FIS) and Sparse Random Gaussian Model (SRG), the SRG model is used to estimate the initial state vector, and then FIS is used to update all current states to obtain the optimal predicted state vector. During the interruption of GNSS signal, the measurement data trained by FIS is jointly provided by INS and GNSS. In order to improve the required prediction accuracy, time sliding is used to control the data flow generated by INS and GNSS, Fully utilize the linear velocity and angular velocity increments output by INS to update the attitude, velocity, and position of unmanned aerial vehicles, improve the filtering convergence speed, navigation positioning accuracy, and reliability in the event of GNSS signal interruption. This article designs a multi-source fusion positioning system framework and integration scheme for unmanned aerial vehicle applications, and develops a high-precision fusion positioning software system, mainly including GNSS real-time data reception, GNSS data preprocessing, GNSS/INS integrated navigation data processing, real-time positioning result forwarding and other modules. The test results show that the positioning accuracy of complex environment integrated navigation is better than 0.5 meters.

Key words:Geological disasters;Unmanned Aerial Vehicle;Integrated navigation;High precision

How to cite: Wu, J., Wang, X., and Zhang, Q.: High precision positioning and navigation technology for unmanned aerial vehicles in high-risk environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3695, https://doi.org/10.5194/egusphere-egu24-3695, 2024.

EGU24-3726 | ECS | Orals | G2.6

Precise point positioning with LEO augmentation: results from two experimental satellites 

Wenwen Li, Min Li, Tengda Huang, Chuntao Chang, and Qile Zhao

Using LEO satellites for positioning and navigation has been a research hotspot in the GNSS community in recent years. As the LEO satellites are much closer to earth and move much faster relative to earth than GNSS, precise point positioning (PPP) convergence time can be substantially improved. Various simulation studies on LEO augmentation have been carried out, but its performance with real LEO observations in a real-world environment is rarely reported. The CENTISPACETM system, which is developed by Beijing Future Navigation Tech Co., Ltd., has launched four experimental satellites in the last two years, providing a good opportunity for studying LEO augmentation. We collect real LEO navigation observations from two CENTISPACETM satellites using a regional network. Before conducting LEO-augmented PPP, orbit determination and time synchronization (ODTS) for the experimental LEO satellites are first investigated, and a data-processing framework is established using the space-borne GNSS observations from LEO satellites and the LEO augmentation observations from ground stations. The LEO-augmented PPP algorithm is then derived, with a focus on the LEO relativistic effect. With these bases, we analyze the LEO-augmented PPP performance with different GNSS systems (including GPS, BDS, and Galileo) combined with LEO satellites. The static PPP tests using one (G/C/E), two (GC/GE/CE), and three (GCE) GNSS systems show that the average convergence time is significantly reduced with the participation of the two LEO satellites, from 32.7, 17.9, and 14.2 min to 16.7, 8.9, and 5.7 min, respectively. This indicates that adding only two LEO satellites improves the convergence times of static PPP with one, two, and three GNSS systems by 48.9%, 50.2%, and 59.8%, respectively. For PPP precision evaluation, the GNSS-only 3D positioning errors are 6.1, 4.6, and 4.6 cm with one, two, and three systems, respectively. They are reduced to 5.2, 3.9, and 3.8 cm by adding two LEO satellites, respectively. The corresponding improvements are 13.9%, 16.4%, and 18.8%, respectively. The above study not only validates the customized processing framework and strategy for LEO augmentation processing but also demonstrates the great potential of LEO augmentation. With more LEO satellites to be deployed in the future, much larger improvements can be achieved.

How to cite: Li, W., Li, M., Huang, T., Chang, C., and Zhao, Q.: Precise point positioning with LEO augmentation: results from two experimental satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3726, https://doi.org/10.5194/egusphere-egu24-3726, 2024.

EGU24-3956 | Posters on site | G2.6

Determination of realistic uplift rate and noise assessment using GNSS coordinate time series 

Hamed Karimi, Mahsa Heydari, and Urs Hugentobler

The Earth deformation generally is divided into horizontal and vertical components. The vertical component has different behaviour and complexity caused by the tidal and non-tidal loading and other effects. In this contribution, the vertical motion rate of the Earth crust is considered and studied based on GNSS coordinate time series. The focus of this presentation is the signal processing algorithm applied to the time series. One of the challenges in signal extraction and data processing in the sequential steps is the error budget. The strategy which we considered in the uplift determination process after data-cleaning and outlier detection is to firstly detect the significant signals in the time series and the change points. Then, after removing the aforementioned signals e.g. annual, semi-annual, diurnal, tidal etc., the rate of the up component of the GNSS time series and the related uncertainty is estimated. To achieve this, we employed Monte-Carlo Singular Spectrum Analysis i.e. Monte-Carlo SSA for the signal detection process, Bayesian Estimator of Abrupt change, Seasonal change, and Trend (BEAST) for the change point detection, variance estimation algorithm e.g. LS-VCE, Allan variance etc. for noise characteristic determination and Least-Squares estimation for the estimation of uplift rate and the related uncertainty. In an overall view, in this contribution, the importance of realistic errors is highlighted to estimate the uplift rate and the related uncertainty e.g. as geophysical boundary value for mantle convection models.

How to cite: Karimi, H., Heydari, M., and Hugentobler, U.: Determination of realistic uplift rate and noise assessment using GNSS coordinate time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3956, https://doi.org/10.5194/egusphere-egu24-3956, 2024.

Before 2016, the users had access only to the position-velocity-time (PVT) information from the GNSS chipsets, and the raw GNSS observations were not available. The GNSS module's positioning accuracy on smartphones typically ranged from 3 to 5 meters under favorable multipath conditions, but over 10 meters in challenging environments. This level of accuracy was not sufficient for some applications. Fortunately, in May 2016, during the "Google I/O" conference, Google announced that the raw GNSS measurements, i.e., the pseudorange, carrier-phase, Doppler shift and carrier-to-noise density ratio (C/N0) observations, would be accessible through the Android Nougat (version 7) operating systems. Google has officially released Android 7 (Nougat) on August 22, 2016, marking a breakthrough for the GNSS community. Since then, research has been conducted to develop new algorithms to improve GNSS positioning performance using these mass-market devices. In 2021 and 2022, the Android GPS team of Google hosted two Google smartphone decimeter challenges (GSDC), where various smartphone GNSS datasets of real vehicular applications were used to determine smartphone positioning accuracies. As has been revealed, meter-level accuracy is generally achieved by the leading participants, which is still not enough to enable smartphone precise positioning. This indicates an ongoing demand to enhance the positioning accuracy with smartphones.

Different positioning algorithms, such as absolute or relative positioning methods can be applied to the smartphone observations as well. Precise point positioning (PPP) is a powerful method for conducting accurate real-time positioning using a single receiver. Research papers have reported PPP smartphone positioning accuracy ranging from decimeter to sub-meter accuracy, depending on different factors such as the environment and positioning mode (static and kinematic). Most studies have so far focused on utilizing the GNSS only observations obtained from the smartphone's API. However, incorporating additional information as constraints can enhance accuracy and overall stability (for example height information).

The Android operating system incorporates a set of functions known as APIs, allowing the users to use the system's features. Each Android version has distinct types of APIs. Among these, the android.location API is dedicated to the location-related services, with the "Location" class being one of them. This class consists of parameters such as latitude, longitude, altitude, timestamp, accuracy, bearing and velocity. The "AltitudeMeters" from this class provides the height above the WGS84 ellipsoid in meters, serving as supplementary information in this research. Although the vertical positioning accuracy of GNSS is generally lower than the horizontal accuracy, utilizing recorded height from the smartphone GNSS chipset can still be beneficial. This incorporation increases the degree of freedom and strengthens the geometry of the receiver and satellites. In this study, we assess the effectiveness of the uncombined PPP model in the presence of height constraints. We will utilize both pedestrian walking and vehicular datasets collected by a dual-frequency Xiaomi Mi8 device to evaluate the effect of adding height constraint to PPP model. We expect an improvement on the root-mean-square (RMS) of horizontal positioning, the 50th percentile error, and the convergence time when employing the height constraints.

How to cite: Zangenehnejad, F. and Gao, Y.: Height-constrained uncombined PPP for enhanced pedestrian and vehicular positioning with an Android smartphone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4153, https://doi.org/10.5194/egusphere-egu24-4153, 2024.

EGU24-4188 | Posters on site | G2.6

Extracting and filtering the Common Mode Signal of GNSS coordinate time series via Independent Component Analysis and Multiresolution analysis 

Giordano Teza, Arianna Pesci, Letizia Elia, and Marco Meschis

Time series related to a GNSS network at regional scale, or larger, generally show a spatially correlated component, called common-mode signal (CMS), related to both unmodelled geophysical processes, including environmental loading effects, and technique-dependent systematic errors that persist after data processing. The CMS estimation is very useful for two reasons: (i) untreated CMS leads to long-period noise in coordinate time series which induces bias and higher uncertainty in velocity estimates, so that many authors prefer the term CME (Common Mode Error) instead of CMS; (ii) whether it is possible to adequately discriminate between the components of the CMS, it is then possible to obtain relevant information regarding some geophysical phenomena.

Independent Component Analysis (ICA) is particularly useful for estimating the CMS because the ICA components show insightful correlations, e.g., with atmospheric and non-tidal ocean loading displacements. For this reason, we propose a small MATLAB toolbox, partially compatible with GNU Octave, for ICA-based CMS estimation and, if required, filtering.

The ICA is implemented using a FastICA algorithm in which data whitening is carried out using a Principal Component Analysis (PCA) modified in order to allow the use of incomplete time series. In this way, in the case of short periods of data loss (a few days or also some weeks), the ICA is obtained without use of data interpolation. The only used preprocessing technique is detrending. The spectral content of each ICA component can be studied by means of both frequency and time-frequency analysis and the filtering can be carried out either in the frequency domain or by means of Multiresolution analysis (MRA), according to the user’s choice. This filtering requires continuity of the time series and, therefore, in the case of short periods of data loss (a few days, at most a few weeks), interpolation is needed to build the required continuity; for non-short periods of data loss, no interpolation is implemented. The fact that the interpolation occurs after the CMS analysis, and therefore has no possible effect on its estimate, should be noted.

The toolbox, which is designed to be used both independently and together with the StaVel/GridStrain toolbox developed by the same authors, will soon be made available on the Harvard Dataverse. Development of the Python version is planned.

In order to test the validity of the proposed approach in the case of real data, it is applied to vertical data related to a network of some dozens of GNSS stations located in Southern Italy (Sicily and Calabria) and Greece (North-Western Greece and Peloponnese).

How to cite: Teza, G., Pesci, A., Elia, L., and Meschis, M.: Extracting and filtering the Common Mode Signal of GNSS coordinate time series via Independent Component Analysis and Multiresolution analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4188, https://doi.org/10.5194/egusphere-egu24-4188, 2024.

EGU24-4474 | ECS | Posters on site | G2.6

LEO constellation-augmented SBAS and performance simulation analysis 

Le Wang, Weicong Yang, Guanwen Huang, and Ziwei Wang

Satellite-Based Augmentation System (SBAS) relying on ground monitoring networks can only provide regional services in their own countries or regions. DFMC can expand service coverage and improve service quality, but it still needs the support of the ground monitoring network. Equipped with a spaceborne receiver, LEO has a unique advantage in space-based monitoring, which is expected to expand the service coverage and improve the service performance of SBAS. A global integrity monitoring method of SBAS combining LEO satellites and regional ground station data is proposed. Based on simulation data, the improvement effect of this method compared with that of relying solely on ground station data is verified from the aspects of correction sequence, monitoring arc integrity, enhanced satellite number and coverage. The results of global user positioning accuracy, integrity and usability evaluation are also given. The results show that this method can effectively extend the service coverage of SBAS and improve its performance. On a global scale, the average horizontal positioning accuracy of users is better than 0.5m and the average vertical positioning accuracy is better than 1 m. The pseudo-range residual reduction reached 21%, and the availability met the requirements of APV-I. The addition of LEO can effectively expand the monitoring and service scope of BDSBAS and improve its performance.

How to cite: Wang, L., Yang, W., Huang, G., and Wang, Z.: LEO constellation-augmented SBAS and performance simulation analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4474, https://doi.org/10.5194/egusphere-egu24-4474, 2024.

Global Navigation Satellite System (GNSS) plays an increasingly important role in all walks of life. In order to meet the demands of different users, it is crucial to establish corresponding correct mathematical models, especially in the field of precise positioning and navigation. However, due to the spatiotemporal complexity of and limited knowledge on GNSS errors, some residual errors would inevitably remain even after being corrected with differencing and linear combination, empirical model correction, and traditional parameterization. These residual observation errors are referred to as unmodeled errors. In fact, the unmodeled errors have adverse impacts on high-precision GNSS positioning. However, most existing studies mainly focus on handling the part of systematic errors that can be adequately modeled and then simply ignore the part of unmodeled errors that may actually exist. To make a breakthrough in the precision and reliability of GNSS applications currently, this study focuses on the theory and method for processing the GNSS unmodeled errors based on the mathematical model compensation, including resilient functional model adjustment and resilient stochastic model optimization. Specifically, according to the significance and properties of unmodeled errors, the unmodeled-error-ignored model, unmodeled-error-corrected model, unmodeled-error-fixed model, unmodeled-error-float model, and unmodeled-error-weighted model are proposed, where the approaches of significance testing, geometry-free/based/fixed models, hemispherical/hierarchy maps, composite stochastic model, multi-epoch partial parameterization, and inequality and equality constraints are adopted. Ultimately, an unmodeled error processing flow that can adaptively adjust as the external conditions change is proposed, then one can obtain high-precision GNSS positioning solutions.

How to cite: Zhang, Z. and Li, B.: GNSS unmodeled error processing based on the resilient mathematical model compensation in high-precision GNSS positioning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4504, https://doi.org/10.5194/egusphere-egu24-4504, 2024.

EGU24-4900 | Posters on site | G2.6

Hurricane Harvey evolution process monitoring based on PWV 

Wei Zhan and Xiao Liu

In 2017, Hurricane Harvey made two consecutive landfalls along the Gulf Coast of the United States on August 25th and August 30th, resulting in extreme precipitation and widespread flooding. The impacts were devastating, causing the loss of over 80 lives and significant economic damage. To understand the evolution of Hurricane Harvey, we utilized data from densely distributed permanent GPS stations for precipitable water vapour (PWV) and rainfall tracking from the Tropical Rainfall Measuring Mission (TRMM) 3B42 product, examining spatial and temporal characteristics. Applying the empirical orthogonal function (EOF) method, we analyzed typical spatial patterns of PWV before and after Harvey's passage, revealing an overall increasing trend in atmospheric moisture at various sites across the study area. This trend was particularly pronounced in regions affected by the first and second landfalls. By comparing the time series of PWV with the distance between GPS stations and the hurricane's eye, we calculated their correlation, finding a negative relationship, especially when the hurricane is gradually approaching the GPS stations, the correlation coefficient can reach -0.6 or a higher value. Notably, when the distance between GPS stations and the hurricane's eye was approximately 1000 km, PWV rapidly increased. As the water vapour values rose to around 55mm and maintained an upward trend, sustained precipitation occurred. During the passage of the hurricane, PWV remained at elevated levels, resulting in maximum rainfall. Once the hurricane moved away, PWV values rapidly decreased.

How to cite: Zhan, W. and Liu, X.: Hurricane Harvey evolution process monitoring based on PWV, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4900, https://doi.org/10.5194/egusphere-egu24-4900, 2024.

To achieve highest precision in positioning and navigation, frequency transfer, ionosphere monitoring, etc. with global navigation satellite system (GNSS) data, the technique of uncombined precise point positioning (PPP) ambiguity resolution holds great potential. Unified data processing and reliable ambiguity resolution for multi-GNSS are essential prerequisites. Consequently, we propose a refined approach for quality control of multi-GNSS uncombined PPP ambiguity resolution employing a sequential Kalman filter. In addition to addressing the implementation of uncombined PPP ambiguity resolution, our focus extends to the selection of the reliable ambiguity datum, computational efficiency and refining the ambiguity resolution strategy. When quad-constellation GNSS data are processed, the results demonstrate that employing the sequential Kalman filter with OpenMP can enhance computational efficiency by approximately three times compared to the standard filter. Additionally, the sequential Kalman filter is also convenient to incorporate the ambiguity datum or the fixed ambiguity as a strong constraint and complete the post-residuals check for further validating the ambiguity resolution. Following the consideration of a set of indicators, e.g., arc length, cutoff angle, ratio value and success rate, for controlling reliable ambiguity resolution, the incorrect ambiguity fixing rate can be effectively reduced, especially during the convergence stage.

How to cite: Cao, X. and Soja, B.: Quality control for multi-GNSS uncombined PPP ambiguity resolution using a sequential Kalman filter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5099, https://doi.org/10.5194/egusphere-egu24-5099, 2024.

EGU24-5179 | ECS | Orals | G2.6

Improving troposphere mapping function by ERA5 for better space geodetic estimates 

Yaozong Zhou, Yidong Lou, Weixing Zhang, Xiaopeng Gong, and Guo Chen

Troposphere mapping function plays a very important role in space geodetic tropospheric correction, estimation, and application in meteorology. In the past decades, a series of mapping functions, such as NMF, GMF, VMF1 and VMF3, were successively developed for pursuing better mapping function performance. However, limited by modeling data source of numerical weather model, the mapping functions temporal-spatial resolutions are stuck in 6 h and 1°×1°, existing problems of bad applicability in extreme weather and regions with complex terrains. As the release of the generally acknowledged best global reanalysis ERA5, we have a chance to improve current mapping function modeling by taking full advantage of accuracy and temporal-spatial resolution (1h and 0.25°×0.25) of ERA5. In this contribution, we used the ERA5 reanalysis to establish the hourly site-wise Wuhan University Mapping Function (WMF) covering 1583 GNSS, VLBI and DORIS stations, and compared the accuracy and GNSS PPP performance of WMF with VMF3 at globally distributed stations. We found the significant accuracy improvements of WMF to VMF3 as well as the non-negligible vertical coordinate and ZTD difference biases between the two mapping functions.

How to cite: Zhou, Y., Lou, Y., Zhang, W., Gong, X., and Chen, G.: Improving troposphere mapping function by ERA5 for better space geodetic estimates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5179, https://doi.org/10.5194/egusphere-egu24-5179, 2024.

Annual signals derived from GNSS position time series have become a very important source of information on a variety of geophysical phenomena occurring in the closer or farther vicinity of the antennas. In this research, we investigated the vertical position time series obtained from the International GNSS Service (IGS) third reprocessing (repro3) and PPP times series from the Nevada Geodetic Laboratory (NGL). We selected 1019 globally distributed stations with good quality data and time spans longer than 5 years. First, we pre-processed them for outliers and identified the epochs of offsets using manual inspection. Then, we inspected the differences between the annual signals contained in both sets of time series. We noticed from the map of annual signal differences that there is a worldwide annual common mode in the series of “IGS-NGL” station position differences, with a median amplitude of the order of 2 mm, and a maximum around August. We hypothesized that those differences could be explained by different strategies of alignment to the reference frame, and in particular by the alignment of the NGL series to the scale of the ITRF. To investigate this, we produced additional series by applying different types of constraints to the daily repro3 normal equations. Namely, we compared four sets of time series: “IGS” which are the official repro3 solutions, aligned by no-net-rotation nor translation (NNR+NNT) constraints to the IGSR3 reference frame via the well-distributed IGSR3 core network; “IGa” which are repro3 solutions aligned by no-net-rotation, translation nor scale (NNR+NNT+NNS) constraints to IGSR3 via the same core network; “IGb” which are repro3 solutions aligned by NNR+NNT+NNS constraints to IGSR3 via the same daily sets of reference stations as used by Jet Propulsion Laboratory (JPL) to align their orbit and clock products; and “IGc” which are repro3 solutions aligned by NNR+NNT+NNS constraints to the IGb14 reference frame via the same set of reference stations as used by JPL. A comparison of these four sets of time series with the NGL PPP time series reveals that c.a. half of the systematic differences in vertical annual signals between IGS and NGL comes from the alignment of the NGL solutions in scale to the reference frame, and another half comes from the use of different station networks for the alignment to the reference frame.

How to cite: Bogusz, J., Rebischung, P., and Klos, A.: Differences in annual signals between IGS- and NGL-derived position time series: testing different strategies of alignment to the reference frame, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5351, https://doi.org/10.5194/egusphere-egu24-5351, 2024.

EGU24-5540 | ECS | Orals | G2.6

An enhanced stochastic approach for code observations collected from Android smartphones 

Berkay Bahadur and Steffen Schön

Smartphone-based positioning, navigation, and timing applications have been among the most popular topics within the GNSS community since 2016 when Google announced that raw GNSS observations are publicly available. However, achieving high positioning accuracy with smartphones is troublesome because of their specific limitations, such as the high noise level of observations, low protection against multipath, and discontinuities in carrier phase observations. Due to considerable discontinuities in carrier phase observations, code observations still play a crucial role in smartphone-based positioning applications. Subsequently, a realistic stochastic approach is mandatory to obtain the utmost positioning performance. This is especially true since the stochastic behavior of code observations for geodetic receivers and Android smartphones are quite different i.e., GNSS observations obtained from a smartphone are much noisier. The signal strength of GNSS signals collected from Android smartphones is also not very stable and is significantly lower when compared with geodetic receivers. Unlike observations obtained from geodetic receivers, no significant dependency between observation noise and elevation angle can be observed in smartphone observations. Therefore, conventional stochastic models, mainly based on the satellite elevation angle, are not enough to represent the stochastic behavior of smartphone observations. In this context, this study provides an enhanced stochastic approach for code observations obtained from Android smartphones. The corresponding approach includes a weighting scheme based on carrier-to-noise ratio (C/N0) values representing the signal strength of GNSS code observations. Besides, depending on their observation noises, this approach assigns different model coefficients for each constellation, which means differences between the navigation systems can be considered in adequate observation weighting. This approach also uses a robust Kalman filter method based on the IGG (Institute of Geodesy and Geophysics) III function to compensate for the effects of outliers and incorrectly weighted observations on the filtering performance. In this study, GPS, GLONASS, Galileo, and BeiDou code observations collected from a Xiaomi Mi 8 are processed to evaluate the performance of the proposed stochastic model. Firstly, observation noises are analyzed utilizing code-minus-phase observations, and the results show that GLONASS observations are considerably noisier than observations from other systems. Following, probability distributions of observation noises are evaluated to determine a realistic stochastic model, and the SIGMA- model with different coefficients for each constellation is adopted in this study. The Standard Point Positioning (SPP) method is also used to analyze the positioning performance of the proposed model. The results indicate that the proposed model can provide a 3D positioning accuracy of 1.5 m with the smartphone in static mode, which means the model improves the positioning accuracy by 36.9% compared to the conventional elevation-dependent stochastic approach. From these results, it can be said that the enhanced stochastic approach, based on C/N0 values and computing model coefficients for each constellation differently, can better reflect the stochastic behavior of code observations collected by Android smartphones.

How to cite: Bahadur, B. and Schön, S.: An enhanced stochastic approach for code observations collected from Android smartphones, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5540, https://doi.org/10.5194/egusphere-egu24-5540, 2024.

EGU24-5714 | Orals | G2.6 | Highlight

GLONASS modernization: initial characterization of the first K2 spacecraft 

Peter Steigenberger, Steffen Thoelert, and Oliver Montenbruck

The current operational GLONASS constellation comprises three different types of spacecraft: GLONASS-M, GLONASS-M+ and GLONASS-K1. All satellites transmit legacy frequency division multiple access (FDMA) signals in the L1 and L2 frequency bands, where individual satellites make use of different transmit frequencies. For the M+ and K1 satellites, an L3 code division multiple access (CMDA) signal was added. CDMA signals are transmitted at the same frequency but with satellite-specific ranging codes.

K2 is the latest generation of GLONASS adding CDMA signals in the L1 and L2 frequency bands. The first GLONASS-K2 satellite was launched in August 2023 and started signal transmission in early September 2023. Unfortunately, as of early 2024, no commercial GNSS receiver is able to track the L1 and L2 CDMA signals. Thus, measurements of a 30 m high-gain antenna are used for the characterization of these signals.

The FDMA and CDMA signals of GLONASS-K2 are transmitted via dedicated antennas separated by about 1 m. The differential baseline vector between the phase centers of the two antennas is estimated from an ionosphere- and geometry-free linear combination of L1 and L2 FDMA and L3 CDMA signals observed by a global tracking network. Furthermore, the FDMA L1/L2 ionosphere-free phase center offsets (PCOs) w.r.t. the center of mass are estimated. Both types of estimates are compared to PCOs obtained from the FDMA and CDMA navigation message.

The spacecraft body size of GLONASS-K2 is twice as large as the previous K1 generation. Due to the increased size and the more stretched shape of the satellite body, a proper modeling of the solar radiation pressure is of particular importance for precise orbit determination. Based on approximate dimensions of the satellite and default optical properties, an initial box-wing model is constructed. The performance of this model is evaluated by day boundary discontinuities, clock residuals, and the magnitude of estimated empirical orbit parameters. Finally, the latter quantities are used for an empirical tuning of the box-wing model.

How to cite: Steigenberger, P., Thoelert, S., and Montenbruck, O.: GLONASS modernization: initial characterization of the first K2 spacecraft, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5714, https://doi.org/10.5194/egusphere-egu24-5714, 2024.

EGU24-5987 | ECS | Posters on site | G2.6 | Highlight

Analysis of the Global Multi-GNSS Network Processing Raw Observation Approach using BeiDou 

Patrick Dumitraschkewitz, Torsten Mayer-Guerr, Sandro Krauss, Felix Oehlinger, Barbara Suesser-Rechberger, Andreas Strasser, and Cornelia Tieber-Hubmann

Global Navigation Satellite System (GNSS) products are an integral part of a wide range of scientific and commercial applications such as precise orbit determination for low Earth orbit satellites, earthquake monitoring, GNSS reflectometry, tropospheric and ionospheric research, surveying and many more. These products, consisting of GNSS orbits, clocks, phase biases and more, are generated by the International GNSS Service (IGS) analysis centres by processing observations from a global network of ground stations to one or more GNSS constellations. The processing consists of a combined station position and GNSS satellite orbit determination using a least squares approach donated as global multi-GNSS processing.

Within the IGS 3rd reprocessing (repro3) campaign for the new release of the International Terrestrial Reference Frame (ITRF), Graz University of Technology (TUG), Working Group Satellite Geodesy has contributed as an Analysis Centre (AC) for global multi-GNSS processing. TUG has demonstrated high quality results on par with other ACs using its self-developed geodetic processing software Gravity Recovery Object Oriented Programming System (GROOPS). Within GROOPS the global multi-GNSS processing uses the raw observation approach. The raw observation approach uses all measurements as observed by the receivers without explicitly creating any linear combinations or differences. This allows the information contained in each individual observation to be fully exploited.

GROOPS has been shown to be capable of global multi-GNSS processing using GPS, Galileo and GLONASS. With more publicly available metadata for the BeiDou system, GROOPS has been further developed to use BeiDou within global multi-GNSS processing using the raw observation approach. Therefore, in this contribution we present the improvements in GROOPS global multi-GNSS processing using BeiDou and discuss the quality of the resulting orbit, station position time series, clock and phase bias products.

How to cite: Dumitraschkewitz, P., Mayer-Guerr, T., Krauss, S., Oehlinger, F., Suesser-Rechberger, B., Strasser, A., and Tieber-Hubmann, C.: Analysis of the Global Multi-GNSS Network Processing Raw Observation Approach using BeiDou, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5987, https://doi.org/10.5194/egusphere-egu24-5987, 2024.

EGU24-7066 | ECS | Orals | G2.6

Multi-GNSS double/triple-frequency PPP-AR/RTK performance evaluation in the European region 

Bobin Cui, Shi Du, Xinyuan Jiang, Le Wang, Guanwen Huang, Maorong Ge, and Harald Schuh

With the continuous development and updates of GNSS systems, an increasing number of satellites now emit triple-frequency signals. Currently, research on triple-frequency positioning is predominantly focused on the Asian region, with limited attention given to the multi-frequency positioning performance in Europe. This study utilizes triple-frequency signals from BDS-3/GPS/Galileo satellites and employs observations from EUREF Permanent GNSS Network (EPN) to evaluate the performance of Precise Point Positioning Ambiguity Resolution (PPP-AR) and Atmosphere-augmented Real-Time Kinematics (PPP-RTK) modes in the European region. We calculate Uncalibrated Phase Delay (UPD) using 46 EPN stations and perform PPP-AR on all 138 stations to derive ionospheric and tropospheric delays. The fixing residuals of EWL/WL/NL UPD achieve 99.9%/98.2%/84.9% for BDS, 100.0%/97.1%/89.9% for Galileo, and 99.9%/94.9%/88.7% for GPS satellites within 0.15 cycles, respectively. Double and triple-frequency PPP-AR 68th percentile results achieve 7.0/3.5 and 7.0/6.0 minutes for horizontal and vertical components using GPS/Galileo/BDS constellations. Additionally, the ionospheric delays derived from double and triple frequencies show only slight differences, measured at the centimeter-level among GPS/Galileo/BDS constellations. Relying on atmospheric delay augmentation, i.e., PPP-RTK, we further analyze the positioning performance under varying inter-station distances from 100 km to 400 km. The triple-frequency brings about a 5% improvement in convergence for BDS and Galileo satellites with respect to double-frequency solutions, while only slightly enhancing GPS satellites. Combining GPS/BDS/Galileo achieves nearly instantaneous convergence even at distances up to 400 km. Overall, the European region using GPS/Galileo/BDS constellations can achieve rapid positioning by triple-frequency signals, and instantaneous convergence can be achieved for double and triple-frequency solutions when atmosphere delays are implemented.

How to cite: Cui, B., Du, S., Jiang, X., Wang, L., Huang, G., Ge, M., and Schuh, H.: Multi-GNSS double/triple-frequency PPP-AR/RTK performance evaluation in the European region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7066, https://doi.org/10.5194/egusphere-egu24-7066, 2024.

EGU24-7274 | ECS | Posters on site | G2.6

Extracting planes from sparse 3D LiDAR data with measurement noise model 

Linkun He and Bofeng Li

Global Navigation Satellite System (GNSS) can provide accurate absolute position but requires fine observational conditions. In urban canyons and indoor scenes, GNSS suffers from severe performance degradation and is even unavailable. Thereby, to provide ubiquitous positioning solutions, it is very necessary to incorporate other complementary sensors. A popular option is the 3D LiDAR sensor, which emits its own light and thus is robust to illumination variation. 3D LiDAR sensors can efficiently capture plentiful point patterns of the ambient environment. Besides perception tasks, the obtained point clouds are also used for relative localization in a registration fashion, known as the LiDAR odometry (LO). Generally, LO is based on structural information, where edge and planar features are extensively exploited.

In this work, we propose a novel method aiming to efficiently extract planes from the sparse and noisy 3D LiDAR point clouds. To fully exploit the scanning pattern of this sensor, our method follows a framework of point-to-line-to-plane. The point cloud is firstly projected onto a range image by investigating the azimuth and elevation of each point. In the point-to-line stage, consecutive flat points in a column are grouped into line segments, where a new flat point detector is introduced. In the line-to-plane stage, we extend the classical line extraction method, i.e., Douglas-Peucker algorithm, to find planes in line segments. Considering the over-segmentation caused by occlusion and deformation, we finally conduct region growing and merging to acquire more complete results. Most importantly, we bridge the measurement noise model and the parameter uncertainty via error propagation to determine reasonable thresholds throughout our method.

We test the proposed method on datasets collected by various LiDAR sensors. The experiments are conducted in indoor scenes and urban scenes, which contains abundant planar objects such as walls and building facades. Three point-level metrics, namely positive predictive value (PPV), true positive rate (TPR) and F1 score, are employed for quantitative evaluation. The average PPV, TPR, F1 of the proposed method are 89.92%, 86.38% and 88.11%, respectively. The results show that the proposed method is able to recover the dominant planar structure, which is valuable to LO. Moreover, compared to the rotation rate of the LiDAR sensor, which is generally set to 10 Hz, the average runtime of the proposed method is 15.6 ms/frame, so it is qualified for online operation.

How to cite: He, L. and Li, B.: Extracting planes from sparse 3D LiDAR data with measurement noise model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7274, https://doi.org/10.5194/egusphere-egu24-7274, 2024.

EGU24-7563 | Orals | G2.6

Quality analysis of the low-cost GNSS receiver pseudorange data.  

Rafal Sieradzki, Jacek Paziewski, Katarzyna Stepniak, and Jakub Banach

The last decade has brought us rapid developments in low-cost GNSS receiver technology. The performance level of such receivers can be unexpectedly close to that offered by high-grade geodetic ones. Nevertheless, the further growth of applicability for these types of devices still needs a more detailed analysis of observations.

Motivated by such developments, we focused on the quality of multi-GNSS pseudorange data acquired by three low-cost receivers: u-blox ZED-F9P, Septentrio Mosaic-X5, and Skytraq PX1122R and its comparison with reference values adopted from the geodetic receiver - Trimble Alloy. We investigated two main characteristics of code data – observation noise and correlation in the time domain. In contrast to a typical pseudorange data analysis based on a single-receiver scenario performed with multipath combinations, we extended our tests with data acquired at zero-baseline formed of homogeneous receiver pairs. Such an approach allowed us to analyze the quality of more realistic data, i.e., affected by multipath, and data with multipath removed through between-receiver differencing.

The investigations revealed significant discrepancies in data quality between selected low-cost receivers and recorded signals. Generally, the pseudorange noise was the lowest for Septentrio Mosaic-X5, whereas the noisiest observations were found for Skytraq PX1122R. More interestingly, considering the deviation of code data, Septentrio Mosaic-X5 outperformed the geodetic receiver. On the other, we noted that the low-cost receivers' measurements are noticeably correlated in the time domain, even for between-receiver differences of multipath combinations. 

How to cite: Sieradzki, R., Paziewski, J., Stepniak, K., and Banach, J.: Quality analysis of the low-cost GNSS receiver pseudorange data. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7563, https://doi.org/10.5194/egusphere-egu24-7563, 2024.

EGU24-8163 | ECS | Posters on site | G2.6

Stability analysis of the GNSS reference stations for displacement monitoring 

Katarzyna Stepniak, Pawel Wielgosz, Grzegorz Kurpinski, Mateusz Seta, Jacek Paziewski, and Rafal Sieradzki

Satellite measurements are of great importance in monitoring the deformations of the Earth's crust, which have resulted from the impact of natural forces and human activities. The example of human activities that cause surface deformations is mining activity. Geodetic monitoring of deformations and displacements caused by mining activities is of key importance for ensuring the safety of people's activities on the surface. To perform geodetic surveys, the establishment and maintenance of a local control network with reference stations of the highest accuracy is essential. The stability of the reference network should be constantly monitored and controlled to assessed the quality of the actual solutions of the reference stations and the reliability of the entire network.

The goal of this study is to perform the stability analysis of the GNSS permanent stations located at a mining area where significant mining activity is observed. Daily coordinate solutions obtained from over 2 years of GNSS data processing performed in Bernese GNSS Software v.5.4 are collected and analyzed. The results show that the station coordinates are characterized by high stability over time. The standard deviation is below 2 mm for the horizontal components and below 3.5 mm for the height for all stations. The results also reveal a continuous movement of one station located near a mine shaft. In addition, a jump in the station coordinates was registered which was caused by a mining shock on the 7th of April, 2022. As a results, the station moved 50 mm northwards, 48 mm in the eastwards and 88 mm downwards.

How to cite: Stepniak, K., Wielgosz, P., Kurpinski, G., Seta, M., Paziewski, J., and Sieradzki, R.: Stability analysis of the GNSS reference stations for displacement monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8163, https://doi.org/10.5194/egusphere-egu24-8163, 2024.

EGU24-8485 | ECS | Orals | G2.6

VTEC Estimation Performance of Real-Time PPP with Galileo High Accuracy Service 

Caneren Gul and René Warnant

Precise positioning with Global Navigation Satellite Systems (GNSS) requires a significant amount of effort for deliberate modeling of various effects on transmitted signals. Among these error sources, the ionosphere has a special place with its daily variations of total electron content (TEC), disrupting signals and degrading positioning performance. Some attempts to remove ionospheric effects, such as forming ionosphere-free combinations in Precise Point Positioning (PPP) can cause the amplification of observation noise. Using data-driven Global Ionospheric Maps (GIM) from GNSS analysis centers could be an alternative solution. However, precise GIMs are available after 10-11 days from the observation campaign and are not accessible in real-time. Therefore, the demand for real-time and reliable solutions is a hotspot research field in precise positioning.

Real-time PPP (RT-PPP) with undifferenced and uncombined observables can convert the limitations of the ionosphere into an opportunity to make GNSS a versatile tool that is capable of monitoring the ionosphere and achieving high-accuracy positioning in real time. Our work focuses on the performance of ionospheric delay estimation with RT-PPP, using a newly developed real-time correction service, Galileo High Accuracy Service (Galileo HAS). First, International GNSS Service (IGS) stations from low, mid, and high latitudes for day-of-year 140,141, and 143 were selected for RT-PPP data processing. Next, we performed station-based Vertical TEC (VTEC) modeling and compared the results with GIM from the Centre for Orbit Determination in Europe (CODE). In addition, we processed the data from two receivers co-located on the rooftop of the University of Liège Sart Tilman campus B5a building. Finally, characteristics of the between-receiver single difference of estimated ionospheric delays are presented to assess the precision of slant ionospheric delays.

How to cite: Gul, C. and Warnant, R.: VTEC Estimation Performance of Real-Time PPP with Galileo High Accuracy Service, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8485, https://doi.org/10.5194/egusphere-egu24-8485, 2024.

EGU24-9080 | ECS | Orals | G2.6

How Observation Noise impacts the Estimation of Codephase- and Phase-Center Correction with a Robot in the Field 

Yannick Breva, Johannes Kröger, Tobias Kersten, and Steffen Schön

To ensure an accurate and precise position in GNSS applications, phase center corrections (PCC) have to be taken into account. PCC are antenna and frequency dependent correction values. They describe the distance along the line-of-sight direction between the electrical phase center, where the GNSS signal is received, and the antenna reference point. In Melbourne-Wübenna or code-minus-carrier linear combinations, which are often used in highly precise GNSS applications, the codephase of the GNSS signal plays a key role. Similar to the PCC, also correction values for the codephase observation exist, called codephase center corrections (CPC), also known as group delay variations (GDV). The definition of CPC as well as their estimation process with a robot in the field is similar as for PCC.

The team at Institut für Erdmessung is optimizing the established absolute antenna calibration approach for estimating CPC and PCC for multi GNSS signals in terms of repeatability, noise reduction and multipath impact. In this calibration process, an antenna under test (AUT) is precisely tilted and rotated around a fixed point in space by using a robot. A nearby reference station allows the calculation of time differenced single differences (dSD), which are used to estimate absolute CPC and PCC with spherical harmonics of degree and order 8. The pattern quality and also the repeatability of this approach depends, among other effects, on the observation noise of the GNSS signals.

In this contribution, a detailed study about the influence of observation noise on the estimated patterns is presented. To this end, dSD are simulated based on an existing pattern and the robot positioning. The dSD are modified before the estimation process by polluting them with different kind and magnitude of noise. The estimated patterns are compared using e.g. the root-mean-square or the absolute difference between two runs. Our analysis shows, that 18% of the white noise magnitude is reflected in the repeatability of the pattern estimation in terms of absolute differences between two calibration runs. 

How to cite: Breva, Y., Kröger, J., Kersten, T., and Schön, S.: How Observation Noise impacts the Estimation of Codephase- and Phase-Center Correction with a Robot in the Field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9080, https://doi.org/10.5194/egusphere-egu24-9080, 2024.

EGU24-9332 | ECS | Orals | G2.6 | Highlight

Smartphone PPP with the Galileo High Accuracy Service 

Marcus Franz Wareyka-Glaner and Gregor Möller

With the release of Android 7.0 in 2016, it became possible to retrieve raw GNSS measurement data from Android smartphones. The capability of directly accessing the GNSS measurements allows, among other things, a more reliable estimation of the user’s position by applying external correction data and sophisticated algorithms. However, the GNSS hardware in smartphones is simple and cost-effective, clearly impacting the quality of the measurements. This results in higher levels of noise and frequently occurring effects like outliers, cycle slips, and multipath.

Precise Point Positioning (PPP) is an excellent technique for smartphone positioning due to its features and flexibility. PPP is characterized by applying precise satellite products (orbits, clocks, and biases) and complex models and algorithms to estimate the user's position. Due to this concept, PPP does not require nearby reference stations because these precise satellite products are globally valid. Furthermore, the concept of PPP allows the development of resilient and flexible algorithms, providing a remarkable advantage considering the challenging nature of GNSS measurements from smartphones.

The Galileo High Accuracy Service (HAS) started its service in January 2023. This service is free of charge and provides real-time corrections to the broadcasted navigation message for GPS and Galileo over signal-in-space (E6 frequency) and the internet. The design of the Galileo HAS makes it particularly interesting for low-cost GNSS and smartphone applications. According to the system operator, the Galileo HAS enables position accuracies at the decimeter level, depending on the PPP processing algorithms and the GNSS hardware of the user.

This contribution addresses challenges originating from the ultra-low-cost smartphone equipment and suggests suitable solutions (e.g., data-cleaning algorithms). Furthermore, PPP results with state-of-the-art smartphones (e.g., Google Pixel 7) and the Galileo HAS are presented. The corresponding PPP calculations are performed with our open-source software raPPPid using the uncombined PPP model with ionospheric constraint in quasi-real-time settings. The results demonstrate that it is possible to achieve position accuracies down to the decimeter level with the Galileo HAS under good conditions.

How to cite: Wareyka-Glaner, M. F. and Möller, G.: Smartphone PPP with the Galileo High Accuracy Service, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9332, https://doi.org/10.5194/egusphere-egu24-9332, 2024.

EGU24-9416 | ECS | Posters on site | G2.6

Large Earthquakes Monitoring using High-Rate Global Navigation Satellite System Data through a Deep Learning approach 

Claudia Quinteros-Cartaya, Javier Quintero-Arenas, Johannes Faber, Jonas Köhler, and Nishtha Srivastava

The High-rate Global Navigation Satellite System (HR-GNSS) instruments are devices that can detect seismic wave arrivals and measure ground displacement generated by an earthquake with high precision. By integrating HR-GNSS data with other sensors and models, we can improve the accuracy of earthquake assessments and provide valuable information for early warning and disaster preparedness. Our focus lies in developing deep-learning models leveraging HR-GNSS waveform data. These models significantly empower our capacity to detect and estimate the magnitude of large earthquakes. Yet, the rapid analysis of HR-GNSS data using deep learning algorithms remains a current challenge. To overcome this challenge, it is crucial to have access to large and high-quality datasets. Since the presence of noise in GNSS recordings particularly impacts data quality, especially for earthquakes measuring below magnitude 7, our training of Deep Learning (DL) models primarily relies on the data available from the largest earthquakes. This comes with a trade-off as these events provide a limited dataset because they occur less frequently, making the data poorly representative for model training. To overcome this limitation, we have used both synthetic earthquake signals combined with synthetic and real noise for model training, validation, and testing. Our investigation explores how diverse factors, such as noise, earthquake magnitude, station density, distance from the epicenter, and duration of the signal, affect the performance of our models. We aim to generalize the detection methodology and magnitude estimation for real-time monitoring of large earthquakes across diverse tectonic regions. The DL models proposed in this work will be integrated as complementary algorithms to the open-source Python package SAIPy.

How to cite: Quinteros-Cartaya, C., Quintero-Arenas, J., Faber, J., Köhler, J., and Srivastava, N.: Large Earthquakes Monitoring using High-Rate Global Navigation Satellite System Data through a Deep Learning approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9416, https://doi.org/10.5194/egusphere-egu24-9416, 2024.

EGU24-9540 | ECS | Posters on site | G2.6

QC-MAINS: A Quality Control-based Multi-Antenna GNSS/INS Tightly Integrated Model 

guang'e chen and bofeng li

The integration of Global Navigation Satellite System (GNSS) and Inertial Navigation System (INS) has been widely used in civilian vehicular navigation, which can provide precise position and attitude for vehicle control and trajectory planning. Nevertheless, the accuracy of the GNSS/INS combined system inevitably diminishes when GNSS signals are frequently obstructed or interrupted, leading to an insufficient number of GNSS observations to mitigate INS drift. To improve the performance of the GNSS/INS system in such GNSS-compromised environments, nowadays the mainstream solution is further combining other sensors, i.e., Lidar, Camera or odometer. The crux of these approaches lies in introducing external pose information to supplement the missing GNSS signals. However, more sensors mean more complex system, as well as higher cost.

In many so-called GNSS-compromised environments (i.e., routes under trees, urban canyons), GNSS signals do not completely vanish but are characterized by reduced quantity and weakened quality. This raises the question: Has the GNSS information under harsh environments been completely utilized? The answer obviously is no. To realize the fully utilization of the GNSS information, this work studied a Quality Control-based Multi-Antenna GNSS/INS Tightly Integrated Model (QC-MAINS). The tight integration of INS and the multiply antennas located at different positions on a vehicle can explore potential GNSS observations as much as possible. Furthermore, the low-quantity GNSS observations can be detected and isolated through cross-checks with multiple antennas. Experiment results show that the horizontal position root-mean-square errors (RMSEs) are reduced by about 42, 54, and 48% for three harsh routes, respectively.

How to cite: chen, G. and li, B.: QC-MAINS: A Quality Control-based Multi-Antenna GNSS/INS Tightly Integrated Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9540, https://doi.org/10.5194/egusphere-egu24-9540, 2024.

EGU24-9735 | ECS | Posters on site | G2.6

LEO satellite clock determination in real-time with predicted orbits introduced 

Wei Xie, Hang Su, Kan Wang, Min Zou, and Xuhai Yang

Low Earth Orbit (LEO) satellites have been discussed to augment the traditional GNSS-based Positioning Navigation and Timing (PNT) service in real-time, in which the high-precision real-time LEO satellite clock products are the prerequisite. As the complicated systematic effects contained in the LEO satellite clock estimates hamper high-precision mid- to long-term clock prediction, a typical and efficient method to obtain high-precision real-time LEO satellite clocks is Kalman-filter-based clock estimation with short-term prediction. The strong correlation between the LEO satellite clock and the radial orbital component, however, leads to poorer clock precision than needed. In this contribution, reduced-dynamic LEO satellite orbits are first estimated in batch least-squares adjustment with high accuracy in near real-time. The short-term predicted orbits are introduced and constrained during the Kalman-filter-based clock estimation process. The variance-covariance matrix of the introduced orbital errors is carefully considered and tested for different sets of values in the radial, along-track and cross-track directions. One week of GPS data from the Sentinel-3B onboard receiver in 2018 were used for the purpose of validation. When introducing high-accuracy predicted orbits at the first 5 min, i.e., with an accuracy of 3.33, 1.78 and 2.03 cm in the along-track, cross-track and radial direction, respectively, the precision of the estimated clocks can be improved from 0.268 ns to 0.233 ns, with an improvement of 13.06%. Moreover, the Signal-In-Space Range Error (SISRE) of the LEO satellite to the Earth can be improved from about 9.59 to 7.62 cm after introducing the predicted orbits. The results have demonstrated that the proposed method helps to improve the precision of the real-time LEO satellite clock estimates.

How to cite: Xie, W., Su, H., Wang, K., Zou, M., and Yang, X.: LEO satellite clock determination in real-time with predicted orbits introduced, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9735, https://doi.org/10.5194/egusphere-egu24-9735, 2024.

EGU24-9955 | Posters virtual | G2.6

Performance evaluation of a high-precision timing receiver based on the BDS-3 PPP-B2b service 

Daqian Lyu, Jifei Pan, Fangzheng Liu, and Jie Wang

    The precise point positioning (PPP) timing service has been proposed in recent years and has been demonstrated to achieve sub-nanosecond accuracy. As an integral part of BDS-3, the PPP services via b2b signals (hereafter referred to as PPP-B2b) are provided by BDS-3 GEO satellites with better than decimeter-level accuracy for users around China. In this research, a high-precision timing receiver based on the BDS-3 PPP-B2b service has been established, which obtains the local clock offset with respect to Beidou Time (BDT) through PPP time transfer, and controls the local clock of the receiver according to the clock offset. The 1PPS output of the receiver clock is adjusted to the BDT.

    First, the performance of the time transfer is evaluated. The experimental results of two links show that a level of 0.20 ns can be achieved with a convergence time of 20 minutes. Second, the timing performance of the receiver is examined using UTC(NTSC) as a reference. The timing accuracy is better than 0.2 ns in terms of standard daily deviation, and the frequency stability could reach about 2 × 10-14 in 1 day. Third, we compare the time synchronization performance between two receivers using rubidium and a crystal oscillator as the external clock, respectively. When the average time exceeds 10s, the time variance and the Allan variance of the scheme using rubidium clocks is better than the scheme using crystal oscillators.

How to cite: Lyu, D., Pan, J., Liu, F., and Wang, J.: Performance evaluation of a high-precision timing receiver based on the BDS-3 PPP-B2b service, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9955, https://doi.org/10.5194/egusphere-egu24-9955, 2024.

EGU24-10125 | Posters on site | G2.6

Ionospheric Disturbance Index for GNSS Precise Positioning: Comparison between GIX and ROTI over China  

Zhihao Fu, Xuhui Shen, Ningbo Wang, and Ang Li

The spatial gradient of Total Electron Content (TEC) demonstrates a notable correlation with occurrences of ionospheric scintillation and degradation in Global Navigation Satellite Systems (GNSS) performance. To assess the degree of the ionosphere perturbation over China, we utilize two ionospheric disturbance indices, i.e., the Gradient Ionospheric Index (GIX) and Rate of Total Electron Content Index (ROTI). Analyzing data from over 230 GNSS stations in China, we investigated the consistency and differences in ionospheric irregularities as indicated by GIX and ROTI, focusing particularly on the impact of horizontal gradients of vertical TEC (VTEC) on GNSS positioning. Experimental results indicate that the occurrence of ionospheric irregularities and the degradation of kinematic Precise Point Positioning (PPP) performance are more closely aligned with the strong horizontal VTEC gradients indicated by GIX, both in evolutionary characteristics and temporal variations, compared to ROTI. Notably, severe position errors and strong horizontal gradient of VTEC were consistently observed throughout the entire duration of St. Patrick's Day storm, including the prestorm period (06-16 UT on 16th March), the main phase (06-13 UT on 17th March), and the late recovery phase (05-14 UT on March 19th). Furthermore, significant PPP degradation (3-D PPP>1m) occurred not only preceded the intensification of ROTI but also in periods of stable ionospheric conditions indicated by ROTI values below 0.4 TECU/min, particularly on March 19th. The degradation primarily occurred in regions with significant irregularities, especially when the horizontal VTEC gradient surpassed a specific threshold (GIXx, P95+ > 55 mTECU/km, 1 mTECU/km = 10−3 TECU/km). These findings indicate the potential of GIX in effectively capturing the effects of ionospheric disturbances and enhancing the safety and accuracy of GNSS navigation and positioning.

How to cite: Fu, Z., Shen, X., Wang, N., and Li, A.: Ionospheric Disturbance Index for GNSS Precise Positioning: Comparison between GIX and ROTI over China , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10125, https://doi.org/10.5194/egusphere-egu24-10125, 2024.

The Global Navigation Satellite System (GNSS) carrier phase and pseudorange measurements exhibit different levels of accuracy, and there are differences in observation accuracy among different observation systems, satellites and receivers. A reasonable stochastic model is crucial for improving Precise Point Positioning (PPP) results. We propose a method for constructing stochastic models in PPP using triple-frequency observations. By forming geometry-free and ionosphere-free (GFIF) combinations and subtracting inter-frequency clock biases (IFCB), the accuracies of phase and pseudorange observations are evaluated using residuals to determine weights. Data from 278 International GNSS Service (IGS) stations on September 1, 2023 are processed to calculate the accuracies of carrier phase and pseudorange observations in GPS, Galileo, and BDS-3 systems. The results show that the accuracies of carrier phase observations among different receivers are relatively close, while there are obvious disparities in pseudorange observation accuracies. The average Root Mean Square (RMS) of Galileo carrier phase and pseudorange observations is the smallest among three systems. In BDS-3 system, there are certain disparities in carrier phase observation accuracies among different types of satellites. Specifically, for LEICA and SEPT receivers, the average RMS of IGSO satellites is greater than that of MEO satellites. To validate the effectiveness of the proposed model, the static and dynamic PPP solutions are conducted using 80 IGS stations. The results demonstrate that compared to the empirical model, the proposed model shortens the average convergence time by 22.5%, 31.5%, and 24.1% in static PPP for GPS, Galileo, and BDS-3 systems, respectively. At 0.5h, the average three dimensions (3D) positioning accuracies improve by 2.1, 3.5 and 2.9 cm, respectively. For dynamic PPP within the range of 0.5 to 1 hour, the average RMS of the 3D positioning are reduced by 2.6, 4.7 and 3.0 cm, respectively. Furthermore, for multi-system PPP of GPS+Galileo+BDS-3, the average convergence time and positioning accuracy are also improved with the proposed stochastic model.

How to cite: Xiao, J. and Li, H.: Construction and Evaluation of the Stochastic Model in Precise Point Positioning based on Triple-Frequency Geometry-Free Combination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10780, https://doi.org/10.5194/egusphere-egu24-10780, 2024.

EGU24-12883 | ECS | Orals | G2.6

Applying non-tidal atmosphere and ocean loading corrections on the observation, normal equation, and parameter levels in GNSS data analysis 

Jungang Wang, Henryk Dobslaw, Kyriakos Balidakis, Susanne Glaser, Benjamin Männel, Maorong Ge, Robert Heinkelmann, and Harald Schuh

To achieve the 1 mm accuracy and 0.1 mm/year stability of Terrestrial Reference Frame (TRF) required by Global Geodetic Observing System (GGOS), various surface displacements have to be precisely modeled. Non-tidal atmosphere, ocean, and hydrology loading displacements are major sources causing stochastic and systematic effects in station coordinates estimated by space geodetic techniques such as Global Navigation Satellite Systems (GNSS). Studies show that the correction of non-tidal loading displacements in GNSS station coordinate time series reduces coordinate repeatability and thereby improves stability. Currently, non-tidal loading displacements are corrected on the observation level in Very Long Baseline Interferometry (VLBI) data analysis for standard IVS (International VLBI Service for Geodesy and Astrometry) products, but not in GNSS data analysis. We applied the ESMGFZ non-tidal atmosphere and ocean loading displacements (NTAOL) on the observation, normal equation, and parameter levels for global GNSS network solutions in 2005-2019. We demonstrate that the station coordinate repeatability can be significantly improved when correcting NTAOL displacements, especially in the up component where a reduction of 20-30% can be observed at middle and high latitudes. Whereas for other geodetic parameters, such as satellite orbits, Earth Rotation Parameters (ERP), and geocenter motion, however, the impact of NTAOL displacements is insignificant. The difference between applying NTAOL displacements on the observation to that on the normal equation level is on sub-daily scales and we show that most of these differences are absorbed by receiver clocks. As for the differences of applying NTAOL on the observation and on the parameter levels, small but systematic effects on the horizontal components of station coordinates appear, which are mainly due to network alignment. We also demonstrate that the a priori tropospheric delay modeling affects the non-tidal atmosphere loading signals in station coordinates, i.e., when applying empirical tropospheric delay models, e.g., GPT3, NTAL correction introduces a significantly smaller improvement of station coordinate repeatabilities (below 5% in up component). Hence, we recommend always using discrete tropospheric delay products from Numerical Weather Model (NWM) as a priori values when NTAL corrections are applied.

How to cite: Wang, J., Dobslaw, H., Balidakis, K., Glaser, S., Männel, B., Ge, M., Heinkelmann, R., and Schuh, H.: Applying non-tidal atmosphere and ocean loading corrections on the observation, normal equation, and parameter levels in GNSS data analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12883, https://doi.org/10.5194/egusphere-egu24-12883, 2024.

EGU24-13425 | ECS | Orals | G2.6

The Galileo for Science project: Bernese GNSS Software applications for Fundamental Physics 

Marco Cinelli, Feliciana Sapio, David Lucchesi, Massimo Visco, Alessandro Di Marco, Emiliano Fiorenza, Carlo Lefevre, Pasqualino Loffredo, Marco Lucente, Carmelo Magnafico, Roberto Peron, Francesco Santoli, and Francesco Vespe

The Galileo for Science Project (G4S_2.0) is an ongoing project funded by the Italian Space Agency that has several goals in the field of Fundamental Physics by exploiting the Galileo-FOC Constellation and, in particular, GSAT0201 (E18) and GSAT0202 (E14), the two satellite in elliptical orbit. By exploiting the accuracy of the atomic clocks on board the satellites, in particular of the clock-bias estimated in the process of data reduction of the tracking observations during a Precise Orbit Determination (POD), it allows on the one hand to measure the gravitational redshift, constraining the Local Position Invariance (LPI) and, on the other hand, to place constraints on the possible presence of dark matter in our galaxy in the form of Domain Walls. A fundamental point is obtaining a suitable satellite orbit solution by performing an accurate POD. In this context, the activities carried out with the Bernese code will be presented.

How to cite: Cinelli, M., Sapio, F., Lucchesi, D., Visco, M., Di Marco, A., Fiorenza, E., Lefevre, C., Loffredo, P., Lucente, M., Magnafico, C., Peron, R., Santoli, F., and Vespe, F.: The Galileo for Science project: Bernese GNSS Software applications for Fundamental Physics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13425, https://doi.org/10.5194/egusphere-egu24-13425, 2024.

With more continuous Global Navigation Satellite System (cGNSS) network stations becoming available around the world and with improved data processing techniques, it is possible to observe and model subtle motions in the Earth’s crust that were previously undetectable. Critical to studying these subtle motions is understanding the contributions of various signals mixed into the cGNSS time-series, for example non-tidal atmospheric and ocean loading (NTAOL) and hydrologic loading. We investigate the effect that atmospheric and surface mass loading has on the stochastic properties of GPS time series around the Great Lakes (GL) region of the U.S. and Canada. This region is ideal for studying these effects because it is covered by a dense network of GPS stations and it is known to be affected by significant hydrological loading due to water level changes in the GL. We use readily available NTAOL and hydrologic loading models to remove these signals from the cGNSS time-series and track the variance changes in the residual time-series in order to quantify the effect of each loading component. In order to assess whether the loading models fully capture the full magnitude of displacement we also perform common mode filtering in order to extract the remaining spatially correlated signal. We estimate the stochastic parameters (white noise amplitude, power law amplitude and spectral index) and compare between the raw, loading corrected, and filtered loading corrected time series in order to evaluate the contribution of the different loading signals to the time series noise properties. The outcomes of this study will help validate existing loading models and where improvement may be needed. Results will also support GNSS data providers in assessing the quality of available GNSS stations for use in scientific and surveying applications.

How to cite: Krcmaric, J. and Kreemer, C.: Evaluating the effect of atmospheric and surface mass loading on the stochastic properties of GPS time series in the Great Lakes region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13929, https://doi.org/10.5194/egusphere-egu24-13929, 2024.

EGU24-14958 | ECS | Orals | G2.6

An attempt to model the accuracy of GNSS Positioning from GIPSY-X PPP-AR Referring to  JPL’s 2019 Experiment 

Deniz Çetin, D. Ugur Sanli, and Sermet Ogutcu

Multi-GNSS techniques are continuously improving themselves and strengthening their infrastructures. In response, companies producing GNSS hardware and software are enhancing their products with refined techniques, leading to improved positioning precision. In line with these advancements, efforts are being made to enhance algorithms which predict the accuracy of GNSS positioning. Following these improvements, users who conduct field works or optimize networks would want to know about the improved accuracy of GNSS positioning. After GPS, the new members of the GNSS are continually improving their infrastructure. To achieve the desired coordination in terms of a common processing ground among these techniques remains a challenge. This is particularly crucial for organizations developing GNSS software. For instance, NASA JPL has been making efforts to produce a PPP-AR solution. The transition from GIPSY OASIS II to GIPSY-X allowed for the processing of combined GPS, GLONASS, and GALILEO data in a JPL experiment in 2019. However, today, there is yet no AR infrastructure for the combined solution of all techniques beyond the float solution. In this study, we investigated whether JPL's 2019 AR solution is still applicable to current research. Initial attempts yielded promising results as we conducted experiments with 50 points from the IGS MGEX network's shared data. By comparing the differences between the 2019 PPP-AR solution and the 2019 and 2023 float solutions, we found that the discrepancies are not significantly large in today's GNSS accuracy. We concluded that an accuracy model generated from the 2019 AR solution could provide a satisfactory estimate for today's users. Initial findings indicate that GPS performs well with the combination of three techniques, while the synergy of techniques significantly contributes to the improvement of the vertical positioning. The accuracy produced by the combination is witnessed to be dependent on the observation period, emphasizing the need for attention from those conducting campaign measurements in this context.

How to cite: Çetin, D., Sanli, D. U., and Ogutcu, S.: An attempt to model the accuracy of GNSS Positioning from GIPSY-X PPP-AR Referring to  JPL’s 2019 Experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14958, https://doi.org/10.5194/egusphere-egu24-14958, 2024.

EGU24-18577 | Posters on site | G2.6

The influence of the PPP-RTK reference station network configuration on position accuracy and real-time performance 

Christian Rost, Franziska Riedel, Martin Freitag, Markus Vennebusch, Vitaly Winter, Timon Stockhaus, Christian Trautvetter, and Christoph Knöfel

PPP-RTK is a GNSS-based method for absolute positioning in real-time that has gained importance in recent years. Unlike network RTK, correction data can be provided as broadcast to an unlimited number of users.

In Germany, a nationwide PPP-RTK service is about to be implemented. The service is being set up in cooperation with the surveying authorities of the federal states and the Bundesamt für Kartographie und Geodäsie (BKG). Two independent computing facilities at BKG and Zentrale Stelle SAPOS® guarantee a high level of reliability of the service. Although both facilities use the GNSS processing software GNSMART, the analysed reference station networks differ. The service is currently being tested with various scenarios and setups. Due to its redundancy, different configurations can be analysed in parallel.  The service performance is monitored in a nationwide monitoring network. Three of these monitoring stations are equipped with two identical receivers that are connected to the same antenna and can be used for detailed comparisons of the two service setups. We present results how the network configuration impacts the service performance with a special focus on the present ionosphere activity.

How to cite: Rost, C., Riedel, F., Freitag, M., Vennebusch, M., Winter, V., Stockhaus, T., Trautvetter, C., and Knöfel, C.: The influence of the PPP-RTK reference station network configuration on position accuracy and real-time performance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18577, https://doi.org/10.5194/egusphere-egu24-18577, 2024.

EGU24-19312 | ECS | Posters on site | G2.6

Real-time GPS vs full-GNSS time series accuracies estimations at RING INGV research infrastructure 

Pietro Miele, Antonio Avallone, Ciriaco D'Ambrosio, Luigi Falco, Du Shi, Ge Maorong, Jiang Xinyuan, Devoti Roberto, Famiglietti Nicola Angelo, Grasso Carmine, Pietrantonio Grazia, and Vicari Annamaria

The RING (Rete Integrata Nazionale GNSS) is a research infrastructure developed for accurately measuring deformations at different spatial and temporal scales in the Eurasia-Africa plate boundary region (Avallone et al., 2010). Currently, the RING network (http://ring.gm.ingv.it/) is composed of 280 real-time transmitting remote sites, 70% of which are now equipped with full-GNSS (GPS, Galileo, Glonass and Beidou) instrumentation. The data streaming, in standard RTCM v.3 format, from these sites to the acquisition centre in southern Italy (Sezione Irpinia, Grottaminarda, AV) is managed by a tuned Ntrip Caster (https://igs.bkg.bund.de/ntrip/bkgcaster).

The typical magnitude of the strongest events that occurred in the last century in this region (5.5-7) should require high accuracy (2-3 cm) GPS/GNSS time series to properly observe both static and dynamic coseismic displacements and, then, to properly model the earthquake source. Furthermore, the detection of any afterslip or, in general, any transient deformation should require even better accuracy (< 2 cm). The real-time GPS/GNSS data analysis has been implemented by means of the RTPPP software developed by GFZ (Ge et al., 2012). This software allows the determination of various Precise Point Positioning products with increasing accuracy (standard PPP, PPP with ambiguity resolution [PPP-AR], and PPP with regional augmentation [PPP-RA]). We performed some preliminary investigations on different (limited in time) datasets and we compared GPS-only and full-GNSS results. In the case of GPS-only PPP-RA solutions, the accuracies estimated on 24-hour data for the whole network amount up to 1.7 cm and 6 cm for the horizontal and vertical components, respectively. In the case of full-GNSS solutions, the same approach (PPP-RA) allowed an improvement of about 22% on both horizontal and vertical components (1.3 cm and 4.6 cm). Furthermore, we compared both GPS-only and full-GNSS solutions with another method, i.e. by using a short-term accuracy analysis. Using 60-s or 120-s sliding windows, that should better simulate the time span for detecting coseismic displacements, we can achieve 0.5 cm and 1 cm for horizontal and vertical components, respectively, for GPS-only solutions, and 0.3 cm and 0.5 cm for full-GNSS ones.

Finally, for a few examples of earthquakes that recently occurred in Italy, we will show comparisons between post processed high-rate solutions carried out by Gipsy-Oasis II solutions and those obtained by RTPPP simulating real-time time series. The obtained accuracies will demonstrate the reliability of the RING infrastructure real-time GNSS solutions for early warning and rapid response applications.  

How to cite: Miele, P., Avallone, A., D'Ambrosio, C., Falco, L., Shi, D., Maorong, G., Xinyuan, J., Roberto, D., Nicola Angelo, F., Carmine, G., Grazia, P., and Annamaria, V.: Real-time GPS vs full-GNSS time series accuracies estimations at RING INGV research infrastructure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19312, https://doi.org/10.5194/egusphere-egu24-19312, 2024.

EGU24-20505 | ECS | Posters on site | G2.6

Noise Characteristics in Single and Multi-GNSS Precise Point Positioning with Ambiguity Resolution: A Comparative Analysis of GPS, GLONASS, and Galileo 

Eshetu Erkihune, Felicia Teferle, Addisu Hunegnaw, and Hüseyin Duman

In Precise Point Positioning (PPP) GNSS processing strategy, understanding the stochastic noise, particularly white plus power-law and white plus flicker noise, is essential for improving precision of coordinate estimates. In this study, we present an analysis of single-system and multi-GNSS PPP AR solutions using observations from the GPS, GLONASS and Galileo constellations. We employed three independent software packages, the Bernese GNSS Software v5.4 (BSW5.4), PRIDE-PPPAR (PRIDE) and GipsyX v2.1 (GX2.1), each employing their recommended set of products and processing settings, while attempting to keep settings as consistent as possible between the software packages and processing runs. We processed data from 50 globally distributed IGS stations, carefully selected for known quality and network geometry, for 2019.0 – 2023.5. In our recently showed that Galileo's single-GNSS solutions outperform GPS and GLONASS in precision (AGU2023 conference poster presentation). Combining GPS with Galileo provide the highest precision in coordinate estimates. This was confirmed through consistent results from three PPP-AR tools. We highlight the advantage of combining GPS and Galileo for superior GNSS positioning precision. In this study, we conduct a comprehensive noise and power spectra analysis of the position time series, focusing on solutions from GPS, GLONASS, and Galileo constellations and combinations. A comprehensive exploration was performed, initially delving into the precision of coordinate estimates through both single system (GPS, GLONASS, and Galileo) solutions and multi-GNSS solutions (including all possible binary and triple combinations) followed by an investigation of the noise characterstics using the Hector v2.0 software. We employed both power-law plus white noise and flicker plus white noise models to assess the behavior and amplitude of the different noises. Moreover, this research uses spectral analysis to emphasize power reduction strategies for periodic signals in single-system and multi-GNSS solutions. 

How to cite: Erkihune, E., Teferle, F., Hunegnaw, A., and Duman, H.: Noise Characteristics in Single and Multi-GNSS Precise Point Positioning with Ambiguity Resolution: A Comparative Analysis of GPS, GLONASS, and Galileo, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20505, https://doi.org/10.5194/egusphere-egu24-20505, 2024.

EGU24-3806 | ECS | PICO | G2.7

A low-cost commercial off-the-shelf GNSS receiver for space 

Gregor Moeller, Alexander Wolf, Flavio Sonnenberg, Gerald Bauer, Benedikt Soja, and Markus Rothacher

The era of tracking artificial Earth satellites using Global Navigation Satellite Systems (GNSS) began in the early 1980s when a GPS receiver was launched onboard the Landsat-4 mission. Since then, a large number of Low Earth Orbiters has utilized constantly improved GPS receivers for timing and positioning. GNSS has become a key technique not only for satellite orbit determination but also for atmosphere sounding. With the increasing popularity of miniaturized satellites in recent years, the need for an adapted GNSS payload for nanosatellites arose. Therefore, we developed a small-size, versatile payload board using commercial-off-the-shelf (COTS) low-cost multi-GNSS receivers with extremely small weight, size, and power consumption.

The receiver firmware enables multi-constellation navigation solutions and GNSS raw data output in space with a sampling rate of up to 20 Hz. With this configuration, we can retrieve the required GNSS code and carrier phase measurements, e.g. for precise orbit and attitude determination, to monitor the total air density from drag, the distribution of the electron content, or scintillation effects. The high demands on GNSS receiver performance lead to particular requirements for hardware, payload software, onboard computing, data downlink, and remote control, which will be briefly discussed in the presentation. The resulting low-cost GNSS board fits into a 0.25U form factor, and the modular design makes it a scalable and adaptable payload for CubeSat missions.

In this presentation, we will provide insight into the performance of the GNSS payload under simulated orbit conditions and highlight the necessary modifications that allow us to transform a COTS GNSS receiver into a scientific instrument for space applications.

How to cite: Moeller, G., Wolf, A., Sonnenberg, F., Bauer, G., Soja, B., and Rothacher, M.: A low-cost commercial off-the-shelf GNSS receiver for space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3806, https://doi.org/10.5194/egusphere-egu24-3806, 2024.

Real-Time Single-Frequency Precise Point Positioning (PPP) is a cost-effective and promising method for achieving highly accurate navigation at sub-meter or centimeter levels. However, its success heavily relies on real-time ionospheric state estimations to correct delays in Global Navigation Satellite System (GNSS) signals. This research employs the Dynamic Mode Decomposition (DMD) model in conjunction with global ionospheric vertical total electron content (vTEC) Root Mean Square (RMS) maps to create 24-hour forecasts of global ionospheric vTEC RMS maps. These forecasts are integrated with C1P forecast products, and the performance of L1 single-frequency positioning solutions is compared across various ionospheric correction models. The study assesses the impact of assimilating predicted RMS data and evaluates the practicality of the proposed approach using the IGRG product. The results demonstrate that the IGSG RMS prediction-based model significantly enhances positioning accuracy for up to five hours ahead, yielding results comparable to alternative models. This approach holds promise for achieving high precision navigation.

How to cite: Reuveni, Y. and Landa, V.: Advancing Real-Time GNSS Single-Frequency Precise Point Positioning through Ionospheric Corrections, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5282, https://doi.org/10.5194/egusphere-egu24-5282, 2024.

EGU24-5511 | ECS | PICO | G2.7

New neutral density estimates and forecasts in the framework of project ESPRIT 

Andreas Strasser, Sandro Krauss, Manuel Scherf, Barbara Suesser-Rechberger, and Helmut Lammer

In the ongoing project ESPRIT, a goal is to investigate the contribution of the chemical composition and associated chemical reactions to the Earth’s upper atmosphere. This is realized through a combined analysis of thermospheric neutral density estimates and the exploration of external parameters of the interplanetary space, including variations in the magnetic field and the merged electric field. Regarding changes in the chemical composition of the Earth’s atmosphere, which might cause heating and cooling effects, we investigated TIMED/SABER measurements in conjunction with findings from the 1D first-principles hydrodynamic upper atmosphere model Kompot code, which shows some significant expansion in the density profile mainly based on the increased XUV flux from the Sun. The neutral mass densities were processed based on accelerometer measurements as well as on kinematic orbit information (Süsser-Rechberger et al. 2022). This allowed us to successfully process kinematic orbits for 19 different satellites at an altitude range of approximately 400 to 1300 km. Both approaches are realized using the in-house software package GROOPS. During the evaluation, significant improvements in the processing and parametrization could be achieved compared to previous solutions, especially through refined models for solar radiation pressure, the Earth’s re-radiation, the thermal radiation of the satellite itself and the consideration of the chemical composition of the atmosphere. Based on these new neutral density estimates, investigations regarding the effects of solar eruptions on the various satellites are performed and used for attempting to forecast the orbital decay of LEO satellites.

How to cite: Strasser, A., Krauss, S., Scherf, M., Suesser-Rechberger, B., and Lammer, H.: New neutral density estimates and forecasts in the framework of project ESPRIT, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5511, https://doi.org/10.5194/egusphere-egu24-5511, 2024.

EGU24-5567 | PICO | G2.7

Sequential calibration and data assimilation for predicting atmospheric variability 

Ehsan Forootan, Saeed Farzaneh, Masoud Dehvari, Leire Retegui-Schiettekatte, and Maike Schumacher

Estimating global and multi-level variations of the atmospheric variables and being able to predict them are very important for studying coupling processes within the atmosphere, and for various geodetic and space weather applications. These variables include the thermosphere neutral density, the ionospheric electron density, and the tropospheric water vapour, which are relevant to applications such as orbit determination, satellite navigation, and weather/climate monitoring. Available models have difficulties in realistic prediction of these variables due to the simplicity of their structure or sampling limitations. In this study, we present an ensemble-based simultaneous Calibration and Data Assimilation (C/DA) algorithm to integrate freely available satellite geodetic data (e.g., CHAMP, GRACE(-FO), Swarm, and GNSS) into empirical models with the focus on improving the predictability of atmospheric variables. The improved model, called `C/DA-model' will be assessed in relevant geodetic and space weather applications. For demonstration, the CDA-NRLMSISE-00 is examined during seven periods with relatively high geomagnetic activity and CDA-IRI-ZWD during extensive rainy events.

How to cite: Forootan, E., Farzaneh, S., Dehvari, M., Retegui-Schiettekatte, L., and Schumacher, M.: Sequential calibration and data assimilation for predicting atmospheric variability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5567, https://doi.org/10.5194/egusphere-egu24-5567, 2024.

The upcoming low earth orbit (LEO) constellations can bring new opportunities for ionospheric sounding below the LEO satellite altitude. The CENTISPACETM LEO satellites working with an altitude of 700 km broadcasting navigation augmentation signals to the ground stations. This study established a regional bottomside ionospheric map (RBIM) using navigation augmentation signals from two CENTISPACETM satellites on April 1, 2023, under moderate solar activity and quiet geomagnetic conditions. The RBIM accuracy was subsequently validated through comparison with multiple datasets, including Global and Regional Ionospheric Maps (GIMs and RIMs) constructed from ground-based GNSS observations, as well as the differential Slant Bottomside Electron Content (dSBEC) derived from LEO observations. To build the RBIM, the vertical bottomside electron content (VBEC) is fitted by two distinct methods, which are grid map and polynomial methods. The root mean square (RMS) values of the RBIM fitting residuals are 1.2 TECU and 0.7 TECU for the two methods, respectively. The RBIM precision evaluated by LEO dSBEC is better than 1.0 TECU. Comparing the VBEC from established RBIM to the GIM/RIM indicates that the RMS values mostly within 3-8 TECU, which can attribute to the limited modelling precision of the latter two models. What’s more, the RBIM facilitates the probe of the proportional variation of the VBEC over the total electron content using experimental data. The results derived from LEO observations indicate that the VBEC proportion is 83% at noon and 53% at night in the north mid-latitude region, presenting a reduction of 35.36%, which is more realistic than that calculated values from the empirical International Reference Ionosphere (IRI-2020) model (4.65%). Thus, the RBIM can not only benefit LEO navigation augmentation but also provide significant observations on the vertical distribution of ionospheric electron content.

How to cite: He, R., Li, M., Li, W., and Zhang, Q.: Estimating bottomside ionosphere electron content using navigation augmentation observations from two CENTISPACETM LEO satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8540, https://doi.org/10.5194/egusphere-egu24-8540, 2024.

EGU24-9779 | ECS | PICO | G2.7

Monitoring short-term dynamic motion with single-frequency observations from a low-cost GNSS receiver 

Mert Bezcioglu, Berkay Bahadur, Ahmet Anil Dindar, and Cemal Ozer Yigit

In the last few decades, GNSS observations have frequently been used in Structural Health Monitoring (SHM) and Earthquake Early Warning (EEW) systems. The primary advantage of high-frequency GNSS techniques is to detect displacements directly in a terrestrial reference frame compared to conventional geotechnical sensors. Among GNSS techniques, the real-time kinematic (RTK) has predominantly been employed in dynamic displacement monitoring because it provides high accuracy simultaneously. Nevertheless, an external GNSS infrastructure is essential in RTK applications to achieve high positioning accuracy, which restricts its use in possible mega earthquake events. On the other hand, Precise Point Positioning (PPP), which can provide high positioning accuracy with a standalone GNSS receiver on a global scale, emerged as an alternative to traditional GNSS techniques. However, the requirement of an external internet connection for real-time PPP applications is the main restriction of this technique in the employment of possible mega earthquake events like the RTK technique. Instead, the variometric approach (VA) can provide high accuracy in determining dynamic behaviors with a standalone GNSS receiver and broadcast ephemeris only, which means it doesn't require any external infrastructure and connection. Furthermore, the emergence of new navigation systems, such as Galileo and BeiDou, brings considerable opportunities to improve the performance of the VA technique in detecting dynamic behaviors. Thanks to progress in GNSS receiver technology, low-cost GNSS receivers have been introduced and taken considerable attention from the GNSS community. Their more compact design makes low-cost GNSS receivers very usable for establishing monitoring networks in harsh environments, such as high-rise buildings and bridges. In this context, this study aims to evaluate the capability of the VA technique with a low-cost GNSS receiver in detecting horizontal dynamic motion simultaneously. For this purpose, this study employs single-frequency (SF) observations of GPS, GLONASS, Galileo, and BeiDou satellites from the u-blox ZED-F9P receiver for the VA technique. Harmonic motions from 5 to 20 mm with frequencies between 0.3 and 5.0 Hz were generated by a single-axis shake table to analyze the capability of the SF-VA technique in detecting structural motion. Also, a simulation of Mw 6.9 Kobe, 1995 earthquake was performed using the shake table to understand the feasibility of the SF-VA technique in possible EEW systems. In the evaluation, displacements from the Linear Variable Differential Transformer (LVDT) were selected as the reference to assess the capability of the SF-VA technique. The results indicated that the peak frequency value of short-term harmonic oscillations up to 5 Hz can be detected with the SF-VA technique adopting GNSS observations from the low-cost receiver. Besides, the results demonstrated that the SF-VA technique can determine the strong ground motions resulting from mega earthquakes at mm-level.

How to cite: Bezcioglu, M., Bahadur, B., Dindar, A. A., and Yigit, C. O.: Monitoring short-term dynamic motion with single-frequency observations from a low-cost GNSS receiver, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9779, https://doi.org/10.5194/egusphere-egu24-9779, 2024.

EGU24-10188 | PICO | G2.7

A new low-cost GNSS instrument for monitoring of ground motions and critical infrastructures within the Greek “Supersite” 

Athanassios Ganas, George Mavropoulos, Ioannis Karamitros, Konstantinos Nikolakopoulos, Vassiliki Charalampopoulou, Dimitrios Anastasiou, Theodoros Athanassopoulos, Aggeliki Kyriou, and Varvara Tsironi

There is a continuous need for integrating multi-parameter instrumental observations and measurements with Satellite Earth observation data towards continuous monitoring of the environment and infrastructures. This task attains more importance within the tectonic and seismically active area of the Greek "Supersite" (Corinth Gulf, Ionian Islands, etc.). The significant level of geohazards in this region have made necessary the implementation of new technological approaches that could offer reliable augmentation to permanent networks (both geodetic and seismological). In this contribution, we demonstrate the design, construction and installation of a new technological infrastructure that is based on the collaboration of a multidisciplinary research team and on low-cost equipment. Our low-cost instrumentation includes a multi-GNSS dual-frequency chip (Ublox ZED F9P module) mounted on a Raspberry-Pi 4 compute module IO board together with an industry-standard MEMS accelerometer. It provides signal tracking for most of GNSS systems (GPS, GLONASS, Galileo and BeiDou). The GNSS data are collected 24/7/365, quality-checked and processed by use of open-source software. The combined-synergistic use of these new sensors is compatible with ground motion data provided by GNSS reference stations and accelerometers used by seismic agencies. Current work includes the collection, homogenization, processing and archiving of daily data from three test sites using 4G telemetry. The GNSS data support the on-going, pre-operational monitoring of three test sites together with InSAR Copernicus data (Tsironi et al. 2022).

 

Tsironi, V., Ganas, A., Karamitros, I., Efstathiou, E., Koukouvelas, I., Sokos, E. 2022. Kinematics of Active Landslides in Achaia (Peloponnese, Greece) through InSAR Time Series Analysis and Relation to Rainfall Patterns. Remote Sens., 14(4), 844. https://doi.org/10.3390/rs14040844

How to cite: Ganas, A., Mavropoulos, G., Karamitros, I., Nikolakopoulos, K., Charalampopoulou, V., Anastasiou, D., Athanassopoulos, T., Kyriou, A., and Tsironi, V.: A new low-cost GNSS instrument for monitoring of ground motions and critical infrastructures within the Greek “Supersite”, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10188, https://doi.org/10.5194/egusphere-egu24-10188, 2024.

The sensitivity of Global Navigation Satellite Systems (GNSS)  receivers to ionospheric disturbances and their constant growth is nowadays resulting in an increased concern of GNSS-users about the impacts of ionospheric disturbances at mid-latitudes. The geomagnetic storm of June 22-23, 2015, is an example of a rare phenomenon of a spill-over of equatorial plasma bubbles well north from their habitual region of ~+/- 20º around the magnetic equator.

We study the occurrence of small- and medium-scale irregularities in Southern Europe by analysing the behaviour of the amplitude scintillation index S4 and of the Rate Of Total Electron Content Index (ROTI) during the geomagnetic storm of June 22-23, 2015. To the scope, we leverage data obtained by local GNSS receivers for scintillation monitoring located in Lisbon (Portugal) and Lampedusa (Italy). Data is complemented with total electron content (TEC) data both from the local GNSS receivers and from global ionospheric maps.

The multi-source data allows for a better understanding of the ionospheric dynamic during the studied event.

How to cite: Morozova, A., Estaço, D., Spogli, L., and Barata, T.: Scintillations in the Southern Europe during the geomagnetic storm of June 2015: analysis of a plasma bubbles spill-off using local data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10792, https://doi.org/10.5194/egusphere-egu24-10792, 2024.

EGU24-12608 | ECS | PICO | G2.7

NeGIX and TEGIX: two new indices to characterize the topside ionosphere with Swarm 

Juan Andrés Cahuasquí, Mohammed Mainul Hoque, Norbert Jakowski, Dmytro Vasylyev, Stephan Buchert, Grzegorz Nykiel, Martin Kriegel, Paul David, Youssef Tagargouste, and Jens Berdermann

Since its launch in 2013, ESA’s Swarm satellite constellation has pushed the frontiers of space weather research and monitoring by means of its broad spectrum of high-quality experiments on-board. Particularly, Swarm observations are being used to globally characterize small- to mid-scale perturbations in the topside ionosphere that may cause severe amplitude and phase scintillations of trans-ionospheric radio signals. Ionospheric scintillation can cause radio signal outage, as well as disruption of modern technological systems used for telecommunication, navigation and remote sensing.

While performing the Swarm DISC project “Monitoring of Ionospheric Gradients at Swarm (MIGRAS)”, the MIGRAS team has profited from the close orbits and synchronization of Swarm satellites Alpha (A) and Charlie (C) to develop two new products that focus on the monitoring of small- to mid-scale plasma density irregularities with horizontal spatial scales in the order of about 100 km - the electron density (Ne) Gradient Ionospheric indeX (NeGIX), and the Total Electron Content (TEC) Gradient Ionospheric indeX (TEGIX). NeGIX estimates spatial Ne gradients using Langmuir probe measurements, and TEGIX estimates spatial TEC gradients using GNSS Precise Orbit Determination (POD) data of Swarm.

In this work, we provide a comprehensive analysis of the capability of these two novel Swarm data products to characterize the perturbation state of the ionosphere at different geographic locations and conditions of geomagnetic activity. Our analysis covers the whole period of available Swarm observations to quantitively describe expected signatures of ionospheric variability, e.g. gradients at sunrise and sunset time, or equatorial crests. The analysis concentrates also on events of perturbed geomagnetic conditions to compare the performance of NeGIX and TEGIX with existing ground-based indices (e.g. GIX) and Swarm products (e.g. IPIR). Moreover, these indices have been developed technically compatible with Swarm’s and DLR’s operational data services. Therefore, our analysis validates and discusses their applicability for space weather science and purposes.

Acknowledgement: The work is funded by the MIGRAS (Monitoring of Ionospheric Gradients At Swarm) project under the Swarm DISC Subcontract Doc. no: SW‐CO‐DTU‐GS‐133, Rev: 1, 13 September 2022.

How to cite: Cahuasquí, J. A., Hoque, M. M., Jakowski, N., Vasylyev, D., Buchert, S., Nykiel, G., Kriegel, M., David, P., Tagargouste, Y., and Berdermann, J.: NeGIX and TEGIX: two new indices to characterize the topside ionosphere with Swarm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12608, https://doi.org/10.5194/egusphere-egu24-12608, 2024.

EGU24-14279 | PICO | G2.7

Tectonic monitoring with low-cost multi-GNSS installations in Greece 

Jonathan Bedford, Konstantinos Chousianitis, Athanassios Ganas, Vasiliki Mouslopoulou, Efthimios Sokos, Zafeiria Roumelioti, Konstantinos Nikolakopoulos, Christoforos Pappas, Markus Ramatschi, Carsten Falck, Benjamin Männel, Cristian Garcia, Carlos Peña, Kaan Cökerim, Elvira Latypova, Michail Gianniou, Paraskevi Io Ioannidi, Chris Pikridas, Ilias Lazos, and Vasiliki Saltogianni

In 2023, we began installing a low-cost tectonic multi-GNSS network in Greece, funded by the European Research Council. We have installed a total of 45 permanent/continuous-mode stations, with another 15-20 to be installed in 2024. Installations so far have been mainly on the Peloponnese peninsula, with the strategy of increasing spatial resolution in between the existing research and privately operated GNSS networks. Station maintenance is funded by the project (ERC StG: TectoVision) until 2027, but it is the intention that as many as possible of these stations can stay installed (as permanent installations).

The scientific purpose of the new stations is to increase spatial resolution of microplate motions in Greece but these data will also be of use to other research fields needing single- or multi-GNSS observables. Accordingly, these data are being released without embargo subject to completion of quality control checks (with the data publication and link to download to be finalized before EGU 2024).

We consider this installation campaign to be a pilot project in affordable, rapid densification of tectonic-grade GNSS stations. Part of our strategy has been to use relatively low-cost monumentation for the geodetic marker onto which the low-cost installations are installed. Most stations are connected to mains electricity supplies of public buildings, with the monumentation being installed on flat roofs of these buildings. In higher altitude areas where flat roofs are rare, we have made 3 special installations at bedrock sites, with radio telemetry linking to a radio-receiving station in the nearby villages. We use a range of telemetry solutions, with the most common being the transfer of the 30s sampling data via a router containing a Machine-to-Machine (M2M) sim card.

In this presentation, we will show data quality metrics from the initial analysis of 6-11 months of observations and compare to the time series that can be processed from more expensive receiver-antenna combinations. We will also discuss what the team has learned practically (on-site) and logistically about installing low-cost GNSS stations at scale.

How to cite: Bedford, J., Chousianitis, K., Ganas, A., Mouslopoulou, V., Sokos, E., Roumelioti, Z., Nikolakopoulos, K., Pappas, C., Ramatschi, M., Falck, C., Männel, B., Garcia, C., Peña, C., Cökerim, K., Latypova, E., Gianniou, M., Ioannidi, P. I., Pikridas, C., Lazos, I., and Saltogianni, V.: Tectonic monitoring with low-cost multi-GNSS installations in Greece, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14279, https://doi.org/10.5194/egusphere-egu24-14279, 2024.

EGU24-14661 | ECS | PICO | G2.7

Assessing measurement noises from low-cost GNSS receivers and antennas 

Ibaad Anwar and Balaji Devaraju

Observations from the Global Navigation Satellite System (GNSS) play a crucial role in numerous applications, but are prone to measurement noise, especially when utilizing low-cost receivers and antennas. These measurement noises are crucial as they significantly impact the accuracy and reliability of positional data. This study investigates the characteristics and implications of measurement noises in low-cost GNSS systems, with a particular focus on the effects of receiver and antenna quality, environmental factors, and satellite dynamics. It employs a geometry-free approach to GNSS measurement analysis, aiming to identify and quantify the various noise sources in code-pseudorange and carrier phase observations. The analysis utilized data from two low-cost GNSS stations, each equipped with a u-blox dual-frequency receiver. These stations are equipped with survey-grade and navigational antennas. Additionally, data from the IGS station IITK has been used for comparative analysis.

How to cite: Anwar, I. and Devaraju, B.: Assessing measurement noises from low-cost GNSS receivers and antennas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14661, https://doi.org/10.5194/egusphere-egu24-14661, 2024.

EGU24-14817 | ECS | PICO | G2.7

The emergence of low-cost GNSS-IR sensors for surface change monitoring: a case study of the RPR network for measuring the Rhine River level 

Makan A. Karegar, Luciana Fenoglio-Marc, Kristine M. Larson, Jürgen Kusche, and Hakan Uyanik

GNSS Interferometric Reflectometry (GNSS-IR) is redefining its role as an innovative technique in environmental sensing. However, geodetic-quality GNSS receivers and antennas are still very expensive instruments which limits their use as dedicated environmental sensors. Recently, low-cost GNSS-IR sensors have been developed for monitoring surface changes such as water level, snow depth and soil moisture. Real-time signal-to-noise ratio (SNR) observation, the key observable of ground-based GNSS-IR, can open up a range of possibilities for environmental monitoring with low cost sensors that can operate unattended for long periods of time. We have recently successfully developed a low-cost water-level sensor called Raspberry Pi Reflector (RPR) based on GNSS-IR technique (Karegar et al. 2022, Water Resources Research, 58). In spring and summer 2023, a network of eight RPRs was installed along the Rhine, the largest river in Germany, from Petersau to Sankt Goar. We installed some of these RPRs in a relatively steep and narrow middle Rhine valley, where the terrain relief around the instrument can influence the effectiveness of the GNSS-IR approach. The water level measurements provided by these sensors are used to validate the SWOT observations of surface water levels. In this presentation, we will present the results of the deployment of the RPRs and discuss the challenges associated with these low-cost sensors.

How to cite: A. Karegar, M., Fenoglio-Marc, L., M. Larson, K., Kusche, J., and Uyanik, H.: The emergence of low-cost GNSS-IR sensors for surface change monitoring: a case study of the RPR network for measuring the Rhine River level, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14817, https://doi.org/10.5194/egusphere-egu24-14817, 2024.

EGU24-14867 | ECS | PICO | G2.7

GFZRNX-QC: Advanced GNSS Data Processing and Quality Control for Multi-System Observations 

Xinghan Chen, Thomas Nischan, Zhiguo Deng, Benjamin Männel, and Jens Wickert

GFZRNX-QC software is designed to streamline the processing of Receiver Independent Exchange Format (RINEX) observations and the generation of overall information by providing a robust and efficient solution for data cleaning and quality control. With a focus on multiple Global Navigation Satellite System (multi-GNSS) observations, GFZRNX-QC offers a comprehensive approach to ensuring data accuracy and reliability. GFZRNX-QC can allow users to efficiently manage and analyze data from various GNSS receivers, especially for low-cost GNSS receivers. The software incorporates advanced algorithms for data cleaning, helping users to eliminate inconsistencies and enhance the overall quality of GNSS observations. GFZRNX-QC conducts comprehensive quality control assessments on GNSS observations. This ensures that the processed data meets the highest standards of accuracy. The software generates detailed statistical results, offering insights into the performance and reliability of observations across the five major GNSS systems. This information aids researchers and analysts in making informed decisions. GFZRNX-QC produces various outputs that can be e.g. compatible to former processing tools like teqc. This can enhance user convenience and interoperability with other geodetic processing tools.

GFZRNX-QC has been extensively tested by utilizing multi-year data from IGS stations to enable comprehensive long-term statistical analysis. By combining efficient data processing, advanced cleaning algorithms, and extensive quality control measures, GFZRNX-QC serves as a valuable tool for researchers, geodesists, and GNSS professionals seeking reliable and accurate observations and overall information from multiple satellite systems.

How to cite: Chen, X., Nischan, T., Deng, Z., Männel, B., and Wickert, J.: GFZRNX-QC: Advanced GNSS Data Processing and Quality Control for Multi-System Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14867, https://doi.org/10.5194/egusphere-egu24-14867, 2024.

EGU24-17705 | PICO | G2.7

Atmospheric and Soil Moisture Monitoring in Agriculture Using GNSS: First Results from the MAGDA Project 

Andrea Gatti, Alessandro Fumagalli, Stefano Barindelli, and Eugenio Realini

The Meteorological Assimilation from Galileo and Drones for Agriculture (MAGDA) project aims to advance the integrated use of satellite-borne, drone-borne, and in-situ sensors, enhancing irrigation optimisation and weather hazard mitigation in agriculture. At its core, MAGDA employs low-cost Galileo-enabled GNSS ground stations for retrieving atmospheric water vapour and soil moisture. This data, combined with information from other technologies, is intended for assimilation into numerical weather prediction and hydrological models.

MAGDA’s demonstration sites are strategically located in three diverse agricultural regions of Europe: fruit plantations in Italy’s Piedmont, vineyards in France’s Burgundy, and mixed crops in Romania’s Braila county. Each of these sites is equipped with three low-cost GNSS stations, operational since mid-2023, providing valuable data for testing the efficacy and adaptability of GNSS technology in different agricultural and climatic conditions.

In addition to the three demonstration sites, MAGDA leverages data from pre-existing GNSS permanent stations across these countries. A comprehensive dataset from 397 stations in the Italy-France domain and 74 stations in the Romania domain has been downloaded. This data is specifically designed for the assimilation of GNSS-derived water vapour data, covering the entire weather model domains, complementing the localised information from the project’s targeted low-cost stations.

GNSS data processing utilises GReD’s proprietary Breva software, capable of analysing multi-frequency and multi-constellation observations. Atmospheric water vapour estimates are obtained through an undifferenced and uncombined batch least squares Precise Point Positioning (PPP) approach. This method has been employed to analyse six weather events that significantly impacted agricultural operations at the demonstration sites, two events per site.

Soil moisture results have been obtained by a newly developed module of Breva software that applies GNSS reflectometry based on the analysis of SNR measurements influenced by the humidity of the superficial soil. The methodology has been tested and validated at various previously studied sites, as well as directly at the low-cost GNSS stations established by the MAGDA project.

This work presents the preliminary results achieved in the first half of the MAGDA project, outlining encountered limitations and future development plans related to the analysis of MAGDA’s GNSS stations.

How to cite: Gatti, A., Fumagalli, A., Barindelli, S., and Realini, E.: Atmospheric and Soil Moisture Monitoring in Agriculture Using GNSS: First Results from the MAGDA Project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17705, https://doi.org/10.5194/egusphere-egu24-17705, 2024.

EGU24-17764 | ECS | PICO | G2.7

GNSS low-cost prototype on ship for caching tsunami wave propagation  

Paul Jarrin, Lucie Rolland, Maurin Vidal, Pierre Sakic, Frédérique Leclerc, Jean-Xavier Dessa, and Sylvain Palagonia

Ship navigation data records are proposed to be complementary information for monitoring offshore tsunami currents following great earthquakes. Offshore GPS measurements on the research vessel Kilo Moana of the University of Hawaii following the 2010 Mw 8.8 Maule earthquake have illustrated the potential of GPS kinematic positioning solutions, together with a filtering approach, for detecting the ship's vertical displacement promoted by the tsunami travel velocity. However, kinematic positioning of GPS observations on ships is challenging due to the load, ship speed, and wavefield changes on the open ocean that might produce fast changes in the ship's drift and vertical motion. Wavefield could also introduce additional noise frequencies to the GPS positioning, thus decreasing its precision. Herein, we present a dual-frequency Global Satellite Navigation System (GNSS) low-cost prototype based on the Septentrio Mosaic-X5 card and a low-cost AS-ANT2BCAL antenna. Such a low-cost GNSS station has been installed on a non-commercial ship fleet in order to assess the precision and noise content of offshore GNSS positioning and ionosphere Total Electron Content measurements. We discuss our preliminary results by comparing the precision of the multi-GNSS solution (GPS, GLONASS, Galileo) relative to the one from only the GPS solution using both long-baselines and Precise Point Positioning approaches in post-processing mode. In the second step, we simulate a real-time multi-GNSS positioning solution to evaluate their ability to catch wavefield changes. We finally discuss the detectability of tsunamis with the newly developed GNSS low-cost prototype under various conditions.

How to cite: Jarrin, P., Rolland, L., Vidal, M., Sakic, P., Leclerc, F., Dessa, J.-X., and Palagonia, S.: GNSS low-cost prototype on ship for caching tsunami wave propagation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17764, https://doi.org/10.5194/egusphere-egu24-17764, 2024.

G3 – Geodynamics and Earth Fluids

EGU24-327 | ECS | Orals | G3.1

Using Inverse GNSS Methods for the Determination of C20 and C30 Gravity Field Coefficients for the Support of GRACE Solutions    

Adrian Nowak, Radosław Zajdel, Filip Gałdyn, and Krzysztof Sośnica

The distribution of atmospheric, hydrological, and oceanic mass loads on the lithosphere affects the deformation of the Earth's surface over time. Monitoring of the relative displacements of the dense global network of permanent Global Navigation Satellite System (GNSS) stations enables the direct measurement of these loads on a global scale. The application of inverse GNSS methods provides an independent tool to retrieve the time variable gravity (TVG) models of the Earth system and to support hydrogeodesy studies, including the monitoring of the water storage cycle or polar ice mass loss.

The goal of this study is to investigate the effectiveness of using inverse GNSS methods to provide independent C20 and C30 coefficients. These coefficients are essential for deriving highly accurate Gravity Recovery and Climate Experiment (GRACE)-based TVG models. In this study, surface mass variations of low-degree TVG coefficients are derived from the displacements of continuously tracking GNSS sites based on the 21 years (2000-2021) of the Center for Orbit Determination in Europe solutions of the 3rd data reprocessing campaign of the International GNSS Service in the framework of the preparation of the International Terrestrial Reference Frame 2020. The geometrical displacements of the GNSS stations calculated by inverse methods are compared with changes in the gravity field based on independent estimates obtained from the GRACE and GRACE Follow-On (GRACE-FO) satellite missions and the Satellite Laser Ranging (SLR).

As an alternative to the solutions provided by SLR, it is shown that the C20 and C30 coefficients can be derived based on GNSS station displacements. The challenge of the inverse GNSS approach is to properly choose the maximum degree of TVG expansion. Compared with the SLR-based solution, the most consistent GNSS estimate of the temporal gravity variation rate of the C20 coefficient (−1.73 ± 0.10 × 10−11/year) and annual variation (4.7 ± 0.6 × 10−11/43.9° ± 7.5°) was obtained by expansion of the spherical harmonics to degree and order of 8. The GNSS-based C30 series is superior to the SLR-based estimates before the launch of the Laser Relativity Satellite. From August 2016, when the C30 estimates are essential for correcting the GRACE solutions, the root mean square between GNSS and SLR solutions is 4.2 × 10−11. GNSS could potentially support GRACE/GRACE-FO solutions that face problems in deriving C20 and C30, which are fundamental to estimates of ice mass changes in the polar regions. Recovery of mass change in the Antarctic ice sheet from April 2002 to December 2020 based on the coefficients replaced by GNSS estimates results in a linear trend of −111 ± 3 Gt/year. In comparison, the trend for the SLR-based replacement from Technical Note 14 shows a trend of −114 ± 2 Gt/year.

How to cite: Nowak, A., Zajdel, R., Gałdyn, F., and Sośnica, K.: Using Inverse GNSS Methods for the Determination of C20 and C30 Gravity Field Coefficients for the Support of GRACE Solutions   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-327, https://doi.org/10.5194/egusphere-egu24-327, 2024.

EGU24-385 | Posters on site | G3.1

Long-term gravity field changes from SLR data and the combination with GRACE  for improving low-degree coefficients 

Filip Gałdyn, Krzysztof Sośnica, and Radosław Zajdel

In recent two decades, monitoring of changes in the Earth’s gravity field has been carried out mainly by the Gravity Recovery And Climate Experiment (GRACE) and its successor GRACE Follow-On. However, before the GRACE era,  very little information is available on the temporal evolution of the Earth's gravity field prior to that date. Moreover, through these missions, we have many gaps between 2010 and 2019. Fortunately, GRACE and GRACE Follow-On are not the only missions that can be used to recover variations in the Earth's gravity field. For the recovery of the mass redistribution processes on a large scale, we may employ precise Satellite Laser Ranging (SLR) observations.

We propose a set of long-term, continuous solutions based on SLR data. In our solutions, we use observations from spherical geodetic satellites. The gravity field is expanded up to a degree and order 10 with a monthly resolution from 1/1995 to 10/2021. The main solution has been decomposed into solutions expanded to degree and order 4, 6, 8, and 10 and stacked, taking advantage of the stability of the low-degree expansion and the better resolution of the high-degree expansion. The results show the reduction of the correlations between obtained parameters, stabilization of the ice mass estimates in polar regions – in Greenland and Antarctica, and a reduction of the noise over oceans by a factor of four.

In the GRACE and GRACE Follow-On datasets, the replacement of the spherical harmonics C20 and C30 with SLR-derived data is necessitated by suboptimal quality resulting from thermal effects impacting satellites and accelerometer malfunctions. In both SLR and GRACE solutions, coefficients of the same order and parity exhibit strong correlations. Merely replacing two specific coefficients could introduce bias into the solution. Therefore, we propose a comprehensive approach, combining GRACE with SLR solutions up to a degree and order of 10x10. This strategy ensures a proper consideration of the sensitivity of each technique to gravity field coefficients. The combined solution exhibits reduced noise compared to standard GRACE COST-G solution and effectively address the distinct sensitivities of SLR and GRACE techniques to low-degree time-variable gravity field coefficients.

How to cite: Gałdyn, F., Sośnica, K., and Zajdel, R.: Long-term gravity field changes from SLR data and the combination with GRACE  for improving low-degree coefficients, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-385, https://doi.org/10.5194/egusphere-egu24-385, 2024.

EGU24-891 | ECS | Posters on site | G3.1

Vertical Land Motion Detection Using Satellite Altimetry Data at the Hadera Tide Gauge Station 

Milaa Murshan, Balaji Devaraju, Nagarajan Balasubramanian, and Onkar Dikshit

Vertical Land Motion (VLM) estimation involves various methods such as Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Satellite Laser Ranging (SLR). However, satellite altimetry presents an alternative approach for estimating VLM independently. This study compares altimetry-based VLM estimates with those obtained from Tide Gauge (TG) devices. The VLM is determined by calculating the difference between the linear trends of sea-level time series derived from altimetry-based data Instantaneous Sea Surface Height (ISSH) and TG data. Additionally, VLM can be estimated by comparing the linear trends of altimetry-based Sea Level Anomalies (SLA) and TG SLA time series.
 To estimate VLM, absolute ISSH measurements from satellite altimetry, unaffected by the Earth's crust, are contrasted with relative sea level measurements recorded by TG stations with respect to a fixed land point. By differentiating and aligning temporal pairs of TG and altimetry data, only the linear trend remains, representing the vertical displacement of the TG station relative to the reference surface. Removing satellite altimetry instrumentation drifts enables the extraction of VLM from the difference in linear trends. 
The VLM estimate obtained for the Hadera TG station, covering 1992-2016, shows a positive trend of 0.24 ± 0.07 mm/year. This finding aligns with GNSS-based VLM estimations at the same station, indicating land uplifting in the region. Consequently, the study suggests that there is no immediate concern about the rise of sea level. These findings enhance our understanding of regional geodetic processes and their implications for assessing sea level changes. By providing valuable information on VLM estimation, this research contributes to our knowledge of vertical displacement on land and its significance for future studies.

How to cite: Murshan, M., Devaraju, B., Balasubramanian, N., and Dikshit, O.: Vertical Land Motion Detection Using Satellite Altimetry Data at the Hadera Tide Gauge Station, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-891, https://doi.org/10.5194/egusphere-egu24-891, 2024.

EGU24-3658 | ECS | Orals | G3.1

A Geodetic Drought Index Driven by Hydrologic Loading Estimates Calculated from Three-Dimensional GPS Displacements   

Zachary M. Young, Hilary R. Martens, Zachary H. Hoylman, and W. Payton Gardner

During periods of drought, quantifying the intensity of water loss within hydrologic reservoirs, both on and below the surface, is critical to sustain water resources. Drought intensity is typically characterized using drought indices which are driven by meteorologic observations, such as precipitation. These drought indices provide good insight into the quantity of water entering the hydrologic system, however, they are unable to quantify the amount of water retained in a watershed or the amount lost due to runoff and evapotranspiration. We address this by leveraging the sensitivity of three-dimensional Global Positioning System displacements to local and regional hydrologic-storage fluctuations, and produce a new geodetic drought index (GDI), derived from estimated hydrologic-storage deviations, to directly characterize hydrologic storage anomalies. The GDI is derived comparably to the Standardized Precipitation Evapotranspiration Index such that it may be easily incorporated into current drought management workflows. We directly compare the GDI to hydrologic observations within California and find strong associations between specific time scales of the GDI and groundwater well, artificial-reservoir storage, and stream discharge observations. The GDI is most sensitive to groundwater, exhibiting a correlation coefficient of 0.87 at the 3-month time scale. Both artificial-reservoir storage and stream discharge exhibit peak correlation coefficients when considering the 1-month GDI, at 0.81 and 0.47 respectively. No relationship is observed with soil moisture observations. The correlation coefficients decline rapidly away from the optimal time scale, indicating the 1- and 3-month GDI are strong predictors of hydrologic variation within California. In addition to capturing long-term trends, rapid changes in the GDI initiate during clusters of large atmospheric-river events that closely mirror fluctuations in the hydrologic observations. The GDI provides an opportunity to improve hydrologic models for drought-management and to advance our understanding of the water cycle.

 

How to cite: Young, Z. M., Martens, H. R., Hoylman, Z. H., and Gardner, W. P.: A Geodetic Drought Index Driven by Hydrologic Loading Estimates Calculated from Three-Dimensional GPS Displacements  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3658, https://doi.org/10.5194/egusphere-egu24-3658, 2024.

EGU24-5267 | ECS | Posters on site | G3.1

Reconciling ocean mass changes from 20 years of GRACE and GRACE Follow On observations 

Carsten Bjerre Ludwigsen, Ole Baltazar Andersen, Christopher Watson, and Matt King

The total mass change of the Earth's land surface precisely offsets the combined changes in the atmosphere and oceans, resulting in a net-zero change for the entire system (land+ocean+atmosphere).

Closing the ocean mass budget is crucial for understanding current and future sea-level changes. Recent efforts to reconcile ocean mass observations from GRACE and GRACE-Follow On satellites (hereafter unitedly referred to as ‘GRACE’) with both steric-corrected altimetry and and land/ice to ocean estimates have revealed a discrepancy in the mass budget (Wang et al, 2022; Barnoud et al, 2022). This finding indicates a concerning misalignment in our global observation system or understanding of earth mass transport.

This study uses GRACE-independent estimates/models of land surface mass changes to validate 20 years of GRACE observations. By calculating the monthly Gravitational, Rotational, and Deformational (GRD) response to 20 years of land mass changes, we reconstruct the global, regional, and seasonal ocean mass changes observed by GRACE from 2003 to 2022.

Over the 20-year period, the ocean mass reconstruction aligns well with the GRACE observations. However, a significant deviation emerges after 2020, with the reconstruction showing a larger ocean mass change than GRACE. We demonstrate that this deviation is likely caused by an underestimation of Western Africa precipitation in the ERA5 reanalysis, commonly used by hydrological models to estimate changes in land water storage. Land mass observations from GRACE further confirmvthis underestimation and shows great alignment between models and observations when excluding sub-Saharan Africa.

Our results show a global agreement between GRACE and GRD-induced ocean mass changes, suggesting that the misalignment between GRACE and steric-corrected altimetry is likely due to errors in the ARGO observing system. A reported 'salinity-drift' is the primary source of error, and together with an error in the wet path delay originating from drift in the radiometer of the Jason-3 satellite explains most of the post-2016 difference between GRACE and steric-corrected altimetry is identified. The remaining differences likely originate from GIA and/or Argo-biases.

How to cite: Ludwigsen, C. B., Andersen, O. B., Watson, C., and King, M.: Reconciling ocean mass changes from 20 years of GRACE and GRACE Follow On observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5267, https://doi.org/10.5194/egusphere-egu24-5267, 2024.

The accuracy of global ocean tide models (OTMs) in shallow waters and along coasts impacts on their numerous applications. For example, the use of OTMs to provide tide corrections (‘de-tiding’) for satellite altimetry observations is required for, e.g., sea level studies and marine gravity field recovery. OTMs are also indispensable in the mitigation of striping errors in GRACE and GRACE-FO time-variable gravity field solutions. It therefore follows that OTM errors in coastal and shelf ocean may then introduce biases into the ‘corrected’ satellite altimetry and gravimetry observations with the potential to impact models using these data. The purpose of our study is to assess the accuracy of two high resolution assimilated OTMs (TPXO9v5, and FES2014b) using an updated set of >100 coastal and shelf tide gauges across the northern Australia and Papua New Guinea region. TPXO9v5 and FES2014b are used here because they have previously compared better than other tidal models in adjacent coastal and shelf areas. This study will also provide insight into the tides in this region which contain a mix of shallow and medium depth waters adjacent to the coast, in addition to land and island barriers that result in a complex tidal regime. This study takes advantage of the large number of short-term tide gauges situated on the coast or offshore islands in Northern Australia and Papua New Guinea. This set of tide gauges have observation periods of >30 days, with a number being more than 90 days long which allows the resolution of the major semidiurnal and diurnal tidal constituents. We use harmonic analysis to estimate tidal constants of major diurnal and semi-diurnal constituents from tide gauges then compare them with corresponding values from TPXO9v5 and FES2014b at the tide gauge location. This comparison identifies improvements and also limitations in these OTMs in this region, and their potential impact on tide corrections provided for satellite altimetry products that may propagate into coastal sea surface, and gravity at the coast. The results also provide additional insight into the local tidal patterns in this region, with particular interest in the Torres Strait and surrounding area.

How to cite: Filmer, M., Seifi, F., and Claessens, S.: Evaluation of ocean tide models in coastal ocean regions of northern Australia and Papua New Guinea using an updated set of short term tide gauges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7127, https://doi.org/10.5194/egusphere-egu24-7127, 2024.

EGU24-7430 | ECS | Posters on site | G3.1

Regional modelling of water storage variations from combined GRACE/-FO and GNSS data in a Kalman filter framework 

Viviana Wöhnke, Annette Eicker, Matthias Weigelt, Marvin Reich, and Andreas Güntner

Water mass changes at and below the surface of the Earth cause changes in the Earth’s gravity field which can be observed by at least three geodetic observation techniques: ground-based point measurements using terrestrial gravimeters, space-borne gravimetric satellite missions (GRACE and GRACE-FO) and geometrical deformations of the Earth’s crust observed by GNSS. Combining these techniques promises the opportunity to compute the most accurate (regional) water mass change time series with the highest possible spatial and temporal resolution, which is the goal of a joint project with the interdisciplinary DFG Collaborative Research Centre (SFB 1464) "TerraQ – Relativistic and Quantum-based Geodesy".

A method well suited for data combination of time-variable quantities is the Kalman filter algorithm, which sequentially updates water storage changes by combining a prediction step with observations from the next time step. As opposed to the standard way of describing gravity field variations by global spherical harmonics, we introduce space-localizing radial basis functions as a more suitable parameterisation of high-resolution regional water storage change. An estimation environment has been set up for the combination of GRACE/-FO satellite gravimetry with GNSS station displacements. The feasibility and stability of the approach is first demonstrated in a closed-loop simulation to test the setup and tune the algorithm. Subsequently, it is applied to real GRACE and GNSS observations to sequentially update the parameters of a regional gravity field model for Central Europe. The implementation was designed to flexibly include further observation techniques (e.g. terrestrial gravimetry) at a later stage. This presentation will outline the Kalman filter framework and regional parameterisation approach, and addresses challenges such as the relative weighting between the GRACE and GNSS data, and the appropriate choice of the Kalman filter process model and radial basis function parameterisation.

How to cite: Wöhnke, V., Eicker, A., Weigelt, M., Reich, M., and Güntner, A.: Regional modelling of water storage variations from combined GRACE/-FO and GNSS data in a Kalman filter framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7430, https://doi.org/10.5194/egusphere-egu24-7430, 2024.

EGU24-7669 | ECS | Orals | G3.1

Evaluation of extreme events in global coupled climate models by satellite gravimetry 

Klara Middendorf, Annette Eicker, Laura Jensen, and Henryk Dobslaw

Under the assumption that a warming climate leads to an intensification of the global water cycle, it can be hypothesized that also the occurrence frequency and severity of extreme events such as droughts or floods will increase in the upcoming decades to centuries. Global coupled climate models, which project the future evolution of various variables of the Earth's climate system are important tools for the analysis of such expected changes. To assess the reliability of the models and to identify possible systematic discrepancies, it is essential to evaluate the model output against observations.

In this study, present and future occurrences of extreme events are analysed in water storage time series simulated by coupled global climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) and compared against spatio-temporal changes in water mass derived from GRACE and GRACE-FO. This comparison is based on Extreme Value Theory, as the exact timing of modelled extreme events cannot be assessed by observations due to the stochastic behavior of climate variability in unconstrained model experiments. From estimated extreme value distributions return levels are calculated, a quantity describing the magnitude or frequency of extreme values.  Challenges that have to be overcome in the analysis are the non-stationary data and the relatively short time span of the GRACE observations. The latter issue is addressed by additionally assessing GRACE-based water storage reconstructions available over many decades.

This study provides insights into the ability of global climate models to model the occurrence of TWS extremes, namely unusual dry and wet phases. It also examines whether the climate model projections predict an increasing intensity of extreme events.

How to cite: Middendorf, K., Eicker, A., Jensen, L., and Dobslaw, H.: Evaluation of extreme events in global coupled climate models by satellite gravimetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7669, https://doi.org/10.5194/egusphere-egu24-7669, 2024.

Changes in soil water storage can be studied on a global scale using a variety of satellite observations. With active or passive microwave remote sensing, we can study the upper few centimeters of the soil, while satellite gravimetry allows us to detect changes in the entire column of terrestrial water storage (TWS). The combination of both types of data can provide valuable insight into hydrological dynamics in different soil depths towards a better understanding of changes in subsurface water storage.

We use daily Gravity Recovery and Climate Experiment (GRACE) data and satellite soil moisture data to identify extreme hydroclimatic events, focusing on prolonged droughts. To enhance our comprehension of the subsurface, we utilize not just surface soil moisture data but also integrate information on root zone soil moisture. Original level-3 surface soil moisture data sets of SMAP and SMOS are compared to post-processed level-4 data products (both surface and root zone soil moisture) and a multi-satellite product provided by the ESA CCI.

We analyse the correspondence between high and low percentiles in TWS and soil moisture time series, which allows us to identify extreme events in different integration depths and storage compartments. Furthermore, we compute the rate of change of anomalies to assess how quickly the system accumulates storage deficits during drought conditions and recovers from them for different soil depths. Our investigation focuses on the temporal dynamics of near-surface soil moisture and TWS, highlighting the cascading effects that propagate from the surface into the subsurface. The results we obtained indicate characteristic patterns of the temporal dynamics of drought recovery in varying soil depths. Specifically, our analysis shows that surface soil moisture recovers faster than TWS, and that this recovery process slows down as soil integration depth increases.

How to cite: Blank, D., Eicker, A., and Güntner, A.: From surface to subsurface: Investigating drought cascades and recovery patterns with (daily) satellite observations of soil moisture and terrestrial water storage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7888, https://doi.org/10.5194/egusphere-egu24-7888, 2024.

EGU24-8727 | Posters on site | G3.1

20-year-long sea level changes along the world’s coastlines from satellite altimetry: a new data set of coastal virtual stations 

Anny Cazenave, Lancelot Leclercq, Fabien Leger, Florence Birol, Fernando Nino, Marcello Passaro, and Jean Francois Legeais

In the context of the ESA Climate Change Initiative (CCI) Coastal Sea Level project, a complete reprocessing (including retracking of the radar waveforms) of high resolution (20 Hz, i.e. 350 m) along-track altimetry data of the Jason-1, Jason-2 and Jason-3 missions since January 2002 was performed along the world coastal zones. Different versions have been provided so far. The latest release (SL_cci+ coastal altimeter sea level dataset, v2.3) is now available to users. It is an extension in time of the previous data set (v2.2) which covers the period January 2002 to June 2021. A new improved processing for the waveform retracking and computation of the coastal sea level anomalies was developed and a new editing procedure for the coastal sea level trend computation was implemented. This new data set shows spectacular reduction of the data noise compared to previous versions, both in terms of sea level anomaly time series and trends. As a consequence, compared to the previous versions we now obtain an important increase of the number of virtual coastal stations (i.e., the location of the first valid point along the satellite track, with about 1200 sites at an average distance from the coast of about 3 km, including more than 200 stations at less than 2 km from the coast). The coastal sea level anomalies and trends of the altimetry-based virtual stations have been validated with tide gauge data where possible. An example in the Mississippi Delta is presented.

How to cite: Cazenave, A., Leclercq, L., Leger, F., Birol, F., Nino, F., Passaro, M., and Legeais, J. F.: 20-year-long sea level changes along the world’s coastlines from satellite altimetry: a new data set of coastal virtual stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8727, https://doi.org/10.5194/egusphere-egu24-8727, 2024.

EGU24-8830 | Orals | G3.1 | Highlight

Will the MAGIC mission improve the observability of extreme hydrological events? 

Eva Boergens, Josefine Wilms, Markus Hauk, Christoph Dahle, Henryk Dobslaw, and Frank Flechtner

NASA and DLR will launch in 2028 GRACE-C (Gravity Recovery and Climate Experiment – Continuation). This mission will again be launched into a polar orbit at 500 km initial altitude and extend the observation of the time-variable Earth’s gravity field from GRACE (2002-2017) and GRACE-FO (GRACE Follow-On, 2018-today). ESA plans to launch a Next Generation Gravity Mission (NGGM) in 2032, which shall fly in a lower and inclined orbit and be based on improved instrumentation. GRACE-C and NGGM will then form the double-pair Mass-Change and Geosciences International Constellation (MAGIC) to significantly increase the spatial and temporal resolution of mass transport products and deduce water mass redistribution over the oceans, ice sheets and continents.

Thanks to the 20+ years period of GRACE and GRACE-FO observations, scientists are able to analyse extreme hydrological events, such as flooding and droughts. However, due to the rather coarse spatial resolution of the GRACE and GRACE-FO data sets of approximately 350 km, finer spatial details of such extreme events are kept hidden. Further, spatial leakage limits the value of these data for smaller-scale regional investigations.

In this contribution, we will employ five years of simulated data for both a single polar pair (GRACE-FO-like) and a MAGIC baseline scenario. Thanks to the simulation, we can also assess the true values of the hydrological input models. Both simulated data sets are filtered with the same DDK filters for comparison. The filter strength can be reduced for the MAGIC baseline scenario without introducing more striping errors.

With these simulated data sets, we investigate extreme hydrological events. For example, the localisation of extreme wet events along the northern coast of Australia is much improved, with less signal leakage into the surrounding ocean.

How to cite: Boergens, E., Wilms, J., Hauk, M., Dahle, C., Dobslaw, H., and Flechtner, F.: Will the MAGIC mission improve the observability of extreme hydrological events?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8830, https://doi.org/10.5194/egusphere-egu24-8830, 2024.

EGU24-8938 | Orals | G3.1

Strategies for assimilating GRACE/-FO terrestrial water storage anomalies into hydrological models 

Anne Springer, Yorck Ewerdwalbesloh, Helena Gerdener, Kerstin Schulze, and Jürgen Kusche

After more than 15 years of experience with GRACE/-FO data assimilation (DA) into hydrological models, numerous studies have conducted various tests on GRACE product and preprocessing options as well as DA strategies. However, a commonly accepted standard procedure has yet to emerge. This contribution comprises (1) a review on the prevalence of GRACE-DA options based on existing studies together with (2) insights from applying two GRACE assimilating frameworks: the high-resolution CLM-DA framework over Europe and the global WGHM-based calibration and data assimilation framework.

We discuss the selection of different GRACE/-FO products for DA into hydrological models, including spherical harmonics, MASCONS, level 3 products, and the recently evolved along-orbit line-of-sight gravity differences. Additionally, we explore processing choices such as filtering and rescaling, possible corrections for phenomena like glacial isostatic adjustment, large lakes and reservoirs or earthquakes, observation grid representation, and various approaches to handle observation errors. We evaluate the impact of these processing strategies on simulated water storage trends and the representation of selected extreme events.

Through this research, we contribute to understanding optimal strategies in assimilating GRACE/-FO data, addressing critical aspects influencing hydrological model reliability.

How to cite: Springer, A., Ewerdwalbesloh, Y., Gerdener, H., Schulze, K., and Kusche, J.: Strategies for assimilating GRACE/-FO terrestrial water storage anomalies into hydrological models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8938, https://doi.org/10.5194/egusphere-egu24-8938, 2024.

EGU24-10138 | ECS | Posters on site | G3.1

Reconstructing GRACE-like TWSA maps from 1992 on by combining data-driven methods with time-variable gravity fields from SLR range analyses 

Charlotte Hacker, Jürgen Kusche, Anno Löcher, and Fupeng Li

The Gravity Recovery And Climate Experiment (GRACE) and its follow-on mission, GRACE-FO, have observed global mass changes and transports, expressed as total water storage anomalies (TWSA), for over two decades. However, for climate change attribution and other applications, multi-decadal TWSA time series are required. This need has triggered several studies on reconstructing TWSA via regression approaches or machine learning techniques, with the help of predictor variables such as rainfall or sea surface temperature. Here, we combine such an approach, for the first time, with low-resolution information from geodetic satellite laser ranging (SLR). The reconstruction is formulated on a GRACE-derived empirical orthogonal functions (EOFs) basis and complemented with the Löcher and Kusche (2021) approach, in which global gravity fields are solved from SLR ranges in a GRACE EOF basis for the pre-GRACE time frame. Although our technique works globally, we focus mainly on European basins and reconstruct water storage anomalies from 1992 onward.

How to cite: Hacker, C., Kusche, J., Löcher, A., and Li, F.: Reconstructing GRACE-like TWSA maps from 1992 on by combining data-driven methods with time-variable gravity fields from SLR range analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10138, https://doi.org/10.5194/egusphere-egu24-10138, 2024.

EGU24-10234 | ECS | Posters on site | G3.1

Sub-Monthly Mass Change Signal in Greenland from GRACE-FO Laser Interferometry Data 

Barbara Jenny, Marcus Jepsen, Sebastian Bjerregaard Simonsen, René Forsberg, and Tim Enzlberger Jensen

GRACE and GRACE-FO have proven valuable for monitoring the health of ice sheets by showing seasonal mass changes along with the decadal trends of mass loss. Two years stand out in the Greenland ice sheet mass loss record with record melt: 2012 and 2019. On the West coast of Greenland, the ice mass fluctuations act on remarkably short time scales during these events, as evident at Ilulissat isbræ, which nearly doubled its ice speed in just one week. Here, we study if these sub-monthly ice mass change variations can be measured using GRACE-FO line-of-sight measurements.

It has been shown several times that using dynamic orbits and Laser Ranging Interferometer (LRI) data, one can calculate residual Line-of-sight gravity signals. This method was primarily used to study hydrological signals such as storm surges or heavy rainfall. In this study, we focus on ice mass changes in Greenland, and we compare these GRACE-FO measurements to the expectation based on the monthly gravity field and the signal from mass change based on IceSat2 data for 2019-2021.

How to cite: Jenny, B., Jepsen, M., Simonsen, S. B., Forsberg, R., and Jensen, T. E.: Sub-Monthly Mass Change Signal in Greenland from GRACE-FO Laser Interferometry Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10234, https://doi.org/10.5194/egusphere-egu24-10234, 2024.

EGU24-10483 | ECS | Orals | G3.1

Resolving the interannual to multi-decadal variability in ocean heat content, a simulation study of current and future satellite gravity missions 

Marius Schlaak, Roland Pail, Alejandro Blazquez, Benoit Meyssignac, and Jean-Michel Lemoine

Ocean Heat Content (OHC) is an essential indicator of Earth’s climate state. Climate change is driven by the disequilibrium of Earth’s radiation budget. This abundant energy in the system is the Earth Energy Imbalance (EEI), which is challenging to measure globally. About 90% of EEI is accumulated in the oceans, resulting in an increase in ocean heat content. Therefore, OHC is a suitable proxy for EEI and can be measured globally using a combination of geodetic satellite techniques. By combining satellite altimetry and satellite gravimetry, it is possible to measure the change in global ocean heat content over the mission’s lifetime. While the altimeter record covers several decades, satellite gravity missions have been observing global mass transports for two decades. To steadily estimate the system’s long-term behavior, an extended observation period of the satellite systems is needed. The upcoming satellite gravity mission Grace-C, planned to be launched in 2028 by NASA, is meant to ensure continuity and extension of the data record. At the beginning of the 2030s, an additional inclined pair will be launched by ESA to form together with GRACE-C the Mass change And Geosciences International Constellation (MAGIC), for which higher spatial and temporal resolutions are expected.

This contribution presents the results of multi-decadal closed-loop simulations of current and future satellite gravity observations. It shows the benefit of an increased duration of the observation and an improved observational system while comparing processing strategies for long-term trends in ocean mass changes. The observed climate signal is based on projections of mass change signals of oceans, ice sheets, and glaciers derived from CMIP6 climate projection under a shared socio-economic pathway scenario without drastic reduction of Greenhouse gases emissions (SSP5-8.5). A particular focus here is on the accuracy of long-term ocean trends. The direct estimation of long-term trends benefits from an increasing observation period and allows improved spatial resolution compared to trends estimated from monthly temporal gravity fields. The global ocean heat content is estimated from the steric sea-level change which is derived by subtracting the observed ocean mass change from the overall sea level change. The resulting long-term trends in ocean heat content are then compared to initial inputs to the simulation to illustrate the difference in performance between current and future satellite gravity constellations.

How to cite: Schlaak, M., Pail, R., Blazquez, A., Meyssignac, B., and Lemoine, J.-M.: Resolving the interannual to multi-decadal variability in ocean heat content, a simulation study of current and future satellite gravity missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10483, https://doi.org/10.5194/egusphere-egu24-10483, 2024.

EGU24-10526 | Orals | G3.1

Assessment of global high-resolution water storage simulations from the LISFLOOD hydrological model 

Henryk Dobslaw, Laura Jensen, Robert Dill, and Kyriakos Balidakis

Simulated terrestrial water storage (TWS) data from global hydrological models are indispensable for various geodetic applications, e.g., for simulating Earth orientation parameters, deriving time series of deformations of the Earth’s surface needed for the realization of global reference systems, or de-aliasing purposes of GRACE/-FO gravity products. So far, the Land Surface Discharge Model (LSDM) has been routinely used for such tasks at the GFZ. However, the current standard experiment of LSDM is already several years old, and many limitations are known, in particular a limited spatial resolution of 0.5°, which limits the accuracy of crustal deformation predictions close to rivers and lakes. In this contribution, we evaluate the suitability of LISFLOOD (https://ec-jrc.github.io/lisflood/), an open source, high-resolution hydrological rainfall-runoff-routing model, for geodetic purposes.

We compare the performance of various global LISFLOOD model runs for the time period 2000 – 2022 against the current LSDM configuration. In addition to two LISFLOOD model generations, which differ in their spatial resolution (0.1° and 0.05°) and their input land surface parameter data set, we also explore a number of high-resolution (0.05°) model runs with respect to the influence of the soil depth on simulated TWS. Model results are validated against mass anomalies from the satellite gravimetry missions GRACE and GRACE-FO on different spatial and temporal scales. Furthermore, to demonstrate the benefit of the higher spatial resolution of LISFLOOD, we utilize data from selected ground based GNSS stations to validate the models’ performance regarding mass-induced loading.

We find that LISFLOOD significantly outperforms LSDM in many regions, especially on interannual time scales, in terms of various validation metrics (i.e., correlation, root mean squared deviation, and explained variance). Analyzing the different LISFLOOD runs reveals advantages of the new (0.05°) over the old (0.1°) model version, and a large impact of the choice of soil depth on simulated TWS.

How to cite: Dobslaw, H., Jensen, L., Dill, R., and Balidakis, K.: Assessment of global high-resolution water storage simulations from the LISFLOOD hydrological model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10526, https://doi.org/10.5194/egusphere-egu24-10526, 2024.

EGU24-11213 | Posters on site | G3.1

GNSS Precipitable Water Vapour for Climate Monitoring 

Galina Dick, Florian Zus, Jens Wickert, Benjamin Männel, and Markus Ramatschi

Aside from main geodetic applications, the Global Navigation Satellite System (GNSS) is now an established observing system for atmospheric water vapour which is the most important greenhouse gas as it is responsible for around 60% of the natural greenhouse effect. Water vapour is under-sampled in the current climate-observing systems. Obtaining and exploiting more high-quality humidity observations is essential for climate research.

Established in 2006, the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN), is an international reference observing network of sites measuring essential climate variables above the Earth's surface. Currently, this network comprises more than 30 reference sites worldwide, designed to detect long-term trends of key climate variables such as temperature and humidity in the upper atmosphere. GRUAN observations are required to be of reference quality, with known biases removed and with an associated uncertainty value, based on thorough characterization of all sources of measurement.

A complementary small scale regional climate station network is the Austrian WegenerNet, which provides since 2007 measurements of hydrometeorological variables with very high spatial and temporal resolution. GNSS precipitable water vapour (GNSS-PWV) measurement has been included as a priority one measurement of the essential climate variable water vapour to both GRUAN and WegenerNet climate station networks.

GFZ contributes to climate research within GRUAN and WegenerNet with its expertise in processing of ground-based GNSS network data to generate precise PWV products. GFZ is responsible for the installation of GNSS hardware, data transfer, processing and archiving, derivation of GNSS-PWV data products according to GRUAN and WegenerNet requirements including PWV uncertainty estimation. GNSS-PWV products and results of selected validation studies will be presented.

How to cite: Dick, G., Zus, F., Wickert, J., Männel, B., and Ramatschi, M.: GNSS Precipitable Water Vapour for Climate Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11213, https://doi.org/10.5194/egusphere-egu24-11213, 2024.

EGU24-11433 | ECS | Posters on site | G3.1

Solid Earth’s response to climate change in Svalbard monitored by space geodesy  

Alicia Tafflet, Joelle Nicolas, Jean-Paul Boy, Jean-Michel Lemoine, Félix Perosanz, Frédéric Durand, Achraf Koulali, Lissa Gourillon, Agnès Baltzer, and Jérôme Verdun

The Svalbard archipelago in the Arctic is extremely sensitive to climate change. The resulting redistribution of mass, including recent and past ice melt, induces deformations of the Earth's surface and temporal variations in its gravity field, which can be detected by space geodesy. The cross-comparison of different techniques takes advantage of their complementary temporal and spatial resolutions, helping to distinguish between local, regional and global signals. We analyse more than 20 years of GNSS (Global Navigation Satellite System) satellite 3D positionning solutions at 17 permanent sites. The results are compared with deformations computed from time gravity field variations observed by the space gravimetry missions GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On. The mean vertical motion is of about 9 mm/year and can reach 15 mm/year. We then compare these GNSS and GRACE datasets with Little Ice Age (LIA) and Global Isostatic Adjustment (GIA) models as well as with satellite altimetry observations from Cryosat-2 and IceSat-2. We infer the various contributions and quantify the impact of the current climate change on Svalbard. In addition to better estimate the acceleration of the current ice melting we apply an innovative seasonal adjustment method. The results are then discussed in relation to in situ observations.

How to cite: Tafflet, A., Nicolas, J., Boy, J.-P., Lemoine, J.-M., Perosanz, F., Durand, F., Koulali, A., Gourillon, L., Baltzer, A., and Verdun, J.: Solid Earth’s response to climate change in Svalbard monitored by space geodesy , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11433, https://doi.org/10.5194/egusphere-egu24-11433, 2024.

Since March 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite and its following mission GRACE-FO have measured the time-variable gravity fields of the Earth, by which water shifts around Earth can be captured. Among its innovations, GRACE has monitored the change of ice mass from Earth's ice sheets and glaciers, which is essential for the better understanding of the changing climate system. Over the past few decades, glacier mass loss has been significant across the globe. The European Alps are among the regions experiencing the greatest shrinkage of glaciers, which becomes the main focus of this work.
In this work, we will challenge the information of satellite gravimetry, hydrological models, and satellite geodesy to monitor the ice mass loss in the Alps in central Europe. The temporal variations of total water storage (TWS) in the Alpine region are determined from GRACE- and GRACE-FO-based Level-2 products provided by COST-G and Mascon surface mass change fields calculated by JPL. Furthermore, the correction of GIA effects and hydrological signals in the study area is indispensable to isolate the estimate of glacier melting. For the GIA correction, the GIA model ICE-6G_D and the regional dataset of surface displacements obtained from geodetic observation techniques are applied to GRACE data respectively, resulting in obvious different results. For the hydrological correction, the WaterGAP Global Hydrology Model (WGHM) model and the Global Land Data Assimilation System (GLDAS) model are used to estimate the mass change of the liquid part. In addition, the ice mass loss in the Alps between 2000 and 2014 based on glacier inventory was estimated in another publication, which can be a reference (-1.34 Gt/yr). Glaciers in the Alps lost mass at a rate of around -1.4 Gt/yr and around -2.2 Gt/yr depending on different ways of GIA correction during the 21-year period, which have similar magnitudes with the reference value.

How to cite: Liu, S. and Pail, R.: The estimation of glacier changes in the Alps in 2002-2022 with the use of satellite gravimetry data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11913, https://doi.org/10.5194/egusphere-egu24-11913, 2024.

EGU24-11918 | ECS | Posters on site | G3.1

Estimating terrestrial water storage trends by developing a joint inversion scheme using GRACE and GRACE-FO data 

Sedigheh Karimi, Amin Shakya, Roelof Rietbroek, Marloes Penning de Vries, and Christiaan van der Tol

Climate change and global warming can affect the water cycle, leading to increased hydrological extremes, such as droughts affecting the environment, agricultural activities, and human life and causing serious social and economic problems worldwide. Therefore, monitoring changes in the water cycle can be helpful for effective water resources management and provide a management plan for sharing with stakeholders, water managers, and local people.

This study focuses on terrestrial water storage changes (e.g., trends and seasonal shifts) that potentially indicate climate change patterns like droughts and large scale flooding events within watersheds across the Horn of Africa.

In this study, an inversion scheme is being developed to process level-2 data obtained from the Gravity Recovery and Climate Experiment (GRACE) and subsequent measurements from GRACE Follow-On (GRACE-FO) spanning the period from 2002 to 2023 considering the variance-covariance matrix (error matrix) of observations for estimating TWS variations monthly at basin scale. We expect that our inversion scheme will be independent of filters, and there will be no need for empirical rescaling factors to amplify the primary signal after filtering and damping effect. The TWS changes estimated from the developed inversion scheme will be compared with the TWS trends of basins that have been derived using the basin averaging standard approach and Mascon solutions TWS changes products. Additionally, the atmospheric reanalysis products will be used, along with hydrological model discharge estimates, to assess the accuracy of time derivatives of TWS changes.

How to cite: Karimi, S., Shakya, A., Rietbroek, R., Penning de Vries, M., and van der Tol, C.: Estimating terrestrial water storage trends by developing a joint inversion scheme using GRACE and GRACE-FO data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11918, https://doi.org/10.5194/egusphere-egu24-11918, 2024.

EGU24-11963 | ECS | Orals | G3.1

Combination of GRACE/GRACE-FO and CryoSat-2 data resolves Glacial Isostatic Adjustment spatially and temporally in the Amundsen Sea Embayment, West Antarctica 

Matthias O. Willen, Bert Wouters, Taco Broerse, Eric Buchta, and Veit Helm

An effective spatial resolution of a few hundred kilometres, typically assessed for mass variations derived from GRACE/GRACE-FO data, is a major limitation for the rigorous investigation of local causes of mass variations. This is crucial for analyzing mass changes of the West Antarctic Ice Sheet, which is one of the tipping elements in the Earth’s climate system. In this region, ice mass changes occur on spatial scales smaller than the typical GRACE/GRACE-FO resolution. Furthermore, this is also the case for the solid-Earth deformation induced by ice load changes, which in turn can affect the glacier flow. Especially in the Amundsen Sea Embayment, mass changes due to the ongoing Glacial Isostatic Adjustment (GIA) have been postulated to vary on spatial scales smaller than 200 km and to feed back significantly on ice flow dynamics. Here, we present results from a data combination approach with a focus on the Amundsen Sea Embayment, West Antarctica. This approach utilizes data from GRACE/GRACE-FO and CryoSat-2 satellite altimetry with regional climate and firn model results over a time span of 10 years from 2011 to 2020. Improved GRACE/GRACE-FO gravity-field processing and a study area in a high latitude region, where the signal-to-noise is high, benefit a high spatial resolution of the results. One processing step is the smoothing of the input data sets in order to unify their different spatial resolution. We find a best fit of the combination results with independent GNSS observations by applying a Gaussian smoother of 135 km half-response width. The weighted rms difference is 3.8 mm/a in terms of estimated bedrock motion. It is almost twice as large when the input data sets are smoothed with a 300 km half-response filter. The determined effects of solid-Earth deformation may be a useful boundary information for GIA modelling in this region, e.g. for testing rheological models or (centennial) glacial histories.

How to cite: Willen, M. O., Wouters, B., Broerse, T., Buchta, E., and Helm, V.: Combination of GRACE/GRACE-FO and CryoSat-2 data resolves Glacial Isostatic Adjustment spatially and temporally in the Amundsen Sea Embayment, West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11963, https://doi.org/10.5194/egusphere-egu24-11963, 2024.

Drought is one of the most complex recurring natural disasters, defined by a deficiency of precipitations that causes prolonged water scarcity. Failure to manage drought risk has the potential to have dire consequences for people, livelihoods, economy and ecosystems.
In northern Italy, particularly in the highly productive industrial area of the Po river basin, the 2021-2022 period culminated in the most severe drought of the last two centuries.
In order to evaluate the best policies to address the problems caused by water scarcity, it is crucial to measure and monitor variations in terrestrial water storage (TWS). For drought monitoring, in fact, changes or anomalies in TWS provide direct observations of total water availability, complementing model-based measures such as drought severity indices.
To estimate the quantities and spatial distribution of TWS loss, we analyze vertical ground displacement time-series data from Global Navigation Satellite System (GNSS) stations in the Po river basin.
We use a regularization model, based on L1-norm, to reconstruct the long-term temporal evolution of vertical ground displacement trends. Next, we performed a Principal Component Analysis (PCA) on GNSS time series to extract a spatially consistent signal in vertical ground displacements. The temporal evolution of the first principal component is well-correlated with trend changes of the Po river level and with the  SPEI-12 drought index, with stations moving upward during periods of river/index level decrease and vice versa, indicating that common long-term variations in vertical ground displacements are driven by the hydrology of the area.
The inversion of the displacements associated with the first principal component allows us to estimate variations in equivalent water height (EWH) and find that between January 2021 and August 2022, the GNSS stations underwent uplift, up to 7 mm, which corresponds to ~70 Gtons of water loss. The results are compared with the Global Land Data Assimilation System (GLDAS) model and the Gravity Recovery and Climate Experiment (GRACE) data: while the temporal evolution of the three products, when averaged over the study area, is similar, the spatial distributions are different. This is likely due to the fact that GLDAS only takes surface water into account, and GRACE has a too-coarse spatio-temporal resolution.
Our results show that multi-year changes in water storage can be effectively monitored both in terms of temporal evolution and spatial distribution using space geodetic measurements, such as GNSS. This approach eliminates the need to rely solely on large-scale models or satellite measurements, which cannot reach the spatial resolution required at the scale of river basins such as the Po.

How to cite: Pintori, F. and Serpelloni, E.: Drought‐Induced Vertical Displacements and Water Loss in the Po River Basin (Northern Italy) From GNSS Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12650, https://doi.org/10.5194/egusphere-egu24-12650, 2024.

Since the beginning of the precision satellite altimeter era in the early 1990s, efforts have been focused on computing the mean height of the ocean surface for use in various geodetic and oceanographic studies. With 30 years of satellite measurements now available, it is time to rethink how we model the mean sea surface (MSS) in the era of climate change.

There are linear changes in the height of the ocean surface due to melting ice and increasing ocean heat content that will not average to zero when computing the mean. Today, there are places in the ocean that are 15 cm higher than they were at the start of the altimetric era some 30 years ago. Today, conventional MSS models like CLS15/22 or DTU15/21 are roughly 5 cm lower than what is observed by present-day satellites like Sentinel6-MF.

We propose that linear sea level changes are estimated simultaneously and consistently with the mean sea surface computation and added to the definition of the MSS, which is tied to a particular date in time. This is possible because the MSS are tied to the 2003.01.01 period for the DTU MSS models. 

We also investigated the acceleration of sea surface height but found these small and still unstable [Nerem et al., 2018]. We also found that these are still somewhat dependent on the Side A correction of the TOPEX mission. We conclude that a longer time series is needed before a stable map of the accelerations can be computed and applied.

There is considerable evidence that using a 30-year trend pattern in sea surface height is stable and is driven by the “forced response” of Greenhouse gases and aerosols. These patterns will be reasonably persistent as we move forward in time.

Testing a new DTU23MSS mean surface tailored to the year 2023 to our processing of the recently available 2023 SWOT data, we find this new DTU23MSS reduces the spatial variability of the SWOT data which is important to the processing and particularly the roll-error correction applied to the 2D SWOT sea surface height data. Applying the new DtU21MSS to conventional satellites like Sentinel-3A/B and 6 reduces both offset and spatial variability of the data indicating that the new MSS is actually very close to a “present-day mean”

 

How to cite: Andersen, O. B., Nerem, S., and Nielsson, B.: Consistent Mean Sea Surface and sea level change estimation in the Era of Climate Change – application to SWOT processing. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12785, https://doi.org/10.5194/egusphere-egu24-12785, 2024.

EGU24-13313 | ECS | Posters on site | G3.1

On the uncertainty of the uncertainty of long-term trends derived from geophysical and climate time series 

Kevin Gobron, Paul Rebischung, Roland Hohensinn, Janusz Bogusz, and Anna Klos

Quantifying the uncertainty associated with parameter estimates is crucial for a wide range of geophysical and climate applications. This is particularly important for interpreting the long-term trends of quantities of interest, such as ground displacement, sea level, and water storage (among others), estimated from geophysical time series. Unfortunately, our imperfect understanding of measurement error sources and of the intrinsic stochastic behavior of the quantities of interest often makes it difficult to realistically assess the uncertainty of long-term trend estimates. 

One pragmatic approach to obtaining realistic trend uncertainties is to model all the stochastic variations observed in the time series (that is, the “noise”) by stochastic processes, and then derive the trend uncertainty using the variance propagation law. In practice, such noise models often include unknown stochastic parameters controlling, e.g., the amplitudes or time correlations of the stochastic processes, which need to be estimated from the observations. Estimated stochastic parameters, however, come with uncertainty, just like any estimated quantity. And an uncertainty on the parameters of the noise model implies an uncertainty on the long-term trend uncertainty based on that noise model. In view of trend analysis from geophysical and climate time series data, the importance of considering such “uncertainty on the uncertainty” remains so far to be investigated.

In this study, we address this issue by assessing, using numerical simulation, how the uncertainty of stochastic models derived from sparse geophysical time series (a few hundred data points) translates into the uncertainty of long-term trend uncertainty estimates. We demonstrate that uncertainty in the time-correlation structure can result in significant uncertainty on trend uncertainty estimates. We then discuss the impact of such “uncertainty on the uncertainty” on the assessment of long-term trend significance from geodetic time series and provide recommendations on how to deal with the issue in practice.

How to cite: Gobron, K., Rebischung, P., Hohensinn, R., Bogusz, J., and Klos, A.: On the uncertainty of the uncertainty of long-term trends derived from geophysical and climate time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13313, https://doi.org/10.5194/egusphere-egu24-13313, 2024.

EGU24-14224 | ECS | Orals | G3.1

Climate Change Studies through SWOT Phenomenology Research 

Jessica Fayne

Climate change is driving extreme spatial and temporal variability in surface water resources. This is particularly important for lake and wetland features, which have been under-characterized on the global scale. This under-characterization is largely due to the complex structural properties of these surfaces relative to available remote sensing data.  

The Surface Water and Ocean Topography Mission, as the first-of-its-kind 2D mapping and satellite interferometer using Ka-band SAR, was developed for mapping water surface extents and water surface elevations, providing a significant improvement in how we characterize and monitor surface water. Because of the novelty of the Ka-band SAR data for surface mapping, there have been limited studies of additional utilities SWOT can provide to complement water surface extent and elevation observations.  

First-look images from SWOT over Toulouse, France and Long Island, New York, USA, revealed strong signal returns over non-water surfaces, including agricultural fields and urban regions. Subsequent images highlighted by the SWOT Science Team also demonstrated wind-driven water surface signal variability, akin to NASA-JPL airborne AirSWOT investigations.  

This project provides early assessments of SWOT phenomenology for estimating characteristics that could contribute to novel datasets, such as wind speed, wind direction (for long wave formations), vegetation moisture, vegetation structure, and land surface moisture fraction. This work provides the foundation for a multi-year study to further develop the Ka-band Phenomenology Scattering Model (KaPS), and the wind model Ka-SWOT Model (Ka-SMOD), and will additionally discuss necessary reference datasets, models, and in-situ sampling necessary to complete this these assessments.

This project will increase the utility of the SWOT mission for studying diverse water and land features and significantly improve our understanding of fine-scale terrestrial hydrology. Given the relatively short temporal availability of the preliminary SWOT data, this work will focus on spatial variability across global sites, within the fast-sampling orbit, for observations taken for available dates in 2023. This preliminary analysis of the spatial and temporal variability of SWOT-derived phenomena aims to demonstrate how SWOT can be used in novel ways to study climate change. 

How to cite: Fayne, J.: Climate Change Studies through SWOT Phenomenology Research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14224, https://doi.org/10.5194/egusphere-egu24-14224, 2024.

EGU24-14655 | Orals | G3.1

The Big Soak:  Change in Water in 2023 in North America's Pacific Mountain System  

Donald Argus, Hilary Martens, Wiese David, Swarr Matthew, Borsa Adrian, Peidou Athina, Nicholas Lau, Dain Kim, Kevin Gaastra, Matthias Ellmer, Zachary Young, Ellen Knappe, Noah Molotch, Sarfaraz Alam, Felix Landerer, Payton Gardner, and Reager John

We are strengthening the application of GPS's capability to estimate change in total water using measurements of elastic displacements of Earth's surface; breaking down total water into its components such as snow, soil moisture, and groundwater; and integrating GRACE gravity data to infer change in total water in groundwater basins.

In California's Sierra Nevada, GPS each day tracks the dumping and dissipation of storm water.  In Water Year 2023, total water increased abruptly during each of two sequences of snow-dominated atmospheric rivers.  Subsurface water, which we take to be total water inferred from GPS minus snow water equivalent, to rise in early January at the time of the first AR sequence, remain constant from late Jan through March (with no increase during the second AR sequence), and rise from April to June as the snowpack melts.  Subsurface water increases in the Sierra Nevada by 0.6 m from Oct 2022 to Jun 2023, 45 per cent of cumulative precipitation of 1.4 m.  Such a big rise in subsurface water begins to rejuvenate the Sierra Nevada critical zone (Earth's living outer layer between the top of the trees and the bottom of groundwater) and to replenish subsurface water lost during the prior 3 years of drought from 2020 to 2022.

Change in total water in California's Central Valley can be determined neither by GRACE alone nor GPS alone.  There GPS records primarily Earth's poroelastic response, from which water change is difficult to infer.  GRACE cannot distinguish water change in Central Valley from water change in the Sierra Nevada without assuming a hydrology model.  We integrate GPS elastic displacements and GRACE gravity to estimate water change in the Central Valley.  In the rigorous inversion, GPS determines water change in the Sierra Nevada and Coast Ranges and the remaining water change from GRACE is placed in the Central Valley.  We find Central Valley groundwater increased by 0.75 m in the first nine months of Water Year 2023 (the biggest gain ever recorded), replenishing more groundwater than lost during the prior 3 years of drought.

How to cite: Argus, D., Martens, H., David, W., Matthew, S., Adrian, B., Athina, P., Lau, N., Kim, D., Gaastra, K., Ellmer, M., Young, Z., Knappe, E., Molotch, N., Alam, S., Landerer, F., Gardner, P., and John, R.: The Big Soak:  Change in Water in 2023 in North America's Pacific Mountain System , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14655, https://doi.org/10.5194/egusphere-egu24-14655, 2024.

EGU24-14952 | ECS | Posters on site | G3.1

Impact of Climate Change and Terrestrial Water Storage on the Himalayan Seismicity  

Sukanta Malakar and Abhishek K. Rai

The Himalayan terrain epitomises continuing convergence and geodetic deformation caused by tectonic and non-tectonic factors. Climate change and induced secondary factors are some of the dominant non-tectonic forces. A small change in stress and pore-fluid pressure caused by precipitation and temperature fluctuations may trigger seismic activity in the vicinity of already critically stressed faults and fractures at local and regional scales. The increase in temperature has also resulted in the melting of mountain glaciers in the Himalayan region and the release of the glacial load, leading to post-glacial rebound and elastic deformation. This study investigates the correlation and causal relationship between climatic parameters and earthquakes in the Himalayas. Further, we study the hydrological loading effect (derived from the GRACE/GRACE-FO satellite) and correlate it with the seismic hazard map. The results show that temperature anomalies have a relatively strong influence (r ~0.36-0.54) on the occurrence of minor-magnitude earthquakes in the Eastern Himalayas. However, the North-western Himalayas show a moderately positive correlation with precipitation anomalies (r ~0.23-0.37). Furthermore, a positive correlation has been found between regional terrestrial water storage (TWS) influence and the seismic hazard, ranging from 0.04-0.45. The result shows higher positive correlation values in the post-monsoon period for the North-western and Eastern Himalayas, whereas the Central Seismic Gap and Eastern Nepal and Sikkim show a higher value for the pre-monsoon period.

How to cite: Malakar, S. and Rai, A. K.: Impact of Climate Change and Terrestrial Water Storage on the Himalayan Seismicity , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14952, https://doi.org/10.5194/egusphere-egu24-14952, 2024.

EGU24-15227 | Orals | G3.1

Homogenization of GNSS IWV time series and estimation of climatic trends 

Olivier Bock, Ninh Khanh Nguyen, and Emilie Lebarbier

Water vapor plays a key role in the Earth's climate as a dominant greenhouse gas. It is also the most efficient actor of heat transfer from the surface to the atmosphere and from low to high latitudes which shapes the global atmospheric circulation and weather systems. Monitoring and understanding the spatial and temporal variability and changes of water vapor are thus of crucial importance.

This work aims at computing decadal trends of total column Integrated Water Vapour (IWV) from a global network of ground-based GNSS observations. Although GNSS observations are available with high accuracy in all weather conditions, it has been shown that, over long periods of time, changes in instrumentation, in station location and environment, and in processing methods can introduce spurious shifts in the IWV time series and bias trend estimates. Homogenization is a crucial step to detect and correct such non-climatic signals.

We have developed a relative homogenization method which involves three steps.

  • Segmentation. First, change-points are detected from the difference series (GNSS – reference) with the help of the GNSSseg segmentation package (Quarello et al., 2022). The method uses a difference series in order to cancel out the common climatic variations. It also accounts for changes in the variance on fixed intervals (monthly) and a periodic bias (annual) due to representativeness differences between GNSS and the reference (in our case the ERA5 reanalysis). Because the change-points detected in the difference series could be either due to GNSS or to the reference (ERA5), the next step is the attribution.
  • Attribution. Second, the detected change-points are attributed to either GNSS or to the reference (ERA5) using a statistical test based on linear regression and a predictive rule based on the Random Forest learning algorithm (Nguyen et al., 2023). This step requires additional neighbors stations (at least one).
  • Correction. The last step is the correction. Here the initial GNSS series is corrected only for the shifts which are attributed to the GNSS in the second step.

We will present results of the homogenization procedure applied to a global network of GNSS stations and discuss the impact of homogenization on linear trend estimates for stations that have more than 20 years of observations.

Quarello et al., 2022, https://doi.org/10.3390/rs14143379

Nguyen et al., 2023, https://hal-obspm.ccsd.cnrs.fr/IGN-ENSG/hal-04014145v1

How to cite: Bock, O., Nguyen, N. K., and Lebarbier, E.: Homogenization of GNSS IWV time series and estimation of climatic trends, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15227, https://doi.org/10.5194/egusphere-egu24-15227, 2024.

EGU24-15647 | ECS | Posters on site | G3.1

Spatio-temporal analysis of the ice mass changes over Greenland from GRACE and GRACE-FO. 

Florent Cambier, José Darrozes, Muriel Llubes, Lucia Seoane, and Guillaume Ramillien

Prediction of the trends of ice mass loss in Greenland can help for understanding what occurred during the last 20 years and in the future. The Level-2 GRACE and GRACE-FO solutions provided by the official computing centres CSR and ITSG as well as the combined products of the COST-G project give access to the spatio-temporal variations of the ice mass balance of Greenland from 2002 to present. We first reduce the GRACE data from post-glacial rebound. We propose to analyse these solutions by applying Singular Value Decomposition (SVD) and Empirical Mode Decomposition (EMD) to extract the trend. This trend is then removed from the timeseries for the Fast Fourier Transform (FFT) and 1-D Continuous Wavelet Transform (CWT) analysis. CWT and FFT analysis enable to unravel the long-term trend of the ice loss ranging from 6-9 years, as well as the annual and semi-annual part. The period of 6 to 9 years shows some correlation with meteorological and climate indexes such as North Atlantic Oscillation (NAO). The spatial component of the first SVD mode indicates that the ice melting is the most important along the west and southeast coast at the rate of -30 to -40 Gt/yr. Globally, the trend is not linear, it consist of different phases of acceleration and deceleration with rates between -60 and -340 Gt/yr.

How to cite: Cambier, F., Darrozes, J., Llubes, M., Seoane, L., and Ramillien, G.: Spatio-temporal analysis of the ice mass changes over Greenland from GRACE and GRACE-FO., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15647, https://doi.org/10.5194/egusphere-egu24-15647, 2024.

EGU24-16124 | ECS | Orals | G3.1

ACC Volume Transport: A Geodetic Analysis via Satellite Data 

Juan Adrián Vargas Alemañy, Isabel Vigo Aguiar, David García García, and Ferdous Zid

Geostrophic currents, driven by the Coriolis and pressure gradient forces, are crucial for understanding ocean circulation. The Antarctic Circumpolar Current (ACC) in the Southern Ocean, encircling Antarctica, has substantial global impact, and its volume transport (VT) remains challenging to measure. We utilize satellite data, combining Altimetry and Gravity Satellite missions, to estimate VT within the ACC. Our study offers a comprehensive spatial and temporal analysis, encompassing barotropic and baroclinic VT components. We validate our results with in-situ measurements from the Drake Passage. Our analysis reveals a steady spatial VT of 210.44 ± 3.4 Sv, with maxima near critical choke points. Temporally, we identify a mean VT of 15.86 ± 0.05 Sv per 1º grid cell, a linear trend of -0.007 ± 0.002 Sv per month, and significant seasonal and biannual signals. Zonal VT predominantly influences total VT, while meridional VT remains near zero. The baroclinic component drives low-frequency variations, while the barotropic component controls high-frequency variations. We propose a specific ACC zonal VT of 201.63 ± 0.71 Sv. In summary, our satellite-based approach offers valuable insights into ACC VT. This methodological extension enhances our understanding of the ACC's ocean circulation dynamics, showcasing the utility and robustness of satellite data in oceanographic research.

How to cite: Vargas Alemañy, J. A., Vigo Aguiar, I., García García, D., and Zid, F.: ACC Volume Transport: A Geodetic Analysis via Satellite Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16124, https://doi.org/10.5194/egusphere-egu24-16124, 2024.

EGU24-16767 | Posters on site | G3.1

A seafloor deformation study using A-0-A pressure instruments and ocean models to contribute to the monitoring of the Mayotte volcanic crisis. 

Valerie Ballu, Yann-Treden Tranchant, Denis Dausse, and Laurent Testut

The sudden 2018 volcanic eruption offshore Mayotte, in the western Indian Ocean, demonstrated, once again, the crucial need for means to monitor telluric activity occurring on the seafloor and threatening coastal zones. In the Mayotte case, on-land GNSS stations were of primary importance to detect the subsidence induced by the emptying of a deep magma chamber (Peltier et al. 2022), however they are not adequate to properly characterize and monitor the deformation created by further offshore or shallower processes.

Ocean bottom pressure (OBP) records can be used to monitor seafloor motion. However, detecting small or slow deformation is challenging due to instrumental drift and oceanic variations at different timescales. New Ambient-Zero-Ambient (A0A) pressure systems allow the estimation of the instrumental drift in situ by periodic venting from ocean pressures to a reference atmospheric pressure (Wilcock et al., 2021) and therefore allow access to the accurate monitoring of slow deformation. A A0A drift-controlled pressure gauge has been deployed since 2020 (four successive deployments) to monitor the seafloor vertical deformation on the flank of Mayotte island. The deployment site is located within a seismically active circular-shape zone, called the proximal cluster (Lavayssière et al., 2022). During the last deployment (2022-2023), an additional reference instrument was installed outside the proximal cluster, to allow for differential deformation analysis.

Beside volcanic activity monitoring, the objective of this study is to assess the performance of these new A0A pressure gauges and our ability to reduce the oceanic “noise” in corrected OBP records and characterize seafloor deformation in the Mayotte region. We investigate the use of numerical models, including available global ocean circulation reanalyses (OGCMs) and barotropic simulations, to account for the different oceanic processes contributing to the seafloor pressure variations and therefore limiting our ability to identify crustal deformation in the integrated pressure records.

We also use temperature and salinity profiles from repetitive glider transects to validate OGCMs in the region and quantify the contribution of unresolved fine-scale processes to OBP records. Our results provide valuable insights into the feasibility of using numerical modeling for improving the accuracy of OBP-based monitoring at different timescales, in the context of the Mayotte seismic crisis as well as for other seafloor deformation monitoring. Finally, we present a preliminary work on the combination of sparse regional altimetric data with the glider observations to compute a seafloor pressure series to be compared to the recorded data. Current altimetry spatio-temporal coverage is limited, however, newcoming SWOT observations are likely to provide new perspectives in seafloor geodesy.

Our results bring insights for future A0A deployments, especially in the perspective of the planned MARMOR seafloor cabled observatory offshore Mayotte.

How to cite: Ballu, V., Tranchant, Y.-T., Dausse, D., and Testut, L.: A seafloor deformation study using A-0-A pressure instruments and ocean models to contribute to the monitoring of the Mayotte volcanic crisis., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16767, https://doi.org/10.5194/egusphere-egu24-16767, 2024.

EGU24-16813 | Orals | G3.1

Global mean and local sea level budget from updated observations andresiduals analysis (SLBC_cci+ project) 

Marie Bouih, Anne Barnoud, Robin Fraudeau, Gilles Larnicol, Anny Cazenave, Benoit Meyssignac, Alejandro Blazquez, Martin Horwath, Thorben Döhne, Jonathan Bamber, Anrijs Abele, Stéphanie Leroux, Nicolas Kolodziejcyk, William Llovel, Giorgio Spada, Andrea Storto, Chunxue Yang, Sarah Connors, Marco Restano, and Jérôme Benveniste and the SLBC_cci+ team

The closure of the Sea Level Budget (SLB) at monthly, yearly, and interannual scales, with the utmost precision, remains a fundamental challenge in modern physical oceanography. Firstly, this closure is crucial to assert that all major contributors to sea level variability are accurately identified and quantified. Secondly, it serves as a valuable means for cross-validating complex global observation systems, such as the Argo in-situ network, satellite gravimetry missions GRACE/GRACE-FO, and the satellite altimetry constellation, while closely monitoring their performances. Thirdly, this closure proves to be an effective approach for testing the consistency of various observed variables within the climate system, including sea level, ocean temperature and salinity, ocean mass, land ice melt, and changes in land water storage, in accordance with conservation laws, notably those governing mass and energy.

In this presentation, we will share the latest results obtained for the sea level budget, including 1) an up-to-date estimate of the global mean budget closure from 1993 to 2022; 2) advancements in the analysis of regional patterns of each component of the budget, as well as of the budget residuals, allowing the identification of regions where the SLB does not close, with a focus on the North Atlantic and the Arctic Ocean where the residuals are significantly high. When and where the SLB closes, we can interpret the causes of the total sea level variations. The analysis at regional scales allows us to assess the relative importance of the individual components all over the oceans. When the SLB does not close, we investigate in each component the potential errors causing non-closure (e.g., in-situ data sampling, geocenter correction in gravimetric data) and how potential inconsistencies in their processing can impact large-scale patterns (e.g., geocenter and atmosphere corrections).

Future works will address questions related to the structural deficiency of the observing system, inconsistent effective resolution across different observing subsystems (in-situ data, satellite gravimetry, and satellite altimetry), potential measurement errors in a single observing subsystem, and the isolation of errors in terms of time and space. To address these questions, we will assess an SLB using synthetic components derived from oceanic models. This novel approach will enable us to estimate the spatial and temporal resolutions inherent in each observation, thereby enhancing the estimation of their respective uncertainties. We will also analyse the signature of internal climate variability on sea level budget components interannual changes, by using state-of-the-art model simulations and reanalyses.

This work is performed within the framework of the Sea Level Budget Closure Climate Change Initiative (SLBC_cci+) programme of the European Space Agency (ESA).

How to cite: Bouih, M., Barnoud, A., Fraudeau, R., Larnicol, G., Cazenave, A., Meyssignac, B., Blazquez, A., Horwath, M., Döhne, T., Bamber, J., Abele, A., Leroux, S., Kolodziejcyk, N., Llovel, W., Spada, G., Storto, A., Yang, C., Connors, S., Restano, M., and Benveniste, J. and the SLBC_cci+ team: Global mean and local sea level budget from updated observations andresiduals analysis (SLBC_cci+ project), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16813, https://doi.org/10.5194/egusphere-egu24-16813, 2024.

EGU24-17367 | Orals | G3.1

Assessing daily to interannual geocenter motion variations from Low Earth Orbiters 

Alexandre Couhert, Flavien Mercier, John Moyard, and Pierre Exertier

The ever-changing fluid mass (oceans, continental water, snow, atmosphere, …) redistributions on the Earth's surface give rise to a motion of the deformable terrestrial crust, that is its geometrical center-of-figure (CF), with respect to the center-of-mass (CM) of the Earth, about which satellites naturally orbit. This motion, called “geocenter motion”, is the largest scale variability of mass within the Earth system. Yet, non-tidal geocenter motion, which reflects major water and atmosphere mass transports occurring over large regions, is traditionally neglected.

However, new climate-driven precise monitoring of geocenter motion is needed. Indeed, satellite altimetry and gravimetry precise orbits connect sea level and global water budgets to the Earth’s center of mass. As such, the geocenter motion is now the leading error term in Regional Mean Sea Level and mass changes over polar ice sheets estimates. Reliable solutions of geocenter motion are thus crucial for assessing the current status of climate change and its future evolution (e.g., for the Earth’s Energy Imbalance).

Global Navigation Satellite Systems (GNSS) measurement models and derived products are currently aligned to the International Terrestrial Reference Frame (ITRF) origin (which is referenced to the crust), instead of CM. Looking at sub-daily cross-track perturbations estimated with the GNSS receivers on board the Jason-3 and Sentinel-6 MF altimetry satellites during their tandem phase (December 18, 2020 – April 7, 2022) revealed consistent diurnal oscillations with an impressive temporal resolution. These could only be related to the miscentering effect of the constellation solution around the Earth’ CM. In this paper, a parametric model is derived, representing the translation of the GNSS ground station networks with respect to the center of mass of the whole Earth system. This model is estimated with GNSS-based low Earth satellite precise orbits and unambiguously validated with independent altimetry satellite missions (e.g., Sentinel-3A, Sentinel-6 MF, Jason-3). It helps to clearly identify interannual variations in the geocenter motion, as short as a day long.

How to cite: Couhert, A., Mercier, F., Moyard, J., and Exertier, P.: Assessing daily to interannual geocenter motion variations from Low Earth Orbiters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17367, https://doi.org/10.5194/egusphere-egu24-17367, 2024.

EGU24-18031 | Posters on site | G3.1

Inferring North Atlantic Deep Water Transports from Ocean Bottom Pressure at the Western Boundary 

Maik Thomas, Linus Shihora, and Henryk Dobslaw

Estimating oceanic transports of volume, heat, carbon, and freshwater is fundamental to understanding the ocean’s role in the evolving climate system. Unique in this context is the Atlantic Meridional Overturning Circulation (AMOC) that comprises a net northward transport of relatively warm water at depths of ≲1 km throughout the Atlantic basin, compensated at ≳1–5 km by a colder net southward return flow.
While in-situ measurements, such as the RAPID array at 26.5°N, are considered the 'gold standard' to monitore changes in the AMOC, measurements at many latitudes and the detection of e.g. basin-wide modes are non feasible.
However, variations in the overturning are to a good degree accompanied by associated changes in oceanic bottom pressure which opens up new avenues of AMOC monitoring through bottom pressure recorders or even through future satellite gravimetry measurements. 

Here, we investigate the connection between changes in the Atlantic overturning and associated variations in bottom pressure along the western continental shelf in a suite of ocean models. This includes high resolution simulations from a CMIP6 FESOM run by AWI, the regional VIKING20X model by GEOMAR. We investigate to what degree the transport variations can be inferred from bottom pressure signatures alone, limitations of the approach and especially how such signatures could be implemented into a future iteration of the ESA ESM. This would allow the inclusion the these transport-related OBP changes in dedicated simulation studies for future satellite gravimetry missions.

How to cite: Thomas, M., Shihora, L., and Dobslaw, H.: Inferring North Atlantic Deep Water Transports from Ocean Bottom Pressure at the Western Boundary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18031, https://doi.org/10.5194/egusphere-egu24-18031, 2024.

EGU24-18783 | Posters on site | G3.1

A New Knowledge Portal on Mass Transport Satellite Missions: www.globalwaterstorage.info 

Ulrike Sylla, Pia Klinghammer, Antonia Cozacu, Frank Flechtner, Henryk Dobslaw, Julian Haas, Eva Boergens, Josef Zens, and Jörn Krupa

Dedicated satellite gravity missions orbiting the Earth at very low altitudes have greatly improved our knowledge about mass transport processes. That includes the terrestrial water cycle, ice sheet and glacier dynamics, ocean mass variability, and changes deep within the solid Earth, like the adjustment in the upper mantle in response to massive deglaciations since the last ice age. Initiated with the original GRACE (Gravity Recovery and Climate Experiment) mission launched in 2002, the record of monthly gravity fields now spans 22 years and is still being extended by GRACE-FO which has been in orbit since 2018. To enhance the visibility of the missions within society and to inform about the various contributions of GRACE/GRACE-FO to various scientific fields, GFZ  is maintaining a new knowledge portal accessible via www.globalwaterstorage.info.

On the one hand, this new portal provides overview information on satellite technology, various geophysical applications, and the numerous industrial and scientific partners who were vital for the success of the GRACE/GRACE-FO missions with the specific aim of informing European stakeholders. On the other hand, we also work towards developing the portal into a publicity channel for the gravimetry community to highlight recent developments towards future satellite missions or new research insights  based on mission data. International colleagues interested in advertising their latest achievements through a blog post (ca. 5000 characters) in the knowledge portal are kindly invited to contact globalwaterstorage@gfz-potsdam.de.

How to cite: Sylla, U., Klinghammer, P., Cozacu, A., Flechtner, F., Dobslaw, H., Haas, J., Boergens, E., Zens, J., and Krupa, J.: A New Knowledge Portal on Mass Transport Satellite Missions: www.globalwaterstorage.info, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18783, https://doi.org/10.5194/egusphere-egu24-18783, 2024.

EGU24-21332 | ECS | Orals | G3.1 | Highlight

Mass Balance of Greenland and Antarctic Ice Sheets since the 1970s 

Athul Kaitheri, Ines Otosaka, and Andrew Shepherd

Ice sheets in Antarctica and Greenland have continued to undergo rapid changes since the 1970s causing a significant rise in global mean sea level. The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) community has produced reconciled estimates of ice sheet mass changes for both ice sheets from the 1970s till 2021 by combining more than 50 independent mass balance estimates produced from varied satellite observations. Ice sheet mass changes are driven by competing processes due to their interaction with the atmosphere (surface mass balance) and ocean (ice dynamics). Here, we present an updated IMBIE assessment and partition mass trends into their surface mass balance (SMB) and ice dynamics components. This new assessment shows that Antarctica and Greenland contributed 29.3 mm to the global mean sea level between 1979 and 2021. While in Antarctica, almost all ice losses were driven by ice dynamical imbalance, we find that 60 % of Greenland’s ice losses were caused by increased ice discharge with reduced SMB accounting for the remainder. This exercise reveals the different drivers of Antarctica and Greenland mass changes and highlights their high interannual variability. Finally, we are aiming at producing reconciled regional ice sheet mass balance estimates for the main drainage basins of Antarctica and Greenland for the first time and will be presenting preliminary results for some of the key regions of the ice sheets that have been undergoing rapid changes. Partitioning mass trends and producing regional assessments will contribute to a better understanding of the remaining differences between the different satellite geodesy techniques employed within IMBIE and will provide a key dataset for both the Earth Observation and ice sheet modelling communities. 

How to cite: Kaitheri, A., Otosaka, I., and Shepherd, A.: Mass Balance of Greenland and Antarctic Ice Sheets since the 1970s, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21332, https://doi.org/10.5194/egusphere-egu24-21332, 2024.

EGU24-1271 * | Orals | G3.3 | Highlight

Understanding sea level rise using polar motion from 1979 to 2010 

Ki-Weon Seo, Dongryeol Ryu, Kookhyeon Youm, Jianli Chen, and Clark Wilson

Sea level rise is one of the most significant consequences of the warming climate. GRACE and GRACE Follow-On satellites have been providing critical clues about the primary contributor to recent sea level rise, such as the melting ice sheets and mountain glaciers, and the depletion of terrestrial water storage. However, due to the limited availability of satellite gravity data (only since 2002) and other direct observations, understanding changes in ocean mass during the 20th century had to rely on global hydrological or Earth systems modeling.

On the other hand, efforts have been made to understand the past sea level rise using a combination of optical/microwave satellite imagery of polar regions, along with glaciological and geodetic data for mountain glaciers, global databases for large dams, and climate models for terrestrial water storage. Despite these efforts, verifying the accuracy of the combined estimates requires independent long-term observational evidence.

In this presentation, we show that studying Earth’s polar motion presents a unique opportunity to comprehend historical sea level rises predating the GRACE satellite era. Observed polar motion data from 1979 to 2010 agree well with estimates derived from various observations and climate models. During this period, the total increase in ocean mass is estimated to 52.94 mm (equivalent to 1.65 mm per year), encompassing contributions from ice melting in Antarctica (9.11 mm), Greenland (8.95 mm), mountain glaciers (20.16 mm), and the depletion of terrestrial water storage (13.72 mm). This approach utilizing polar motion offers a valuable means for historical sea level rise assessments, filling gaps in our understanding before the advent of the GRACE satellite missions.

How to cite: Seo, K.-W., Ryu, D., Youm, K., Chen, J., and Wilson, C.: Understanding sea level rise using polar motion from 1979 to 2010, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1271, https://doi.org/10.5194/egusphere-egu24-1271, 2024.

EGU24-3096 | Posters on site | G3.3

Effects of topographic coupling at core-mantle boundary in rotation and orientation changes of the Earth. 

Véronique Dehant, Jeremy Rekier, Mihaela Puica, Marta Folgueira, and Tim Van Hoolst

We study coupling mechanisms at the core-mantle boundary (CMB) of the Earth in the frame of nutations and Length-of-Day (LOD) variations. The CMB is usually considered to have a smooth spherical or elliptical shape inducing a Poincaré flow in the nutation case and a global rotation in the LOD case. However, in reality, the CMB is bumpy and there are mountains and valleys representing local height differences of the order of a kilometer. The existence of a topography induces inertial waves that need to be considered in the flow of the core. This is in addition to the Poincaré fluid motion when the nutations are computed and in addition to a relative rotation of the fluid opposite and of the same amplitude as that of the mantle for LOD variations. The additional pressure and the topographic torque depend on the shape of the CMB and can be related to the spherical harmonic coefficients of the CMB topography. We follow the philosophy of the computation of Wu and Wahr [Geophys. J. Int., 128(1), 18-42, 1997] and determine the coefficients of the velocity field in the core at the CMB in terms of the topography coefficients. We used an analytical approach instead of a numerical one. We confirm that some topography coefficients may enhance length-of-day variations and nutations at selected frequencies, and show that these increased rotation variations and nutations are due to resonance effects with inertial waves in the incremental core flow. While they could be at a detectable level for LOD, they are very small for nutations (except for the flattening of the core), enhancing the importance of the electromagnetic coupling at the CMB.

How to cite: Dehant, V., Rekier, J., Puica, M., Folgueira, M., and Van Hoolst, T.: Effects of topographic coupling at core-mantle boundary in rotation and orientation changes of the Earth., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3096, https://doi.org/10.5194/egusphere-egu24-3096, 2024.

EGU24-3582 | Posters on site | G3.3

Using Optimal Estimation and Robust Curve-Fitting Tools to Enhance Predicted Earth Angular Momentum for Earth Orientation  

Nicholas Stamatakos, Dennis McCarthy, David Salstein, Mark Psiaki, and Jessica Page

Previous investigations have shown the potential of enhancing the accuracy of estimates of the direction of the rotational pole and velocity of rotation of the Earth by using improved pre-processing (along with improved optimal estimation codes) of atmospheric and/or ocean angular momentum data. (These data are useful for prediction of the Earth orientation parameters because of conservation of the angular momentum in the Earth system).  Recent investigations have shown that predictions of UT1 – UTC estimates can be improved by 45% for 1- day predictions and 30% for 7-day predictions. This poster is a continuation of previous efforts to investigate procedures to handle outliers in EOP input data using improved robust curve-fitting tools and improved optimal estimation tools.

How to cite: Stamatakos, N., McCarthy, D., Salstein, D., Psiaki, M., and Page, J.: Using Optimal Estimation and Robust Curve-Fitting Tools to Enhance Predicted Earth Angular Momentum for Earth Orientation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3582, https://doi.org/10.5194/egusphere-egu24-3582, 2024.

EGU24-4521 | Orals | G3.3

Multidisciplinary Implications from the post-2015 Chandler Wobble Anomaly 

Masato Furuya and Ryuji Yamaguchi

Given the disappearance of the 6-year beat in recent polar motion data, we have pointed out that the Chandler Wobble (CW) has not been excited since 2015 and further examined if the presently available Earth-system-modeling data can explain the anomaly  (Yamaguchi and Furuya 2024, doi:10.1186/s40623-023-01944-y).  Here we discuss its implications from meteorological and geodynamical points of view.

We confirmed that two independent atmospheric angular momentum (AAM) data from ERA5 and JRA-55 were almost in perfect match with each other in terms of their persistently smaller contributions to the CW excitations in recent years. We thus examined the temporal changes in the regional contributions to the global AAM, using JRA-55 reanalysis data. While the mass term exhibited no significant changes in any latitude zones throughout the analysis period, the motion term in some latitude zones exhibited larger amplitudes since 2015 than before. We speculate its possible connections to the recent anomalies of the quasi-biennial-oscillation in 2015/2016 and 2019/2020.

Another important conclusion in Yamaguchi and Furuya (2024) is that the quality factor (Q) of the CW is not as high as 100, which has been preferred in previous studies, whereas there have been a couple of times differences even in the recent Q estimates; e.g., from 49 by Furuya and Chao (1996), 97 by Seitz et al (2012), 127 by Nastula and Gross (2015). While Smith and Dahlen (1981) preferred Q~100 and quantitatively interpreted the period and Q in terms of a frequency-dependent mantle anelasticity, the lower Q than previously thought will suggest a need to revise the theory and have an implication for the lower-mantle rheology.  

How to cite: Furuya, M. and Yamaguchi, R.: Multidisciplinary Implications from the post-2015 Chandler Wobble Anomaly, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4521, https://doi.org/10.5194/egusphere-egu24-4521, 2024.

EGU24-5858 | Posters on site | G3.3

Atmospheric excitation of the annual wobble over the 21st-century from CMIP6 predictions under different scenarios 

Sigrid Böhm, Anne Strümpf, and David Salstein

The annual wobble is the second distinct feature of polar motion after the Chandler wobble. It is a seasonally forced oscillation driven mainly by significant pressure differences between boreal winter and summer over Siberia. In this study, we investigate the future evolution of the annual wobble amplitude from 21st-century model projections of atmospheric pressure and wind velocities. The model variables are provided within the Coupled Model Intercomparison Project Phase 6 (CMIP6) for different scenarios that simulate possible future anthropogenic drivers of climate change. We use the simulations of 11 models for five such scenarios, which range from very mild to quite extreme future climate changes. The 21st-century simulations span 85 years, from 2015 to 2100. Our analysis focuses on the temporal evolution of the amplitude of the annual oscillation in equatorial atmospheric angular momentum functions. More intense scenarios involving more substantial global warming show an increase in the magnitude of the annual wobble towards the end of the century. More extreme annual pressure anomalies over the North Asian landmass probably cause the rising amplitudes.

How to cite: Böhm, S., Strümpf, A., and Salstein, D.: Atmospheric excitation of the annual wobble over the 21st-century from CMIP6 predictions under different scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5858, https://doi.org/10.5194/egusphere-egu24-5858, 2024.

EGU24-6342 | ECS | Orals | G3.3

The excitation of free core nutation: a reappraisal 

Mostafa Kiani Shahvandi, Michael Schindelegger, Lara Börger, Siddhartha Mishra, and Benedikt Soja

Free Core Nutation (FCN) is a rotational normal mode of the Earth arising from the misalignment of the rotation vectors of the mantle and the fluid outer core. There has long been suggestive evidence that this mode is excited against dissipation by variations in Atmospheric and Oceanic Angular Momentum (AAM and OAM, respectively), but efforts to reconcile model-based AAM and OAM estimates with the FCN in geodetic data (the Celestial Pole Offsets, CPO) have remained futile. In particular, prior assessments suggest that the power of geophysical excitation from AAM/OAM data exceeds the power of geodetic excitation at the FCN frequency by a factor of 10 or more. Here we reassess the geophysical excitation of FCN using 3-hourly AAM and OAM series from two latest-generation atmospheric reanalyses and consistently forced ocean forward models, called MERRA-2. We focus on the pressure terms and transform them to the celestial frame by complex demodulation. In addition, we use the latest CPO series of the International Earth Rotation and Reference Systems Service (IERS 20 C04) and convert it to geodetic excitation using a digital filter based on the broad-band Liouville equation. By filtering the geodetic and geophysical excitation series near the FCN frequency band (approximately –440 to –420 days in the celestial frame) we show that the agreement between these two series is improved relative to previous studies, such that the ratio of the power spectrum of geophysical to geodetic excitations is ~4.6. Moreover, we find clear similarities between observed and modeled (excitation) time series in the FCN band. Among the different drivers, the impact of AAM is at least 3 times larger than that of OAM. Our results represent progress in finding the cause of continuous FCN excitation, which is most probably the variability of atmospheric pressure over continental landmasses.

How to cite: Kiani Shahvandi, M., Schindelegger, M., Börger, L., Mishra, S., and Soja, B.: The excitation of free core nutation: a reappraisal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6342, https://doi.org/10.5194/egusphere-egu24-6342, 2024.

EGU24-8315 | Posters on site | G3.3

Exploiting the SLR+GRACE/GRACE-FO Hybrid Solutions to Determine Gravimetric Excitations of Polar Motion 

Jolanta Nastula, Justyna Śliwińska-Bronowicz, Małgorzata Wińska, and Aleksander Partyka

In this study, we investigate the excitation of polar motion (PM) caused by changes in the distribution of hydrosphere mass. This phenomenon is expressed through hydrological angular momentum (HAM) series, which can be estimated using global models of the continental hydrosphere, Earth's gravity field variations, and numerical climate models.

The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions have provided crucial data for understanding the time-variable gravity field affected by changes in global mass distribution. These missions also reveal how mass variations in the continental hydrosphere and cryosphere affect PM. However, it has been identified that GRACE/GRACE-FO solutions have certain limitations when determining geopotential coefficients of lower degrees. As a remedy, it has become standard practice to replace the C20 values obtained from GRACE/GRACE-FO solutions with corresponding estimates from Satellite Laser Ranging (SLR). Similar substitutions are also recommended for the C21 and S21 coefficients.

In our study, we employ hybrid SLR+GRACE/GRACE-FO time-variable gravity solutions, made available by the Institute of Geodesy at Graz University of Technology (ITSG) and Centre National D'Etudes Spatiales (CNES), to determine hydrological/gravimetric angular momentum (HAM). To evaluate the SLR+GRACE/GRACE-FO-based HAM series, we compare them with the hydrological signal in observed PM excitation, referred to as geodetic residuals (or GAO). Additionally, we compare these series with HAM derived from GRACE/GRACE-FO data, focusing on seasonal and non-seasonal variations.

Our findings indicate that the excitation functions derived from the hybrid solution closely align with the GAO. In fact, they are similar or even better consistent with GAO than the series derived from the GRACE/GRACE-FO data.

How to cite: Nastula, J., Śliwińska-Bronowicz, J., Wińska, M., and Partyka, A.: Exploiting the SLR+GRACE/GRACE-FO Hybrid Solutions to Determine Gravimetric Excitations of Polar Motion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8315, https://doi.org/10.5194/egusphere-egu24-8315, 2024.

EGU24-8834 | ECS | Orals | G3.3

Dynamic Mode Decomposition-based short-term prediction of UT1-UTC and LOD using Atmospheric Angular Momentum time series. 

Maciej Michalczak, Marcin Ligas, Henryk Dobslaw, and Robert Dill

We present preliminary results of ultra-short-term prediction (10-day forecast horizon) of UT1-UTC and LOD. Forecast procedure is based on Dynamic Mode Decomposition (DMD) and uses IERS EOP 14 C04 as a reference as well as Atmospheric Angular Momentum (AAM) as auxiliary data (AAM come from GFZ Potsdam and ETH Zurich).

Two main prediction experiments (using different types of input data) were conducted: the ideal and the operational case. The ideal one was based on final (historical) data (both C04 and AAM); predictions performed within one year time span starting on a random MJD with 7 day step between subsequent 10 day forecasts, each yearly time span includes 51 10-day predictions. The operational case was based on operational data, covers the period of the 2nd Earth Orientation Parameters Prediction Comparison Campaign, each variant of this case includes 69 10-day predictions.

Within each experiment and for each considered EOP we prepared some additional analysis. In case of LOD, we conducted predictions using 2 types of input LOD time series: directly on published IERS EOP 14 C04 time series and computed as a derivative of IERS EOP 14 C04 UT1-UTC time series. The final UT1-UTC predictions vary depending on the method of determining the constant of integration restoring the proper scale of UT1-UTC.

In the ideal case the mean absolute prediction errors for UT1-UTC vary from 0.009 ms – 0.036 ms for the 1st day and 0.224 ms – 0.292 ms for the 10th day of prediction, whilst those values vary from 0.016 ms – 0.028 ms and 0.045 ms – 0.063 ms for LOD prediction. Corresponding values in the operational case are within the range of 0.058 ms – 0.065 ms and 0.438 ms – 0.463 ms for UT1-UTC, whilst for LOD these values are 0.032 ms – 0.040 ms and 0.093 ms – 0.099 ms.

In operational settings of UT1-UTC prediction, we can observe that our results are slightly worse than the accuracy of IERS predictions (Bulletin A), while comparable to the accuracy of the forecast of methods from 2nd EOPPCC. The results demonstrate that the proposed techniques can efficiently forecast UT1-UTC and LOD. Nevertheless, a deeper analysis is needed on efficient incorporation of Effective Angular Momentum Functions information to improve presented prediction procedure.

How to cite: Michalczak, M., Ligas, M., Dobslaw, H., and Dill, R.: Dynamic Mode Decomposition-based short-term prediction of UT1-UTC and LOD using Atmospheric Angular Momentum time series., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8834, https://doi.org/10.5194/egusphere-egu24-8834, 2024.

EGU24-9388 | ECS | Posters on site | G3.3

Exploring the effect of different VLBI Networks on EOPs estimation. 

Lucía D. del Nido Herranz, Santiago Belda, Maria Karbon, Esther Azcue, Víctor Puente, and José M. Ferrándiz

One of the key determinants influencing the accuracy and reliability of Earth Orientation Parameters (EOP) is the network Very Long Baseline Interferometry (VLBI) geometry. VLBI is a high-precision radio astronomy technique that involves multiple radio telescopes spread across the globe, working together as a network. The geometric configuration of these telescopes plays a crucial role in the quality of the data collected and, consequently, the accuracy of EOP measurements. The distribution and arrangement of the VLBI network antennas impact the triangulation process used to determine the positions of celestial radio sources, contributing to the calculation of Earth's rotation parameters. An optimal VLBI geometry ensures a well-constrained and robust observational setup, leading to more precise EOP results crucial for many scientific applications.

In this study, we analyze the impact of using different VLBI networks on the EOP estimation. Due to its nature the Continuous VLBI Campaigns (CONT) give a good basis to investigate these effects. For this purpose, we artificially create different networks with distinct configurations (e.g. removing VLBI antennas located in the northern hemisphere and vice versa, taking out the longest north-south baselines or the east-west baselines…). This sensitivity analysis will contribute to the refinement of the EOP and will help to fulfill the stringent GGOS targets (i.e. a frame with accuracy at epoch of 1 mm or better and a stability of 0.1 mm/y).

Acknowledgment. This research was supported partially by Spanish Projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033); PROMETEO/2021/030 and SEJIGENT/2021/001, funded by Generalitat Valenciana; and the European Union—NextGenerationEU (ZAMBRANO 21-04).

How to cite: del Nido Herranz, L. D., Belda, S., Karbon, M., Azcue, E., Puente, V., and Ferrándiz, J. M.: Exploring the effect of different VLBI Networks on EOPs estimation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9388, https://doi.org/10.5194/egusphere-egu24-9388, 2024.

EGU24-9457 | ECS | Posters on site | G3.3

Consistently combined Earth Rotation Parameters at BKG - Adding SLR data to VLBI and GNSS 

Lisa Klemm, Daniela Thaller, Daniel König, Claudia Flohrer, and Anastasiia Walenta

We present BKG´s current activities in the field of combined data processing of different space-geodetic techniques. The primary goal of the combined analyses is the improvement of the consistency between the techniques through common parameters, mainly Earth Rotation Parameters (ERP), and thereby to improve also the resulting ERPs. In previous studies, we have investigated different combination approaches using VLBI and GNSS data and generated ERP series with latencies of about 1-2 or 14 days, depending on the input data used. In this way, we achieved a significant improvement in accuracy, especially for the dUT1 series, compared to the individual technique-specific solutions. The processing is based on datum-free normal equations (provided via SINEX files), which allow a rigorous combination on the normal equation level instead of the observation level.

Our current activities in the area of multi-technique combination are focused on augmenting the combination of GNSS and VLBI data with SLR data. It is expected that the SLR technique has the potential to improve the combined ERP solution, especially the highly variable dUT1 parameter, by providing a stable LOD contribution. Due to its short latency of about 1 day, the SLR-DAILY product is basically well suited to expand the database of our Rapid EOP series, which is currently only based on GNSS Rapid and VLBI Intensives data. However, the official SLR-DAILY product of the ILRS is a 7-day solution that explicitly contains polar motion (only as constant offsets over 24 hours) and LOD, but no dUT1 parameters and no polar motion rates. Therefore, this solution is not optimal for our combination approach because the parameterization of the ERPs is not identical to the other techniques that uses offsets and rates for all ERPs. However, the in-house ILRS Analysis Center allows us to generate a customized SLR solution that has an improved parameterization of the ERPs and, thus, is optimized for the multi-technique combination. We investigated the SLR data with respect to the quality of the resulting ERP series and integrated the data into our combination process. We present the impact of SLR on the combined ERP product and the challenges of extending the combination with this data.

How to cite: Klemm, L., Thaller, D., König, D., Flohrer, C., and Walenta, A.: Consistently combined Earth Rotation Parameters at BKG - Adding SLR data to VLBI and GNSS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9457, https://doi.org/10.5194/egusphere-egu24-9457, 2024.

EGU24-9603 | Orals | G3.3

Accurate Inertial Earth Rotation Measurements 

Karl Ulrich Schreiber and Jan Kodet

The complex interaction between the fluids of the Earth and the solid Earth results in small variations in the rotational velocity of the Earth at the level of ∆Ω ≈ 10e-8, which are not predictable. These signals are usually observed utilizing the GNSS constellation and the global IGS receiver network. Stability is provided by the VLBI technique. Inertial Earth rotation sensing, based on ring laser gyroscopes, is now capable of detecting these signals with high temporal resolution. Therefore it is important to closely examine the inherent accuracy of the utilized gyroscope technology. 

This presentation outlines the latest improvements in sensor operation, reviews some crucial sensor properties and puts them into perspective with the established techniques in space geodesy.

How to cite: Schreiber, K. U. and Kodet, J.: Accurate Inertial Earth Rotation Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9603, https://doi.org/10.5194/egusphere-egu24-9603, 2024.

EGU24-9835 | ECS | Posters on site | G3.3

Revisiting excitation of length-of-day using recent GRACE/GRACE-FO, SLR, SLR+GRACE/GRACE-FO gravity solutions and geophysical models 

Justyna Śliwińska-Bronowicz, Jolanta Nastula, Małgorzata Wińska, and Aleksander Partyka

Variations in Earth’s rotation, encompassing polar motion (PM) and the length-of-day (LOD) changes, result from a variety of factors influencing mass distribution and movement. These factors include the redistribution of air and water masses within the climate system and the solid Earth, and exchanges of angular momentum between the core and mantle. The ability to differentiate between these diverse sources is crucial for comprehending processes occurring at or near the Earth's surface, as well as within its interior.

Fluctuations in the low-degree spherical harmonic coefficients of Earth's gravitational potential are linked to the redistribution of mass on a large scale within and on the planet. Observing changes in these coefficients provides a means to investigate the movement of mass within the Earth system. The degree-2 order-0 coefficient (C20) of geopotential holds particular significance for Earth rotation studies since C20 variations (ΔC20) are directly linked to the corresponding excitations of LOD. ΔC20 can be determined from various methods, of which Satellite Laser Ranging (SLR) measurements have the longest tradition. Launching Gravity Recovery and Climate Experiment (GRACE) in 2002 and GRACE Follow-On (GRACE-FO) in 2018 brought new measurements of changes in the Earth's gravitational field, including estimates of the ΔC20. However, estimates of ΔC20 from GRACE/GRACE-FO have limitations due to orbital geometry, the relatively short distance between the two satellites, and tide-like aliases. In practice, GRACE/GRACE-FO computing centres replace ΔC20 with an estimate from SLR measurements. Combining GRACE/GRACE-FO and SLR observations could enhance the accuracy of determining low-degree coefficients of geopotential, including ΔC20, ΔC21, and ΔS21.

In this study, we reassess the excitation of LOD over the period 2002–2023, estimated from five different data sources: SLR, GRACE/GRACE-FO, a combination of SLR+GRACE/GRACE-FO, geodetic observations, and geophysical fluid models. To each of the time series we apply the same processing to isolate long-period, seasonal and non-seasonal short-term fluctuations. For every component, we conduct a comparative analysis aiming to evaluate the consistency among various estimates and identify discrepancies between the series. We show that combining GRACE/GRACE-FO with SLR data improves the consistency between ΔC20-derived and observed LOD excitation for the studied oscillations.

How to cite: Śliwińska-Bronowicz, J., Nastula, J., Wińska, M., and Partyka, A.: Revisiting excitation of length-of-day using recent GRACE/GRACE-FO, SLR, SLR+GRACE/GRACE-FO gravity solutions and geophysical models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9835, https://doi.org/10.5194/egusphere-egu24-9835, 2024.

EGU24-10644 | ECS | Orals | G3.3

Chaotic oceanic excitation of low-frequency polar motion variability 

Lara Börger, Michael Schindelegger, Mengnan Zhao, Rui M. Ponte, Anno Löcher, Bernd Uebbing, Jean-Marc Molines, and Thierry Penduff

Studies of Earth rotation variations generally assume that changes in non-tidal oceanic angular momentum (OAM) manifest the ocean's forced response to atmospheric pressure, wind, and heat and freshwater fluxes. However, on monthly and longer time scales, changes in OAM may also arise from chaotic intrinsic ocean variability, which has its origin in local non-linear (e.g., mesoscale) dynamics that can further map into mass fluctuations at basin scales. To examine whether or not such chaotic mass redistributions appreciably affect Earth’s polar motion, we compute monthly OAM anomalies from a 50-member ensemble of eddy-permitting global ocean/sea-ice simulations that sample intrinsic variability through a perturbation approach on model initial conditions. The resulting OAM (i.e., excitation) functions are compared both amongst each member and with Earth rotation data from 1995 to 2015. We find that intrinsic variability plays an important role in the excitation of the Chandler wobble, where it modulates the band-integrated excitation power due to forced OAM changes (2.5 mas² over 1995–2015, mas = milliarcseconds) by up to ±2 mas2. At interannual frequencies below the Chandler band, intrinsic signals (ensemble spread) account for 16–36% of the variability in the total equatorial oceanic excitation, with contributions being split almost equally between mass and motion terms. More than half of the variance in the mass term contribution is associated with one mode of intrinsic bottom pressure variability, which has opposite polarity between the Atlantic and the Southern Ocean and largest amplitudes around Drake Passage. Overall, chaotic oceanic excitation represents a factor to consider when interpreting low-frequency polar motion changes in terms of natural climate oscillations or core-mantle interactions.

How to cite: Börger, L., Schindelegger, M., Zhao, M., Ponte, R. M., Löcher, A., Uebbing, B., Molines, J.-M., and Penduff, T.: Chaotic oceanic excitation of low-frequency polar motion variability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10644, https://doi.org/10.5194/egusphere-egu24-10644, 2024.

EGU24-12573 | Orals | G3.3

Polar Motion Prediction with Derivative Information 

Marcin Ligas, Maciej Michalczak, Santiago Belda, Jose M. Ferrandiz, and Sadegh Modiri

Our study introduces a hybrid model that combines least-squares (LS) extrapolation of a linear trend and periodic components with a vector autoregression applied to LS residuals in an attempt of enhancing polar motion (x, y) predictions through incorporating its rates (derivatives; x', y'). We used the historical daily sampled final IERS EOP 20 C04 time series available on https://www.iers.org as a reference for all computations. The prediction experiment covers 10 years, 01.03.2013 – 01.03.2023. Within this period, 1000 random samples with a length of one year were generated, with the starting modified Julian date (MJD) of each yearly sample randomized. Within each sample, a 30-day forecast was performed every 7 days, resulting in a total of 48 forecasts in each random trial. Polar motion rates were incorporated to the prediction procedure in various combinations, i.e., {x, x'}, {y, y'}, {x, y, x'}, {x, y, y'}, {x, y, x', y'} and the prediction results based on them were compared to the predictions obtained from the reference data combination {x, y}, which does not include derivative information. As a basic measure of prediction accuracy, we used the mean absolute prediction error (MAPE) as well as a number of measures indicating improvement through incorporating rates into the prediction procedure. The results indicate a noticeable gain in prediction accuracy with the use of derivatives, although not substantial, it is systematic. This improvement is particularly apparent for the first few days of the forecast, which might indicate its potential use in ultra-short-term prediction. This promising data combination (and prediction method) is worth further analysis and an attempt of adapting it for operational settings (real time forecast).

How to cite: Ligas, M., Michalczak, M., Belda, S., Ferrandiz, J. M., and Modiri, S.: Polar Motion Prediction with Derivative Information, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12573, https://doi.org/10.5194/egusphere-egu24-12573, 2024.

EGU24-14969 | Posters on site | G3.3

Current deficiencies and potential for improvement in the realisation of consistently combined Earth Orientation Parameter time series 

Florian Seitz, Alexander Kehm, Mathis Bloßfeld, Bingbing Duan, Urs Hugentobler, and Robert Dill

Accurate knowledge of the Earth’s orientation and rotation in space is essential for a broad variety of scientific and societal applications such as near-Earth and deep space navigation, global positioning and satellite orbit determination as well as monitoring geodynamics and climate change phenomena. Consequently, an essential basis for any of the above-mentioned applications is the accurate determination and prediction of Earth Orientation Parameters (EOP), which describe the instantaneous relation between reference frames fixed to the Earth and to inertial space at any epoch. High-precision EOP are determined by combining the observations of four different geodetic space techniques.

Due to different standards for the processing of the observations – most notably the parameterisation of the EOP in the observation-type-specific processing softwares – current EOP combination approaches lack consistency. Such inconsistencies represent a major limiting factor of today’s accuracy of determined EOP as well as of short-term EOP predictions, which are an essential prerequisite for any application in (near-)real time.

This study identifies current deficiencies that limit the consistency and achievable accuracy of combined EOP series. It provides recommendations on how to improve the parameterisation and processing standards of the technique-specific input, and it outlines strategies to achieve a more consistent and accurate EOP combination. The proposed processing strategies shall serve as a basis for improved EOP prediction algorithms in a later stage of the study.

How to cite: Seitz, F., Kehm, A., Bloßfeld, M., Duan, B., Hugentobler, U., and Dill, R.: Current deficiencies and potential for improvement in the realisation of consistently combined Earth Orientation Parameter time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14969, https://doi.org/10.5194/egusphere-egu24-14969, 2024.

EGU24-15551 | ECS | Posters on site | G3.3

Advancing EOP Prediction: Bridging the Gaps 

Sadegh Modiri, Daniela Thaller, Santiago Belda, Dzana Halilovic, Lisa Klem, Daniel König, Sabine Bachmann, Claudia Flohrer, and Anastasiia Walenta

Understanding Earth's orientation parameters (EOP) is paramount for unraveling intricate mass redistribution, gravitational interactions, and geodynamic processes within the Earth's system. With a growing interest in EOP across diverse scientific disciplines such as Earth science, astronomy, and climate change studies, the demand for accurate and timely real-time information has become increasingly crucial. This is particularly evident in applications like satellite navigation, interplanetary spacecraft tracking, and weather forecasting. Despite the precision enabled by modern space geodetic techniques (e.g., Very Long Baseline Interferometry - VLBI, Global Navigation Satellite Systems - GNSS, and Satellite Laser Ranging - SLR), the complexity of data processing and associated delays necessitates significant progress in EOP prediction, especially for applications requiring timely information.

This study addresses these challenges by introducing a redesigned prediction package that effectively bridges the gap between observational data and final estimated products. Utilizing a sophisticated combination of deterministic and stochastic methods, our prediction algorithm is applied to both the official International Earth Rotation and Reference Systems Service (IERS) EOP series and the Federal Agency for Cartography and Geodesy (BKG) single-specific and combined technique time series.

The results of this study make a significant contribution to efforts that aim to enhance the accuracy of predicted Earth Orientation Parameters (EOP). By thoroughly exploring the selection of input data and prediction methods, our research strives to improve the dependability of EOP forecasts, especially for short-term predictions. By tackling crucial challenges in the field, this work not only deepens our understanding of Earth's dynamic processes but also opens doors for more accurate and timely applications across various scientific disciplines that rely on EOP data.

How to cite: Modiri, S., Thaller, D., Belda, S., Halilovic, D., Klem, L., König, D., Bachmann, S., Flohrer, C., and Walenta, A.: Advancing EOP Prediction: Bridging the Gaps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15551, https://doi.org/10.5194/egusphere-egu24-15551, 2024.

EGU24-16150 | Posters on site | G3.3

Consistency assessment of EOP estimated by different VLBI correlators 

Santiago Belda Palazón, Maria Karbon, Alberto Escapa, José M. Ferrándiz, Esther Azcue, Mariana Moreira, and Sadegh Modiri

The VLBI technique provides an extremely precise measurement of the geometric relationship between the receiving radio observatory and the celestial target. It utilizes methods of recording the signals at each antenna. These recordings are physically brought together and played back into a processing device, known as a correlator, which combines the signals in such a way that delivers the fundamental observables of geodetic VLBI, the time delays between signals arriving at the individual antennas as a function of time. Nowadays, numerous correlator software and strategies are employed which may result in inconsistencies on the geodetic products.

In this study, we empirically assess the consistency between the different correlators by analyzing the R1/R4 VLBI sessions from 2002 to 2022 to reflect the impact on the EOP estimates. To compare the different pairs of EOP time series estimates, we calculated the Weighted Mean (WM) of the differences and the Weighted Root Mean Square (WRMS) differences between each of them. Besides, we empirically evaluate the consistency, systematics, and deviations of the IAU 2006/2000A precession-nutation model using several CPO time series derived from the different correlators, providing a new set of empirical corrections to the precession offsets and rates, and to the amplitudes included in the nutation models. Finally, we study the impact on the estimation of new free core nutation (FCN) models.

This research was supported partially by Generalitat Valenciana (SEJIGENT/2021/001) and the European Union—NextGenerationEU (ZAMBRANO 21-04); and also by Spanish Projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033/) and  PROMETEO/2021/030 funded by Generalitat Valenciana.

How to cite: Belda Palazón, S., Karbon, M., Escapa, A., Ferrándiz, J. M., Azcue, E., Moreira, M., and Modiri, S.: Consistency assessment of EOP estimated by different VLBI correlators, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16150, https://doi.org/10.5194/egusphere-egu24-16150, 2024.

EGU24-18774 | Orals | G3.3

Analysis of the impact of enhanced predicted EOP on satellite orbit prediction 

Leonor Cui Domingo Centeno, Víctor Puente García, José Carlos Rodríguez Pérez, Santiago Belda, and Sadegh Modiri

Earth Orientation Parameters (EOP) constitute the set of parameters that describe the rotation of the Earth with respect to an inertial reference frame. Apart from proper force modelling, EOP are also needed in orbit prediction to calculate the position and velocity of satellites in space. The accuracy of EOP prediction is essential for orbit determination since any error in its computation will propagate to the predicted state vector of the satellite.

The magnitude of the impact of EOP prediction errors depends on the type of orbit and the time interval over which the predictions are made. These EOP prediction inaccuracies can lead to significant position errors as small errors in the EOP accumulate rapidly, thus resulting in larger deviations from the nominal satellite position. Therefore, this effect can be significant and become a concern for applications requiring high precision, such as positioning.

In this contribution, we present numerical results of the discrepancies in the GNSS orbit prediction found when propagating the satellite orbits employing different time series of EOP predicted values. We show a comparison and assessment of the EOP values obtained by different prediction methods used in the 2nd Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC), aiming to study the validation of those EOP that yield the most accurate results in the GNSS orbit prediction.

How to cite: Domingo Centeno, L. C., Puente García, V., Rodríguez Pérez, J. C., Belda, S., and Modiri, S.: Analysis of the impact of enhanced predicted EOP on satellite orbit prediction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18774, https://doi.org/10.5194/egusphere-egu24-18774, 2024.

EGU24-19345 | Posters on site | G3.3

New Data Set of Hydrological Angular Momentum With its Associated 6 Days-Long Forecasts 

Robert Dill, Laura Jensen, and Henryk Dobslaw

Since more than 15 years, GFZ routinely provides daily updated hydrological effective angular momentum functions (HAM) and its 6 days-long forecasts for the study of Earth orientation parameter variability and for improving polar motion and UT1-UTC predictions. GFZ’s HAM time series are part of a consistent set of effective angular momentum functions (EAM) covering the Earth’s major subsystems atmosphere, oceans, and the terrestrial hydrosphere. In addition, all EAM products are consistent with the GRACE/GRACE-FO atmosphere-ocean dealiasing product AOD1B release 06 which is used for gravity field processing and precise orbit determination.


For the new HAM data set we switch our hydrological model setup from the Land Surface Discharge Model (LSDM) to the open source, high-resolution hydrological rainfall-runoff-routing model LISFLOOD (https://ec-jrc.github.io/lisflood/). We slightly adapted the latest LISFLOOD 0.05° version for geodetic applications by modifying the snow melting parameterization, the soil depth parameterization, and implementing a seasonal snow storage model for Antarctica to optimize the agreement of simulated terrestrial water storage with mass anomalies from the satellite gravimetry missions GRACE and GRACE-FO on different spatial and temporal scales. Due to (I) up-to-date surface parameter maps; (ii) increased temporal resolution of 3 hours; (iii) enhanced parameterization of hydrological processes such as evapotranspiration, soil infiltration, snow accumulation and dynamic river routing; and (iv) a much more extensive set of atmospheric forcing parameters from ECMWF’s latest global atmospheric reanalysis ERA5, the derived HAM time series could be substantially improved in terms of long-term stability, seasonal amplitudes, sub-seasonal and episodic variations, and short-term forecasts. Furthermore, the new HAM data set is consistent with the new AOD1B release 07.

How to cite: Dill, R., Jensen, L., and Dobslaw, H.: New Data Set of Hydrological Angular Momentum With its Associated 6 Days-Long Forecasts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19345, https://doi.org/10.5194/egusphere-egu24-19345, 2024.

EGU24-25 | Orals | G3.4

Enabling Subglacial Geodesy Through High-Precision Radar Sounding and GNSS Time Series Observations 

Dustin Schroeder, Jasmin Falconer, and Matthew Siegfried

Our capacity to estimate vertical motion of the solid Earth with high precision has transformed our understanding of a variety of Earth processes, including mantle dynamics, plate tectonics, volcanic hazards, earthquake rupture, and surface-water balance. Geodetic observations of solid Earth deformation were first achieved on land with conventional surveying techniques, global navigation satellite system (GNSS) deployment, and satellite remote sensing, then expanded to the global ocean with seafloor geodesy techniques like GNSS-Acoustic (GNSS-A) experiments and fiber-optic sensing. Although we can now assess solid Earth deformation nearly everywhere on Earth, we still have not achieved subglacial geodesy: directly observing uplift or subsidence beneath glaciers and ice sheets. Due to decreasing ice mass, we expect high rates of uplift beneath Earth’s ice masses (i.e., glacial isostatic adjustment, or GIA), but available GNSS observations from exposed rock on the periphery of the Greenland and Antarctic ice sheets suggest uplift rates can be highly variable on 10s of km length scales. Recent observational and modeling studies have suggested that GIA could provide a critical stabilizing feedback for ice-sheet mass loss on decadal and centennial timescales, therefore developing and deploying the technology needed for subglacial geodesy is critical for accurate projections of sea level change, particularly in Antarctica where areas of exposed bedrock are rare. To address this challenge, we present a suite of combined radar sounding / GNSS experiments and systems under development to constrain uplift rates beneath both slow-flowing (< 10 m/yr) and fast-flowing ( > 10 m/yr) ice. We also discuss a range of related systems and experiments under development to constrain and correct for potentially confounding firn compaction signals.

How to cite: Schroeder, D., Falconer, J., and Siegfried, M.: Enabling Subglacial Geodesy Through High-Precision Radar Sounding and GNSS Time Series Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-25, https://doi.org/10.5194/egusphere-egu24-25, 2024.

EGU24-2515 | ECS | Posters on site | G3.4

Towards exact free oscillation spectra through generalised normal mode coupling 

Alex Myhill and David Al-Attar

Long period free oscillation spectra provide one of the main constraints on large-scale lateral structures within the Earth’s mantle. These observations are particularly noteworthy for their direct sensitivity to density variations, which gives them the potential to resolve long-standing questions relating to the nature of the two Large Low Shear Velocity Provinces. However, due to both computational expediency and incomplete theory, there are inaccuracies within existing codes for forward modelling of free oscillation spectra. This has limited the ability of previous studies to reliably infer Earth structure using such observations.

This poster outlines work on a new open-source code for modelling free oscillation spectra within laterally heterogeneous Earth models. We apply a generalised normal mode coupling method that overcomes various limitations with the traditional mode coupling approach. We account fully for the non-linear dependence of the matrix elements on density and boundary topography, and exactly solve the equations of motion. Computational costs have been minimised by using high-performance libraries, and efficient numerical linear algebra, in addition to parallelisation. Our code is also suitable for calculation of sensitivity kernels using the adjoint method. Benchmarks against current codes as well as performance benchmarks are shown to demonstrate the accuracy and efficiency of our new method.

How to cite: Myhill, A. and Al-Attar, D.: Towards exact free oscillation spectra through generalised normal mode coupling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2515, https://doi.org/10.5194/egusphere-egu24-2515, 2024.

EGU24-3467 | ECS | Posters on site | G3.4

A comparison of linear and non-linear theories for modelling solid Earth dynamics 

Ziheng Yu, Matthew Maitra, and David Al-Attar

To date, most computational work in solid Earth geophysics has been based on linearised continuum mechanics. This is justified so long as deformation from the reference state remains sufficiently small. The dependence on linearisation also reflects computational limitations of the past: most tractable problems relied on geometric symmetries along with linearity to reduce the calculation to the solution of decoupled systems of ordinary differential equations.

Increases in computational power have allowed for increasingly routine applications of fully numerical techniques such as finite-difference, finite-element, and finite-volume methods. This has allowed geophysical problems to be solved in increasingly realistic Earth models. Although for the most part, the equations being solved are the same as linearised ones used previously, keeping nonlinear terms significantly increases the complexity of solution schemes. Within the context of fully numerical methods, non-linear problems are solved using iterative schemes that involve repeated solution of the corresponding linearised equations. This implies that solving non-linear equations should only be appreciably more expensive if non-linear effects are physically important.

Within this presentation, we compare the use of linearised and non-linear equations of motion, focusing on quasi-static elastic and viscoelastic loading problems of relevance to studies of glacial isostatic adjustment. This is achieved using the open-source finite-element package FeniCSx which facilitates rapid development and testing. Starting from simple representative examples, we quantify the errors associated with linearisation along with the added cost of solving non-linear problems.

How to cite: Yu, Z., Maitra, M., and Al-Attar, D.: A comparison of linear and non-linear theories for modelling solid Earth dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3467, https://doi.org/10.5194/egusphere-egu24-3467, 2024.

EGU24-4786 | Posters on site | G3.4

Towards closing the Australian vertical land movement budget 

Matt King, Carsten Ankjær Ludwigsen, and Christopher Watson

GPS analysis of Australian vertical land motion (VLM) consistently suggests widespread subsidence of Australia of about 1-1.5mm/yr since ~2000, in contrast to most models of Glacial Isostatic Adjustment which predict motion closer to zero or slightly positive. These GPS findings have been corroborated by estimates from altimeter-minus-tide gauge measurements, suggesting they are robust within their terrestrial reference frame. Here we revisit the potential causes for this misfit, exploring a new reconstruction of global ice-loading changes and its impact on vertical land motion. We show this likely produces a subsidence of Australia of about 0.5mm/yr. We explore this in combination with estimates of hydrological, atmospheric and non-tidal ocean loading displacements. The residual signal is discussed within the context of different GIA model predictions, reference frame errors, and the possible impact of far-field postseismic signal.

How to cite: King, M., Ludwigsen, C. A., and Watson, C.: Towards closing the Australian vertical land movement budget, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4786, https://doi.org/10.5194/egusphere-egu24-4786, 2024.

EGU24-5259 | ECS | Orals | G3.4

The lateral heterogeneity of Glacial Isostatic Adjustment modelling across the Arctic 

Tanghua Li, Timothy Shaw, Nicole Khan, F. Chantel Nixon, W. Richard Peltier, and Benjamin Horton

The Arctic has been key area for glacial isostatic adjustment (GIA) studies because it was covered by large ice sheets at the Last Glacial Maximum. Previous GIA studies applied mainly 1D Earth models. The few studies that did include 3D Earth structures have not considered the lateral heterogeneity differences across different regions of the Arctic. Here, using the latest standardized deglacial relative sea-level (RSL) databases from Norway and Russian Arctic, we investigate the effects of 3D structure on GIA predictions and explore the magnitudes of the lateral heterogeneity in both regions.

The 3D Earth structure consists of 1D background viscosity model (ηo) and lateral viscosity variation, the latter is derived from the shear velocity anomaly from seismic tomography model and controlled by scaling factor (ß) denoting the magnitude of lateral heterogeneity.

The Norway RSL database includes 413 sea-level index points (SLIPs), 175 marine limiting data and 433 terrestrial limiting data, while the Russian Arctic database includes 353 SLIPs, 78 marine limiting data and 92 terrestrial limiting data.

We find 3D Earth structures have significant influences on RSL predictions and the optimal 3D model notably improves the fit with RSL data. However, we realize RSL data from Norway and Russian Arctic prefer different 3D structures to provide the best fits. The Russian Arctic database prefers a softer background viscosity model (ηo), but larger scaling factors (ß) than those preferred by Norway database. We further test the extent to which the 3D structure can be eliminated by refinement of ice model.

How to cite: Li, T., Shaw, T., Khan, N., Nixon, F. C., Peltier, W. R., and Horton, B.: The lateral heterogeneity of Glacial Isostatic Adjustment modelling across the Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5259, https://doi.org/10.5194/egusphere-egu24-5259, 2024.

EGU24-5642 | Orals | G3.4

Polar motion of a 3D viscoelastic earth model: Consequences for GIA signals in GRACE-FO 

Volker Klemann, Meike Bagge, Robert Dill, Jan M. Hagedoorn, Zdeněk Martinec, and Henryk Dobslaw

Surface deformations due to changes in the rotation of the Earth are significantly impacted by glacial isostatic adjustment (GIA). The long-term trend of polar motion contributes to global observations like that of the current satellite gravity mission GRACE-FO. The theory and how to apply this contribution to correct GRACE observational data is well understood and goes back to the concise studies of Mitrovica et al. (2005) and Wahr et al. (2015), respectively. According to the International Earth Rotation Service (IERS), a standard correction method is suggested, where the observed long-term trend of the polar motion is considered to originate from GIA. Recent studies show that the modelled GIA contribution to polar motion strongly depends on structural features of the Earth's interior as well as on the glacial history. Other processes like mantle convection or more recent climatic processes are attributed to contribute as well (Adhikari et al. 2018).

In this presentation we focus on the impact of the Earth's viscosity structure on the modelled polar motion. In addition to its radial stratification, we discuss the influence of lateral variability. We apply the numerical 3D viscoelastic lithosphere and mantle model VILMA, which solves the gravitationally self-consistent field equations in a spherical geometry, and which considers the rotational feedback and the sea-level equation. The theory of Martinec and Hagedoorn (2014) applied here is not based on the normal mode theory, but solves the field equations in the time domain. We show the consistency of the chosen approach and rate the influence of lateral changes in viscosity against the impact of radial viscosity stratification. The study was motivated by the ESA Third Party Mission 'GRACE-FO' and contributes to the German Climate Modelling Initiative 'PalMod'.

Lit:
Adhikari, S, Caron L, Steinberger, B, ..., Ivins, ER (2018). What drives 20th century polar motion? Earth Planet. Sci. Lett. doi:10.1016/j.epsl.2018.08.059
Martinec, Z, Hagedoorn, JM (2014). The rotational feedback on linear-momentum balance in glacial isostatic adjustment. Geophys. J. Int. doi:10.1093/gji/ggu369
Mitrovica, JX, Wahr, J, Matsuyama, I, Paulson, A (2005). The rotational stability of an ice-age earth. Geophys. J. Int. doi:10.1111/j.1365-246X.2005.02609.x
Wahr, J, Nerem, RS, Bettadpur, SV (2015). The pole tide and its effect on GRACE time-variable gravity measurements: Implications for estimates of surface mass variations. J. Geophys. Res. Solid Earth. doi:10.1002/2015JB011986

How to cite: Klemann, V., Bagge, M., Dill, R., Hagedoorn, J. M., Martinec, Z., and Dobslaw, H.: Polar motion of a 3D viscoelastic earth model: Consequences for GIA signals in GRACE-FO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5642, https://doi.org/10.5194/egusphere-egu24-5642, 2024.

EGU24-5655 | Posters on site | G3.4 | Highlight

Causes of Global Elastic Vertical Land Movement from 1900 to 2022 

Per Knudsen, Carsten Bjerre Ludwigsen, Ole Baltazar Andersen, Matt King, and Christopher Watson

Elastic vertical land movement (eVLM) is the lithosphere's immediate elastic response to the loading and unloading of the Earth's surface mass. Understanding eVLM is crucial for interpreting relative sea level changes, particularly in coastal regions where subsidence or uplift can significantly alter the impacts of sea level changes recorded by tide gauges. Here we present a comprehensive global eVLM model, offering valuable insights for geodesy and related fields, especially in assessing observations from tide gauges and GNSS.

Our eVLM model spans from 1900 to 2022, featuring a 0.5-degree spatial resolution. It provides annual data from 1900 to 1990 and monthly data from 1991 to 2022, enabling both long-term and seasonal assessment. The dataset is available in three different reference frames: Centre of Mass (CM), Centre of Figure (CF), and ITRF2020, and thus suitable for many geodetic applications.

This study incorporates mass change estimations from Greenland, Antarctica, global glaciers, and land water storage (LWS), divided into natural LWS variations and anthropogenic water management like groundwater depletion and dam retention. Thus, we can explain regional VLM patterns that cannot be solely attributed to Glacial Isostatic Adjustment (GIA) models, for example, subsidence across Australia or uplift in Scandinavia that is larger than modeled GIA.

Methodology: We employed a composite loading model, integrating ice models from Greenland (Mankoff et al., 2021) and Antarctica (Otosaka et al, 2022; Nilsson et al, 2022) and glacier models (Hugonnet et al., 2022), GRACE observations, and a land water storage model (Müller-Schmied et al, 2023). Each of the aforementioned five causes of eVLM was perturbed with its uncertainty a thousand times, and the sea level equation was resolved for each variant using the ISSM-SEESAW framework (Adhikari et al., 2016). To align the results with observations in the ITRF2020 reference frame, which mirrors CM on secular timescales and CF on non-secular timescales (Dong et al, 2003). To accommodate this, we applied CM and CF Love loading numbers (Blewitt, 2003) in our calculations, enabling analysis in all three reference frames.

How to cite: Knudsen, P., Ludwigsen, C. B., Andersen, O. B., King, M., and Watson, C.: Causes of Global Elastic Vertical Land Movement from 1900 to 2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5655, https://doi.org/10.5194/egusphere-egu24-5655, 2024.

EGU24-5748 | ECS | Orals | G3.4

Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle 

Maaike F. M. Weerdesteijn and Clinton P. Conrad

Along the periphery of the Greenland ice sheet, Global Navigation Satellite System (GNSS) stations observe uplift of a few mm/yr, reflecting Earth’s response to past and contemporary changes in Greenland’s ice mass. On the coast of southeast Greenland, near the Kangerlussuaq glacier, GNSS stations show abnormally rapid ground uplift, faster than 10 mm/yr. Current earth deformation models, which employ a layered Earth structure, cannot explain such rapid uplift. Here we develop 3D regional models of uplift in response to deglaciation occurring over timescales corresponding to the last glacial cycle (past 1000s of years), the last millennium (past 100s of years), and recent rapid deglaciation (past 10s of years). These 3D models incorporate a track of low-viscosity upper mantle and thin lithosphere, consistent with the passage of Greenland over the Iceland plume during the past ~50 Myr. We find that the fastest ground uplift occurs where rapid deglaciation occurs above the low-viscosity plume track of the Iceland plume. This uplift reflects viscous deformation of the upper mantle, and is much larger than the (instantaneous) elastic deformation that also results from this deglaciation. Above the low-viscosity plume track, the uplift contribution is greatest for the most recent deglaciation (past decades), followed by the contribution from deglaciation during the last millennium. The combination of these viscous contributions can explain uplift observations of more than 10 mm/yr near the rapidly deglaciating Kangerlussuaq glacier, which lies above the Iceland plume track, and slower uplift in the surrounding areas. Rapid uplift observed to the south of the Kangerlussuaq glacier can be explained if the low-viscosity plume track extends farther southward beneath the Helheim glacier, which is also rapidly deglaciating. Such rapid viscous uplift from recent and local ice melt is not usually considered in glacial isostatic adjustment (GIA) models, but likely happened in the past in response to previous deglaciation. It will also become increasingly important in the future as deglaciation accelerates.

How to cite: Weerdesteijn, M. F. M. and Conrad, C. P.: Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5748, https://doi.org/10.5194/egusphere-egu24-5748, 2024.

EGU24-6043 | ECS | Posters virtual | G3.4

A parametric study of sea level and grounding line projections in the Amundsen Sea sector for coupled solid Earth - ice sheet models. 

Luc Houriez, Eric Larour, Lambert Caron, Nicole-Jeanne Schlegel, Tyler Pelle, and Hélène Seroussi

The evolution of the Antarctic Ice Sheet (AIS) represents one of the most important and uncertain contributions to sea level rise in the upcoming centuries. Thwaites glacier and the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) have been identified as the continent's most critical areas. The retreat of Thwaites' glacier grounding line - the transition area where ice is no longer grounded and becomes afloat - is the subject of considerable study for modelers as it governs the collapse of the glacier.

 

Recent advances towards coupling of dynamical ice models with Glacial Isostatic Adjustment (GIA) models has provided the means to improve grounding line projections by considering solid-Earth processes and their interactions with the cryosphere and hydrosphere. However, the spatial and temporal model resolution necessary to fully capture these interactions, and its sensitivity to model parametrization, remains elusive.

 

We investigate the grounding line retreat of Thwaites Glacier through 2350 using the parallelized coupled physics capabilities of the Ice-sheet and Sea-level System Model (ISSM) which capture the complex interactions between solid-Earth, ice-sheets, and ocean. We incorporate realistic climatology, ocean melt rates, and GIA models and we discuss the impact of spatial and temporal model resolution, and solid-Earth parametrization, on the grounding line retreat and sea level change.

 

© 2024 California Institute of Technology. Government sponsorship acknowledged.

How to cite: Houriez, L., Larour, E., Caron, L., Schlegel, N.-J., Pelle, T., and Seroussi, H.: A parametric study of sea level and grounding line projections in the Amundsen Sea sector for coupled solid Earth - ice sheet models., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6043, https://doi.org/10.5194/egusphere-egu24-6043, 2024.

EGU24-6485 | Posters on site | G3.4

Body tides and elastic stresses in the Earth’s crust 

Marianne Greff-Lefftz and Laurent Métivier

Solid tides, predominantly diurnal and semi-diurnal, are commonly observed on Earth's surface through horizontal and vertical movements (a few tens of centimeters), along with gravity measurements (~100 microgal). This study focuses specifically on tidal effects within the elastic stress field at the surface, which is approximately 1000 Pascals.

We initially established a correlation between tidal elastic pressure and natural hydrogen emission. Hydrogen, in its gaseous form, escaping from Proterozoic basins, represents a potential source of carbon-free energy, leading to extensive research on vents. A notable characteristic of these emissions is the consistent daily cycle observed in specific regions. While atmospheric pressure effects have been shown to account for this cycle, solid tides could serve as an alternative explanation. Considering that tidal waves do not have a uniform spatial distribution on the Earth's surface, we computed time series of elastic pressure at two locations where natural hydrogen emissions are observed: one near the equator in the Sao Francisco basin (Brazil) and another near the North Pole in the Lovozero deposits (Kola Peninsula).

We then explored the maximum shear stress generated by tidal potential in areas experiencing tectonic stresses. We demonstrated that in expansive regions, the maximum shear stress correlates with the peak of the tidal potential, while in compressive regions, it is associated with the minimum tidal peak.

How to cite: Greff-Lefftz, M. and Métivier, L.: Body tides and elastic stresses in the Earth’s crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6485, https://doi.org/10.5194/egusphere-egu24-6485, 2024.

EGU24-6863 | ECS | Orals | G3.4

Modelling Glacial Isostatic Adjustment in Firedrake  

William Scott, Mark Hoggard, Sia Ghelichkhan, Angus Gibson, Stephan Kramer, and Rhodri Davies

Melting ice sheets transfer water from land into ocean basins. The resulting sea-level rise is, however, highly spatially non uniform and time dependent due to complex feedbacks between viscoelastic deformation of the solid Earth in response to these evolving surface loads and coupled perturbations in the gravitational field and rotation axis. Together, these processes are referred to as Glacial Isostatic Adjustment (GIA) and accurate models of GIA are crucial for robust interpretation of both modern and paleo measurements of sea-level change and ice-mass balance. 

A limitation with many existing GIA modelling codes is their inability to incorporate lateral variations in Earth structure. Nevertheless, there is mounting evidence for the presence of significant lateral changes in mantle viscosity, for example beneath West Antarctica, that give rise to complex interactions between rates of surface rebound, sea-level change and ice retreat. Understanding these processes requires development of a new generation of GIA codes capable of handling such variations in rheology at increasingly fine spatial and temporal evolution. 

In this presentation, we will introduce a new project to model GIA using the Firedrake finite element framework and present results for several community benchmarks. Firedrake leverages automatic code generation to create a separation of concerns between employing the finite-element method and implementing it. This approach maximises the potential for collaboration between computer scientists, mathematicians, scientists and engineers and enables sophisticated high performance simulations. A key advantage of Firedrake is the automatic availability of sensitivity information through the adjoint method, allowing us to investigate inverse problems. We are developing an open-source tool highly suited to the challenge of modelling complex Earth structure in GIA, building on the Firedrake-based G-ADOPT project for mantle convection. We envision that future applications might include, but are not limited to, investigating non-linear and transient rheologies, feedbacks between sea-level and glacier dynamics, and reducing uncertainty on sea-level projections into the future. 

How to cite: Scott, W., Hoggard, M., Ghelichkhan, S., Gibson, A., Kramer, S., and Davies, R.: Modelling Glacial Isostatic Adjustment in Firedrake , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6863, https://doi.org/10.5194/egusphere-egu24-6863, 2024.

EGU24-6898 | Posters on site | G3.4

Mid-Holocene ice history inferred from GIA-induced crustal motion around Lützow-Holm Bay, East Antarctica 

Jun'ichi Okuno, Akihisa Hattori, Koichiro Doi, Yoshiya Irie, and Yuichi Aoyama

The history of ice melting and the viscoelastic properties of the mantle heavily influence Antarctic crustal deformation caused by Glacial Isostatic Adjustment (GIA). The interaction between ice history and mantle viscosity further complicates the complex Antarctic GIA. Nonetheless, geodetic observations, such as GNSS, are crucial for constraints on the GIA model parameters.

For over two decades, the Japanese Antarctic Research Expedition (JARE) has been using GNSS and absolute gravity measurements to obtain data along the coast of Lützow-Holm Bay, primarily at Syowa Station. This study examines the geodetic signals associated with GIA from observations along the Lützow-Holm Bay coastline in East Antarctica, and we also conduct GIA simulations based on the recent report of rapid ice thinning in the target region during the mid-Holocene.

Based on geomorphological surveys and surface exposure ages, Kawamata et al. (2020: QSR) showed that the region experienced rapid ice thinning of over 400 m from about 9 to 6 ka. Representative deglaciation models, such as ICE-6G, do not account for this rapid thinning process. Therefore, we investigate the variability of the geodetic signals using the ice history, including this rapid thinning. Our predictions demonstrate that incorporating the modified ice history results in consistent outcomes with the observations. This finding supports the notion that rapid ice melting occurred in the Holocene and suggests that geodetic observations can help constrain this region's ice sheet melting process. Additionally, we will present a possibility of the readvance following the rapid retreat based on the precise GIA modelling.

How to cite: Okuno, J., Hattori, A., Doi, K., Irie, Y., and Aoyama, Y.: Mid-Holocene ice history inferred from GIA-induced crustal motion around Lützow-Holm Bay, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6898, https://doi.org/10.5194/egusphere-egu24-6898, 2024.

EGU24-7839 | ECS | Posters on site | G3.4

Holocene water-level indicator database for the Dutch coastal plain 

Kim de Wit, Roderik S.W. van de Wal, and Kim M. Cohen

The evolution of the Holocene coastal plain in the Netherlands is strongly influenced by global sea-level rise and regional subsidence patterns. Added up these components are known as relative sea-level rise (RSLR), and explain the coastal plain build-up and accommodation space. Due to RSLR, geological indicators of gradual-drowning formed, such as basal peat layers. These indicators have been sampled and dated from different depths and locations across the coastal plain and are used to document rising coastal sea levels and inland groundwater levels. Databasing and spatial-temporal analysis of the large set of indicators (N=~720) serves to assess local and regional variabilities in RSLR.

Collection of geological water level indicators in the Netherlands started as early as the 1950ies. It was carried out for various purposes: RSLR reconstruction, geological mapping of the coastal-deltaic plain, wetland paleoenvironmental reconstructions. Full formal overview of this data did not exist, as past reviews and data compilations (N=50-300) were subregion restricted and usage specific. Regional differences within the Netherlands, e.g. greater RSLR in the north than in the SW, are also long noticed, and mostly attributed to  differential subsidence as caused by glacial isostatic adjustment (GIA: Scandinavian forebulge collapse, at non-linear rate) and longer-term North Sea Basin tectono-sedimentary subsidence (at a linear rate).

Here, we present a uniform database of Holocene coastal plain water level indicators for the Netherlands, using the HOLSEA workbook format. By compiling a database of geological water level indicators, with an explicit and consistent  standardized treatment of dealing with vertical uncertainties, age uncertainties, and indicative meaning of each indicator (e.g. does it resemble former inland  groundwater level, or former sea-level), we enable more accurate break down of differential subsidence and its source components.

Database compilation included documentation of all vertical corrections applied, such as for water depth, (paleo-)tides, long-term background land motion and for compaction, as well as the propagation of uncertainties associated with these corrections.  The ~720 indicators are further categorized into sea level index points (SLIPs), sea-level upper limiting data (ULD) and sea-level lower limiting data (LLD). ULD data is further categorized to separate tidally, river gradient and local-hydrology influenced indicators. Vertically corrected relative sea-level positions and relative groundwater-level positions are reported separately.

Spatial-temporal analysis of the Holocene water level data allowed for an interpolated reconstruction of Holocene RSLR, resulting in map-output that has continuous coverage of the Dutch coastal plain. Furthermore, this data-driven RSLR reconstruction is used to further disentangle components of RSLR: the Holocene water level rise part versus the two main land subsidence parts, independently from global sea-level analysis, basin-geological subsidence reconstructions and geophysical GIA-modelling  output.  We  compare our reconstructed sea level plains to the RSLR output of glacio-isostatic adjustment modelling, which incorporate ice sheet deglaciation history and Earth-rheological models. This enhances our ability to quantify the contributions of GIA and basin subsidence to past and ongoing RSLR and subsidence in the Netherlands.

How to cite: de Wit, K., van de Wal, R. S. W., and Cohen, K. M.: Holocene water-level indicator database for the Dutch coastal plain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7839, https://doi.org/10.5194/egusphere-egu24-7839, 2024.

EGU24-8753 | ECS | Posters on site | G3.4

Internal Mass-Induced Elastic Deformation: A Semi-Analytic Approach     

He Tang, Wenke Sun, and Yuting Ji

This research presents an innovative semi-analytical method to study the deformation of a viscoelastic, spherical, layered Earth model under periodic loading. We explore the effects of surface mass changes on deformation over various timescales, including annual and interannual, using a linear rheology profile. Our approach leverages a novel set of formulas in the spectral domain, linking mass, geoid, and displacement through complex Love numbers and Stokes coefficients. This technique bypasses the traditional reliance on viscoelastic Green’s functions.

In our analysis, we particularly focus on the impact of annual cyclic mass loading on viscoelastic loading deformation. We consider both steady-state creep and additional transient creep across a broad spectrum of viscosities. Our findings reveal that while steady-state viscosity values, constrained by Glacial Isostatic Adjustment (GIA) data, show minimal viscoelastic impact on annual load deformation, the inclusion of transient creep, primarily informed by post-seismic data and modeled through the Burgers model, significantly alters the deformation's amplitude and phase. This underscores the importance of rheological properties in understanding Earth's deformation.

Furthermore, our results demonstrate a notable difference in how the horizontal displacement, as opposed to geoid and vertical displacement, responds to viscosity changes. This disparity is observed regardless of the rheological model applied, indicating a greater sensitivity of horizontal displacement to viscosity variations in periodic load deformation. Our study provides new insights into the complexities of Earth's viscoelastic response to cyclic loading, contributing to a deeper understanding of geophysical processes.

How to cite: Tang, H., Sun, W., and Ji, Y.: Internal Mass-Induced Elastic Deformation: A Semi-Analytic Approach    , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8753, https://doi.org/10.5194/egusphere-egu24-8753, 2024.

EGU24-10534 | ECS | Posters on site | G3.4

Reduction of temporal variations in tidal parameters by application of the local response models at globally distributed SG stations 

Adam Ciesielski, Thomas Forbriger, Walter Zürn, Andreas Rietbrock, and Przemysław Dykowski

The already 100 years old harmonic analysis of tides is based on the assumption of separable and non-separable contributions depending on the time series length (Rayleigh criterion in tidal analysis). A priori wave groups had to be composed of different harmonics, which leads to an inaccurate (biased) estimate of tidal parameters. An alternative Regularization Approach to Tidal Analysis, RATA, constrains the solution to be close to a reference model what stabilises the linear regression, making wave grouping obsolete. In this way, the resolution power of the harmonic analysis is exploited to a much larger extent, since the risk of over-fitting is strongly reduced.

We used RATA method to analyse data from globally distributed superconducting gravimeters (SGs) and we are able to achieve super resolution that even highly violates the Rayleigh criterion. The results from double-sphere SG instruments give an indication of the minimum error for the accuracy. We estimated local response models for over 10 stations in Europe, which confirms the consistency of the method. The small differences in phases and amplitudes are most likely caused by ocean loading with varying distance to the ocean. The investigation of stations on other continents reveals significant disparities between the observed tidal response (which accounts for the loading signals as well) and the Earth body model assumptions (like Wahr-Dehant-Zschau elastic analysis model).

Temporal variations of tidal parameters, seen in the moving window analysis (MWA), are known for all tidal wave groups at different SG stations around the globe. The amplitude of variations usually is greater than the standard deviation by a factor of 2 (minimum) to 32 (maximum). In our investigation, we approximated the effect of the time-invariant ocean loading and radiation tides in the data by application of the local response models, already estimated with RATA. We repeated the MWA of 12 wave groups composed from summed harmonics. We found that the periodic variations of groups M2, K1, µ2, N2, L2, and S2 are reduced by up to a factor of 9 compared to earlier studies. Some long-period variations previously seen in the M1, O1, Q1, and J1 groups are captured as well. The previously neglected influence of radiation tides, degree 3 tides, and significant satellite constituents were the main causes of apparent modulations in previous studies. Hence, with the local model correction, a proper investigation of the remaining temporal variations to study instrument stability or time-varying contributions of ocean loading is more applicable.

How to cite: Ciesielski, A., Forbriger, T., Zürn, W., Rietbrock, A., and Dykowski, P.: Reduction of temporal variations in tidal parameters by application of the local response models at globally distributed SG stations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10534, https://doi.org/10.5194/egusphere-egu24-10534, 2024.

EGU24-10834 | ECS | Orals | G3.4

Towards imaging 3D crust and mantle structure by means of ocean tidal loading tomography 

Andrei Dmitrovskii, Federico Munch, Christian Boehm, Hilary Martens, and Amir Khan

Ocean tide loading (OTL) brings about recurring deformation of the Earth’s surface. Some of the OTL harmonics, e.g. M2, O1, Mf, cause sufficiently large surface displacement to be registered by the Global Navigation Satellite Systems (GNSS). These displacements are sensitive to the interior structure of the planet in a broad range of temporal and spatial scales making them a potentially unique source of information about the planet’s response at low frequencies. Comparison between observations and predictions for 1D elastic Earth models result in discrepancies of up to 3 mm (Bos et al., 2015, Martens et al., 2016). Spatial coherency of these discrepancies hints to 3D interior structure as one of the main sources of such residuals.
In this context, we present a framework to invert OTL observations for 3D crustal and mantle structure based on a trust-region Newton-type iterative algorithm. Furthermore, we resort to the adjoint approach as an efficient means of computing the gradient for the high-dimensional model space. Focusing on the design of the inverse algorithm, we constrain ourselves to deformations of an isotropic elastic planet, which are governed by a self-adjoint forward operator. In order to assess the robustness of the method, we perform a suite of 3D synthetic inversions that mimic the distribution of the GNSS stations in South America. Preliminary results indicate enhanced sensitivities to the crustal and upper mantle density and elastic properties in the vicinity of the coastlines.

How to cite: Dmitrovskii, A., Munch, F., Boehm, C., Martens, H., and Khan, A.: Towards imaging 3D crust and mantle structure by means of ocean tidal loading tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10834, https://doi.org/10.5194/egusphere-egu24-10834, 2024.

We compute daily GPS solutions for about 200 permanent stations in Greenland, Scandinavia and Canada for the 2000 – 2023 period, using the CNES/GINS software in precise point positioning with integer ambiguity resolution (IPPP) mode. The observed vertical displacements are caused by both past- and present-day ice mass (PDIM) changes. The glacial isostatic adjustement (GIA) is the visco-elastic Earth’s response to the Pleistocene glaciation and deglaciation, whereas the PDIM is often estimated assuming an elastic Earth’s response.

We revisit the problem of the separation of GIA and PDIM using state-of-the-art ice models (for example, ICE-6G and ICE-7G) and observations from space gravimetry (GRACE and GRACE Follow On) and altimetry (CryoSat-2 and ICESat-2).

In particular, we investigate different rheology models, including the classical Maxwell model used in GIA modeling, but also the Burgers model allowing transient anelastic deformation at timescales of 10 to 20 years.

We found that the Burgers model with a transient viscosity of about 1018 Pa.s in the upper mantle, combined with the VM5a or VM7 viscosity profiles (Maxwell component) is in better agreement with the observed GPS vertical displacements.

 

How to cite: Boy, J.-P. and Taghiyev, V.: Vertical deformation in Greenland: separation of past and present-day ice mass loss contributions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12953, https://doi.org/10.5194/egusphere-egu24-12953, 2024.

EGU24-13658 | Orals | G3.4

GIA constraints for Greenland from combined GRACE and GNSS observations 

Valentina R. Barletta, Andrea Bordoni, and Shfaqat Abbas Khan

Currently, many different glacial isostatic adjustment (GIA) models have been proposed for Greenland, as a consequence of a still largely unknown deglaciation there. GNSS trends are often used to constrain GIA models regionally. However, the GNSS uplift rates contain a large contribution from present-day mass changes (mostly due to ice melting) that must be removed to extract the GIA uplift rates. The elastic uplift rates estimates are potentially affected by uncertainties. They depend on the Earth model chosen (usually PREM-based models) and on high-resolution mass changes estimates, usually obtained from volume changes measured with altimetry. The volume changes need to be converted into mass variations, mostly using models (surface mass balance and firn compaction models) that can introduce biases. Since the elastic uplift rates are proportional to the mass changes, any uncertainty in the mass variations directly affects the elastic uplift rates eventually, as well as the GIA GNSS residuals uplift rates obtained from them. And in turn, these biases reflect directly in the GIA models constrained with those GNSS.

Here we propose a novel additional GIA constraint based on both GRACE and GNSS observations. We start from a very simple model, based on three basic and general assumptions: 1) Elastic uplift rates at a given distance from a mass distribution (e.g. a disk changing height) are proportional to the mass variation. 2) The GIA induced uplift rates can be considered proportional to the apparent mass changes produced by GIA gravity changes (e.g. Wahr et al 2000 and Riva et al. 2009). 3) The total uplift rate measured by a GNSS is the sum of the elastic uplift rate caused by any surface mass changes and the GIA induced uplift rate (assuming that uplifts rates due to plate tectonics are negligible in Greenland). We then show that this simple model can be applied to Greenland, and still retain most of its validity. The three points above become three equations in four unknowns, namely the surface mass changes and the related elastic uplift rate, the GIA uplift rate and its related apparent mass change.  Using the average uplift rate measured by the whole GNET (Greenland GNSS Network) and the total GMB (Greenland Mass Balance) measured with GRACE, from the three equations we derive a global consistency relation between the average GIA uplift rate and its related apparent mass change for the whole Greenland.

In this way, the combined analysis of the GMB from GRACE and GNET provides a very solid constraint for Greenland-wide GIA models. GIA models constrained only regionally might provide estimates that are not consistent in other Greenland regions. The four GIA models that we tested do not respect the consistency relation we found. This relation does not allow to determine the GIA uplift rate uniquely, but we show that together with some basic considerations about the plausible deglaciation scenarios, it allows to identify a reasonable range for the GIA component in the average GNSS uplift rate.

How to cite: Barletta, V. R., Bordoni, A., and Khan, S. A.: GIA constraints for Greenland from combined GRACE and GNSS observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13658, https://doi.org/10.5194/egusphere-egu24-13658, 2024.

EGU24-13928 | ECS | Orals | G3.4

The impact of regional-scale variability in upper mantle viscosity on GIA in West Antarctica 

Erica Lucas, Natalya Gomez, Konstantin Latychev, and Maryam Yousefi

West Antarctica is underlain by a laterally heterogenous upper mantle, with localized regions of mantle viscosity reaching several orders of magnitude below the global average. Accounting for 3-D variability in upper mantle structure in glacial isostatic adjustment (GIA) simulations has been shown to significantly impact the predicted spatial rates and patterns of crustal deformation, geoid and sea-level changes. Uncertainty in constraining the viscoelastic structure of the solid Earth remains a major limitation in GIA modeling. To date, investigations of the impact of 3-D Earth structure on GIA have adopted solid Earth viscoelastic models based on global- and continental-scale seismic imaging with variability at spatial scales >150 km. However, regional body-wave tomography shows mantle structure variability at smaller spatial scales (~50-100 km) in central West Antarctica (Lucas et al., 2020). Here, we investigate the effects of incorporating this smaller-scale lateral variability in upper mantle viscosity into 3-D GIA simulations. Lateral variability in upper mantle structure at the glacial basin scale is found to have a significant impact on GIA model predictions, especially in coastal regions undergoing rapid ice mass loss. For example, incorporating a transition from lower viscosity at the mouth of Thwaites Glacier to higher viscosity further upstream impacts the predicted rate and pattern of solid Earth deformation and sea-level change in response to ongoing and projected ice mass loss, with possible implications for the evolution of the overlying ice and the interpretation of geophysical observables.

How to cite: Lucas, E., Gomez, N., Latychev, K., and Yousefi, M.: The impact of regional-scale variability in upper mantle viscosity on GIA in West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13928, https://doi.org/10.5194/egusphere-egu24-13928, 2024.

EGU24-15498 | Posters on site | G3.4 | Highlight

Earth’s hypsometry and what it tells us about global sea level 

Vivi Kathrine Pedersen, Natalya Gomez, Jerry X. Mitrovica, Gustav Jungdal-Olesen, Jane Lund Andersen, Julius Garbe, Andy Aschwanden, and Ricarda Winkelmann

Over geological time scales, the combination of solid-Earth deformation and climate-dependent surface processes have resulted in a distinct hypsometry (distribution of surface area with elevation), with the highest concentration of surface area focused near the present-day sea surface. However, this distinctive signature of Earth’s hypsometry does not constitute a single well-defined maximum at the present-day sea surface (0 m). Earth’s hypsometry also shows a prominent maximum ~5 m above the present-day sea surface. Here we explore the nature of this 5-m maximum and examine how it evolved over the last glacial cycle and may evolve moving towards a near-ice-free future. We find that the current elevation of this 5-m hypsometric maximum cannot be explained by ongoing sea-level adjustments following the last glacial cycle. Instead, we suggest that global sea level must have been higher for a significant portion of Earth’s recent multi-million-year history. Indeed, global sea level must have been higher by as much as ~9.5 m to bring this hypsometric maximum in accordance with the sea surface, to account for glacial isostatic adjustments such as ocean syphoning. This signifies that our current polar ice-sheet and sea-level state (and our global reference level) should be considered an anomaly in a geological perspective.

How to cite: Pedersen, V. K., Gomez, N., Mitrovica, J. X., Jungdal-Olesen, G., Andersen, J. L., Garbe, J., Aschwanden, A., and Winkelmann, R.: Earth’s hypsometry and what it tells us about global sea level, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15498, https://doi.org/10.5194/egusphere-egu24-15498, 2024.

EGU24-15975 | ECS | Posters on site | G3.4

A rapid numerical routine for viscoelastic earthquake cycle simulations.  

Sharadha Sathiakumar and Rishav Mallick

Earth’s largest quakes and trans-oceanic tsunamis emanate from subduction zones around the world. Following such large earthquakes, viscoelastic processes and on-fault aseismic fault slip play a crucial role in dissipating the stresses induced by the earthquake, facilitating the solid Earth's return to equilibrium.  The rheological properties of lithospheric rocks govern these postseismic processes and influence time-dependent deformation during the earthquake cycle. Geodetic observations offer an opportunity to constrain these rheological properties, providing valuable insights into the regional lithospheric structure, and potentially improving our understanding of earthquake-related hazards.   

To build intuition for geodetically recorded postseismic deformation, we develop a robust and efficient two-dimensional quasi-static periodic earthquake cycle simulator exploiting the boundary element method and semi-analytical solutions to systems of coupled ordinary differential equations. We investigate the impact of lateral and depth-dependent variations in the viscosity structure of the mantle wedge and the oceanic mantle, to discern their respective contributions and roles in surface deformation observations. We account for the long-term viscous flow rate in the mantle and show that neglecting this term in the earthquake cycle introduces biases in the effective viscosity structure of the lithosphere-asthenosphere system, particularly in the context of power-law rheologies. The low computational cost of our numerical routine makes it ideal for incorporating into future inverse modelling frameworks to estimate regional rheological structure from geodetic observations of subduction zone earthquake cycles.  

How to cite: Sathiakumar, S. and Mallick, R.: A rapid numerical routine for viscoelastic earthquake cycle simulations. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15975, https://doi.org/10.5194/egusphere-egu24-15975, 2024.

EGU24-16655 | ECS | Orals | G3.4

Does thicker ice cover cause stronger glacially triggered earthquakes? - A case study from the southwestern Baltic Sea 

Elisabeth Seidel, Holger Steffen, Rebekka Steffen, Niklas Ahlrichs, and Christian Hübscher

Increasing and decreasing ice masses cause an isostatic adjustment of the crust, which can trigger fault reactivation. It could be assumed that the higher the ice load, the stronger the glacially induced fault reactivation, leading to stronger earthquakes. Here we focus on glacially triggered fault reactivation in the southern Baltic Sea over the past 200,000 years (since the Upper Saalian). Our study area comprises the Caledonian Suture Zone between the East European Craton and the West European Platform as well as the trans-regional Tornquist Zone. Consequently, it reflects a polyphase tectonic history. The fault zones and systems in this geoarchive have been mapped and studied through several reflection seismic investigations. They display variations in their characters, strike and dip directions, age, and depths, documenting the complex evolution.

We focus on faults indicating reactivation during the Quaternary, determined by the seismic sections. After documenting their fault properties, we calculated the glacially induced Coulomb Failure Stress changes (∆CFS) at the faults over the past 200,000 years using finite-element simulations of various glacial isostatic adjustment models. The results show significant local and temporal differences in fault reactivation. We observe that shorter ice advances and lower ice loads correlate with higher ∆CFS, suggesting a higher potential for fault reactivation, which could potentially lead to stronger earthquakes if released in one event. Moreover, we will discuss if the lateral ice thickness gradient or the steepness of the flanks of the ice sheet might play a major role.

How to cite: Seidel, E., Steffen, H., Steffen, R., Ahlrichs, N., and Hübscher, C.: Does thicker ice cover cause stronger glacially triggered earthquakes? - A case study from the southwestern Baltic Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16655, https://doi.org/10.5194/egusphere-egu24-16655, 2024.

EGU24-18171 | ECS | Posters on site | G3.4

Impact of the Earth's mantle transient rheology on surface deformation induced by decades of hydrological mass redistribution 

Maxime Rousselet, Alexandre Couhert, Kristel Chanard, and Pierre Exertier

Over the past decades, modern geodetic observations have provided crucial constraints on the Earth's rheological properties over a wide range of time scales. Whole mantle steady-state viscosity has been inferred from geodetic observations related to glacial isostatic adjustment. More recently, geodesy has helped probing Earth’s upper mantle transient response to stresses induced by rapid regional changes in hydrology, including recent ice melting, during which viscosity rapidly increases from an elastic to a viscous regime. Here we investigate the potential of using decades of global hydrological mass redistributions, mainly driven by recent ice melting, to constrain the Earth's mantle transient rheology. We quantify the sensitivity of the Earth surface deformation and gravity field to mass redistribution at very large spatial scales to variations in the Earth’s mantle rheology using a spherically layered model and considering Maxwell and Burgers behaviors. Mass redistribution is estimated using low-degree spherical harmonics of the Earth’s gravity field inferred from over 30 years of Satellite Laser Ranging (SLR) observations. We discuss the importance of accounting for the Earth's lower mantle transient rheology at timescales of a few decades and evaluate to what extent it can be constrained by combining long geodetic time series of the Earth’s gravity field and surface deformation.

How to cite: Rousselet, M., Couhert, A., Chanard, K., and Exertier, P.: Impact of the Earth's mantle transient rheology on surface deformation induced by decades of hydrological mass redistribution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18171, https://doi.org/10.5194/egusphere-egu24-18171, 2024.

EGU24-18865 | ECS | Posters on site | G3.4

Towards constraining Venus structure by means of atmospheric loading displacement response  

Federico Daniel Munch, Amir Khan, Hilary Martens, and Christian Boehm

Surface mass loads produce a wide spectrum of deformation responses in planetary bodies that can be exploited to probe material properties in planetary interiors. In particular, the redistribution of fluid mass associated with Venus’s atmospheric dynamics leads to periodic changes in the Venusian surface displacements and thus gravitational field. These periodic variations could potentially be detected by upcoming Venus missions, e.g., VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) and EnVision, which are expected to greatly  improve our knowledge of Venus’s gravity field. 

By combining a state-of-the-art general circulation model of Venus’s atmosphere with a novel approach to the solution of the quasi-static momentum equations in the coupled gravito-elastic problem, we explore the sensitivity of the atmospheric loading response to mantle structure. In addition, we investigate the effect of 3-D crustal and lithospheric variations on Venus’s gravity field and the tidal and load Love numbers. Preliminary results suggest that an accurate estimation of the time-varying gravity field and surface displacements can provide important constraints on the interior structure of Venus through the measurement of the load Love numbers.

How to cite: Munch, F. D., Khan, A., Martens, H., and Boehm, C.: Towards constraining Venus structure by means of atmospheric loading displacement response , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18865, https://doi.org/10.5194/egusphere-egu24-18865, 2024.

EGU24-146 | ECS | Posters on site | HS6.5 | Highlight

Improving Flood Mapping Capabilities and Hydrological Model Calibration in India through the Surface Water and Ocean Topography (SWOT) Mission 

Girish Patidar, Jayaluxmi Indu, and Subhankar Karmakar

Even though altimetry has redefined our understanding of global rivers and lakes, the sparse temporal sampling of altimeters is often a cause of concern for many applications. This study explores the efficiency of temporal sampling offered by the recently launched Surface Water and Ocean Topography (SWOT) mission for hydrological applications over India. In particular, two research hypotheses are being investigated, namely a). Potential of SWOT data for enhancing flood mapping capabilities across India and b) Impact of SWOT-based discharges for calibrating a hydrological model calibration. Toward answering the first hypothesis, we considered a hypothetical launch date for SWOT, generating overpass data based on the mission's spatiotemporal orbital configuration. These overpass data were then compared with flood-affected areas identified in the Indian Flood Inventory (IFI) data to assess SWOT's potential for flood mapping. Results show that the spatio-temporal resolution of SWOT facilitates the monitoring of diverse proportions of Indian districts based on the cycle. More specifically, 0.67%, 15.79%, 29.24%, 45.54%, and 8.06% of Indian districts have one, two, three, four, and more than four observations per SWOT cycle (~21 days), respectively. To evaluate the second hypothesis, namely, the feasibility of SWOT discharge in hydrological model calibration, we created proxy-SWOT data by sampling in-situ data in accordance with the SWOT orbit configuration. Subsequently, errors were introduced into the in-situ gauge data based on recommendations from the SWOT science team. Results are presented over selected case study region of the Mahanadi river basin in India.

How to cite: Patidar, G., Indu, J., and Karmakar, S.: Improving Flood Mapping Capabilities and Hydrological Model Calibration in India through the Surface Water and Ocean Topography (SWOT) Mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-146, https://doi.org/10.5194/egusphere-egu24-146, 2024.

EGU24-242 | ECS | Orals | HS6.5

Assessment of Surface Water Dynamics between 1984-2021 in Madhya Pradesh, Central India, using Remotely Sensed Dataset 

Somil Swarnkar, Asari Sushma Surjibhai, Roshan Nath, Shobhit Singh, and Biswajit Patra

The measurement of surface water bodies plays a vital role in assessing the magnitude of floods and droughts despite their relatively little contribution to the overall hydrosphere on Earth's surface. The distribution and accessibility of water resources have been greatly impacted by global climate change and unsustainable human activities. These factors have resulted in heightened strain on surface water supplies, causing shortages that hinder both human consumption and socioeconomic progress. Therefore, the mapping and identification of surface water reserves are essential for achieving optimal utilization and sustainable management. Madhya Pradesh, henceforth referred to as MP, possesses a highly diverse range of geographical features within the Central Indian area. According to prior research, a total of thirty-six out of fifty-one districts within the state of Madhya Pradesh have seen significant hydrological drought conditions in recent years, mostly attributed to the scarcity of surface water resources. Despite the challenges faced in the MP area, there remains a lack of sufficient understanding of the long-term and seasonal variations in surface water dynamics within districts, as well as the overall availability and accessibility of surface water resources. Field-based observations of surface water bodies in regions with vast expanses, such as Madhya Pradesh (MP), pose considerable obstacles. However, the comprehension of spatiotemporal fluctuations in surface water can be enhanced with the utilization of remote sensing datasets for observations. Hence, to gain an understanding of the long-term fluctuations in surface water patterns in different regions of Madhya Pradesh, India, over a span of 38 years, we employed a publicly accessible global surface water dataset provided by the Joint Research Centre (JRC) of the European Commission. This dataset covers the time period from 1984 to 2021. Based on the results of our investigation, it is apparent that a disparity exists in the per capita accessibility of permanent water resources in the majority of MP districts, notably during periods of low precipitation, as well as in the per capita availability of seasonal water resources, particularly during months characterized by high levels of rainfall. While the monsoon period generally results in increased surface water availability, the Bundelkhand and Malwa Plateau regions experience severe shortages of surface water during dry periods, which, therefore, leads to the over-exploitation of groundwater resources. The implications of these findings are significant for the management of freshwater bodies in the Madhya Pradesh area, particularly in light of their depletion caused by climate change and human activities. Furthermore, these findings have broader implications for promoting sustainable development in the region.

How to cite: Swarnkar, S., Surjibhai, A. S., Nath, R., Singh, S., and Patra, B.: Assessment of Surface Water Dynamics between 1984-2021 in Madhya Pradesh, Central India, using Remotely Sensed Dataset, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-242, https://doi.org/10.5194/egusphere-egu24-242, 2024.

EGU24-1621 | ECS | Posters on site | HS6.5

Groundwater storage change in Victoria, Australia observed by GRACE and ESA CCI soil moisture products 

Taejun Park, Ki-Weon Seo, and Dongryeol Ryu

Accelerating groundwater depletion, driven by climate change and growing groundwater extraction for irrigation, has increased the need for accurate monitoring of this indispensable resource. Traditional methods, such as in-situ water table observations and pumping tests, have proven valuable for continued monitoring of groundwater availability and aquifer characteristics but are limited in assessing groundwater variations at a larger basin scale. In contrast, the Gravity Recovery and Climate Experiment (GRACE) offers a method to estimate basin-scale groundwater changes, although its estimates encompass not only groundwater in the aquifer but also surface water (e.g., lakes, rivers) and soil moisture in the vadose zone. To delineate groundwater variations accurately from GRACE observations, additional data sources are necessary.

In this study, we use the European Space Agency’s Climate Change Initiative for Soil Moisture (ESA CCI SM) in the surface layer (top 0-2cm), which is extrapolated to the profile moisture content for the entire root zone (0-120cm). Utilizing the estimated profile soil moisture, we derive groundwater variations in the southern Victoria region of Australia by subtracting the ESA CCI SM derived soil moisture component from GRACE observations. The estimated groundwater variations agree well with the groundwater mass changes estimated from in-situ observations. This study presents an approach that integrates GRACE observations with profile soil moisture estimates derived from the ESA CCI SM product to assess groundwater variations. The validation against in-situ data indicates that satellite observations of soil moisture and gravity changes can provide robust estimation of basin-scale variations in both profile soil moisture and groundwater.

How to cite: Park, T., Seo, K.-W., and Ryu, D.: Groundwater storage change in Victoria, Australia observed by GRACE and ESA CCI soil moisture products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1621, https://doi.org/10.5194/egusphere-egu24-1621, 2024.

EGU24-2399 | ECS | Orals | HS6.5

Satellite-based water surface slope in small mountain river 

Haoyang Lyu and Fuqiang Tian

Satellite altimetry has emerged as a key alternative for inland water level measurement in addition to ground observations. Water surface slope (WSS) is one of the basic parameters of river morphology for discharge calculation. Estimation of WSS can also avoid systematic bias in satellite water levels relative to gauged data. A range of satellite data products are available to provide accurate river water level measurements and estimates of river WSS on a worldwide scale. Nonetheless, satellite-based observation of river water surface remains challenging in small rivers, such as the mountainous river reaches with narrow water surfaces. In this study, we examined the accuracy of the ICESat-2 ATL03 photon height data in estimating WSS over the mountainous river reach of Yongding River flowing across Hebei Province and Beijing City in northern China. With minimum along-track sampling interval of 0.7m, the ICESat-2 ATL03 data provided reliable estimation of WSS over narrow river reaches which are 50 to 100m wide. Satellite virtual stations were located mainly with a histogram-based statistical method, seeking for photon height that corresponds to the peak frequency. The twelve groups of satellite virtual stations chosen for river WSS estimation finally show an overall correlation coefficient of 0.96 in validation. Relative error of WSS estimation ranges from 0.13% to 14.51%. Findings of this study provide further implications for satellite-based river water surface measurement in small mountain river basins that lack of ground observation conditions, bringing in reliable estimation of key hydrological parameters based on satellite observation.

How to cite: Lyu, H. and Tian, F.: Satellite-based water surface slope in small mountain river, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2399, https://doi.org/10.5194/egusphere-egu24-2399, 2024.

EGU24-2603 | ECS | Posters on site | HS6.5

Estimating lake water storage and water level using Sentinel-1 C-band SAR 

Jongmin Park, Yangwan Kim, and Kijin Park

Intensification of climate change and extreme climate conditions around the world caused an increase in the frequency and intensity of water disasters (e.g., drought and flood). Particularly, the Korean Peninsula underwent a significant amount of rainfall during the summer monsoon, along with the increased number of typhoons passing through. In early August 2020, heavy rainfall occurred across the southern part of the Korean Peninsula (e.g., Jeolla and Chungcheong provinces), which resulted in the loss of life and properties. Accordingly, there is a continuous need to establish flood system monitoring over a wide region.

Accordingly, various studies have utilized different types of satellite imagery (e.g., optical, synthetic aperture radar [SAR], LiDAR) for flood inundation mapping. For example, optical satellite imagery (e.g., MODIS, Landsat, Sentinel-2/3) has been widely utilized for flood mapping, while it has limitations with regard to weather conditions. Synthetic Aperture Radar (SAR) imagery has been brought as an alternative as it is not hindered by weather conditions and has relatively high spatial resolution. Therefore, this study utilizes Sentinel-1 C-band backscatter (from 01/2016 to 12/2022) provided by the European Space Agency (ESA) to estimate the inland water body storage as well as water level at Naju Lake located in the Yeongsan River basin, South Korea.

 Prior to estimating the water body storage and water level, two threshold-based methods (i.e., Otsu threshold method, k-mean clustering) were used to distinguish water and no-water pixels based on the bimodal histogram of Sentinel-1 C-band backscatter. The validation of the water body area is conducted by comparing against optical image-based modified normalized difference water index calculated from the harmonized Landsat sentinel-2 (HLS) imagery. The overall evaluation confirmed that the accuracy of the water body area with k-mean clustering (0.8) showed better performance than that from the Otsu threshold method. Especially, the water body area from the Otsu threshold method showed a clear overestimation during the monsoon period. Afterwards, we established support vector regression (SVR) with the number of water pixels and ground-based water storage datasets. Estimation of water storage with SVR showed similar trend with observed water storage with the coefficient of determination (R2) of 0.92, while estimated water storage showed slight underestimation (bias = -899 m3).

Overall, Sentinel-1 C-band backscatter showed the capability to capture the inland water body as well as the volume of the inland lake. Even though there are several limitations (e.g., sensitivity toward vegetation, coarse revisit frequency) in the context of near real-time flood monitoring, it still has value in monitoring the spatio-temporal behavior of inland water body.

Acknowledgement: This work was supported by Korea Environment Industry & Technology Institute(KEITI) through R&D Program for Innovative Flood Protection Technologies against Climate Crisis Program(or Project), funded by Korea Ministry of Environment(MOE)(RS-2023-00218873)

How to cite: Park, J., Kim, Y., and Park, K.: Estimating lake water storage and water level using Sentinel-1 C-band SAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2603, https://doi.org/10.5194/egusphere-egu24-2603, 2024.

EGU24-2637 | Posters on site | HS6.5

A framework for surface water and groundwater modeling by multiple satellites. 

Liwei Chang, Lei Cheng, Lu Zhang, and Pan Liu

A comprehensive understanding of renewable water resources, including surface water and groundwater, is crucial for human sustenance, societal advancement, and ecosystem well-being at both local and global levels. Remote sensing technology offers an opportunity to rapidly and conveniently monitor inland water resources on a large scale. This study presents a framework for modeling water storage changes by integrating data from multiple satellites. Specifically, the GRACE and GRACE-FO gravity satellites are utilized to observe changes in terrestrial water storage (TWS), while the Landsat multispectral and ICESat / ICESat-2 altimetry satellites are employed to simulate changes in surface water storage (SWS). Groundwater changes are calculated by subtracting SWS and soil moisture storage (SM) from TWS, with SM data obtained from GLDAS 2.1. The innovation of this framework lies in the improved simulation of surface water, facilitated by the fine resolution of ICESat-2, enabling the establishment of an area-elevation relationship for very small water bodies (< 1 km2). This framework does not account for variations in river channel storage, making it suitable for regions where river discharge can be disregarded. The framework is applied to four provinces or cities in the North China Plain, where water scarcity constrains the demand of drinking water, irrigation, and environment. The study reveals a decrease in TWS from 2002 to 2020 in the study area. Although surface water increased following the operation of the Middle Route of the South-to-North Water Diversion Project in December 2014, groundwater continued to decline until 2020 and remained stable from 2020 to 2022. This study represents the first use of 4-year ICESat-2 data to monitor water bodies of all sizes (from <1 km2 to >100 km2). Leveraging the exceptional capability of ICESat-2 data in modeling small water bodies, this study advances the prospect of achieving a comprehensive simulation of inland water resources.

How to cite: Chang, L., Cheng, L., Zhang, L., and Liu, P.: A framework for surface water and groundwater modeling by multiple satellites., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2637, https://doi.org/10.5194/egusphere-egu24-2637, 2024.

EGU24-3091 | Posters on site | HS6.5

DREAMing in River Basins 

Philippa Berry and Jerome Benveniste

The contribution of  satellite radar altimetry to river monitoring is well-established, with data forming  valuable inputs to river models.
Surface soil moisture can also be determined from altimetry using DRy EArth Models (DREAMs) which model the response of a completely dry surface to Ku band nadir illumination. New DREAMs over Africa now cover more than 70% of the continent, encompassing more than 30 river basins including the Congo, Niger, Okavango, Zambezi and Volta.  

It was decided to fly multi-mission altimetry over these river DREAMs to assess the potential of this technique to contribute to studies in river basins. As a detailed DREAM exists for the Amazon basin, this was also included. Envisat, ERS-1/2, Jason-1/2, CryoSat-2 and Sentinel-3A altimeter data were utilised in this study, together with a database of over 86000 graded altimeter River and Lake height time series. Soil moisture estimates were generated and validated.

Summative conclusions: the highest data retrieval rate over river DREAMs is found over ‘river’ and ‘wetland’ pixels, with lower percentages over ‘soil’ pixels where soil moisture estimates can be generated. This is an expected outcome, as targeting ‘soil’ pixels will select for rougher topography. 
Within the constraints of satellite orbit and repeat period, data can be successfully gathered over the majority of these overflown DREAM surfaces. It is also clear that very detailed DREAM models, at least 10 arc seconds resolution, are required to capture the intricate structure in river basins. It is noted that many tributaries are below the current 10 arc seconds spatial resolution of the DREAMs, and are classified with their surrounding terrain as wetland pixels.
ERS-2 and Envisat performed best; Sentinel-3A OLTC mask is found to preclude monitoring of almost all ‘soil’ pixels, except those adjacent to the largest rivers.
The ability of nadir-pointing altimeters to penetrate vegetation canopy gives a unique perspective in rainforest areas. Amazon soil moisture time series in the lower Amazon are seen to correlate to river height variations: in the upper Amazon basin the annual rainfall signature is dominant.
Over much of the river DREAMs, along-track time series of soil moisture can be generated at the spatial resolution of the underlying DREAM, currently 10 arc seconds.  The major constraint, as with altimeter height measurements, is the spatio-temporal sampling, so use is envisaged in combination with other remote sensed and in-situ data.  However, DREAMing provides a valuable independent dataset which can be used to validate soil moisture estimates from other techniques.

How to cite: Berry, P. and Benveniste, J.: DREAMing in River Basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3091, https://doi.org/10.5194/egusphere-egu24-3091, 2024.

EGU24-3426 | Orals | HS6.5

Swath altimetry simulations with Radarspy, in preparation of Copernicus mission Sentinel-3 Next Generation - Topography 

Louise Yu, François Boy, Damien Desroches, and Alejandro Bohe

We wish to present the CNES contribution to the Sentinel-3 Next Generation - Topography (S3NG-T) project. In the wake of the SWOT mission, which pioneered the use of SAR interferometry for surface water altimetry, ESA is considering using this new approach for the successor to its current operational mission Sentinel-3 (S3), S3NG. Such so-called “swath altimetry” enables the access to two-dimensional features on water surfaces, much more directly than traditional Nadir altimetry (such as that used aboard S3) does, but it must also stand the test of accuracy requirements.

Scheduled to take flight in 2033, the altimetry component of S3NG, called S3NG-T, is wrapping up its development phase B1 wherein two consortia designed their proposal of a swath altimetry mission, and during which SWOT’s very promising first data released. A Mission Gate Review in early 2024 should lead to the definitive decision whether to adopt this new measurement technique for S3NG-T or not. Rich with the heritage of their contribution to SWOT and convinced of the potential of swath altimetry, the CNES teams bring a technical expertise to the S3NG table.

As such, we developed evolutions for Radarspy, our in-house simulator of swath altimeter data, in order to assess S3NG’s performances over oceans and inland waters. The swath altimetry instrument aboard S3NG-T, called SAOOH, differs from SWOT’s instrument mainly in its 3-meter baseline, its multiple receptors (four per swath – left or right – in order to flatten the gain pattern), and its interleaved observation pattern, where bursts of 128 Radar pulses are sent alternatively left and right. We wish to present the results of our simulations, which test SAOOH over scenes of various reflectivity, water content and topography. These simulations yield encouraging first results and let us see how some choices made in its on-board processing algorithm affect the random noise, the water detection performance and the point-target response.

How to cite: Yu, L., Boy, F., Desroches, D., and Bohe, A.: Swath altimetry simulations with Radarspy, in preparation of Copernicus mission Sentinel-3 Next Generation - Topography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3426, https://doi.org/10.5194/egusphere-egu24-3426, 2024.

EGU24-4412 | ECS | Orals | HS6.5

Effect of Climate Change on Water Level and Surface Area of Lake Iznik (NW Türkiye)  

Muharrem Hilmi Erkoç, Uğur Doğan, Büşra Keser, and Bülent Bayram

The aim of the study is to investigate the changes in the water level and surface area of Lake Iznik in Northwestern Anatolia, Türkiye, between 2014 and 2024. In this context, High-Resolution Satellite images provided by European Space Agency (ESA)'s Sentinel-2 are used to determine the lake surface area, and satellite altimetry data provided by Copernicus Land Service is utilized to determine the lake water level. Additionally, temperature and precipitation data from a meteorological station near the lake are obtained from the Turkish State Meteorological Service due to their significant impact on the lake's water level and surface area changes.

The estimated trend for the change in the water level from 2014 to 2024 is -23±1.9 cm/yr, and the change in the surface area trend is estimated as -1.2±0.2 km²/yr. The results indicate a decrease in both the lake's water level and surface area. Furthermore, Standardized Precipitation Index (SPI) and Standardized Precipitation-Evapotranspiration Index (SPIE) are calculated from precipitation and temperature data obtained from meteorological stations near the lake. These indices reveal a decrease in precipitation and an increase in temperatures in the Lake Iznik basin over the past 10 years.

Consequently, it is observed that the changes in the water level and surface of Lake Iznik are influenced by climate change, and hence,necessary measures need to be taken for the conservation and sustainable use of the lake.

How to cite: Erkoç, M. H., Doğan, U., Keser, B., and Bayram, B.: Effect of Climate Change on Water Level and Surface Area of Lake Iznik (NW Türkiye) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4412, https://doi.org/10.5194/egusphere-egu24-4412, 2024.

EGU24-4660 | Posters virtual | HS6.5

Water Balance Analysis for Reservoirs through Remote Sensing: A Case Study of the Karun (IV) Reservoir in Iran. 

Mohammad Hosein Kachoue, Mahdieh Goli, Ali Bakhtiari, Mohsen Sedghi, Mahdi Hosseinipoor, and Farkhondeh Khorashadi Zadeh

Dams are essential for effectively managing water resources as they serve multiple vital purposes, such as water storage, flood control, hydroelectric power generation, recreation and tourism and ecosystem regulation. The rising number of reservoirs, prompted by population growth, and the urgency for climate change adaptation and mitigation strategies emphasize the importance of developing efficient methods for calculating reservoirs water balance. In this study, we propose a remote sensing-based method for water balance analysis, aiming to facilitate the monitoring and management processes of water storage. The Karun (IV) reservoir, a dam situated in the southwestern region of Iran, is selected as the case study for this research. A conceptual rainfall-runoff model is employed to simulate the daily inflow rate of the reservoir by utilizing hydrological data obtained through remote sensing techniques. This data includes various parameters such as precipitation, evaporation and transpiration, soil moisture, vegetation, and land use. Moreover, a sensitivity analysis of model parameters is conducted to assess the significance of each parameter and simplify the model for future applications. Reservoir water evaporation is estimated by utilizing the reservoir area of the dam, which is obtained from the NDWI water index and the evaporation rate extracted from the WAPOR dataset. Then, altimetry data and reservoir area data are utilized to calculate changes in water storage. Finally, the water balance equation incorporating the calculated balance elements above is applied to determine the daily output of the dam reservoir. This study showcases the utilization of remote sensing data in estimating the output of the Karun (IV) reservoir. The accuracy of the proposed method is verified through comparisons with field data, making it a valuable tool for reservoirs where field data collection is costly or challenging.

How to cite: Kachoue, M. H., Goli, M., Bakhtiari, A., Sedghi, M., Hosseinipoor, M., and Khorashadi Zadeh, F.: Water Balance Analysis for Reservoirs through Remote Sensing: A Case Study of the Karun (IV) Reservoir in Iran., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4660, https://doi.org/10.5194/egusphere-egu24-4660, 2024.

EGU24-5773 | Orals | HS6.5

Performance assessment of Lake Water Level estimation from Sentinel-6 Fully-Focused SAR observations and comparison to SWOT mission 

Carlos Yanez, François Boy, Gabriel Calassou, Jean-Alexis Daguzé, and Kassem Asfour

Remote sensing techniques are crucial for sustaining a continuous and global climate monitoring of inland waters. In particular, recent progress in satellite radar altimetry has enabled the observation of an increasing number of small and medium size lakes and reservoirs, even in complex topography. The arrival of nadir radar altimeters operating in Synthetic Aperture Radar (SAR) mode has considerably improved the resolution of the observations in the along-track direction, passing from several kilometers in conventional limited-pulse altimeters, to hundreds of meters in close-burst altimeters when applying unfocused SAR (UFSAR) processing and even to the theoretical limit of half the along track antenna length in open-burst altimeters that can totally exploit the Fully-Focused SAR (FFSAR) processing technique. Sentinel-6 is the first operational mission to operate in open-burst mode allowing this enhanced performance over inland waters [1]. Complementary to nadir radar altimetry, SWOT mission provides since the beginning of 2023 radar interferometry observations over wide-swaths that could entail great advances in hydrology [2].

The inversion methods to estimate geophysical parameters, such as Lake Water Level (LWL), from the backscattered altimetry signal are commonly called retrackers. These retrackers can be empirical, such as the widely used OCOG method or physically-based, that is to say, a background waveform model is derived from the theoretical knowledge of the microwave scattering process and then fitted to the real backscattered signal received on-board. Several retrackers of the second type have been developed for processing conventional pulse-limited radar observations, like the Brown-like models, and also for UFSAR observations in the case, for example, of the SAMOSA model. Nevertheless, no specific retracker for FFSAR observations has been developed yet. One of the limitations of analytical and numerical physical-based retrackers concerns the assumption that the radar footprint is completely covered by water. This assumption, that holds for large lakes, begins to degrade the accuracy on the retrieved geophysical parameters when monitoring smaller water bodies. For this reason, a retracker based on numerical simulations was proposed in 2021 adapted to UFSAR observations [3]. This latter model has the advantage of taking into account a prior knowledge of the lake contour and, in this way, only in-water areas of the radar footprint contributes to the simulated backscattered waveform. In this work, the derivation of a similar retracker taking into account the FFSAR processing particularities is presented. This results in the first retracking model specifically developed for FFSAR observations. Preliminary performance is assessed with a variety of lakes for which in-situ observations of LWL are available. Furthermore, a comparison with the recently delivered first products of the SWOT mission over lakes will be presented.

[1] Donlon, C.J., et al, 2021. The Copernicus Sentinel-6 mission: Enhanced continuity of satellite sea level measurements from space. Remote Sensing of Environment, 258, p.112395.

[2] Biancamaria, S., et al, 2016. The SWOT mission and its capabilities for land hydrology. Remote sensing and water resources, 117-147.

[3] Boy, F., et al, 2021. Improving Sentinel-3 SAR mode processing over lake using numerical simulations. IEEE Transactions on Geoscience and Remote Sensing, 60, pp.1-18.

How to cite: Yanez, C., Boy, F., Calassou, G., Daguzé, J.-A., and Asfour, K.: Performance assessment of Lake Water Level estimation from Sentinel-6 Fully-Focused SAR observations and comparison to SWOT mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5773, https://doi.org/10.5194/egusphere-egu24-5773, 2024.

EGU24-5830 | Orals | HS6.5 | Highlight

Estimation of water level time series for lakes and rivers using SWOT KaRIn measurements  

Christian Schwatke, Daniel Scherer, and Denise Dettmering

For more than three decades classical satellite altimetry has been successfully used to monitor water levels of inland waters such as rivers, lakes and reservoirs. In December 2022, a new generation of altimeter mission called Surface Water and Ocean Topography (SWOT) was successfully launched. SWOT is equipped with a classical radar nadir altimeter comparable to Jason-3, but also with a new Ka-band Radar Interferometer (KaRIn). KaRIn uses the principle of SAR interferometry, which has the capability to monitor almost every inland water body worldwide because of its swath. 

In this contribution, we present a new approach to derive water level time series for lakes and rivers using the high-resolution SWOT pixel cloud dataset. This dataset allows us to monitor water levels of very small lakes (> 100m²). We use SWOT data measured on the fast sampling orbit (03/2023 – 07/2023, 1-day repeat cycle) and the science orbit (since 07/2023, 21-day repeat cycle). For quality assessment, the resulting water level time series will be validated with in-situ data. All water level time series will be freely available on the web portal of the "Database of Hydrological Time Series of Inland Waters" (DAHITI, https://dahiti.dgfi.tum.de). 

 

How to cite: Schwatke, C., Scherer, D., and Dettmering, D.: Estimation of water level time series for lakes and rivers using SWOT KaRIn measurements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5830, https://doi.org/10.5194/egusphere-egu24-5830, 2024.

EGU24-6828 | ECS | Posters on site | HS6.5

Trends and variability of lake surface water storage in the source region of the Yellow River based on deep learning 

Weixiao Han, Chunlin Huang, Weizhen Wang, Jinliang Hou, Gabriela Schaepman-Strub, Juan Gu, Yanfei Peng, Ying Zhang, and Peng Dou

The source region of the Yellow River is one of the main regions of the Asian water tower, lakes storing standing or slowly flowing water that provides essential ecosystem services of fresh water and food supply, waterbird habitat, cycling of pollutants and nutrients, and recreational services. Lakes are also key components of biogeochemical processes and regulate climate through cycling of carbon. Thus the estimation of trends and variability of the lake surface water storage is very critical, the direct human activities (damming and water consuption) and the natural factors (precipitation, runoff, temperature and potential evaporation) is gradually changing this environmentally sensitive region, especially the glacier retreat and permafrost thawing partially drive alpine lake expansion.

The objective is mainly estimating the trends and variability of lake surface water storage using the deep learning module and long-term multi-source remote sensing data from the source region of the Yellow River. Optical remote sensing time-series images (Landsat 5-9, MODIS, and Sentinel-2) are employed to generate high-resolution, complete and closed lake surface shorelines and areas based on the Deep Convolutional Generative Adversarial Networks (DCGAN) deep learning method. Additionally, radar altimeters (GFO, T/P, Jason-1/2/3, Sentinel-6, ERS-2, Envisat, Cryosat-2, Saral/AltiKa, Sentinel 3/SRAL, ICESat, and ICESat-2) are utilized to recover lake water levels through the application of the Spatial-Temporal Graph Neural Networks (ST-GAN) deep learning method, providing insights into the long-term changes in lake water surface storage from 1992 to 2022. The study aims to assess the contributions of human activities and natural factors, and provids the valuable guidelines for water resource management.

How to cite: Han, W., Huang, C., Wang, W., Hou, J., Schaepman-Strub, G., Gu, J., Peng, Y., Zhang, Y., and Dou, P.: Trends and variability of lake surface water storage in the source region of the Yellow River based on deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6828, https://doi.org/10.5194/egusphere-egu24-6828, 2024.

EGU24-8341 | Orals | HS6.5 | Highlight

Understanding the interaction between inland waters and the coastal zone during extreme events over the Po Delta from space 

Angelica Tarpanelli, Francesco De Biasio, Karina Nielsen, Paolo Filippucci, Rosa Maria Cavalli, and Stefano Vignudelli

The alternation of extreme events is a source of great stress on the territory and forces us to adopt solutions to help mitigate their consequences. In this study, an attempt is made to exploit Earth Observation from space as a means to point out the interaction of inland waters and the coastal areas during hydrological extreme events, i.e. floods and droughts. During a flood event, large volume of water from the river reaches the coast, adding a considerable volume of freshwater. Conversely, during a drought event salt water from the sea enters inland causing severe damage to agriculture and the local population. With this study we attempt to investigate how the systems of sea and river interact during particularly intense events using satellite optical (Sentinel-2 and Sentinel-3) and altimeter (Sentinel-3, Cryosat-2, Icesat-2) sensor data. The area selected is the Po River delta (up to 200 km from the mouth), which in recent years has been exposed to severe events: in November 2019, the Po River was subject to a copious flood that had not occurred since 2000, while in the summer of 2022, it experienced the worst drought in the last 70 years.

The analysis aims at evaluating three fundamental aspects: 1) the ability of satellite altimetry to identify extreme events in the river; 2) the potential of satellite altimetry to detect salt wedge intrusion in the Po River delta; and 3) the potential correlation between the altimetry observations and optical imagery of the river’s plume along the Adriatic coast.

The analysis was conducted by analysing long time series (of about 10 years) for the first objective and by focusing on the drought event of 2022 and the flood events that occurred in the last 5 years for the other two objectives.

The results of the analysis confirm that the satellite observed the significant increase and decrease in water levels in correspondence of the extreme events. In addition, the analysis of the data at the virtual stations in the downstream part of the Po River, together with the data along the tracks crossing the plume closer to the mouth of the river, showed the interaction between the sea and the river. In particular, the temporal series of the river clearly highlight the influence of the sea water several km upstream the river (more than 40 km as reported in the news), probably related to the salt wedge intrusion, which has caused significant damage to agriculture and drinking water aquifers for a long time after the event. The study qualitatively shows that extreme hydrological events can also be captured in the open sea in this region.

The analysis illustrates the great potential of satellite sensors to monitor extreme events and the interaction of inland and coastal waters.

How to cite: Tarpanelli, A., De Biasio, F., Nielsen, K., Filippucci, P., Cavalli, R. M., and Vignudelli, S.: Understanding the interaction between inland waters and the coastal zone during extreme events over the Po Delta from space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8341, https://doi.org/10.5194/egusphere-egu24-8341, 2024.

The current global water body maps offer an approximate resolution of 30 meters, contingent on available remote sensing data. However, to address the needs of advanced applications like global carbon cycle analysis and real-time flood predictions, a water body map with higher spatial resolution becomes imperative, especially for resolving smaller rivers. Traditional water extraction methods rely on water indexes that combine visible and infrared spectra. State-of-the-art remote sensing data, including aerial photography with spatial resolutions in the order of a few meters, often includes only the visible spectrum.

In response to this challenge, we have developed a water extraction method at an impressive 60cm resolution utilizing Bayesian inference based solely on the visible spectrum from aerial photography, without using the infrared spectrum. To enhance our methodology, we integrated references of water existence from a Landsat-based dataset called G1WBM and Open Street Map (OSM), along with a hydrography dataset (J-FlwDir) presumed to be linked to water bodies.

Our method successfully detected the main streams of the Tsurumi River and Tama River in Japan, including their previously unrecognized tributaries in the Landsat-based dataset. Notably, this study identified rivers with a width exceeding 10 meters. Furthermore, it contributed valuable area information for 37% of small rivers represented as "line" features in the OSM.

These findings underscore the effectiveness of our Bayesian water detection approach, which leverages hydrography data and existing water body maps to improve the spatial resolution of large-scale water mapping significantly. Notably, this improvement is achieved using remote sensing data that lacks infrared spectra, showcasing the potential of our method in advancing the accuracy and precision of global water mapping efforts.

How to cite: Watanabe, M. and Yamazaki, D.: A 60-cm Aerial Photography-based Water Body Mapping: Application to the Tama and Tsurumi Rivers in Japan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8805, https://doi.org/10.5194/egusphere-egu24-8805, 2024.

EGU24-8949 | ECS | Orals | HS6.5

Looking beyond nadir: Measuring densely sampled river elevation profiles with the Sentinel-6 altimeter 

Frithjof Ehlers, Cornelis Slobbe, Martin Verlaan, and Marcel Kleinherenbrink

For almost 30 years radar altimeters provide water elevations of rivers and lakes only where a target intersects the satellite’s ground track, called Virtual Stations (VS). This way, the observations have both limited temporal and spatial resolution, because on one hand such intersections occur by chance and because on the other hand the repeat cycle of the orbit ranges from 10 to 35 days, depending on the mission.

Boy et al. [1] illustrated recently that river signals may also be captured when the river is located at cross-track distances of several kilometers, when utilizing high resolution SAR altimeter products (particularly fully-focused SAR [2], FFSAR). Therefore, the concept of the altimeter river measurements can be revisited completely. Based on the idea presented in [1], we developed a novel algorithm to calculate water surface elevations (WSE) of rivers within a ground swath of approximately 14 km width, and with along-track resolutions as fine as 10 m from the Sentinel-6 altimeter signal. All that is needed additionally to the FFSAR-processed signal is an a-priori river polygon or centerline to correct for non-zero cross-track distances.

Our algorithm can provide WSE along most parts of the river that fall within the swath, thus delivering densely sampled WSE profiles instead of a few point measurements over only the nadir crossings (VS). This marks a drastic improvement in the number of available WSE observations and opens completely new research possibilities, as water surface slopes and level changes due to rapids and dams can be studied directly. Essentially, these new Sentinel-6 WSE measurements resemble the river WSE product obtained with the recently launched SWOT mission (albeit with more limited coverage). As such, they can be exploited in similar manners to provide much additional information for hydrological research, e.g. for assimilation in hydrological models and more reliable estimation of river discharge.

We demonstrate and validate the new measurement approach and our algorithm over two rivers in France, the Creuse river and the Garonne river, showing biases that are typically on the order of +-4 cm and random errors on the order of 5 cm, both on 30 m along-track resolution. In our presentation, we will concentrate our attention on the new challenges of the method, including a sophisticated signal detection algorithm, the altered error budget of off-nadir WSE measurements and the limitations due to signal folding, clutter, lacking contrast and the complexity of the scene.

[1] Francois Boy et al. “Measuring longitudinal river profiles from Sentinel-6 Fully-Focused SAR mode”. In: Ocean Surface Topography Science Team (OSTST) meeting. Nov. 2023. doi: 10.24400/527896/a03-2023.3781.

[2] Alejandro Egido and Walter H. F. Smith. “Fully Focused SAR Altimetry: Theory and Applications”. In: IEEE Transactions on Geoscience and Remote Sensing 55.1 (Jan. 2017), pp. 392–406. doi: 10.1109/TGRS.2016.2607122.

How to cite: Ehlers, F., Slobbe, C., Verlaan, M., and Kleinherenbrink, M.: Looking beyond nadir: Measuring densely sampled river elevation profiles with the Sentinel-6 altimeter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8949, https://doi.org/10.5194/egusphere-egu24-8949, 2024.

EGU24-10126 | ECS | Orals | HS6.5

Development of a global and dynamic map of wetland and inundated areas based on microwave remote sensing product (GIEMS-2) over 1992-2020 

Juliette Bernard, Catherine Prigent, Carlos Jimenez, Marielle Saunois, Frederic Frappart, Cassandra Normandin, Pierre Zeiger, Shushi Peng, Yi Xi, Etienne Fluet-Chouinard, and Zhen Zhang

Wetlands and inundated areas cover only a few percent of the Earth's surface. However, they play an important role in freshwater regulation, biodiversity, and climate. In particular, a significant proportion of atmospheric methane is emitted from these areas [1]. There is therefore a need for data that can reliably capture surface water interannual variability over the past decades. 

The Global Inundation Extent from Multi-Satellites (GIEMS-2) [2] is based on microwave remote sensing data (SSM/I and SSMIS). It provides a 0.25° global monthly estimate of inundated and saturated areas and has been extended to 2020 to cover three decades (1992-2020). 

First, an evaluation of GIEMS-2 together with other products is presented. Key findings include consistent spatial patterns, seasonal cycles and time series anomalies observed by GIEMS-2 with the other observational datasets studied (MODIS-derived surface water, CYGNSS-derived surface water, river discharge). This highlights the interest of such a product for the calibration of hydrological models, as has been achieved for example by Xi et al. (2022) for TOPMODEL [3]. 

In a second part, the use of GIEMS-2 for the estimation of methane emissions from wetlands and inundated areas is discussed. GIEMS-2 has been processed with other data sources to derive a dynamic map of wetlands (including peatlands), open water (lakes, rivers, reservoirs) and rice paddies. This comprehensive product allows a consistent view of the area between the different classes, limiting problems of double counting and miss counting. This new database can then be used to constrain the extent of the water surface in models estimating methane flux rates, in order to study the influence of surface water changes on interannual variations in methane emissions.

 

[1] Marielle Saunois et al. “The Global Methane Budget 2000–2017”. In: Earth System Science Data 12.3 (July 2020), pp. 1561–1623. doi: 10.5194/essd-
12-1561-2020. url: https://doi.org/10.5194/essd-12-1561-2020.
[2] C. Prigent, C. Jimenez, and P. Bousquet. “Satellite-Derived Global Surface Water Extent and Dynamics Over the Last 25 Years (GIEMS-2)”. In: Jour-
nal of Geophysical Research: Atmospheres 125.3 (Feb. 2020). doi: 10.1029/2019jd030711. url: https://doi.org/10.1029/2019jd030711.
[3] Yi Xi et al. “Gridded Maps of Wetlands Dynamics over Mid-Low Latitudes for 1980–2020 Based on TOPMODEL”. In: Scientific Data 9.1 (June 2022), p. 347. issn: 2052-4463. doi: 10.1038/s41597-022-01460-w

How to cite: Bernard, J., Prigent, C., Jimenez, C., Saunois, M., Frappart, F., Normandin, C., Zeiger, P., Peng, S., Xi, Y., Fluet-Chouinard, E., and Zhang, Z.: Development of a global and dynamic map of wetland and inundated areas based on microwave remote sensing product (GIEMS-2) over 1992-2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10126, https://doi.org/10.5194/egusphere-egu24-10126, 2024.

EGU24-10856 | ECS | Orals | HS6.5

Toward a global scale runoff estimation through satellite observations: the STREAM model 

Francesco Leopardi, Luca Brocca, Carla Saltalippi, Jacopo Dari, Karina Nielsen, Nico Sneeuw, Mohammad J. Tourian, Marco Restano, Jérôme Benveniste, and Stefania Camici

River discharge monitoring is critical for many activities ranging from water resource management to flood risk reduction. Due to limitations of in situ stations (e.g. low station density, incomplete temporal coverage and delays in data access), river discharge is not always continuously monitored in time and space. This has led researchers and space agencies, among others, to develop new methods based on satellite observations for estimating river discharge.

In recent years, ESA has funded the SaTellite-based Runoff Evaluation And Mapping (STREAM) and STREAM-NEXT projects, which propose to use satellite observations of precipitation, soil moisture and terrestrial water storage within a simple and conceptually parsimonious model, STREAM, to estimate runoff.

The model, applied to five large basins in the world (Mississippi-Missouri basin, Amazon basin, Danube basin, Murray-Darling basin and Niger basin)  has demonstrated a high ability to estimate runoff and river discharge in both natural and non-natural basins with a high anthropogenic impact (i.e. in basins where flow is regulated by the presence of dams, reservoirs or floodplains along the river; or in heavily irrigated areas). In particular, the good results obtained paved the way for the application of the STREAM approach on a global scale. For this purpose, the STREAM-NEXT project will generalise the STREAM model to make it applicable to more than forty basins worldwide. Depending on the availability of in situ discharge data, the selected basins shall be grouped into calibration and validation clusters. The purpose is to use the basins into the calibration cluster to tune the parameters of the regionalized STREAM model and apply the regionalised model parameters to the validation cluster basins to estimate the accuracy of the STREAM model.  Additional satellite observations, such as altimetric water levels, will be used to estimate the water stored in the reservoirs; gravimetric data with different spatial/temporal resolutions will be explored to investigate the impact of these data on the model results.

Finally, a calibration procedure and a regionalisation approach will be developed to make the STREAM model applicable to non-calibrated basins.

Here we present the STREAM-NEXT project and some preliminary results related to the generalization of the STREAM model framework. Different basins with different climate, topography and level of anthropisation will be selected to demonstrate the suitability of the approach for a global scale application. 

How to cite: Leopardi, F., Brocca, L., Saltalippi, C., Dari, J., Nielsen, K., Sneeuw, N., Tourian, M. J., Restano, M., Benveniste, J., and Camici, S.: Toward a global scale runoff estimation through satellite observations: the STREAM model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10856, https://doi.org/10.5194/egusphere-egu24-10856, 2024.

EGU24-10929 | Orals | HS6.5 | Highlight

SWOT lake processing and products 

Claire Pottier, Cécile Cazals, Marjorie Battude, Manon Delhoume, Jean-François Crétaux, and Roger Fjørtoft

The Surface Water and Ocean Topography (SWOT) satellite, launched on December 16th 2022, is a CNES and NASA joint project, in collaboration with the Canadian Space Agency (CSA) and the United Kingdom Space Agency (UKSA). SWOT represents a major breakthrough in space altimetry by using a new technical concept based on interferometric synthetic aperture radar (InSAR): in comparison with conventional altimetry, which provides point data along profiles at resolutions of tens or hundreds of kilometres, wide-swath altimetry provides a two-dimensional image with a horizontal resolution of the order of tens or hundreds of meters. Therefore, this mission will significantly improve both offshore and coastal ocean observation, while enabling global measurement also of the water levels (and their variations over time and space) of rivers, lakes and flood zones, with a repeat period of 21 days.

Over land, SWOT is planned to survey lakes with a surface area larger than 250 m by 250 m (objective: 100 m by 100 m). To do so, three main products are available to the user community. The pixel cloud (L2_HR_PIXC) product provides longitude, latitude, height, corrections and uncertainties for pixels classified as water and pixels in a buffer zone around these water bodies, as well as in systematically included areas (defined by an a priori water occurrence mask). The product specific to lakes (L2_HR_LakeSP) is computed from the pixel cloud for each water feature observed by SWOT and not assigned to a regular river. It consists of polygon shapefiles, delineating the lake boundary and providing the area and average height of each observed lake. A Prior Lake Database (PLD) allows to link the SWOT observations to known lakes and help monitoring them over time. The L2_HR_LakeAvg product aggregates L2_HR_LakeSP data over a 21-day cycle.

The validation of L2_HR_LakeSP water surface elevations is mainly based on existing gauge networks. It is a challenge to obtain reference height data that have an absolute accuracy well below what is required for the SWOT lake products we are validating (10 cm 1-sigma at the lake level). The validation of water surface areas relies on reference water masks obtained mainly from (Very-) High-Resolution optical or radar satellite images (Pléiades, Sentinel-2, Sentinel-1, RCM…), pre-processed so that comparisons can be made at the lake scale.

This presentation will first outline the lake processing and the Prior Lake Database. Then examples of products, preliminary accuracy assessments and associated Cal/Val activities will be presented.

How to cite: Pottier, C., Cazals, C., Battude, M., Delhoume, M., Crétaux, J.-F., and Fjørtoft, R.: SWOT lake processing and products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10929, https://doi.org/10.5194/egusphere-egu24-10929, 2024.

Comprehensive and accurate quantification of inland surface water dynamics is vital to our understanding of terrestrial water cycle. Declining trend in availability of in-situ gauge stations elevates a need to switch to alternate measurement sources. In this context, satellite radar altimetric observations of Water Surface Elevations (WSE) offer vast possibilities, especially in poorly gauged basins.  The potential of altimetry is expected to escalate with the availability of high-resolution point cloud measurements of surface waters from the recently launched Surface Water and Ocean Topography (SWOT) mission. In the proposed research, we evaluate the potential of node averaged vector product of river WSE from SWOT to improve discharge estimation through assimilated hydrodynamic modelling over an entire river basin in India. The study uses proxy SWOT river products generated using an Observing System Simulation Experiment (OSSE), the CNES Large Scale SWOT Hydrology Simulator (Elmer et al., 2020; Nair et al., 2022) and RiverObs software. Here, we use the state-of-the-art CaMa-Flood (Catchment-based Macro-scale Floodplain Model) hydrodynamic model (Yamazaki et al., 2011) and the Local Ensemble Transform Kalman Filter (LETKF) assimilation algorithm (Hunt et al., 2007) with a physically based empirical localization approach (Revel et al., 2019). Normalized assimilation approach is adopted to handle the bias between modelled WSE and observed WSE from SWOT. The integration of SWOT altimetric observations in river modelling presents a promising avenue, considering its unprecedented spatiotemporal resolution and accuracy. The research addresses the challenges associated with the terrestrial water cycle, acknowledging the limitations of hydrodynamic modelling and uncertain space-borne observations. Results provide valuable insights into the potential of node averaged products of WSE from the SWOT mission in enhancing discharge estimation in the context of Indian river systems. The study is highly beneficial to sparsely gauged or ungauged basins, which are very common in India.

How to cite: K Soman, M. and Jayaluxmi, I.: Assimilation of high-resolution node averaged water surface elevations from the SWOT mission towards improve discharge estimates., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11731, https://doi.org/10.5194/egusphere-egu24-11731, 2024.

EGU24-13107 | Orals | HS6.5

Higher Temporal Resolution Global GRACE/GRACE-FO Total Water Storage Products for Assimilation in Hydrology Models 

Himanshu Save, Mark Tamisiea, Nadege Pie, and Srinivas Bettadpur

The Gravity Recovery and Climate Experiment (GRACE) and its Follow-On (GRACE-FO) missions have provided near continuous and unique measurement of total water storage  (TWS) since 2002. These international partnership missions have provided valuable insights in the fields of Hydrology, Oceanography, Ocean dynamics, Cryosphere Sciences, Solid Earth etc. These data from GRACE/GRACE-FO have improved our understanding of the Earth’s water cycle since launch and have become indispensable for climate related studies.

The spatial resolution of the data products from GRACE/GRACE-FO are roughly 300km and they typically have a temporal resolution of a month. These products provide the unique measurement of the total water storage of the entire water column and can provide a constraint for hydrological and ocean models. Several studies have used GRACE products for assimilation into the hydrological models for improved assessment of the reality on the ground and for downscaling the information to a higher spatial resolution using data assimilation. This paper will introduce the techniques that improve of temporal resolution of GRACE/GRACE-FO products from month to shorter than 5 days. That includes production of global 5-day TWS solution and the daily TWS product from GRACE that is estimated as a “swath” over the daily satellite ground-track.  The paper will discuss the analysis results over hydrological and ocean basins and validate the higher frequency signals captured by this product.  The goal for the production of this higher temporal resolution GRACE/GRACE-FO product is to be able to use these signals with a latency of a few days for ingestion into machine learning algorithms for early flood detection applications and for daily assimilation into hydrological models at short latency.

How to cite: Save, H., Tamisiea, M., Pie, N., and Bettadpur, S.: Higher Temporal Resolution Global GRACE/GRACE-FO Total Water Storage Products for Assimilation in Hydrology Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13107, https://doi.org/10.5194/egusphere-egu24-13107, 2024.

EGU24-14002 | Posters on site | HS6.5

Synthetic Aperture Radar Altimetry Processing on Demand at ESA’s Altimetry Virtual Lab 

Jérôme Benveniste, Marco Restano, Salvatore Dinardo, Christopher Buchhaupt, Michele Scagliola, Marcello Passaro, Luciana Fenoglio-Marc, Américo Ambrózio, and Carla Orrù

This presentation updates on the ESA Altimetry Virtual Lab for the exploitation of CryoSat-2 (CS-2), Sentinel-3 (S-3) and Sentinel-6 Michael Freilich (S-6MF) data from L1A (FBR) data products up to SAR/SARin L2 geophysical data products. The following on-line & on-demand state-of-the-art research  algorithm services compose the portfolio:

  • The ESA-ESRIN SARvatore service for CS-2 and S-3 services, which allow users to customise the processing at L1b & L2 (a list of configurable options for, e.g., SAMOSA+/++ and ALES+ SAR retrackers, not yet available in the ESA Ground Segment).
  • The ESA SAMPY (Cryo-TEMPO project) for CryoSat-2, which appends the SAMOSA+ retracker output to official CryoSat-2 Level-2 GOP products.
  • The TUDaBo SAR-RDSAR (TU Darmstadt–U Bonn SAR-Reduced SAR) for CS-2 and S-3, which allows users to generate reduced SAR, unfocused SAR & LRMC data, with configurable L1b & L2 processing options and retrackers (BMLE3, SINC2, TALES, SINCS, SINCS OV).
  • The TU München ALES+ SAR for CS-2 and S-3, which allows users to process official L1b data and produces L2 products by applying the empirical ALES+ SAR subwaveform retracker, including a dedicated Sea State Bias solution.
  • The Aresys Fully-Focused SAR for CS-2 & S-3, to produce L1b products with configurable options and appending the ALES+ FFSAR output.

These services will be extended with the following new services:

  • Appending the SAMOSA+ retracker output in all services.
  • The Aresys FF-SAR service for S-6MF
  • The CLS SMAP S-3 FF-SAR processor extended to process S-6MF
  • The UBonn FF-SAR Omega-Kappa processor for S-3 and S-6MF
  • An upgrade of the TUDaBo SAR-RDSAR extended to S-6MF with new ocean and coastal retrackers.
  • The ESA-ESTEC/isardSAT L1 S-6MF Ground Prototype Processor.
  • SAR services updated to process S-6MF

Output products are generated in netCDF, therefore compatible with the multi-mission “Broadview Radar Altimetry Toolbox” (BRAT, http://www.altimetry.info).

The ESA Altimetry Virtual Lab, a community space for simplified services and knowledge-sharing, is hosted on the EarthConsole® (https://earthconsole.eu), supported by the ESA Network of Resources. This service has more than 120 users and sponsored so far more than 500 CPU years, leading to more than 30 publications and 3 PhD theses.

Brochure at https://earthconsole.eu/knowledge-base/. Info at altimetry.info@esa.int.

How to cite: Benveniste, J., Restano, M., Dinardo, S., Buchhaupt, C., Scagliola, M., Passaro, M., Fenoglio-Marc, L., Ambrózio, A., and Orrù, C.: Synthetic Aperture Radar Altimetry Processing on Demand at ESA’s Altimetry Virtual Lab, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14002, https://doi.org/10.5194/egusphere-egu24-14002, 2024.

EGU24-15163 | ECS | Posters on site | HS6.5

Fault tolerant approach to regenerate Level 1B SAR altimetry waveforms for enhancing Level 2 retrackers performance 

Shahin Khalili, Mohammad J. Tourian, Omid Elmi, Johannes Engels, and Nico Sneeuw

This study deals with the identification and retrieval of anomalous waveforms generated in Level 1B processing chain of satellite altimetry over coastal areas and inland water bodies. Efficient identification of anomalous waveforms greatly improves the retracking performance, leading to the generation of precise water level time series that serve as vital inputs for hydrological studies. Abnormal behaviour in waveforms may be an indication of environmental changes, instrument malfunctions or other critical factors. To find anomalous waveforms, our framework utilizes an unsupervised machine learning technique. We categorise different parameters of the satellite's altimeter like AGC parameter, tracker range and features related to shape of waveforms for instance waveform’s skewness, number and location of peaks and so on for each sample in the dataset. Then we identify abnormal waveforms using a two-step density distribution probability analysis.

The secondary purpose of this study is proposing a robust strategy to retrieve abnormal waveforms in the level 1B SAR processing chain. This step is vital for narrow rivers and small inland water bodies, in which low number of measurements on related cycle cause missing hydrology data. In contrast to previous studies focusing solely on investigating L2 waveforms to determine precise retracking gates for multipeak and noisy waveforms, we propose an additional step in the L1B processing chain, specifically tailored to coastal and inland waters, enabling the retrieval of abnormal waveforms. In both fully focused and unfocused SAR processing, the final waveform is formed through the combination of various beam looks from the altimeter during fixed illumination time in stacks to the desired point on the surface, certain looks in the stack may exhibit undesirable patterns due to variations in environmental characterization, antenna footprint, and sidelobe gain. The proposed methods will mitigate the presence of undesirable waveforms in the stack prior to the generation of the final waveforms.

We apply the proposed methodology for Sentinel 3A and 3B datasets over different inland waters and validated our results against in-situ data. The results demonstrate that the water level time series, obtained by regenerated waveforms have significantly improved. The results show the potential of our proposed framework for detecting and retrieving anomalous waveforms leading to robust water level estimates from satellite altimetry data.

How to cite: Khalili, S., Tourian, M. J., Elmi, O., Engels, J., and Sneeuw, N.: Fault tolerant approach to regenerate Level 1B SAR altimetry waveforms for enhancing Level 2 retrackers performance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15163, https://doi.org/10.5194/egusphere-egu24-15163, 2024.

EGU24-15263 | Posters on site | HS6.5

New Open-Loop Tracking Command (OLTC) platform : AltiGIS 

Florian Wery, François Boy, Sophie Le Gac, Alexandre Homerin, Malik Boussaroque, and Jeremie Aublanc

Over the last decade, there has been a burgeoning interest in altimetry measurements for inland waters, with a focus on comprehensive studies of water levels in lakes, reservoirs, and rivers on a global scale. This research is crucial for the hydrology community to accurately assess the Earth's freshwater resources. Significant advancements have been achieved in enhancing altimeters' capacity to obtain high-quality measurements over inland waters.

The Open-Loop Tracking Command (OLTC) stands out as a noteworthy development in altimeter on-board tracking modes. Its effectiveness has been proven through successful implementation in previous missions and is now designated as the operational mode for current missions, including Sentinel-3, Sentinel-6, and SWOT nadir.

Over the past decade, OLTC data, crucial in tracking inland water bodies from radar altimetry satellites, has undergone substantial refinement. Originally developed for Jason-2, new missions as Jason-3, Sentinel-3A&B, Sentinel-3B, Sentinel-6, SWOT nadir have been incorporated. Algorithms and procedures to compute location and elevation of inland waters targets (rivers, lakes, reservoirs) have also been largely improved. The number of hydrological targets has increased fivefold with an acquisition success rate which is now close to 90%. Presently, each mission tracks between 30,000 to 70,000 hydrological targets.

Despite modifications to a software developed 15 years ago, ongoing advancements and the necessity for covering  land ice surfaces in preparation of upcoming S3C&D missionshave prompted the development of a new software. In addition, the availability of new input data provided by the SWOT mission (water mask and elevation) required also to revise the current software to make their usage efficient. Work is currently underway to establish a new OLTC platform, named AltiGIS. The platform is designed with three primary objectives: facilitate collaboration, enhance data generation validity, and broaden dissemination through the use of DevOps practices. The presentation aims at harvesting new user needs but will also cover both the undergoing software development and roadmap.

How to cite: Wery, F., Boy, F., Le Gac, S., Homerin, A., Boussaroque, M., and Aublanc, J.: New Open-Loop Tracking Command (OLTC) platform : AltiGIS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15263, https://doi.org/10.5194/egusphere-egu24-15263, 2024.

EGU24-15510 | Posters on site | HS6.5

Riparian monitoring using SAR image-based water body detection technique 

Shinhyeon Cho, Seongkeun Cho, Yeji Kim, HyunOk Kim, and Minha Choi

Sandbars on the riparian are ecologically important as they provide and protect habitats for organisms and act as natural septic tanks to filter and purify pollutants. In recent years, the role of sandbars in water pollution in rivers has been highlighted, and monitoring of the riparian is required. Sandbars are common in the lower reaches of deltas and at downstream of rivers, especially where the river is wide, and the flow velocity is relatively slow so that remote sensing can be used effectively. Synthetic Aperture Radar (SAR) imagery is an effective tool for spatial monitoring of the riparian because it provides high resolution and can detect regardless of weather conditions. In recent years, research has been conducted to use SAR imagery with AI to improve accuracy of detecting both riparian and sandbars. In this study, we utilized Sentinel-1 SAR (VV, VH polarized backscatter coefficient imagery), Sentinel-2 optical imagery Normalized Difference Water Index (NDWI), and Normalized Difference Vegetation Index (NDVI) data to identify changes of riparian and sandbars using AI-based clustering techniques. The confusion matrix is performed to validate the performance of deep learning techniques and waterbody detection. Technological advances in remote sensing will improve the data resolution of SAR and optical imagery, allowing detailed features to be observed. In further study is expected to improve the monitoring and management of sandbars on the riparian as monitoring technology advances.

Keywords: Riparian, sandbars, Water body detection, Sentinel-1, Sentinel-2, Deep learning

Acknowledgement
This work was supported by the “Development of Application Technologies and Supporting System for Microsatellite Constellation”project through the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2021M1A3A4A11032019). This research was supported by the BK21 FOUR (Fostering Outstanding Universities for Research) funded by the Ministry of Education (MOE, Korea) and National Research Foundation of Korea (NRF). This work is financially supported by Korea Ministry of Land, Infrastructure and Transport (MOLIT) as 「Innovative Talent Education Program for Smart City」

How to cite: Cho, S., Cho, S., Kim, Y., Kim, H., and Choi, M.: Riparian monitoring using SAR image-based water body detection technique, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15510, https://doi.org/10.5194/egusphere-egu24-15510, 2024.

EGU24-15514 | Posters on site | HS6.5

Remotely-sensed spatiotemporal dynamics of the coupled Trichonida – Lysimachia lake system in Western Greece at the seasonal, annual, and decadal time scale 

Konstantinos Panousis, Konstantinos M. Andreadis, Andreas Langousis, Nikolaos Th. Fourniotis, and Christoforos Pappas

Understanding how the combined effects of hydroclimatic variability and anthropogenic interventions shape lake reservoirs is crucial for sustainable water resources management as well as for numerous ecosystem services. In the present study, we focus on the interplay between two lakes in Western Greece that are part of the Natura 2000 network of protected areas, namely the Trichonida – Lysimachia lake system. Lake Trichonida is the largest natural lake in Greece and is connected to the substantially smaller lake Lysimachia through an open channel. The two lakes, together with the connecting channel, constitute a couple system. The channel regulates the flow from Trichonida to Lysimachia lake based on irrigation needs (summer time) and peak flows in the main river corridor (winter-time discharge of Acheloos river). The spatial variability in the extent of the two lakes was quantified at the seasonal, annual, and decadal time scales with remote sensing spectral indices, compiling a wealth of Earth observations. Moreover, water level data from satellite altimetry and ground measurements were combined to characterize water level fluctuations in each lake and their cross-correlation. Gridded data of key meteorological variables (air temperature, precipitation, etc.) as well as drought indices were used to characterize the hydroclimatic variability in the watersheds associated with the two examined lakes. The combined used of ground measurements together with multivariate Earth observations offers new insights into the spatiotemporal dynamics of the coupled Trichonida – Lysimachia lake system that could support and guide sustainable water resource management in the area under environmental change.

How to cite: Panousis, K., Andreadis, K. M., Langousis, A., Fourniotis, N. Th., and Pappas, C.: Remotely-sensed spatiotemporal dynamics of the coupled Trichonida – Lysimachia lake system in Western Greece at the seasonal, annual, and decadal time scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15514, https://doi.org/10.5194/egusphere-egu24-15514, 2024.

EGU24-15723 | ECS | Posters on site | HS6.5

Monitoring water level and lake extent change with nadir-altimeters and SWOT 

Hakan Uyanik, Jiaming Chen, Luciana Fenoglio, and Jürgen Kusche

Water level and lake extent are estimated from combined in-situ, Sentinel-3 and Sentinel-6 nadir altimeters and SWOT-altimetry. Accuracy and precision of the various techniques are compared, the goal is the validation of the new SWOT data in the river Rhine and in Swiss lakes.

 

The main challenge is the interference among multiple water surfaces which contaminate the signal. Fully-focus and Unfocused SAR and individual echoes processed data have a different sensitivity to the signal coming from non-nadir targets. For nadir-altimeters the accuracy and precision of water level depend on the frequency selected for the low level processing. The accuracy ranges from 10-30 cm and depends on the location. The precision is of few centimeters at 80-140 Hz and decreases with increasing frequency selected in low level processing.

 

SWOT derived parameters are validated against the nadir derived equivalent. A more accurate river slope parameter is expected from the SWOT high spatial resolution data. Water extent is another new parameter from SWOT, which is used to derive river discharge and water storage change. In rivers, Sentinel-3A pass 156, that is parallel to the river centerline for about 30 km, is a test area for a direct comparison of water height, slope and discharge parameters from nadir-altimeters and SWOT.

 

In lakes, SWOT water level and water extent are validated against in-situ lake bathymetry, water area extent from Sentinel-1 and Sentinel-2 satellite imagery and water level from nadir-altimeters. In its 21-day phase, SWOT is used to monitor storage change of lakes and reservoirs.

How to cite: Uyanik, H., Chen, J., Fenoglio, L., and Kusche, J.: Monitoring water level and lake extent change with nadir-altimeters and SWOT, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15723, https://doi.org/10.5194/egusphere-egu24-15723, 2024.

EGU24-16275 | Orals | HS6.5

Cal/Val of HR SWOT products using in-situ networks and in-flight nadir altimetry missions 

Maxime Vayre, Julien Renou, Roger Fjortoft, and Nicolas Picot

The Surface Water and Ocean Topography (SWOT) mission, conducted by CNES and NASA was successfully launched on 16 December 2022. It aims at providing unprecedented 2D observations of the sea-surface height and mesoscale structures as well as water surface elevation, water stocks estimates and discharge over hydrological areas. A SAR-interferometry wide-swath altimeter, namely the Ka-band Radar Interferometer (KaRIn), is designed to cover two 50-km cross-track swaths. During its Calibration (Cal/Val) phase (January to July 2023), SWOT mission provided daily measurements for each swath due to its 1-day repeat cycle. While the spatial coverage during this phase is not as large as for the nominal phase with a 21-day repeat cycle, such short revisit time is relevant for Cal/Val purposes.  

 

The High Rate (HR) mode of KaRIn, dedicated to hydrology surfaces, provides HR SWOT products that are calibrated during the Cal/Val phase. The performance assessment of these SWOT observations can be achieved through the comparison against reference measurements. Although specific in-situ Cal/Val sites have been purposely designed for the validation of HR SWOT products on lakes and rivers, additional in-situ networks can also be useful, particularly if their spatial coverage allows a monitoring of lakes and rivers also observed by the SWOT mission. Such conditions are met for the French network (SCHAPI), providing several hundreds of georeferenced in-situ stations over rivers, and for the Swiss network (BAFU) which measures water surface elevation of main rivers and lakes. Moreover, the combination of measurements from current nadir altimetry missions (e.g. Sentinel-3, Sentinel-6 or ICESat-2) has also the potential to generate reference measurements on a large number of lakes and rivers. 

 

Our analysis will essentially propose a preliminary performance assessment of the distinct high-level HR SWOT products during the Cal/Val phase, using existing in-situ networks and measurements from Sentinel-3, Sentinel-6 and ICESat-2. We will first take advantage of hydrological areas being densely monitored below SWOT swaths, which are relevant to assess the quality and current limitations of the products.

How to cite: Vayre, M., Renou, J., Fjortoft, R., and Picot, N.: Cal/Val of HR SWOT products using in-situ networks and in-flight nadir altimetry missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16275, https://doi.org/10.5194/egusphere-egu24-16275, 2024.

EGU24-16780 | Orals | HS6.5 | Highlight

SMASH: a constellation of small altimetry satellites to monitor daily inland surface waters 

Sylvain Biancamaria, Stephane Calmant, Frederic Frappart, Pierre-Andre Garambois, Marielle Gosset, Manuela Grippa, Alexei Kouraev, Pierre-Olivier Malaterre, Simon Munier, Fabrice Papa, Herve Yesou, Thierry Amiot, Cecile Cheymol, and Sophie Le Gac

At global scale, there is still considerable uncertainty about the spatial and temporal variability of water storage and fluxes at the surface of continents. This is even more critical in the context of global climate change and the increasing human pressure on water resources. Despite this context, the following scientific questions remain difficult to answer, due to the coarse spatio-temporal resolution of current data: what is the global distribution of the heterogeneous change undergone by continental surface waters? What is the impact of anthropogenic pressure on water flows and stocks? What is the impact of these changes on the frequency and intensity of hydrological extremes (high and low waters)? To answer these questions, the Global Climate Observing System (GCOS) has identified river levels/discharges and lake/reservoir levels/volumes as essential climate variables, and recommends daily sampling (GCOS, 2022). Besides, extreme events, such as floods or droughts, cover a wide range of spatio-temporal scales. At present, water volume variations can only be observed by satellite at the coarsest scales (and are therefore of interest only for floods on the scale of the world's largest watersheds). The lack of observation of these events in basins with little or no in situ instrumentation is a major issue to understand, simulate and forecast these events. Observing these events globally, at least on a daily scale, would make it possible to quantify local flooding, thus greatly improving our knowledge of these events.

One of the main issue to tackle these questions is the still rather coarse temporal sampling of current satellite missions, particularly altimetry missions. To overcome it, we are proposing the SMall Altimetry Satellites for Hydrology (SMASH) mission. This is a constellation of around 10 compact nadir radar altimeters optimized to provide daily observations of water levels in rivers, lakes and reservoirs along the constellation tracks. The specifications of the SMASH mission are the following: daily temporal sampling, observe water bodies larger than 100 m x 100 m and rivers as narrow as 50 m, with an accuracy on water elevation ~10 cm, and should provide products in near-real time and over the long term (10 years) in open access (open science and FAIR principles).

Combining "high temporal frequency/low spatial frequency" measurements from the SMASH mission with "high spatial frequency/low temporal frequency" measurements from swath altimetry missions (current SWOT or futur Sentinel-3 Next Generation Topography missions) would cover unprecedented time and space scales and should open new fields of research.

How to cite: Biancamaria, S., Calmant, S., Frappart, F., Garambois, P.-A., Gosset, M., Grippa, M., Kouraev, A., Malaterre, P.-O., Munier, S., Papa, F., Yesou, H., Amiot, T., Cheymol, C., and Le Gac, S.: SMASH: a constellation of small altimetry satellites to monitor daily inland surface waters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16780, https://doi.org/10.5194/egusphere-egu24-16780, 2024.

EGU24-16879 | ECS | Posters virtual | HS6.5

Advancing Inland Water Body Mapping with Self-Supervised Machine Learning 

Ankit Sharma, Mukund Narayanan, and Idhayachandhiran Ilampooranan

Traditional methods of mapping inland water bodies involve labor-intensive and manual data labeling, limiting their scalability to a larger extent. This study introduces a novel approach: self-supervised machine learning (SSML) for mapping inland water bodies. SSML is a training method where a model learns from data without the need for explicit human-labeled annotations. Using this technique, the study mapped inland water bodies in Pudukkottai, India, using LANDSAT-8 imagery from 2021. The training data for SSML were derived from two spectral indices: the Normalized Difference Vegetation Index and the Modified Normalized Difference Water Index. These indices were used to establish a threshold for automatically generating pseudo labels for two categories: water and non-water. This pseudo-labeled dataset was then utilized to train various machine learning models, including random forest, support vector machine, classification and regression tree, and gradient boosting. The accuracy of the final classified map was assessed using a spatial agreement test, which measures the degree of agreement of the classified map in relation to a reference dataset. The spatial agreement test used the Joint Research Commission (JRC) water map of 2021 as the reference dataset. The final inland water body map, derived from the SSML approach, demonstrated a high spatial agreement of 91% with the JRC water map. Among the SSML models, the random forest model outperformed others due to its ensemble nature. Compared to traditionally supervised classifiers (trained with 137 water points and 74 non-water points), the SSML models exhibited superior performance with a spatial agreement of 91%, significantly higher than the 67% achieved by the supervised model. This study is the first to demonstrate the application of SSML for mapping inland water bodies, offering an efficient and cost-effective alternative to traditional manual labeling. This approach holds significant potential for advancing remote sensing applications, particularly in regions where obtaining ground truth labeling is costly or impractical.

How to cite: Sharma, A., Narayanan, M., and Ilampooranan, I.: Advancing Inland Water Body Mapping with Self-Supervised Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16879, https://doi.org/10.5194/egusphere-egu24-16879, 2024.

EGU24-17133 | ECS | Orals | HS6.5

Global 1D river bathymetry estimation from remotely sensed observations 

Isadora Rezende de Oliveira Silva, Pierre-Olivier Malaterre, Christophe Fatras, Hind Oubanas, Igor Gejadze, and Santiago Peña-Luque

Flooding has major economic, social, and environmental implications. Its modeling provides insights into potential risks and contributes to the protection of lives, natural resources, and infrastructure. In flood hazard assessment, the topography representation is a key factor as it dictates the water extent resulting from the simulations. In particular, for small and medium flood scenarios, it is imperative to have good knowledge of the modeled in-channel water height, especially for the river's bank full discharge. As these constitute the majority of flood events, the risk assessment is severely impacted by the quality of their estimates. However, the determination of the water profile can be a challenging task in data-sparse areas, as the bathymetry of the river channels is not well described in open-access digital elevation models (DEMs). Using the global coverage of remote sensing derived water levels and extents, this study builds towards a global estimation of river bathymetry. 
The methodology to achieve this can be divided into two parts, the correction of the river topography that can be directly observed by the sensors, above a minimum water level (the dry bathymetry), and the estimate of the part under the minimum observed water line (wet bathymetry). For the improvement of the dry bathymetry, the contours from water masks derived by optical sensors are projected in DEMs and a smooth profile is built from upstream to downstream. The wet bathymetry is calculated using hydraulic simulation and inverse problem methodologies. It requires as inputs the corrected dry bathymetry, observed water surface elevation and slope, and a prior discharge. The algorithm computes the flow using an integrated version of a modified Manning–Strickler’s equation and probability from beta distribution. It computes the roughness and the bottom depth of the section assuming a rectangular shape. 
Preliminary results are promising; a good agreement with in-situ discharge was achieved for the Po River (NSE > 0.8). It shows the potential and importance of accurate estimates of the river bathymetry for future flood monitoring and forecast.

How to cite: Rezende de Oliveira Silva, I., Malaterre, P.-O., Fatras, C., Oubanas, H., Gejadze, I., and Peña-Luque, S.: Global 1D river bathymetry estimation from remotely sensed observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17133, https://doi.org/10.5194/egusphere-egu24-17133, 2024.

EGU24-17653 | Orals | HS6.5

Merits of Data Assimilation on Improving Flood Forecasting - A case study of Ohio Cannelton-Newburgh 

Sophie Ricci, Thanh Huy Nguyen, Andrea Piacentini, Raquel Rodriguez-Suquet, Santiago Pena-Luque, Quentin Bonassies, Christophe Fatras, Brian Astifan, Raymond Davis, Michael Durand, and Stephen Coss

Flooding is represented with a 2D hydrodynamic model over a reach of the Ohio river between Cannelton and Newburgh locks and dams. The geometry of the river and floodplain was provided by the National Oceanic and Atmospheric Administration (NOAA), based on U.S. Army Corps of Engineers (USACE) survey channel data merged with United States Geological Survey (USGS) LiDAR in the overbank regions. The description of hydraulic structures from USACE and in-situ water depth measurements from USGS stations were also used. Working from the 1D HEC-RAS model from Ohio University that covers a much larger area, the friction for our 2D local model was set uniformly over the floodplain. These values were further calibrated to 45 m1/3s-1 over the river bed and 17 m1/3s-1 with in-situ water depth measurements from USGS stations at Cannelton, Owensboro, and Newburgh over high flows periods in 2022 and 2023. 

The performance of the model was first assessed for the significant flooding event in February 2018, with RMSEs of the order of a few tens of centimeters. Remote-sensing (RS) products provided by satellite missions such as Sentinel-1 SAR, Sentinel-2 optical and Landsat-8 optical imagery undoubtedly offer opportunities to improve our ability to monitor and forecast flooding. For this study, the performance of the TELEMAC-2D (www.opentelemac.org) Ohio model was improved with the joint assimilation of in-situ and remote-sensing data within an EnKF framework that accommodates 2D RS-derived observations alongside with in-situ water level time-series. The RS-derived flood extent maps are expressed in terms of wet surface ratios (WSR) in selected subdomains of the floodplain. The assimilation of in-situ data reduces the RMSE to tenths of a centimeter. Ongoing work on the assimilation of WSR aims at improving the dynamic of the floodplain.  This 2D Ohio model will serve as a demonstrative test case for the FloodDAM-DT (https://www.spaceclimateobservatory.org/flooddam-dt) prototype dedicated to flood detection, mapping, prediction and risk assessment.

How to cite: Ricci, S., Nguyen, T. H., Piacentini, A., Rodriguez-Suquet, R., Pena-Luque, S., Bonassies, Q., Fatras, C., Astifan, B., Davis, R., Durand, M., and Coss, S.: Merits of Data Assimilation on Improving Flood Forecasting - A case study of Ohio Cannelton-Newburgh, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17653, https://doi.org/10.5194/egusphere-egu24-17653, 2024.

EGU24-18194 | ECS | Posters on site | HS6.5

TITRE: ARARAS (Algorithm for Radar Altimetry Retracking on speculAr waveformS), application over the Mana river for long-term multimission Time Series 

Malik Boussaroque, Fernando Niño, Adrien Paris, and Stéphane Calmant

In the context of climate change, it is imperative to have a global understanding of water resources and their use. Long-term water level time series play an essential role in analyzing long-term trends, detecting inter-annual variations, understanding seasonal cycles and estimating long-term hydrological changes. Unfortunately, long time series from in situ stations are seldom available at the global scale, and particularly in remote areas such as tropical forests. Altimetry is emerging as an effective alternative.

We have developed an innovative processing method to optimize the use of historical altimetry missions in low-resolution mode (LRM) and generate extended time series. This retracker uses a physical model to search for sinc-squared patterns in echoes. Adapted to the specific features of each altimeter, it enables the processing of clipped waveforms, a common phenomenon for narrow rivers. This is particularly relevant for Poseidon altimeters, where conventional retracking methods, such as Offset Center of Gravity (OCOG), struggle to produce accurate results with such clipped echoes.

Applying this retracker, we generated time series of water levels along the Mana River in French Guiana, using data from the Jason family missions. These results illustrate the influence exerted on the water cycle by the construction of a run-of-river hydroelectric power plant near Saut Maman Valentin.

 

Keywords – Altimetry, Jason, Topex/Poseidon, Low Resolution Mode Altimetry, Inland Water Altimetry, River

How to cite: Boussaroque, M., Niño, F., Paris, A., and Calmant, S.: TITRE: ARARAS (Algorithm for Radar Altimetry Retracking on speculAr waveformS), application over the Mana river for long-term multimission Time Series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18194, https://doi.org/10.5194/egusphere-egu24-18194, 2024.

EGU24-19761 | ECS | Orals | HS6.5 | Highlight

Establishment of Virtual Station based on Multi-mission Satellites for Near-daily River Discharge Observation 

Debi Prasad Sahoo, Paolo Filippucci, Silvia Barbetta, Sylvain Biancamaria, Alice Andral, Laetitia Gal, and Angelica Tarpanelli

The implementation of action plans for sustainable water resources management requires daily river discharge time series at gauging stations, which are already decreasing in number worldwide. Although the development of remote sensing-based methods for river discharge estimation has proven its effectiveness worldwide, the temporal frequency especially at the daily scale for river discharge estimation is the most important research question to be explored. In this context, the study proposed a methodological framework to establish a virtual station (VS) where the information retrieved from the multi-mission satellites was merged using the non-parametric copula function for river discharge estimation. Here, in the first step, both passive (C/M) and active (altimeter) remote sensing signals can be integrated by deriving the joint probability distribution using the copula functions of the Archimedean family. Subsequently, the Frank copula was evaluated as the best-fit copula function as measured by the goodness-of-fit-test and subsequently selected for establishing the VS by merging the information. The proposed framework was tested on more than 10 rivers around the world. Here, MODIS from Aqua and Terra, Landsat series, and MSI from Sentinel-2 images were used for the C/M approach, whereas SARAL AltiKa, Sentinel-3 A and B, and Cryosat-2 mission altimeters were considered for water level retrieval. The established VSs along the river can be able to derive long near daily discharge time series while evaluating against the in situ discharge with reasonable accuracy measured by Nash-Sutcliffe efficiency, Root Mean Square Error, and Kling-Gupta efficiency. Conclusively, the establishment of this kind of VSs along the river can be able to derive missing discharge data records and long near-daily discharge time series along any world river which is one of the key variables for hydro climatological studies.  

Keywords: Remote Sensing, Virtual Station, Copula, Satellite merging, River Discharge, Altimeters

How to cite: Sahoo, D. P., Filippucci, P., Barbetta, S., Biancamaria, S., Andral, A., Gal, L., and Tarpanelli, A.: Establishment of Virtual Station based on Multi-mission Satellites for Near-daily River Discharge Observation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19761, https://doi.org/10.5194/egusphere-egu24-19761, 2024.

EGU24-20523 | Orals | HS6.5 | Highlight

Coupled hydrological-hydrodynamic and data assimilation of the entire river network of the Maroni basin using SWOT river products and other EO missions 

Kevin Larnier, Pierre-André Garambois, Charlotte Emery, Laetitia Gal, and Adrien Paris

The SWOT mission (NASA, CNES, UK-SA, CSA) launched in December 2022 provides observations of surface of inland water bodies at unprecedented resolution and accuracy. Here we focus on the Level 2 river products (heights and widths at 200m scale) and we assess their usability in creating coupled hydrological-hydrodynamic simulations of large scale basin where in-situ data are sparse. First we use an automated toolchain that generates (i) the mesh and processed input data for the hydrological models SMASH [1] or MGB [2], (ii) the coupling points between the hydrological and the hydrodynamic models, (iii) the mesh for the hydrodynamic 1D model (DassFlow-1D [3]) using either SWOT Level2 river observations of water heights and widths or other EO missions (ICESat-2, Copernicus Sentinels).

Then we conduct experiments of data-assimilation of conventionnal altimetry missions (ICESat-2, Sentinel 3), in-situ level heights and SWOT Level 2 river heights in order to correct the unobserved quantities (channel bathymetry and friction coefficient) and the inflow discharges using advanced techniques taking into account correlated effects of control variables and simulated water surface properties. The accuracy obtained using this method is assessed by comparing with the sparse existing in-situ data and in terms of physical consistency of simulated flow signatures with some EO data selected for validation.

This methodology and the inference capabilities are illustrated on the Maroni basin (French Guyana) which is the first application of variational data assimilation over a multi-branch river network at basin scale. A large parameter vector composed of spatially distributed friction coefficient and channel bathymetry plus inflow/lateral hydrographs are successfully estimated at various spatio-temporal resolution given data cocktails of varying spatio-temporal densities and informative content.

 

[1] SMASH (Spatially distributed Modelling and ASsimilation for Hydrology) -

https://smash.recover.inrae.fr/

[2] https://www.ufrgs.br/lsh/mgb/what-is-mgb-iph/

[3] https://mathhydronum.insa-toulouse.fr/codes_presentation/pres_dassflow/

How to cite: Larnier, K., Garambois, P.-A., Emery, C., Gal, L., and Paris, A.: Coupled hydrological-hydrodynamic and data assimilation of the entire river network of the Maroni basin using SWOT river products and other EO missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20523, https://doi.org/10.5194/egusphere-egu24-20523, 2024.

EGU24-308 | Posters on site | NH6.4

InSAR closure errors: temporal signatures and impact on deformation time series estimation 

Simon Zwieback and Rowan Biessel

Closure errors quantify the inconsistency of seemingly redundant interferograms. Systematic closure errors, associated with e.g. changes in soil moisture or vegetation, can bias estimated InSAR time series. Previous work has shown that the bias can be reduced by including interferograms spanning long temporal baselines. However, it is not clear how the bias reduction depends on the temporal signatures of the closure errors and in what circumstances including long-term interferograms improves or deteriorates the InSAR phase history and ultimately deformation estimates.

To identify how the temporal signatures relate to InSAR time series estimation, we introduce a mathematical framework that quantifies temporal closure signatures as a function of time and time scale. Technically speaking, we construct two complementary bases of the annihilator of the vector space of all temporally consistent phases, with each basis element extracting the closure error corresponding to the element's time and time scale. Applying this framework to Sentinel-1 observations, we find contrasting short-term, seasonal, and multi-annual closure signatures across land cover types. The inclusion of long-term interferograms is associated with characteristic changes in seasonal amplitudes and long-term trends in the InSAR phase history estimates. 

To determine when including long-term interferograms improves InSAR time series estimation, we formulate simple interferometric scattering models for seasonally variable soil moisture and vegetation conditions and sub-resolution deformation as is common in ice-rich permafrost. We find that including long-term interferograms improves the InSAR time series in simulation scenarios dominated by soil moisture wetting and dry down cycles. Conversely, including long-term interferograms can have a deleterious impact on InSAR time series estimates in scenarios with seasonal vegetation and sub-resolution deformation.

We conclude with simple diagnostics on how temporal closure signatures and expert knowledge can inform InSAR processing to maximize deformation time series quality for a range of geohazards, including lowland permafrost deformation, landslides, and sinkholes.

How to cite: Zwieback, S. and Biessel, R.: InSAR closure errors: temporal signatures and impact on deformation time series estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-308, https://doi.org/10.5194/egusphere-egu24-308, 2024.

EGU24-1129 | ECS | Posters on site | NH6.4

Exploring Sentinel-1 for Coastal subsidence monitoring along India’s Gujarat shore using MT-InSAR Technique 

Sona Sharma and Chandrakanta Ojha

India’s long 7500 km coastline covers vast habitats of rich biodiversity and occupants of about 26% of the country’s population in the coastal zone. By 2060, about 60 million of India’s coastal population will be exposed to a low-elevation coastal zone (LECZ) due to global mean sea level rise (GMSL) and its associated hazards (Neumann et al., 2015). However, the low-lying coastal zones are vulnerable to increasing sea levels and coastal subsidence, which threaten the region's socio-economic development (Shirzaei et al., 2021). The erosion assessment report depicts that 60% of the Gujarat shore covering 1600 km of extensive coastline in western India is undergoing erosion. This study investigates and analyzes the combined influence of coastal subsidence and SLR along the south of Gujarat shoreline. In that context, we explored the descending track (path 34) of C-band Sentinel-1 satellite data (92 SAR imageries) in interferometric wide swath mode (IW2 and IW3) of the European Space Agency (ESA) covering the study area from March 2020 to June 2023. The data sets were processed in an open-source GMTSAR software following an advanced Small BAseline Subset (SBAS) based Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technique (Berardino et al., 2002). The results exhibit a deformation rate of  >5 mm/year in various parts of Gujarat's Surat, Bhavnagar, and Bharuch districts. Kododara region in Surat district shows a maximum deformation of >15 mm/year, Navamadhiya in Bhavnagar district is showing subsidence of >20 mm/year, and Chanchvel village in Bharuch is also showing subsidence of >15 mm/year. However, the precipitation data shows a total deviation of -3 % and -5 % in the monthly average compared to normal rainfall observed in Bharuch and Surat districts, respectively, from January 2000 to November 2023 (WRIS, India). Rapid urbanization, dependency on groundwater for basic needs and industrialization, and the impact of increasing sea levels could influence the coastal deformation and inundation hazard risk over the long shorelines and those coastal cities, which needs to be investigated in detail.

References

  • Berardino, P., G. Fornaro, R. Lanari, and E. Sansosti. 2002. "A New Algorithm for Surface Deformation Monitoring Based on Small Baseline Differential SAR Interferograms." IEEE Transactions on Geoscience and Remote Sensing 40 (11): 2375–83. https://doi.org/10.1109/TGRS.2002.803792.
  • Neumann, B., et al. (2015). "Future coastal population growth and exposure to sea-level rise and coastal flooding-a global assessment." PloS one 10(3): e0118571.
  • Shirzaei, M., et al. (2021). "Measuring, modelling and projecting coastal land subsidence." Nature Reviews Earth, Environment 2(1): 40-58.

How to cite: Sharma, S. and Ojha, C.: Exploring Sentinel-1 for Coastal subsidence monitoring along India’s Gujarat shore using MT-InSAR Technique, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1129, https://doi.org/10.5194/egusphere-egu24-1129, 2024.

EGU24-2150 | Orals | NH6.4 | Highlight

Interferometric Digital Elevation Model Generation Using ICEYE Data 

Melanie Rankl, Valentyn Tolpekin, Qiaoping Zhang, and Michael Wollersheim

High resolution, digital representation of surface topography and surface features is key to understanding global changes of terrain due to natural phenomena but also due to manmade changes. Digital Elevation Models (DEMs) can be retrieved from various methods such as SAR Interferometry (InSAR), Photogrammetry or Lidar systems using satellite or aerial data . 

SAR data has the unique advantage that both amplitude and phase are recorded by the SAR antenna. The phase information, which determines the distance from the sensor to a target, is essential for interferometric DEM generation. In comparison to e.g. radargrammetric methods, more accurate DEM results can be derived. Hence, spaceborne SAR interferometry has developed as a key method to derive digital elevation models. The first near global dataset has been presented by the Shuttle Radar Topography Mission in 2000 and since then has been complemented by ESA’s global Copernicus DEM derived from the bistatic TanDEM-X mission . However, other currently commercially available spaceborne SAR systems are not suitable for interferometric DEM generation due to constraints arising from both  normal and temporal baselines between image acquisitions. 

ICEYE has launched 31 satellites up to date (as of December 2023) and operates the largest spaceborne SAR constellation currently available. The fleet of satellites allows for tasking of pursuit monostatic image pairs where both satellites fly in an identical satellite orbit with a short temporal separation. Both satellites individually transmit and receive their own radar pulse. Suitable imaging geometries , i.e., long enough normal baselines and short enough temporal baselines, allow for InSAR derived DEM generation. Pursuit monostatic image pairs with short temporal baselines are hardly affected by atmospheric delay, similarly to bistatic formations, however, as both satellites operate as individual systems, image acquisition and processing is simpler than for bistatic formation flying.

In this study we present 1) results from interferometric DEM generation using high resolution ICEYE SAR data and 2) a quality assessment of the derived pursuit monostatic DEMs. Resulting DEMs have been derived for different study sites using pursuit monostatic image pairs with short temporal baselines acquired in Strip or Spot imaging modes. The suitability of various baseline settings has been tested and limiting baselines determined. A vertical accuracy assessment has been performed against external datasets such as airborne LiDAR derived DEMs or NASA’s ICESat-2 ATL08 Terrain points  (https://nsidc.org/data/atl08/versions/6).

The results show high spatial detail of surface topography with a DEM resolution finer than 3 m for Spot and 5 m for Strip imaging modes. The vertical accuracy has proven to be better than 3 m RMSE in open and relatively flat areas (slopes less than 10 degrees) when compared to external datasets. Yet, interferometric processing has shown to be challenging when affected by temporal decorrelation between image acquisitions, vegetation coverage or steep terrain. 

How to cite: Rankl, M., Tolpekin, V., Zhang, Q., and Wollersheim, M.: Interferometric Digital Elevation Model Generation Using ICEYE Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2150, https://doi.org/10.5194/egusphere-egu24-2150, 2024.

EGU24-2863 | Orals | NH6.4 | Highlight

An InSAR-GNSS Velocity Field for Iran 

John Elliott, Andrew Watson, Milan Lazecky, Yasser Maghsoudi, Jack McGrath, and Jessica Payne

We present average ground-surface velocities and strain rates for the 1.7 million square km area of Iran, from the joint inversion of InSAR-derived displacements and GNSS data. We generate interferograms from seven years of Sentinel-1 radar acquisitions, correct for tropospheric noise using the GACOS system, estimate average velocities using LiCSBAS time-series analysis, tie this into a Eurasia-fixed reference frame, and perform a decomposition to estimate East and Vertical velocities at 500 m spacing. Our InSAR-GNSS velocity fields reveal predominantly diffuse crustal deformation, with localised interseismic strain accumulation along the North Tabriz, Main Kopet Dagh, Main Recent, Sharoud, and Doruneh faults. We observe signals associated with recent groundwater subsidence, co- and postseismic deformation, active salt diaprism, and sediment motion. We derive high-resolution strain rate estimates on a country- and fault-scale, and discuss the difficulties of mapping diffuse strain rates in areas with abundant non-tectonic and anthropogenic signals.

How to cite: Elliott, J., Watson, A., Lazecky, M., Maghsoudi, Y., McGrath, J., and Payne, J.: An InSAR-GNSS Velocity Field for Iran, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2863, https://doi.org/10.5194/egusphere-egu24-2863, 2024.

Climate change has led to increasingly serious flooding in many regions around the world, including Vietnam. The Kon and Ky Lo river basins in Binh Dinh and Phu Yen provinces, Vietnam, have experienced increasingly serious flooding in recent years, which has caused damage to property and people living in the area. This basin lacks the availability of historical flood maps; flood information is mainly in the form of statistical information on people's damage situations.

Floods in Vietnam often appear in the last months of the year, combined with storms and heavy rain, leading to more serious flooding. During such periods of heavy rain, measuring and monitoring the flood situation is very difficult. Currently, with the development of the European Space Agency's (ESA) radar Sentinel-1 remote sensing technology, flood monitoring has become more convenient compared to the use of optical remote sensing technology. Moreover, combined with Google Engine (GE) technology, mapping historical floods became easier.

In this study, we applied the Sentinel-1 satellite images on the GE platform combined with SRTM digital elevation model data to conduct flood mapping for the large floods of 2016 and 2021 along the Kon and Ky Lo rivers. These historical flood maps will be used on the basis of flood risk assessment and as a basis for assessing the accuracy of future hydrological-hydraulic flood simulation models. In addition, the study also delineated areas that are frequently flooded to help local authorities more easily manage disasters and have better response solutions in the future, in order to limit the risk of damage to people in areas affected by flooding.

How to cite: Van Phan, T., Anh Ngo, T., and Willems, P.: Historical Flood Mapping Combining Radar Remote Sensing and Google Engine Technologies for The Kon and Ky Lo River Basin, South Center Coast Vietnam, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4056, https://doi.org/10.5194/egusphere-egu24-4056, 2024.

Synthetic Aperture Radar (SAR) images are becoming increasingly important in a variety of remote sensing applications, leading to new missions with higher resolution and coverage, ultimately resulting in an ever-increasing volume of data. This burden on SAR data storage and transmission has established a serious interest in developing compression methods that can obtain higher compression ratios, while keeping complex SAR image quality to an acceptable level. In computer vision, neural network-based RGB image compression has exceeded traditional methods such as JPEG, JPEG2000 or BPG. The Mean-Scale Hyperprior network [1] is an auto-encoder based architecture exploiting the probabilistic structure in the latents to improve compression performance. Auto-encoders are architectures particularly suited for the inherent rate-distortion trade-off of data compression. They also offer an intuitive solution to the on-board image compression problem, as demonstrate for the Φ-Sat-2 mission [2].

In this work, we explore efficient SAR image compression, in this regard, we adapt the Mean-Scale Hyperprior architecture to SAR data. We use Sentinel-1 IW mode VV polarization SLC images to build a dataset of diverse scenes: urban areas, forests, mountains and water bodies in dry as well as snow/ice conditions. The central idea being to create an open-source and general dataset of SAR images, in order to compare the performance of the studied architecture with traditional codecs and baseline models, such as the work in [3]. We will experiment with latent sizes, patch size as well as different SAR data representations for the network.

References  
[1] D. Minnen, J. Ball ́e, and G. D. Toderici, “Joint Autoregressive and Hierarchical Priors for Learned Image Compression,” in Advances in Neural Information Processing Systems, vol. 31, Curran Associates, Inc., 2018.  
[2] G. Guerrisi, F. D. Frate, and G. Schiavon, “Artificial Intelligence Based On-Board Image Compression for the Φ-Sat-2 Mission,” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 16, pp. 8063–8075, 2023.  
[3] C. Fu, B. Du, and L. Zhang, “SAR Image Compression Based on Multi-Resblock and Global Context,” IEEE Geoscience and Remote Sensing Letters, vol. 20, pp. 1–5, 2023.

How to cite: Léonard, C.: Synthetic Aperture Radar SLC data compression using Mean-Scale Hyperprior architecture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5021, https://doi.org/10.5194/egusphere-egu24-5021, 2024.

On July 1, 2022, a doublet of earthquakes, with a magnitude of Mw6.0 and a Mw5.7 aftershock between them, occurred within a two-hour period in the southeastern part of the Zagros Mountains near the Persian Gulf in Iran. This doublet earthquake event provides a unique opportunity to study the geometric properties of geological faults and the frictional attributes of rocks in the southeastern of the Zagros Mountains, particularly in the vicinity of the Hormoz salt layer. Here, we acquired co-seismic and post-seismic InSAR ascending and descending observations to simultaneously determine fault geometry and slip distribution models for the doublet earthquakes based on Bayesian inference. The inversion results reveal that the doublet earthquakes occurred on two distinct faults with similar strike (101.93°, 93.7°) but notable differences in dip (56.2°, 31.3°), and the slip distribution of the mainshock 2 is shallower and more westward compared to the mainshock 1. Moreover, the reliability of the fault geometry and slip distribution was confirmed through detailed discussions on the distributions of post-seismic kinematic afterslip, the relocated aftershocks beyond five months after the mainshocks, and the changes in positive Coulomb stress triggered by co-seismic events. Additionally, our post-seismic deformation modeling elucidated that post-seismic deformation is predominantly driven by stress induced by co-seismic event, accompanied by the release of both afterslip and aftershocks. Afterslip is distributed both up- and down-dip of the coseismic region on the two faults, with the maximum afterslip concentrated in the shallow portions, reaching approximately 0.45 m. By comparing the temporal evolution characteristics of stress-driven afterslip distributions with those of kinematic afterslip, we observed significant inconsistencies in the frictional properties within the southeastern Zagros Mountains, particularly between the Hormoz salt layer and its upper region. Specifically, above the Hormoz salt layer, the friction is stronger, and the relaxation time of afterslip is shorter. Finally, we also discussed the triggering potential of the mainshock 1 and the Mw5.7 aftershocks on mainshock 2, and from the perspective of Coulomb stress transfer, we found that mainshock 1 and Mw5.7 aftershocks may have triggering effects on mainshock 2.

 

How to cite: zhao, X., dahm, T., and xu, C.: Fault Slip Distribution and Inhomogeneous Frictional Properties in the Southeastern Zagros Mountains of the 2022 Iran doublet Earthquakes Inferred from Bayesian Inference and InSAR observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6273, https://doi.org/10.5194/egusphere-egu24-6273, 2024.

EGU24-6699 | Orals | NH6.4 | Highlight

InSAR Phase Bias Correction Processor: Recent Developments 

Yasser Maghsoudi, Andrew Hooper, Tim Wright, Milan Lazecky, and Muriel Pinheiro

The Sentinel-1 satellite's short revisit time is advantageous for maintaining better coherence in interferograms over short intervals, resulting in more accurate assessments of rapid deformation. However, the use of shorter-interval, multilooked interferograms may introduce a bias, known as a "fading signal," in the interferometric phase, leading to unreliable velocity estimates.

In the first part of our research, funded by the European Space Agency (ESA), we explore characterizing phase bias, focusing on one of its primary indicators—the closure phase. We explore loop closure time-series across various datasets, considering different look directions (ascending and descending), evaluating the impact of filtering and multilooking on closure phases, investigating loop closures across diverse landcovers, and examining the polarization dependency of closure phases. Additionally, we establish correlations between the time series of phase closures and various environmental proxies.

In the second stage, we present our progress on developing a universally applicable phase bias correction. We previously developed an empirical mitigation strategy that corrects the phase bias based on the assumption that the change in strength of the bias in interferograms of different length has a constant ratio (Maghsoudi et al. 2022). In this presentation, we investigate the applicability of the proposed method across various scenarios and compare it with alternative approaches.

Correcting for the phase bias is particularly important for InSAR processing systems, such as the COMET LiCSAR system (Lazecký et al. 2020), which aims to study geohazards over large areas.

 

References

Maghsoudi, Y., Hooper, A.J., Wright, T.J., Lazecky, M., & Ansari, H. (2022). Characterizing and correcting phase biases in short-term, multilooked interferograms. Remote Sensing of Environment, 275, 113022

Lazecký, M., Spaans, K., González, P.J., Maghsoudi, Y., Morishita, Y., Albino, F., Elliott, J., Greenall, N., Hatton, E., Hooper, A., Juncu, D., McDougall, A., Walters, R.J., Watson, C.S., Weiss, J.R., & Wright, T.J. (2020). LiCSAR: An Automatic InSAR Tool for Measuring and Monitoring Tectonic and Volcanic Activity. Remote Sensing, 12

 

How to cite: Maghsoudi, Y., Hooper, A., Wright, T., Lazecky, M., and Pinheiro, M.: InSAR Phase Bias Correction Processor: Recent Developments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6699, https://doi.org/10.5194/egusphere-egu24-6699, 2024.

Interferometric synthetic aperture radar (InSAR) decorrelation that creates great challenges to phase unwrapping has been a critical issue for mapping large earthquake deformation. Some studies have proposed a “remove-and-return model” solution to tackle this problem, but it has not been fully validated yet, and therefore has rarely been applied to real earthquake scenarios. In this study, we use the 2023 Mw 7.8 and 7.6 earthquake doublet in Turkey and Syria as a case example to develop an iterative modeling method for InSAR-based coseismic mapping. We first derive surface deformation fields using Sentinel-1 offset tracking and Sentinel-2 optical image correlation, and invert them for an initial coseismic slip model, based on which we simulate InSAR coseismic phase measurements. We then remove the simulated phase from the actual Sentinel-1 phase and conduct unwrapping. The simulated phase is added back to the unwrapped phase to produce the final phase measurements. Comparing to the commonly-used unwrapping method, our proposed approach can significantly improve coherence and reduce phase gradients, enabling accurate InSAR measurements. Combining InSAR, offset tracking and optical image correlation, we implement a joint inversion to obtain an optimal coseismic slip model. Our model shows that slip on the Çardak Fault is concentrated on a ~100 km segment; to both ends, slip suddenly diminished. On the contrary, rupture on the East Anatolian Fault Zone propagated much longer as its geometry is fairly smooth. The iterative coseismic modeling method is proven efficient and can be easily applied to other continental earthquakes.

How to cite: Chen, J. and Zhou, Y.: Coseismic slip distribution of the 2023 earthquake doublet in Turkey and Syria from joint inversion of Sentinel-1 and Sentinel-2 data: An iterative modeling method for mapping large earthquake deformation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7005, https://doi.org/10.5194/egusphere-egu24-7005, 2024.

Concise and informative target feature descriptions are curial for accurate land cover classification of polarimetric synthetic aperture radar (PolSAR) images. Effective feature selection strategy significantly impacts both classification model design and final accuracy.

Ideally, target features should capture diverse polarization scattering characteristics and physical properties, the foundation for PolSAR image interpretation, and also require all these features satisfy the independent and identically distributed hypothesis, as directly using all these features can lead to sparse sample data in the multi-dimensional space, especially with limited samples, hindering model training.

To this end, existing research attempt to utilize multiple features manually or analyze specific scattering characteristics for classification scenarios. However, these studies mainly focus on manual feature selection or using traditional random forest importance-based feature selection strategy, adaptive feature selection tailored to individual situations remains less explored.

In order to address this gap, we propose a novel target-oriented feature selection framework leveraging multi-scale two-dimensional structural similarity measure (MTSSIM). This framework adaptively selects informative features from an initial PolSAR image feature set, encompassing commonly used polarization scattering features, spatial neighbor context features, and morphological features. The core principle lies in designing an efficient algorithm that selects features maximizing intra-class and minimizing inter-class structural similarity.

For enhanced robustness and practicality, the proposed framework incorporates two key modules: 1) Two-dimensional structural similarity representation: This module quantifies the structural similarity between two samples, and 2) Multi-scale feature structural similarity measurement: This module utilizes local feature images at multiple spatial neighborhood scales to assess the intra-class and inter-class structural similarity of each feature relative to the target category.

To validate the effectiveness of the proposed framework, we conducted classification experiments on two real PolSAR image datasets using identical classification methods and parameters for three feature sets: the manually chosen features that commonly used in PolSAR image classification task (Manual feature set), the random forest importance-based features (RF feature set), and MTSSIM-recommended features (MTSSIM feature set).

Experimental results demonstrate that the proposed MTSSIM feature set consistently outperforms traditional approaches, demonstrating significant improvements in classification accuracy. These benefits include: 1) Reduced misclassification rates: MTSSIM significantly decreases misclassified pixels, leading to more accurate and reliable land cover maps; 2) Enhanced homogeneity: MTSSIM-derived feature sets yield spatially consistent and less noisy classification results, facilitating easier interpretation and analysis. 3) Improved performance in small-sample scenarios: MTSSIM effectively utilizes limited data, enabling accurate classification even with limited training samples.

In conclusion, the MTSSIM framework offers a powerful and practical solution for optimizing feature selection in PolSAR image classification. By addressing feature redundancy and leveraging structural information, MTSSIM improves classification accuracy, making it a valuable tool for enhancing remote sensing applications in land cover mapping, environmental monitoring, and various other domains.

How to cite: Nie, W., Yang, J., Zhang, C., and Qi, Y.: A Target-oriented Feature Selection Framework for Polarimetric SAR Image Classification Based on Multi-scale Two-dimensional Structural Similarity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8174, https://doi.org/10.5194/egusphere-egu24-8174, 2024.

EGU24-8695 | ECS | Posters on site | NH6.4

Fault irregularity of recent large strike slip earthquakes revealed by satellite imagery 

Chen Yu, Bingquan Han, Chuang Song, Zhenhong Li, and Yosuke Aoki

The geometric complexity of strike-slip faults, such as stepovers, bends and branches, is a pivotal indicator of segmented fault rupture. These features act as barriers to the activity of strike-slip faults, leading to uneven stress distribution along the fault zone, thereby influencing the initiation, propagation, and termination of earthquake ruptures.

The East Anatolian Fault (EAF) is a significant sinistral strike-slip fault, connecting with the North Anatolian Fault (NAF) to the north and the Dead Sea Fault (DSF) to the south. Located in southeastern Turkey, it plays a crucial role in accommodating the relative motion between the northward-moving Arabian Plate and the westward-moving Anatolian Block. Despite the relative quietude of the EAF since the beginning of the 20th century, historical seismic activity indicates its potential to generate devastating earthquakes, as evidenced by a series of relatively large earthquakes occurring between 1822 and 1905. On January 24, 2020, the Pütürge segment at the northeastern end of the EAF experienced the Mw6.8 Elaziğ earthquake (2020 event). Subsequently, on February 6, 2023, the southwestern segment of the EAF witnessed the Turkey–Syria Earthquake Sequence (2023 event). The consecutive occurrence of these two seismic events has provided an opportunity to investigate the tectonic activity characteristics and seismic triggering relationships of the EAF.

In this study, we take the two events that occurred on the EAF in 2020 and 2023 as the time nodes and take the EAF as the research object. Utilizing InSAR technology, the research investigated the deformation during seismic cycles (interseismic, coseismic, and postseismic) based on Sentinel-1 radar data. We computed interseismic deformation velocities from 2015 to 2020 and displacement time series from February 2020 to February 2023, as well as from February 2023 to September 2023. Subsequently, this study extensively considered the geometric complexity of faults and established an elastic triangular dislocation model. Based on this model, we derived the interseismic fault slip distribution for the EAF from 2015 to 2020, as well as coseismic and postseismic fault slip distributions for the 2020 and 2023 events. The results indicate that: 1) The slip rate along the EAF exhibits a decreasing trend from the northeastern end (5 mm/yr) to the southwestern end (2 mm/yr); 2) The interseismic slip deficits of the EAF correlate well with the coseismic fault slip distribution of the 2020 and 2023 events; 3) The postseismic fault slip following the 2020 and 2023 events primarily occurs at coseismic slip deficit areas.

How to cite: Yu, C., Han, B., Song, C., Li, Z., and Aoki, Y.: Fault irregularity of recent large strike slip earthquakes revealed by satellite imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8695, https://doi.org/10.5194/egusphere-egu24-8695, 2024.

EGU24-10065 | ECS | Orals | NH6.4

Postseismic deformation of the 2021 Mw 7.4 Maduo earthquake, eastern Tibet: implications for fault friction 

Yuan Gao, Qi Ou, Kali Allison, Tim Wright, Jin Fang, and Manon Carpenter

Postseismic deformation occurs due to stress relaxation following large earthquakes and has been widely captured by space geodetic observations. For some earthquakes, afterslip has been inferred to take place in the fault barriers surrounding the areas of coseismic asperities. This phenomenon can be explained by the velocity-strengthening frictional behavior prevalent in the barriers and velocity-weakening frictional properties in the asperities. However, for some events, afterslip seems to exhibit spatial overlap with the coseimsic slip. Here we used postseismic deformation of the Maduo earthquake to investigate the afterslip pattern and fault friction properties. 

The 2021 Mw 7.4 Maduo earthquake ruptured ~150 km of the Jiangcuo fault, a previously-poorly known NWW-trending, sinistral strike-slip fault which lies within the Bayan Har block of the eastern Tibetan Plateau. Here we use ~2 years (between May 2021 and August 2023) of Sentinel-1 interferometric synthetic aperture radar (InSAR) data to study the postseismic deformation following the Maduo earthquake. Additionally, we use ~7 years (between October 2014 and May 2021) of InSAR data to obtain the interseismic velocity. We remove the interseismic components from postseismic data through transforming both datasets into Eurasian reference frame based on GPS velocities. Both descending and ascending postseismic data reveal notable localized postseismic deformation in the middle segment of the seismogenic fault, and diffused deformation in the far field. 

We apply a kinematic inversion to model the afterslip based on the cumulative postseismic displacement. We find that significant afterslip occurred on shallow (0–5 km) fault segments that also slipped coseismically . We then conduct dynamic earthquake cycle simulations incorporating vertical variations of frictional properties to understand the conditions where this can occur. We show that velocity-strengthening properties in the shallow region can rupture seismically and creep during postseismic period. Our dynamic model partially explains the overlapping slip of co- and postseismic slip of the Maduo earthquake. However, this model requires shallow interseismic creep, which is either not observed, or is obscured by noise in our data. 

Reference 

Lazecký, M., Spaans, K., González, P.J., et al. (2020). LiCSAR: An Automatic InSAR Tool for Measuring and Monitoring Tectonic and Volcanic Activity. Remote Sens., 12, 2430. 

Morishita, Y., Lazecky, M., Wright, T.J., et al. (2020). LiCSBAS: An Open-Source InSAR Time Series Analysis Package Integrated with the LiCSAR Automated Sentinel-1 InSAR Processor. Remote Sens., 12, 424.  

Ou, Q., Daout, S., Weiss, J. R., et al. (2022). Large-scale interseismic strain mapping of the NE Tibetan Plateau from Sentinel-1 interferometry. J. Geophys. Res. Solid Earth, 127, e2022JB024176. 

Amey, R. M. J., Hooper, A., Walters, R. J. (2018). A Bayesian method for incorporating self‐similarity into earthquake slip inversions. J. Geophys. Res. Solid Earth, 123, 6052–6071. 

Allison, K. L., Dunham, E. M. (2018). Earthquake cycle simulations with rate-and-state friction and power-law viscoelasticity. Tectonophysics, 733, 232– 256.

How to cite: Gao, Y., Ou, Q., Allison, K., Wright, T., Fang, J., and Carpenter, M.: Postseismic deformation of the 2021 Mw 7.4 Maduo earthquake, eastern Tibet: implications for fault friction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10065, https://doi.org/10.5194/egusphere-egu24-10065, 2024.

EGU24-10416 | Orals | NH6.4 | Highlight

Tracking three-dimensional growth of magma-filled fractures by joint inversion of high-resolution geodetic and seismicity data 

Pablo J. Gonzalez, Yu Jiang, Maria Charco, Eugenio Sansoti, and Diego Reale

Magma-filled fracture propagation is the primary magma transport mechanism near the surface at ocean island basaltic volcanoes. Therefore, developing and implementing efficient workflows to track magmatic intrusions in the elastic-part of the oceanic lithosphere (<10-20 km depth, usually corresponding to shallower than the Moho) is of great importance for volcano hazard assessment. Here, we implement a kinematic three-dimensional magma-filled fracture geomechanical model capable of jointly inverting observations of surface deformation and seismic data. We combine the strengths of both datasets: first by constraining the magma-filled fracture geometry using satellite radar interferometry and/or GPS, and second by kinematic magma migration using seismic data. The final output is a refined spatio-temporal evolution model of the magma propagation process, parametrized by fracture opening and shear stress changes. We apply this method to simulated cases and also to gain insights on the magma migration process occurring during real volcanic unrests in Canary Islands volcanoes. Our work aims to contribute knowledge that will help hazard assessment and volcanic risk reduction.

Acknowledgements: We thank Spanish Agencia Estatal de Investigación projects PID2019-104571RA-I00 (COMPACT) funded by MCIN/AEI/10.13039/501100011033, and Project PID2022-139159NB-I00 (Volca-Motion) funded by MCIN/AEI/10.13039/501100011033 and “FEDER Una manera de hacer Europa”. Research activities of the CSIC staff during the 2021 La Palma eruption were funded by CSIC -CSIC-PIE project PIE20223PAL008. This work was also partially supported by project PTDC/CTA-GEO/2083/2021 GEMMA, funded by Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES. We thank INTA La Palma Announcement of Opportunity and Hisdesat for providing timely PAZ satellite radar data and also the Italian Space Agency (ASI) for providing Cosmo-SkyMed data within the CEOS Volcano Demonstrator. 

How to cite: Gonzalez, P. J., Jiang, Y., Charco, M., Sansoti, E., and Reale, D.: Tracking three-dimensional growth of magma-filled fractures by joint inversion of high-resolution geodetic and seismicity data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10416, https://doi.org/10.5194/egusphere-egu24-10416, 2024.

With an operating area of 4,380 ha producing approximately 40 million tons per year  of lignite , the Hambach mine is the largest open pit mine in Germany. To extract the lignite in open-cast mining, the groundwater level needs to be lowered down to below the deepest point of the open pit mine. This leads  to major changes in the aquifer conditions which may result in land subsidence that can affect the safety of built-up structures with significant socio-economic impacts.

In this study we perform a regional analysis of ground surface deformation in the Hambach mining area using interferometric observations from the Copernicus Sentinel-1 satellite. We present results from our validation investigation,  where results provided by German and European Ground Motion Services are compared with those obtained from our local surveys using high-resolution TerraSAR-X SAR data. We further investigate the correlation between InSAR measurement points, in-situ observations, and damages to infrastructures, and show evidence for several cases of fault reactivation and damages to infrastructures within the area undergoing mining related subsidence. Fault reactivation has resulted in the formation of fault scarps (offsets > 1 m), with detrimental impacts on existing structures. Finally, we integrate between results from InSAR measurement points with open source geospatial data to create maps that support hazard, exposure and risk assessment related to subsidence at regional scale in the Hambach region.

 

How to cite: Motagh, M., Haghshenas Haghighi, M., Piter, A., and Vassileva, M.: Mining-induced subsidence and fault reactivation due to open pit lignite mining in the Hambach region, North Rhine-Westphalia, Germany: Insights from Sentinel-1 based European Ground Motion Service (EGMS) and field surveys , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11866, https://doi.org/10.5194/egusphere-egu24-11866, 2024.

The fault structures of the 12 November 2017 Sarpol-e Zahab earthquake in Iran, as inferred from geodetic and geological data, exhibit significant distinctions, indicating intricate interactions between the crystalline basement and sedimentary cover. To further investigate this phenomenon, we employ interferometric synthetic aperture radar (InSAR) observations and 2-D Finite Element Models (FEM) with various fault geometries, such as planar, ramp-flat, and splay faults, to analyze mechanical (stress-driven) afterslip models for postseismic deformation. The kinematic coseismic slip model support a planar fault dipping at 15º, which is in good agreement with previously published results. Based on the coseismic model, we vary the fault geometries and explore the relationship between afterslip fault geometries and fault friction properties. We show that the planar frictional afterslip model fails to completely explain the long-wavelength postseismic deformation field. Instead, a ramp-flat fault model explains well the majority of the postseismic observations, with a maximum afterslip of approximately 1.0 m. The friction variations after fault strengthening are estimated to be about 0.001 and 0.0002 for the up-dip and down-dip portions, respectively. Expanding on the optimal ramp-flat fault model, we introduce an additional splay fault, which further improves the model fit, although the splay fault's frictional slip was limited to less than 0.2 m, and there is a trade-off between the splay fault geometries and their friction variations. Considering our results in conjunction with relocated aftershocks and geological cross-sections, we propose that a splay fault may have been weakly triggered after the mainshock, indicating more complex fault interactions than a simple decoupling layer between the basement and sedimentary cover.

How to cite: Guo, Z., Motagh, M., and Baes, M.: Structural Complexity Revealed by Frictional Afterslip Models and InSAR Observations Following the 2017 Mw 7.3 Sarpol- e Zahab (Iran-Iraq) Earthquake: Insights from Numerical Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11944, https://doi.org/10.5194/egusphere-egu24-11944, 2024.

SAR and GNSS are two dominant techniques to measure the Earth's deformation. They have different characteristics in that InSAR has superior spatial resolution, and GNSS has superior temporal resolution. Also, GNSS has better precision than InSAR, and InSAR measurements have significant spatial correlation mainly because of the atmospheric disturbance. Therefore, if available, InSAR measurements will be more precise when combined with GNSS measurements. This study investigates the temporal evolution of land subsidence and slow slip transients in the Boso Peninsula, Japan, from InSAR and GNSS measurements. First, we generated interferograms of available ALOS-2 images. The generated interferograms are corrected to be consistent with GNSS measurements every 20 km or so. The correction assumes that the spatial variation of the noise in InSAR measurements is represented as a polynomial function, the degree of which is constrained adaptively. Then, the corrected interferograms are fed to the time-series analysis. The time series generated allows us to separate continuing subsidence of up to 20 mm/yr with a shorter wavelength and slow slip transients with a longer wavelength. 

How to cite: Aoki, Y.: Imaging land subsidence and slow slip transients by combining InSAR and GNSS , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14246, https://doi.org/10.5194/egusphere-egu24-14246, 2024.

EGU24-14887 | ECS | Posters on site | NH6.4

Ionospheric and Tropospheric Impact for InSAR Time Series Analysis in the Central Andes: A Case Study from Northwestern Argentina 

Sofia Viotto, Bodo Bookhagen, Guillermo Toyos, and Sandra Torrusio

The ionosphere, located 50 km above the Earth's surface is characterized by ionization processes that can significantly impact electromagnetic signals within the microwave wavelength range. The magnitude of the impact depends on the density of free electrons, which have daily and seasonal oscillations but are also tied to the 11-year solar activity cycles. Radar signals are delayed after interacting with free electrons and ions, and the magnitude of such delay is inversely proportional to the radar frequency. Thus, sensors operating in the longer wavelength L-band are more affected than those operating in the C-band. However, even C-band interferograms can be significantly affected if the region is close to the geomagnetic equator.

The Central Andes in Northwestern Argentina, being in proximity to the geomagnetic equator, offer an excellent setting to study the impact of the ionosphere on interferograms. Its low vegetation cover results in highly coherent interferograms, and predominantly dry conditions at high elevations lead to small tropospheric disturbances.

We employ the split spectrum technique extended to time series analysis to identify interferograms that are impacted by ionospheric contributions. Subsequently, we apply statistical methods to those time series to recognize acquisitions more likely to be contaminated by the ionosphere.  The magnitude of ionospheric contribution is compared to tropospheric delay. We demonstrate the impact of the high-solar activity on interferograms by correlating our time series of ionospheric delay to sunspot activity and total electron content maps. The analysis of Sentinel 1 C-band data from both ascending and descending tracks reveals a more significant contribution in ascending passes in response to the daily cycle of free electron density. These findings prove the relevance of the ionosphere as source of disturbance in interferograms from Sentinel C-band, particularly for studies at the regional scale.

How to cite: Viotto, S., Bookhagen, B., Toyos, G., and Torrusio, S.: Ionospheric and Tropospheric Impact for InSAR Time Series Analysis in the Central Andes: A Case Study from Northwestern Argentina, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14887, https://doi.org/10.5194/egusphere-egu24-14887, 2024.

EGU24-15424 | Orals | NH6.4 | Highlight

From meters of subsidence to millimeters of slow slip: monitoring deformation and associated uncertainties from InSAR 

Romain Jolivet, Manon Dalaison, Bryan Raimbault, Béatrice Pinel-Puysségur, Bertrand Rouet-Leduc, and Paul Dérand

Over the past two decades, InSAR evolved from the occasional processing of single interferograms over arid terrains to monitoring continuous time series of SAR acquisitions at the continental scale. Challenges, including atmospheric phase screen mitigation, automatic careful SAR image co-registration, ionospheric phase screen corrections, or discontinuous acquisition planning, were met through various technical and methodological advances by many research groups globally. The resulting methodologies now allow us to image a vast range of processes, from sudden large earthquakes to continuous subsidence involving metric to millimetric displacements. In addition to the ability to process datasets over continental scales, we can now measure natural signals of a few millimeters over distances lower than a kilometer.

In recent years, we proposed technical solutions to issues that were seriously impeding our ability to measure small, millimeter-scale displacements over natural terrains. First, I will discuss the early development of tropospheric corrections using numerical weather models and highlight some of the most recent tools and methods stemming from there. Second, I will illustrate our approach to tackle the issue of continuously incoming SAR acquisitions, which we addressed by developing a data assimilation-based method involving a Kalman filter. This tool allows the rapid update of pre-existing time series of deformation as new SAR images are available while carefully propagating forward some of the uncertainties associated with time series analysis. Third, I will show how we handle the automatic denoising of InSAR time series using a fully convolutional neural network, allowing us to detect sub-millimeter tectonic fault slip with no prior knowledge of the faults. Fourth, I will present some recent developments about the effect of fading signals and time-dependent coherence evolution over temperate regions, depending on land covers.

All these developments allowed us to image surface deformation processes, including several continuously creeping faults globally, transient tectonic slow slip events, intriguing post-seismic deformation signals, and strong subsidence patterns.

How to cite: Jolivet, R., Dalaison, M., Raimbault, B., Pinel-Puysségur, B., Rouet-Leduc, B., and Dérand, P.: From meters of subsidence to millimeters of slow slip: monitoring deformation and associated uncertainties from InSAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15424, https://doi.org/10.5194/egusphere-egu24-15424, 2024.

Distributed scatter interferometric synthetic aperture radar (DS-InSAR) technology has been extensively employed for surface deformation monitoring, with phase optimization as a pivotal step. Currently, phase optimization techniques utilize the statistical intensity distribution of pixels to select homogeneous pixels. Pixels with low temporal intensity stability are excluded from consideration, avoiding their involvement in the phase optimization. However, it is noteworthy that distinguishing between homogeneous and heterogeneous pixels becomes more challenging in mountainous areas. Additionally, pixels with low stability are affected not only by thermal or environmental noise but also by the influence of local incidence angles, causing ground deformation beyond the Maximum Detectable Deformation Gradient (MDDG) of InSAR, resulting in geometric decorrelation. These pixels are often erroneously classified as noise and discarded. Nevertheless, these pixels contain rich and crucial deformation information, indicating disaster risks. Therefore, optimizing the phase of these pixels is essential.

This paper introduces a method for interferometric phase optimization of distributed scatterers in mountainous regions, considering geometric decorrelation (GD-DS). Using real InSAR differential interferometric phases as a basis, the study simulates interferometric phase datasets with rich spatiotemporal features, ensuring the correlation between simulated GD-DS phases and MDDG. Subsequently, K-means clustering is applied to segment the MDDG map, with resulting connected regions representing homogeneous pixels with similar local incidence angles. Convolutional denoising training is performed on homogeneous pixels using the generative adversarial network model (Pix2pix), and the trained model is then applied to real interferometric phase images. The proposed strategy and method are successfully applied to interferometric phase optimization in the Jishishan region of Gansu Province, China. Compared to traditional methods, the new approach demonstrates superior phase optimization performance, particularly in the case of GD-DS. Discussion and analysis of the spatial correlation between GD-DS and MDDG in the real experimental area confirm that introducing MDDG as a reference to optimize GD-DS is a key factor in improving phase optimization. Furthermore, the computational time of the new method is significantly reduced compared to traditional methods.

How to cite: Guo, A. and Sun, Q.: Interferometric Phase Optimization Method for Mountainous Regions Considering Geometric Decorrelation of Distributed Scatterers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15538, https://doi.org/10.5194/egusphere-egu24-15538, 2024.

EGU24-17181 | ECS | Posters on site | NH6.4

Assessing the Impact of Burst Overlap Interferogram of Sentinel-1 TOPS on Near-Fault 3D Displacement Modelling: A Case Study of the 6th February 2023 Mw7.8 and Mw7.5 Kahramanmaraş Earthquakes, Türkiye. 

Muhammet Nergizci, Qi Ou, Milan Lazecky, C. Scott Watson, Jin Fang, Andrew Hooper, and Tim J. Wright

On February 6, 2023, two devastating earthquakes, Mw7.8 and Mw7.5, struck the area surrounding Kahramanmaraş, Türkiye, resulting in extensive and complex surface deformations. The Mw7.8 event created a surface rupture over 310 km along the East Anatolian Fault, while the Mw7.5 earthquake resulted in a 150 km rupture along the Çardak-Sürgü Fault segment. Here we use Sentinel-1 Burst Overlap Interferometry (BOI) to improve 3D displacement mapping and in particular investigate near-fault deformation.In response to the earthquakes, previous studies have utilized various datasets, either separately or in combination. These include near and far-field seismic observations, continuous and campaign GNSS datasets, offset tracking from SAR satellites like Sentinel-1 and ALOS-2 and optical satellites such as Sentinel-2, and InSAR. These diverse data sources are vital for calculating the 3D displacement field. However, extracting information from standard interferograms, critical due to their high spatial resolution, is often challenging because of large phase gradients, particularly in the near field of fault ruptures.This issue frequently complicates the accurate determination of fault displacement and 3D decomposition in impacted areas. For Sentinel-1, with a range resolution of approximately 5 m, displacement in the range direction is usually determined with acceptable accuracy using range offset tracking. However, the azimuth resolution of about 20 m makes azimuth offset tracking less precise. This lower resolution frequently results in less reliable displacement constraints in the azimuth direction. To overcome this limitation, we produced Burst Overlap Interferograms (BOI) from four different tracks of Sentinel-1. These BOI results enabled more precise measurements of along-track displacement near the fault lines, which are theoretically proportional to the number of looks and the decorrelation noise.A key aspect of our methodology was the unwrapping process of the BOI, guided by azimuth offset tracking to handle large displacements exceeding ~1.5 m in the azimuth direction. For the 3D displacement field, we referenced all offset and BOI data to zero points away from the co-seismic ruptures and removed planar ramps. Uncertainties were empirically estimated as the mean absolute deviation in 4x4 pixel windows for offset data and 2x2 pixel windows for BOI. These uncertainties were then used to weight 3D motion inversion and decomposed displacements, providing a more reliable depiction of the earthquake impact. Our approach, combining east and north motion fields, allowed us to extract precise surface slip distributions and highlight surface ruptures through detailed strain analysis. In this study, we explored how to extract more accurate deformation in the north-south direction and reveal detailed deformation near faults by applying 3D decomposition with jointly inverted all datasets in together. We will discuss the implications of our findings for our understanding of earthquakes, and in particular for understanding distributed off-fault deformation that occurs near the fault rupture.

How to cite: Nergizci, M., Ou, Q., Lazecky, M., Watson, C. S., Fang, J., Hooper, A., and Wright, T. J.: Assessing the Impact of Burst Overlap Interferogram of Sentinel-1 TOPS on Near-Fault 3D Displacement Modelling: A Case Study of the 6th February 2023 Mw7.8 and Mw7.5 Kahramanmaraş Earthquakes, Türkiye., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17181, https://doi.org/10.5194/egusphere-egu24-17181, 2024.

EGU24-18703 | ECS | Posters on site | NH6.4

Service for automated processing and correction of DInSAR deformation maps 

Dominik Teodorczyk, Maya Ilieva, and Patryk Balak

One of the enduring facets within contemporary monitoring systems resides in the automation of data processing. This methodology ensures expeditious access to the most current and objectively derived results. Several systems for terrain monitoring have been realised in the last few years, with the leading role of the European Ground Motion Service (EGMS), part of the Copernicus program. Still most of these systems rely on the usage of the advanced Interferometric Synthetic Aperture Radar (InSAR) techniques which are not capable of exploring more dynamic and complex terrain change patterns as those related to underground mining works in Central Europe. A extensive study within the frames of the Polish realisation of the European Plate Observing System (EPOS) project, comprising long term monitoring between the years of 2016 and 2023 revealed the necessity of usage of the classical DIfferential InSAR (DInSAR) for more detailed study of the processes happening in the area of the Upper Silesian Coal Basin (USCB) in Poland. Within the project EPOS-PL+ we have developed an automated system for DInSAR processing of SAR data from Sentinel-1 satellite. The system also includes modules for processing of third party mission X-band data. 
This processing approach excels in managing significant deformations with reduced coherence, unlike methods relying on stable scatterers. The automated framework encompasses data retrieval, Line of Sight (LOS) deformation computation, trend elimination for atmospheric correction, and assessment of interferogram quality. The final step involves decomposing the LOS deformation into vertical and east-west components.
Upon initiation of the application, the user delineates parameters such as the region of interest by a shapefile, the period of study, and ascending and descending orbits. Subsequently, ingress into the Alaska Satellite Facility service repository, and data is procured for subsequent processing utilising the DInSAR method facilitated by the snappy library. This library enables script-based manipulation of the SNAP program using the Python language.
The subsequent phase involves detrending the data. Raw 1D deformation maps exhibit discernible trends, primarily attributable to atmospheric variations between successive acquisitions. To overcome this problem, a plane is fitted to the deformation data, and the estimated values are differentially subtracted from the original dataset. This estimation is implemented through two distinct methodologies. The more intricate approach include sthe identification of stable points based on nine coherence maps correlating with the deformation values, followed by the fitting of a plane. The simpler approach involves the fitting of a plane to the entire set of deformation data.
The quality check stage involves examining the dataset's pixels for coherence levels exceeding a set threshold (e.g., 0.2). Pixels failing coherence criteria are excluded, and linear interpolation is applied only to selected pixels. This approach minimizes phase unwrapping errors' propagation and effectively removes atmospheric effects in the final analysis. In instances of significant data gaps, the ensemble of adjacent images used for interpolation is expanded to reduce the impact of individual map errors. The enhanced DInSAR data are then projected into 2D components, namely the vertical and east-west (horizontal) dimensions.

How to cite: Teodorczyk, D., Ilieva, M., and Balak, P.: Service for automated processing and correction of DInSAR deformation maps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18703, https://doi.org/10.5194/egusphere-egu24-18703, 2024.

EGU24-18815 | ECS | Posters virtual | NH6.4

Assessment of Incoming Sediment with Flash Flood: A Case Study of the 2020 Flood in the Northeastern Part of Bangladesh using SAR Interferometry 

Kh. M. Anik Rahaman, Faizur Rahman Himel, Miftahul Zannat, Shampa Shampa, and Sonia Binte Murshed

Bangladesh, a riverine South Asian country with many Haor areas, is extremely vulnerable to flash flooding, which occurs primarily between the months of April and May (pre-monsoon). A Haor is a type of wetland ecosystem found in Bangladesh's northeastern region that is essentially a tectonically active shallow depression with a bowl or saucer shape where water flows from upstream basins. Floods and the resulting sediment have both positive and negative impacts on the affected Haor region, with broader implications for agricultural, water, fisheries, and other resource planning and management. However, till now there is no measurement or literature on the amount of sediment deposition caused by these flash flooding events. Threfore, the primary goal of this study was to determine the amount of incoming sediments associated with flash floods in Haor regions using remote sensing and to validate it in the field. The amount of incoming sediment associated with the flash flood that occurred in June 2020 was estimated for a selected region in the affected northeastern part of Bangladesh for this purpose. Using Sentinel-1 satellite images, interferometric techniques were used to create Digital Elevation Models (DEMs) of the pre and post-flood period of 2020. A total of eight Sentinel 1 A and Sentinel 1 B images covering the study area were collected from 22 July to 26 July 2019 to assess pre flood land conditions and from 21 July to 27 July 2020 to assess post flood land conditions. Our study revealed that the overall sediment deposition was found to be about 2.8 cm on average for the selected entire region. Furthermore, it has been observed that relatively less flashy areas gained sediment increase of about 7.3 cm on average within this one year interval, and relatively upstream areas with steep gradient gained 4.5 cm increase. Any anthropogenic interventions in this area should take into account the natural sediment distribution pattern and avoid impeding sediment spreading pathways, as sediment acts as a natural countermeasure to tectonic-subsidence of this area.

How to cite: Rahaman, Kh. M. A., Himel, F. R., Zannat, M., Shampa, S., and Murshed, S. B.: Assessment of Incoming Sediment with Flash Flood: A Case Study of the 2020 Flood in the Northeastern Part of Bangladesh using SAR Interferometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18815, https://doi.org/10.5194/egusphere-egu24-18815, 2024.

EGU24-19176 | Orals | NH6.4

EPOS-PL+ project - infrastructure for long-term InSAR monitoring of mining induced deformations in Southern Poland 

Maya Ilieva, Kamila Pawłuszek-Filipiak, Dominik Teodorczyk, Natalia Wielgocka, Patryk Balak, Krzysztof Stasch, Mateusz Karpina, Paweł Bogusławski, and Przemysław Tymków

The second Polish realisation of the European Plate Observing System (EPOS), namely EPOS-PL+ project (2020-2023), comprised a dedicated task for development of an Infrastructure Centre for Satellite Data Research (CIBDS in Polish). The main task of the centre was to create a methodology for monitoring, modelling and prediction of the terrain deformations related with the extensive underground mining works taking place in the region of the Upper Silesian Coal Basin (USCB). This area is characterised with extremely dynamic surface changes consisting of small-scale deformation bowls (200-300m in radius) within short range from each other. The subsidence could reach between 0.6 up to 1.6 m per year, depending on the depth of the coal seams under explorations. The deposits are in depth between 400 and 1200 m, and are exploited in a multi-layer manner. The dynamics of the appearance of the subsidence patterns over time is closely related to the long-wall mining method used in this mining area. 

Within the CIBDS several modules for processing of Synthetic Aperture Radar (SAR) data have been developed. An automatic system for Differential Interferometric SAR (DInSAR) processing and postprocessing was developed based on the Alaska data facility repository of Sentinel-1 data, and the European Space Agency (ESA) tools SNAP and snappy. A new methodology was introduced for integration of lower quality but more detailed DInSAR terrain deformation maps with products created by the usage of Persistent scatterers (PSInSAR) technique, which have higher accuracy but lower coverage. The integrated deformation maps are validated with the results of campaign in-situ GNSS/levelling measurements.

A new methodology for modelling of the subsidence and 1-month prediction of the expected deformations have been designed on the basis of the Knothe-Budryk theory. FOr the purpose, artificial intelligence (AI) capabilities have been applied using the deformation maps generated by the DInSAR processing and external information about the rhythm and range of the mining works.

The newly developed system for terrain changes monitoring target the gaps that left in the commonly used platforms like European Ground Motion Service (EGMS) that cannot cover very extensive deformations and to support and upgrade the mining management and supervision. 

How to cite: Ilieva, M., Pawłuszek-Filipiak, K., Teodorczyk, D., Wielgocka, N., Balak, P., Stasch, K., Karpina, M., Bogusławski, P., and Tymków, P.: EPOS-PL+ project - infrastructure for long-term InSAR monitoring of mining induced deformations in Southern Poland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19176, https://doi.org/10.5194/egusphere-egu24-19176, 2024.

Earthquakes with large magnitude induce massive post-seismic deformation lasting for months to years. Modeling the post-seismic deformation gains invaluable insights to understanding the physics of fault zone and the lower crustal rheology. However, the observed post-seismic deformation is originated from sources with variant mechanisms, including afterslip, poroelastic rebound, and viscoelastic relaxation, which occur at different spatial and temporal scales. Decomposing and interpreting deformation resulted from deep afterslip and viscoelastic relaxation especially remains challenging. The 2021 Mw 7.4 Maduo earthquake, which occurred on a secondary fault ~80 km south of the previously identified major block boundaries, east Kunlun fault, has generated clear afterslip signal reported by several studies. However, the interpretations regarding viscoelastic models remained debated in two aspects: 1) How can we quantify the contribution from deep afterslip and viscoelastic relaxation during the early post-seismic phase? 2) Does the lower crust exhibit the same rheological property across the ruptured Jiangcuo fault and east Kunlun fault? In this context, acquiring high-resolution and extensive coverage of post-seismic deformation data becomes critically important.

Here, we derived a high-resolution post-seismic deofrmation extending over ~1000 kilometers for 2.5 years, using 6 tracks of Sentinel-1 SAR images and 32 continuous GNSS stations. Far-field deformations showed a smooth decay, ranging from 2 cm/year at the fault to 200 kilometers away on both sides of the fault rupture, extending over 500 kilometers along the strike. Notably, no discontinuity was observed along the east Kunlun fault, indicating that the boundary fault kept silent following the Maduo earthquake. We constrained the spatial pattern of post-seismic deformation with high-resolution InSAR observations, offering significant constrains into the depth and viscoelastic structure. Additionally, we utilized GPS time-series data to accurately ascertain the viscosity magnitude. By extracting the contribution of shallow afterslip from the initial observations, we explored the trade-off between deep afterslip and viscoelastic relaxation.

We firstly used a three-layer Maxwell and Burgers model for far-field deformation (100-200 km) and then incorporated deep afterslip and viscoelastic relaxation for mid-field observations (10-100 km). Our best-fit results reveal that deep afterslip dominates in mid-field areas, while viscoelastic relaxation significantly impacts far-field deformation. The optimal model presents an upper crust depth of 20 km, with transient and steady-state viscosities in the lower crust at 10^18 and 4*10^19 Pa·s, respectively, and a steady-state upper mantle viscosity of 10^20 Pa·s. As with the preliminary results, the model did not require a strong variant viscosity to explain the data. Disregarding deep afterslip could lead to overestimating viscosity by 1-1.5 orders of magnitude. Our results imply that the ruptured secondary fault can continue to ~20 km and kept slip after earthquakes. However, for the deeper lower crust and upper mantle, the material keeps the same strength across the northeastern boundary of Bayankara block.

How to cite: Li, Z., Xiong, W., Zhao, Z., and Wang, T.: Deep fault structure and lower crust rheology beneath the northeastern Bayankara block revealed by post-seismic deformation following the 2021 Mw 7.4 Maduo Earthquake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20075, https://doi.org/10.5194/egusphere-egu24-20075, 2024.

EGU24-1801 | Posters on site | TS3.1

Strong (Mw>6.0) earthquakes along the KTFZ: implications for recurrence pattern and seismic coupling 

Eleftheria Papadimitriou and Vassilios Karakostas

The Kefalonia Transform Fault Zone (KTFZ) in central Ionian Islands (Kefalonia and Lefkada Islands), Greece, exhibits the fastest rates of relative plate motion in the Mediterranean. It constitutes an active boundary and comprises five manor fault segments with a total length of nearly 120km, and are characterized by fast long–term rates of displacements of about ~25mm/yr for Kefalonia segments and ~15 mm/yr for Lefkada segments. Strike slip faulting with moment magnitudes Mw up to 7.0 characterizes the largest earthquakes, whereas the five almost along strike faults have been the sites of numerous earthquakes of moment magnitude, Mw, 5.0–7.0 during the past 50 years. The KTFZ in its entire length is much more active at the Mw>6.0 level than a comparable length of either the North Aegean Trough or Corinth rift, which are the most fastly deforming areas in the area of Greece. Alteration of active periods comprising multiple earthquakes with much longer quiescent periods is the mode of strong earthquake occurrence, with prevailing clustering over the period when historical information is available. The fast rate of plate motion, maximum size of earthquakes and relatively short repeat times make these fault segments suitable to seek for recurrence behavior that approaches quasi–periodic and its potential implications to the cyclic mode of seismogenesis. Recurrence of M6.0 earthquakes along nearly the same fault segment is attempted after evaluating the location of the historical events, based on all available macroseismic descriptions. These estimations are then compared with computed simulated catalogs.

The computed depths of earthquakes along the KTFZ are accurate enough to ascertain centroid depths as indicators of the downdip width of seismic faulting. With aftershock relocation we constrained the seismogenic layer in Kefalonia and Lefkada segments equal to 14 km (between depths of 3 and 17 km) and 10 km (between depths of 5 and 15 km) respectively, corresponding to downdip widths of 19 and 12 km, respectively. We compared these constraints with the calculated downdip width from a segment’s length along strike, moment release and relative plate motion ‘assuming’ full seismic coupling. The good correlation between the two support the high degree of coupling along the KTFZ.

Acknowledgments: Funded by the European Union. Views and opions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or European Commission – Euratom. Neither the European Union nor the granting authority can be held responsible for them.

 

 

How to cite: Papadimitriou, E. and Karakostas, V.: Strong (Mw>6.0) earthquakes along the KTFZ: implications for recurrence pattern and seismic coupling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1801, https://doi.org/10.5194/egusphere-egu24-1801, 2024.

EGU24-2188 | ECS | Posters on site | TS3.1

Bridging geological and geodetic observations for the 1700 Cascadia earthquake with an earthquake cycle model 

Weilun Qin, Rob Govers, Mario D’Acquisto, Natasha Barlow, and Riccardo Riva

Subduction earthquake cycles are known to produce distinctive patterns of crustal motion, providing critical insights into the details of plate interface coupling and rupture behavior. Retrieving these patterns in the Cascadia subduction zone poses a significant challenge, particularly because the 1700 great Cascadia earthquake (Mw>=9.0) occurred more than three centuries ago.

Previous studies of the megathrust earthquake cycle along the Cascadia margin focused on either the geologically constrained coseismic rupture, or on the present-day interseismic coupling patterns based on geodetic observations. There thus is a gap in the comprehensive understanding of the earthquake cycle, particularly in the integration of available geological and geodetic evidence.

Our study aims to bridge this gap and unify the insights preserved in both records. To do so, we develop a three-dimensional viscoelastic earthquake cycle model with realistic slab geometry, crustal thickness, and topography. We simulate the coseismic, postseismic, and interseismic stages of the earthquake cycle by alternately locking and releasing asperities, which are derived from geodetic coupling (Li et al., 2018) and geological rupture (Wang et al., 2013) studies.

Our results show a good match to convergence-parallel interseismic velocities from the geodetic observations of McKenzie and Furlong (2021). Considering the subsidence signal in the geological record, a good fit can be obtained by a combination of coseismic slip and early afterslip. We find that our results are largely determined by the slab geometry, although factors like asperity configurations, downdip limits of the slab-crust interface, and mantle viscosity structure influence the model predictions.

How to cite: Qin, W., Govers, R., D’Acquisto, M., Barlow, N., and Riva, R.: Bridging geological and geodetic observations for the 1700 Cascadia earthquake with an earthquake cycle model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2188, https://doi.org/10.5194/egusphere-egu24-2188, 2024.

The 2021 Maduo MS7.4 earthquake occurred in the Jiangcuo fault with left-lateral strike-slip movement. In order to study the movement and deformation characteristics of the Jiangcuo fault before the Maduo earthquake and further analyze the seismogenesis process of the continental strong earthquake, the large-scale strain rate field distribution in western China, the locking degree and the evolution of slip deficit rate of the Jiangcuo fault, and the rupture mechanism of seismogenic fault are analyzed and discussed in this paper using the GPS velocity field on a long time scale and InSAR dynamic velocity field. The results show that: (1) The strain rate field in EW direction shows that the Maduo earthquake is located at the edge of the EW direction strong compression zone of Bayanhar block. The eastern part of the Maduo earthquake is a compression strain accumulation zone, and the western part is a gradual transition from weak compression to tension strain. The results of the maximum shear strain rate field show that the Maduo earthquake is located at the edge and high gradient zone of the high value area of the maximum shear strain rate field. (2) The inversion results of the locking degree show that deep unlocking occurs in some regions in the east and west of the epicenter of the fault during 2015-2021, gradually transitioned to a completely locked state in the middle of the fault, and the focal point of Maduo earthquake is at the edge of the completely locked region in the transition region. The dynamic results from 2015 to 2017 and 2017 to 2019 were basically stable. The whole fracture plane was basically in a state of strong locking, and only partial unlocking with a depth below 15km existed in local areas. From 2019 to 2021, some faults in the east and west of the epicenter have deep and shallow unlocking phenomena, including the overall unlocking of most areas of the western section and the local deep unlocking of the East section of the ruptured fault, while the rapid unlocking of the two sides of the epicenter may contribute to the occurrence of the main earthquake. This work was supported by Science for earthquake resilience (XH23047A).

How to cite: Zhao, J., Yuan, Z., and Wang, Y.: The movement and deformation of the Jiangcuo fault before the 2021 MS7.4 Maduo earthquake reflected by GPS and InSAR data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2226, https://doi.org/10.5194/egusphere-egu24-2226, 2024.

EGU24-2385 | ECS | Posters on site | TS3.1

Do Faults Localize as They Mature? Insight From 17 Continental Strike-slip Surface Rupturing Earthquakes (Mw > 6.1) Measured by Optical and Radar Pixel Tracking Data. 

Chris Milliner, Jean-Philippe Avouac, Saif Aati, James Dolan, and James Hollingsworth

As faults accumulate displacement, they are thought to mature from disorganized and distributed fracture networks to more simplified throughgoing fault structures with a more localized zone of inelastic strain. Understanding the degree of inelastic strain localization holds importance for seismic hazard, as smoother faults are thought to host faster rupture velocities and have different seismic shaking intensities from ruptures along rougher, less mature faults. However, quantifying this evolutionary process of strain localization along major fault systems has been difficult due to a lack of near-field coseismic measurements. Here we test if such an evolutionary process exists by measuring the near-field surface deformation pattern of 17 large (6.0 < Mw < 7.9) continental strike-slip surface ruptures. To do this we use a range of geodetic imaging techniques including, a new 3D optical pixel tracking method, and pixel tracking of radar amplitude data acquired by satellite and UAVSAR platforms. With these geodetic imaging data we measure the total coseismic offset across the surface rupture and difference them from the displacements recorded by field surveys, which we assume captures the on-fault, discrete component of deformation. This differencing allows us to obtain an average magnitude of off-fault deformation for each surface rupturing event, which we compare to a number of known source parameters to test the notion of progressive fault localization. Our results show that progressively smaller amounts of off-fault strain occur along fault systems with higher cumulative displacements, supporting the notion that faults systems localize as they mature. We also find strong correlations of off-fault deformation with the long-term fault slip-rate and the geometrical complexity of the mapped surface rupture, and a moderate correlation with rupture velocity. However, we find a weak-no correlation of off-fault deformation with the fault initiation age and the moment-scaled radiated energy. We also present comparisons of off-fault strain with other known seismic source parameters.

How to cite: Milliner, C., Avouac, J.-P., Aati, S., Dolan, J., and Hollingsworth, J.: Do Faults Localize as They Mature? Insight From 17 Continental Strike-slip Surface Rupturing Earthquakes (Mw > 6.1) Measured by Optical and Radar Pixel Tracking Data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2385, https://doi.org/10.5194/egusphere-egu24-2385, 2024.

EGU24-2389 | ECS | Orals | TS3.1

Decoding inter-seismic deformation: Insights from viscoelastic modeling 

Hugo Boulze, Luce Fleitout, Emilie Klein, and Christophe Vigny

GPS positioning offers millimetric precision in measuring deformation of the lithosphere during the seismic cycle. In particular, during the post-seismic phase, long-lasting and large-scale deformation are measured. They result from the viscoelastic relaxation in the asthenosphere. Consequently, the post-seismic phase is currently modeled using viscoelastic rheologies (e.g., Maxwell or Burgers viscous models). On the other hand, the inter-seismic phase is mainly modeled using purely elastic models. In particular, coupling models, widely used to quantify the accumulation of deformation on the subduction fault, are therefore used to evaluate earthquake hazard. However, such elastic models fail to explain mid-field deformation without the use of an external hypothesis (e.g., a third plate called sliver).

The study of post-seismic deformation has provided important insights into the rheological properties of the asthenosphere during the post-seismic phase. For example, viscous creep has been found Newtonian since the cumulative post-seismic displacements normalized by the co-seismic offset, as a function of distance to the trench, superimpose very well for earthquakes of different magnitudes [Boulze et al. 2022].

By incorporating these different results and using the backslip theory [Savage 1983], we model the inter-seismic phase using viscoelastic models. We explore the impact on coupling distribution along the Chilean subduction zone, in particular discussing differences with the elastic model in terms of depth and lateral extension. We also examine the impact of viscoelastic models in a region of Chile (Taltal region, 25.2°S) where elastic models currently fail to reproduce deformation in the near-field [Klein et al. 2018]. Finally, we show that a 2-Burgers viscous model is necessary to reproduce deformation in Argentina in 2010, before the Maule earthquake.

How to cite: Boulze, H., Fleitout, L., Klein, E., and Vigny, C.: Decoding inter-seismic deformation: Insights from viscoelastic modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2389, https://doi.org/10.5194/egusphere-egu24-2389, 2024.

We have developed a 3D viscoelastic finite element model to study processes that control the postseismic deformation due to the 2021 M8.2 Chignik, Alaska earthquake. Our model employs a bi-viscous Burgers rheology to represent the viscoelastic relaxation of the upper mantle and the first two years GPS data after Chignik event as constraints.

Initially, we investigated the viscoelastic relaxation mechanism and stress-driven afterslip mechanisms individually. We then attempted to reconcile their contributions by assessing the misfit between observed and simulated displacements. And, it is assumed that the afterslip evolution is governed by rate-strengthening friction. The results show that there exists a substantial misfit between the simulated and the observed value of the optimal model under the viscoelastic relaxation mechanism. Notably, at one observation site in the near-field, the observed displacement exceeds 200 mm, whereas the simulated value only less than 5 mm. Similarly, the optimal solution of simulated value under the afterslip mechanism does not align well with the observed value. Furthermore, we also utilized different frictional properties on updip (0-40 km) and downdip (40-100 km) regions of the coseismic rupture. The preferred misfit in this model is lower than that obtained using the model with a uniform friction parameter, but there is still a discrepancy between the simulated and observed values. These results indicate that neither the afterslip nor viscoelastic relaxation mechanisms alone can fully explain the total postseismic deformation.

Subsequently, we utilized an integrated model to simultaneously extract the contributions from both mechanisms. The combined modeling results indicate that the near-field postseismic displacements are dominated by both mechanisms together. However, in the far-field, deformation is primarily controlled by afterslip, with minimal influence from the viscoelastic relaxation mechanism. The inferred frictional properties on the updip and downdip regions of the coseismic rupture exhibit significant differences, which likely reflect variations in fault zone materials at different depths. And the optimal model supports a viscoelastic rheology for the continent mantle, with a steady-state viscosity is 1×1019Pa•s and the transient viscosity is 1×1018Pa•s. 

How to cite: Dong, P. and Zhao, B.: Afterslip and viscous relaxation on the postseismic deformation following the M8.2 Chignik, Alaska earthquake , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2967, https://doi.org/10.5194/egusphere-egu24-2967, 2024.

EGU24-6640 | ECS | Orals | TS3.1

Unveiling the Activity of a Young Fault: Insights from the 2021 Maduo Earthquake 

Wenqian Yao, Jing Liu_Zeng, Yann Klinger, Guiming Hu, Yanxiu Shao, Xiaoli Liu, Kexin Qin, Zhijun Liu, Zijun Wang, Yunpeng Gao, and Longfei Han

Faults grow through fault lengthening and slip accumulation, which are episodic processes related to the repetition of earthquakes. It is most often recorded in geomorphology. Meanwhile, the activity and seismic hazard of the ‘slow-moving’ faults are often overlooked due to their weak imprints in landforms, especially at their initial formation stage. The 2021 Mw 7.4 Maduo earthquake triggered a ~158-km long surface rupture along the poorly-known and geomorphically subtle Jiangcuo fault, which is one of the distributed faults in the Bayan Har block and splays that merge with the Kunlun Pass fault. The slip rate of the Jiangcuo fault is thus crucial for comprehending how the strain is distributed between the major and subsidy faults in the complete fault system of the Bayan Har block, as well as the broader deformation process at a large scale. In this study, we present three sites where the Jiangcuo fault left-laterally displaces Holocene geomorphic features (e.g., terraces, fans, and channels). Through the detailed interpretations of high-resolution Digital Elevation Models (DEMs), field investigations, and credible Optically Stimulated Luminescence (OSL) dating of displaced geomorphic features, we document an average left-lateral slip rate of 2.1 ± 0.2 mm/yr since ~12 ka of the Jiangcuo fault. Furthermore, we conservatively updated existing slip rates of the large strike-slip faults (East Kunlun fault, Ganzi-Yushu-Xianshuihe fault) bounding the Bayan Har block. Synthesizing the slip rate of the Jiangcuo fault with the updated rates of the bounding faults, our findings suggest that the Jiangcuo fault accommodates ∼10% of the total deformation in the Bayan Har block. This study provides valuable insights into the impact of younger faults on regional deformation processes.

How to cite: Yao, W., Liu_Zeng, J., Klinger, Y., Hu, G., Shao, Y., Liu, X., Qin, K., Liu, Z., Wang, Z., Gao, Y., and Han, L.: Unveiling the Activity of a Young Fault: Insights from the 2021 Maduo Earthquake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6640, https://doi.org/10.5194/egusphere-egu24-6640, 2024.

Strike-slip faults of considerable scale play a pivotal role in accommodating crustal deformation resulting from the Cenozoic India-Eurasia collision. The manner in which strike-slip motion is transferred along faults remains a topic of ongoing debate. In this study, we have meticulously compiled millennial strike-slip rates and GPS-derived strike-slip data along the extensive ~1800 km East Kunlun Fault (EKF). Our objective is to discern the slip distribution pattern and evaluate the mode of strike-slip transfer. The findings reveal a segmented pattern of strike-slip activity, characterized by a consistently high strike-slip rate exceeding 10 mm/yr along the central segments. In contrast, the eastern segment exhibits a reduced slip rate, measuring less than 5 mm/yr, and further diminishes to approximately 1 mm/yr along its eastern fault tip zone. Notably, strike-slip drop events occur within the fault bending zone, or in areas where the fault bifurcates, forming a horsetail structure. To complement our observational insights, numerical modeling has been employed to validate that the fault geometry may serve as a crucial controlling factor in the observed variation of strike-slip rates, Additionally, it influences the local stress situation along the fault, further contributing to the earthquake risk along the fault and the associated hazards impacting the local area.

How to cite: Zhang, Y. and Jiao, L.: Mechanism of Strike-slip Transfer along the East Kunlun Fault in Northern Tibet, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7062, https://doi.org/10.5194/egusphere-egu24-7062, 2024.

EGU24-7436 | ECS | Orals | TS3.1

Strain partitioning and fault kinematics in the Northern Qilian Shan (NE Tibet) determined from Bayesian inference of geodetic data  

Yingfeng Zhang, Sam Wimpenny, Luca Dal Zilio, and Xinjian Shan

Strain partitioning between strike-slip faults within mountain ranges and thrust faults along their margins is a common process that accommodates oblique plate convergence in continental collision zones. In these settings accumulated strain is periodically released by earthquakes on the strain-partitioned fault systems, which threatens the densely populated foreland areas. An extreme earthquake rupture scenario in these settings is that multiple faults rupture simultaneously releasing the built up strain – an example being the 2016 Mw 7.8 Kaikoura earthquake where a cascading rupture occurred on many separate faults with different kinematics. Recent work suggests that such cascading ruptures may occur in fault systems that are coupled in the shallow crust that are being loaded by a deeper, creeping fault.

 

This study focuses on understanding earthquake risks in the northern Qilian strain-partitioned fault system, which is important due to the populated areas nearby. We investigate its 2-D kinematic models using available geodetic measurements under a Bayesian inversion frame. Our results prove that the kinematic models of the northern Qilian strain-partitioned fault system can be well determined, and compatible of the geological measurement and seismicity distribution. In contrast to the frequent thrust earthquakes, any thrust faults are not required to explain the available geodetic data indicating that the short-term geodetic measurements cannot reflect the thrust fault kinematics of the northern Qilian Shan in the geological time-scale. The non-thrust fault involved model also present a highly locked wedge beneath the foreland area, reconciling the supposed historical cascading earthquake ruptures in north Qilian Shan.

How to cite: Zhang, Y., Wimpenny, S., Dal Zilio, L., and Shan, X.: Strain partitioning and fault kinematics in the Northern Qilian Shan (NE Tibet) determined from Bayesian inference of geodetic data , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7436, https://doi.org/10.5194/egusphere-egu24-7436, 2024.

Geometric complexity plays an important role for a fault’s seismotectonic behavior as it affects the initiation, propagation and termination of an earthquake and influences stress-slip relationships, fault-segment size, and the probability of multi-segment rupture. Consequently, geometric fault complexity is studied intensively and increasingly incorporated into computational earthquake rupture simulations. These efforts reveal a problem: While a natural fault’s geometry may be well quantifiable at the surface (i.e., the fault trace), its down-dip buried portion cannot be well constrained. At this point, it is not clear how this epistemic uncertainty affects the propagation of individual ruptures and a fault’s seismotectonic behavior (e.g., large-earthquake recurrence).

We address this issue computationally with a physics-based multi-cycle earthquake rupture simulator (MCQsim), enabling us to investigate various aspects of rupture propagation and earthquake cycle in a controlled environment (e.g., with well constrained fault geometry). We approximate fault geometric complexity as a 2-D random field using the “random midpoint displacement” method which allows us to represent fault roughness (i.e., incorporate its epistemic uncertainty) while keeping the fault surface trace unchanged. 

Using MCQsim, we create 20kyr-long synthetic earthquake catalogs for strike-slip faults that share the same complex fault surface trace but have different sub-surface fault geometries. We analyze the resulting variations in single-event rupture propagation (i.e., the kinematic source model) and long-term seismotectonic behavior. We find that kinematic source models of individual events differ substantially between different realizations of sub-surface geometry. However, the long-term seismotectonic behavior (e.g., large-earthquake recurrence) does not differ as much and is less sensitive to the epistemic uncertainties of sub-surface fault geometry.

How to cite: Zielke, O. and Mai, P. M.: Exploring the effects of sub-surface fault geometry on rupture propagation and long-term fault behavior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7556, https://doi.org/10.5194/egusphere-egu24-7556, 2024.

EGU24-7990 | ECS | Orals | TS3.1

Development of a Bayesian non-planar fault geometry inversion using geodetic seismic cycle deformation data 

Guoguang Wei, Kejie Chen, and Luca Dal Zilio

The geometry of faults regulates the spatial patterns of interseismic, coseismic, and post-seismic surface deformation. Geodetic techniques can measure these deformation patterns during a seismic cycle and are expected to constrain the geometry of  seismogenic faults. However, the conventional linear inversion of geodetic data is unable to simultaneously estimate the fault slip distribution and the fault geometry. In this study, we propose a Bayesian framework that treats fault geometry as a time-invariant parameter. It can individually use coseismic deformation data or simultaneously utilize interseismic, coseismic, and post-seismic deformation data to invert for both fault slip distribution and non-planar fault geometry. Within this framework, geometry evidence informed by geophysical imaging, geological surveys, and microseismicity forms the basis for establishing the prior probability density function, while geodetic observations constitute the likelihood function. Our methodology provides an ensemble of plausible geometry parameters by sampling the posterior probability distributions of the parameters using Markov Chain Monte Carlo simulation. The performance of the developed method is tested and demonstrated through inversions for synthetic oblique-slip faulting models. Results demonstrate that assuming constant rake can significantly bias fault geometry estimates and data weighting. Additionally, considering the variability of slip orientations allows for plausible estimates of non-planar fault geometry with objective data weighting.We applied the method to the 2013 Mw 6.5 Lushan earthquake in Sichuan province, China. The results reveal dominant thrust slips with left-lateral components and a curved fault geometry, with the confidence interval of the dip angles ranging between 20° and 25° and 56° and 58°. Furthermore, the application of this method to the 2015 Gorkha earthquake in Nepal sheds light on the Main Himalayan Thrust, which serves as the interface between the Indian Plate and Eurasia. This may provide new insights into future seismic potential and topographic growth in the Nepal Himalaya.

How to cite: Wei, G., Chen, K., and Dal Zilio, L.: Development of a Bayesian non-planar fault geometry inversion using geodetic seismic cycle deformation data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7990, https://doi.org/10.5194/egusphere-egu24-7990, 2024.

EGU24-8280 | ECS | Orals | TS3.1

Kinematics of the Southeastern Tibetan Plateau from Sentinel-1 InSAR and GNSS: Implications for Seismic Hazard Analysis 

Jin Fang, Tim Wright, Kaj Johnson, Qi Ou, Richard Styron, Tim Craig, John Elliott, and Andy Hooper

Earthquakes release strain energy that has accumulated between seismic events. Measuring strain accumulation rates is critical for understanding earthquake cycle and assessing earthquake potential, with fault slip rates serving as essential inputs for seismic hazard models. However, the Tibetan Plateau has been lacking comprehensive estimates of geologic slip rates on numerous faults. To address this gap, geodetic data have been invoked to derive fault slip (or slip deficit) rates using various methodologies. These include the commonly adopted classic and deformable block modelling approaches (Meade & Loveless, 2009) and the newly developed direct inversion of geodetic strain rates (Johnson et al., 2022), which has the advantage of not requiring blocks to be defined.  A comprehensive comparison of slip rates obtained from these different geodetic methods has been notably absent.

In this study, we focus on the southeastern Tibetan Plateau, utilising Sentinel-1 satellite data from 35 ascending and 32 descending frames spanning the period between 2014 and 2023, along with published GNSS velocities. We constructed high-resolution (1 km) maps of velocity and strain rate fields covering 1.3 million km2. Using these maps, we derived slip rates on newly mapped faults (Styron, 2022) using classic block modelling, “deformable block” modelling, and by the direct inversion of strain rates. Our strain rate fields reveal a partition through focused shear on the Kunlun fault, the Xianshuihe-Xiaojiang fault system, the Longriba fault, the Longmenshan fault possibly influenced by the ongoing postseismic deformation of the 2008 Mw 7.9 Wenchuan earthquake, and the Lijiang-Xiaojinhe fault. On the deforming plateau there is diffuse deformation away from the major faults, with average shear strain and dilatation rates of 14.3 and 13.1 nanostrain/year, compared to 9.4 and 11.1 nanostrain/year in the Sichuan basin (which likely reflects the noise floor in the data). The geodetically-determined slip rates from the three methods generally align with available geologic rates, particularly along-strike variations on the Kunlun fault and the Xianshuihe-Xiaojiang fault system. Our block model consists of 103 blocks bounded by 326 fault sections in the southeastern Tibetan Plateau. The model is constrained by the combined geodetic horizontal velocities from 6617 observation points. Classic block modelling without considering internal strain tends to overestimate slip rates on faults that slip faster than 5 mm/yr, compared to deformable block model that accounts for homogeneous intrablock strain, constituting 5% of the total. The two block models explain approximately 45-50% of the geodetic strain, predicting focused strain on block boundaries even in the absence of observed strain concentrations. By directly inverting strain rates, we suggest that 40-50% of the geodetic strain is attributable to elastic coupling (back slip) on faults, while the remaining can be explained by off-fault distributed moment sources (body forces) in a thin elastic plate. We discuss limitations of different geodetic approaches in modelling deformation (velocities or strain rates) and implications for seismic hazard by comparing the seismic moment release rate from earthquakes and the geodetic moment accumulation rate from our geodetic models.

How to cite: Fang, J., Wright, T., Johnson, K., Ou, Q., Styron, R., Craig, T., Elliott, J., and Hooper, A.: Kinematics of the Southeastern Tibetan Plateau from Sentinel-1 InSAR and GNSS: Implications for Seismic Hazard Analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8280, https://doi.org/10.5194/egusphere-egu24-8280, 2024.

EGU24-9097 | ECS | Posters on site | TS3.1

Understanding strain partitioning, segmentation, and the slip-rate history of the Middle Branch of the Northern Anatolian fault, Turkey 

Nicolas Harrichhausen, Julia de Sigoyer, Yann Klinger, Cengiz Yildirim, Melike Karakaş, and Baptiste Camus

We present preliminary results from a paleoseismic study of the middle branch of the Northern Anatolian Fault (MNAF) in Turkey. Despite low instrumental seismicity and geodetic slip rates (~2.5 mm/yr) relative to the northern branch, historical, archeological, and paleoseismic studies indicate the MNAF has hosted several damaging earthquakes in the last two millennia. Recent geomorphic and bathymetric analyses reveal segmentation of the MNAF that may indicate strain partitioning of normal and strike slip along parallel fault strands. However, it remains uncertain whether these fault segments have ruptured simultaneously. Geologic studies have constrained right-lateral slip rates to between 2 and 5.3 mm/yr, with most results contrasting against the present-day geodetic slip rate of ~2.5 mm/yr. Whether this represents a reduction in strain rate along this branch of the Northern Anatolian fault is not clear. Our study has two main objectives: first, to delineate the earthquake history along the newly identified segment of the MNAF beneath Lake Iznik and map its onshore extensions to the east and west of the lake; second, to determine the right-lateral slip rate of the MNAF across different temporal scales. We will present preliminary results from geomorphic mapping, electromagnetic conductivity and ground penetrating radar surveys, and paleoseismic trenching aimed at achieving these objectives. By further establishing the earthquake history and length of the new branch beneath Lake Iznik, we aim to ascertain whether this segment has ruptured concurrently with parallel and along-strike segments, allowing us to estimate paleo-earthquake magnitudes and maximum rupture lengths. Concurrently, by constraining the slip rate of the MNAF over time, we seek to understand whether slip along this branch has decreased and if this reduction is linked to a subsequent increase in slip rate on either the northern or southern branch of the Northern Anatolian Fault.

How to cite: Harrichhausen, N., de Sigoyer, J., Klinger, Y., Yildirim, C., Karakaş, M., and Camus, B.: Understanding strain partitioning, segmentation, and the slip-rate history of the Middle Branch of the Northern Anatolian fault, Turkey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9097, https://doi.org/10.5194/egusphere-egu24-9097, 2024.

EGU24-9399 | ECS | Posters on site | TS3.1

A new deep-learning approach for the sub-pixel correlation of optical images in the near-field of earthquake ruptures 

Tristan Montagnon, Sophie Giffard-Roisin, James Hollingsworth, Erwan Pathier, Mauro Dalla Mura, and Mathilde Marchandon

Precise estimation of ground displacement from correlation of optical satellite images is fundamental for the study of natural disasters. In the case of earthquakes, characterizing near-field displacements around surface ruptures provides valuable constraints on the physics of earthquake slip. Recently, image correlation has been used to investigate the degree of slip localization, and how it may vary as a function of geological parameters (such as fault structural maturity), raising the possibility that slip localization (vs distribution) may be predictable, with important implications for seismic hazard assessment.

Current sub-pixel correlation methods (frequency or spatial domain) all rely on the same general approach: they work at a local scale, with small sliding windows extracted from a pair of co-registered satellite images acquired at different times, and they assume a rigid uniform shift between the two correlation windows. However, in the near-field of fault ruptures, where the correlation window spans the fault discontinuity, this hypothesis breaks down, and may bias the displacements. Additional smoothing associated with the correlation window further complicates the interpretation of sharp features in the displacement field, artificially shifting displacement to the off-fault region.

We developed a U-net-based method to solve the sub-pixel displacement estimation problem at a global scale. Such architecture is able to retrieve full scale surface displacement maps, making use of both global and local features, and potentially tackling different noises of the input images. We trained our model with real satellite acquisitions, warped with ultra-realistic synthetic displacement maps representing realistic faults. The model exhibits promising preliminary results, showcasing its capability to retrieve full-scale surface displacement maps with high accuracy. While direct comparisons with other state-of-the-art approaches (COSI-Corr and MicMac) are pending, our findings suggest that our proposed U-net-based approach has the potential to compete or even outperform these correlators. 

How to cite: Montagnon, T., Giffard-Roisin, S., Hollingsworth, J., Pathier, E., Dalla Mura, M., and Marchandon, M.: A new deep-learning approach for the sub-pixel correlation of optical images in the near-field of earthquake ruptures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9399, https://doi.org/10.5194/egusphere-egu24-9399, 2024.

Geometrical irregularities of faults drive stress heterogeneities that strongly affect the seismic rupture. Here we analyze the effect of fault topography and remote stresses during the interseismic phase on the static stress pattern around faults and on the onset of failure. The analytical solution is derived using perturbation theory for a defined interface topography. We apply our solution for the static stress field near the East Anatolian Fault and we show that a large stress barrier is developed around the segment that ruptured during the Mw 7.8 Kahramanmaraş Earthquake. Considering stress field conditions that are associated with left-lateral strike slip on the fault, we show how the barrier location is affected by the fault geometry, while the amplitude of stress variations are sensitive to the background stress values and their directions. The solution predicts that the value of the accumulated elastic energy in the host rock around the fault is maximal in the barrier region suggesting that in this area the elastic energy available for potential slip is the largest. We therefore suggest that the length of the ruptured segment and magnitude of the strong Kahramanmaraş Earthquake were greatly influenced by the stress heterogeneity generated by the fault geometry during the long interseismic period. This example of the East Anatolian Fault shows that the geometry of the fault is crucial for the location and the extent of earthquakes along it. We further suggest that the presented analytical approach provides a simple yet powerful new tool for assessing seismic hazards before earthquakes occur.

How to cite: Sagy, A., Morad, D., and Lyakhovsky, V.: Stress, energy, and the onset of failure around geometrically irregular faults: Example from the East Anatolian Fault, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9615, https://doi.org/10.5194/egusphere-egu24-9615, 2024.

EGU24-9782 | Orals | TS3.1

Detection of slow slip events along the southern Peru - northern Chile subduction zone 

Jorge Jara, Romain Jolivet, Anne Socquet, Diana Comte, and Edmundo Norabuena

Detections of slow slip events (SSEs) are now common along most plate boundary fault systems at the global scale. However, no such event has been described in the south Peru - north Chile subduction zone so far, except for the early preparatory phase of the 2014 Iquique earthquake. We use geodetic template matching on GNSS-derived time series of surface motion in Southern Peru - Northern Chile to extract SSEs hidden within the geodetic noise. We detect 33 events with durations ranging from 9 to 40 days and magnitudes from $M_w$~5.6 to 6.2. The moment released by these aseismic events seems to scale with the cube of their duration, suggesting a dynamic comparable to that of earthquakes. We compare the distribution of SSEs with the distribution of coupling along the megathrust derived using Bayesian inference on GNSS- and InSAR-derived interseismic velocities. From this comparison, we obtain that most SSEs occur in regions of intermediate coupling where the megathrust transitions from locked to creeping or where geometrical complexities of the interplate region have been proposed. We finally discuss the potential role of fluids as a triggering mechanism for SSEs in the area. 

How to cite: Jara, J., Jolivet, R., Socquet, A., Comte, D., and Norabuena, E.: Detection of slow slip events along the southern Peru - northern Chile subduction zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9782, https://doi.org/10.5194/egusphere-egu24-9782, 2024.

EGU24-11002 | ECS | Posters on site | TS3.1

Simulating normal fault interactions during complex seismic sequences in the southern Apennines 

Constanza Rodriguez Piceda, Zoë K. Mildon, Yifan Yin, Billy J. Andrews, Claudia Sgambato, Martijn van den Ende, and Jean Paul Ampuero

Active faults with low extension rates can generate large magnitude earthquakes with severe damages, as exemplified in the southern Apennines (Italy) by the Irpinia earthquake (Mw 6.8) in 1980 and the Val D’Agri earthquake (Mw 7.1) in 1857. These earthquakes occur within a network of faults, and geological evidence (e.g. paleoseismic trenching) suggest that earthquake activity varies from decennial to millennial time scales on such fault systems. Therefore, improving our understanding and forecasting capabilities of seismic sequences in these areas is crucial. However, studying fault behaviour in slowly deforming regions can often prove challenging due to the long recurrence intervals and low slip rates of these faults, which results in limited instrumental, historical and paleoseismological records.

To address this issue, we use physics-based numerical models, since they allow for controlled experiments that can span thousands of years with relatively low computational costs, thus they are valuable tools to investigate the causal dynamics between seismic events. Here, we model a system of NW-SE oriented normal faults in the southern Apennines, accounting for the variable slip rates and geometry of the faults. The study region is characterized by areas with variable number of across-strike faults, thus it is suitable to study the effects of fault network geometry (across-and along-strike interaction) on the seismic cycle and earthquake statistics (e.g. recurrence time, coefficient of variation) of a geologically realistic fault network. We use the boundary-element code QDYN which incorporates rate-and-state friction and elastic interactions to examine relevant inputs for seismic hazard assessment, including inter-event time within and between faults, magnitude-frequency distribution, and nucleation location. We are able to simulate spontaneous ruptures following power-law relationships of frequency-magnitude distribution. Differences in the recurrence time (periodic vs. aperiodic cycles) and rupture extent (characteristic vs. non-characteristic seismicity) in the fault planes seem to correlate with the number of faults that exist across strike. Our simulations demonstrate how quasi-dynamic earthquake simulators can provide insights into how fault network geometry impacts earthquake occurrence and seismic hazard assessment.

How to cite: Rodriguez Piceda, C., Mildon, Z. K., Yin, Y., Andrews, B. J., Sgambato, C., van den Ende, M., and Ampuero, J. P.: Simulating normal fault interactions during complex seismic sequences in the southern Apennines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11002, https://doi.org/10.5194/egusphere-egu24-11002, 2024.

EGU24-12582 | ECS | Orals | TS3.1

Deformed Holocene coastal notches reinforce the validity of earthquake slip histories implied by in-situ 36Cl exposure fault scarp dating. 

Jenni Robertson, Claudia Sgambato, Gerald Roberts, Zoe Mildon, Joanna Faure Walker, Francesco Iezzi, Sam Mitchell, Athanassios Ganas, Ioannis Papanikolaou, Elias Rugen, Varvara Tsironi, Joakim Beck, Silke Mechernich, Georgios Deligiannakis, Steven Binnie, Tibor Dunai, and Klaus Reicherter

We report the first example where the timing of earthquake slip from in situ 36Cl cosmogenic exposure dating of an active normal fault scarp can be verified using independently 14C dated Holocene coastal notches which are deformed along the strike of the fault. We have remodelled 36Cl data from the active Pisia-Skinos normal fault, Greece, published by Mechernich et al. (2018), which indicates that the fault slip rate fluctuated through time. We model the expected coastal uplift and subsidence induced by slip on the fault using elastic half-space models and surface ruptures observed following the 1981 Pisia-Skinos earthquakes. Coastal uplift is constrained by elevation measurements of Holocene coastal notches that have previously been dated using 14C by Pirazzoli et al. (1994) and agree with time periods consistent with Holocene climate stability. We mapped the elevations and numbers of notches along the strike of the Pisia-Skinos fault, including measurements made underwater for locations where fault slip has submerged the notches below the present-day shoreline. We show that the spatial patterns and timing of uplift and subsidence from the notches agrees with the timing of periods of high slip associated with earthquake clusters and quiescence associated with anti-clusters from the slip histories derived from 36Cl data, and with the uplift and subsidence derived from elastic half-space modelling. In particular, where modelled subsidence is highest, Holocene notches that formed between 6-2 ka can be preserved but are submerged. Notches could form at this time because the 36Cl data show that the Pisia fault had entered a period of relative quiescence with a slip-rate of <0.1 mm/yr, accompanied by uplift from the offshore Strava fault. In contrast, rapid slip on the Pisia fault at 1.4 mm/yr between 2 ka and the present-day did not allow notches to form during this time period in the location of highest subsidence. Our example is the first that independently calibrates the timing of slip derived from 36Cl on a fault plane using 14C dates on a deformed coastline, and is consistent with the idea that slip-rate variations can be measured and should be incorporated into seismic hazard assessment.

How to cite: Robertson, J., Sgambato, C., Roberts, G., Mildon, Z., Faure Walker, J., Iezzi, F., Mitchell, S., Ganas, A., Papanikolaou, I., Rugen, E., Tsironi, V., Beck, J., Mechernich, S., Deligiannakis, G., Binnie, S., Dunai, T., and Reicherter, K.: Deformed Holocene coastal notches reinforce the validity of earthquake slip histories implied by in-situ 36Cl exposure fault scarp dating., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12582, https://doi.org/10.5194/egusphere-egu24-12582, 2024.

The seismic chronicle, derived from the analysis of 14 short sediment cores and three long cores from Lake Iznik (NW Turkey), along with the identification of a subaquatic fault segment belonging to the Middle Strand of the North Anatolian Fault (MNAF), provides insights into both local seismicity and the regional seismic activity over the last 6000 years.

The integration of this seismic chronicle with ground-motion estimations at the core locations for all historical earthquakes, together with the evolution of sedimentation rate through time, allow to discuss the epicentral region and epicentral intensity of each historical earthquake in the western NAF system. This analysis also helps us to discriminate which earthquake is likely to generate an event deposit in the case of several historical earthquake candidate, especially when chronological uncertainty are larges

This approach allows a discussion of the factors influencing the threshold (sedimentation rate, ground motions at different spectral frequencies ) for triggering an event deposit in the Lake Iznik and the type of slope destabilization that can be triggered .

Thanks to these finding and through the established scaling relationship it is then possible to infer a minimum intensity for prehistoric earthquakes recorded in Lake Iznik at a given period.

Combining these data with paleoseismological data from the region allows us to propose a scenario for the long-term seismic cycle of the western NAF system.

How to cite: de Sigoyer, J., Domenge, J., Céline, B., Gastineau, R., Sabatier, P., and Duarte, E.: Information on past seismicity of the western NAF system (Turkey) combining ground-motion models with historical earthquakes and event deposits recorded in the sediments of Lake Iznik (NAF system, Turkey), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12894, https://doi.org/10.5194/egusphere-egu24-12894, 2024.

EGU24-13043 | ECS | Posters on site | TS3.1

PyMDS, a Bayesian inversion algorithm for chlorine 36 dating based on the last No-UTurn Sampler (NUTS) 

Maureen Llinares, Lucilla Benedetti, Ghislain Gassier, and Sophie Viseur

Markov Chain Monte Carlo (MCMC) algorithms are sampling approaches relying on Bayesian inference, theorized in the late 1940s and used in many applications (multi-dimensional integral computations, probability law explorations, inversion problems, etc.). MCMC methods are computationally expensive and many variants have been proposed to optimize them Today, MCMC algorithms are used as inversion tools in different contexts: from receiver functions in seismology . The success and efficiency of those methodologies depends on: the complexity of the forward function, the efficiency of the MCMC strategy and the implementation language. The last MCMC sampler is the No U-Turn Sampler or NUTS (Hoffman and Gelman, 2011), an evolution of the Metropolis Hastings (HMC).

Estimating seismic history along fault scarps from 36Cl profiles is a typical inversion problem. Thus, previous studies have proposed MCMC routines to the forward function described in (Schlagenhauf et al., 2011), to invert 36Cl data and to infer seismic histories on fault scarps  (Beck et al., 2018; Mechernich et al., 2023; Tesson and Benedetti, 2019). The complexity of the forward function implies the necessity of a powerful MCMC sampler such as NUTS (Liesenfeld and Richard, 2008).

Here, we discuss these different approaches and present a new approach, termed as PyMDS, which relies on the NUTS algorithm. We implemented the code in python and performed synthetic tests to evaluate the algorithm ability to retrieve seismic histories.The results for three earthquakes synthetics tests will be presented and show that the algorithm is capable of finding the seismic scenario (ages, slips and slip rate) with a precision of few hundred years on the ages, 10 to 30 cm on the slips and inferior 0.05 mm/yr on the slip rate with a runtime of 4 hours (faster than the previous Fortran code published by Tesson & Benedetti (2019) that required 3 days to complete). We will also present preliminary results obtained on the five sites located on the Velino-Magnola fault system and the implication on seismic cycle. Finally, we will discuss potential improvement and development perspectives, such as the optimization of the forward function, the necessity to invert slips and the parametrization of the NUTS algorithm.

How to cite: Llinares, M., Benedetti, L., Gassier, G., and Viseur, S.: PyMDS, a Bayesian inversion algorithm for chlorine 36 dating based on the last No-UTurn Sampler (NUTS), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13043, https://doi.org/10.5194/egusphere-egu24-13043, 2024.

EGU24-13133 | ECS | Orals | TS3.1

Slip localization on multiple fault splays accommodating distributed deformation across normal fault complexities. 

Francesco Iezzi, Marco Francescone, Alberto Pizzi, Anna Maria Blumetti, Paolo Boncio, Pio Di Manna, Bruno Pace, Tommaso Piacentini, Felicia Papasodaro, Francesco Morelli, Marco Caciagli, Massimo Chiappini, Francesca D’Ajello Caracciolo, Valerio Materni, Iacopo Nicolosi, Vincenzo Sapia, and Stefano Urbini

Features such as fault geometry and slip-rates are key inputs to assess the seismic hazard imposed by either ground motion or fault displacement. However, complexities in the geology of faults, such as relay zones and along-strike fault bends, could lead to settings characterized by high segmentation, with multiple splays arranged both along and across strike. In order to assess the seismic hazard associated with such fault sectors, it is necessary to establish whether the 3D shallow deformation is equally spread over the multiple fault splays or the activity tends to localise on specific splays. This problem is enhanced when these faults are located within urban areas, and therefore their surface expression is altered by intense anthropic activity.

Within the framework of a work on the mitigation of the fault displacement hazard associated with the Mt. Marine active normal fault (Central Italy), we have performed two paleoseismological surveys within the town of Pizzoli (about 10 km NW of L’Aquila), where the fault is expressed with several splays arranged both along and across-strike. The trenches were planned to explore (i) potential fault scarps altered by human activity, identified through aerial photographs, LiDAR and fieldwork analysis, and (ii) discontinuities in the stratigraphic record highlighted by geophysical investigations (ERT, GPR) and borehole data.

The paleoseismological surveys intercepted five fault splays arranged across-strike, three synthetic and two antithetic to the main Mt. Marine fault. The fault splays show evidence of multiple Late Pleistocene/Holocene surface-rupturing seismic events, marked by colluvial wedges and infilled fractures. Moreover, we constrained the Late Pleistocene slip-rate of the Mt. Marine fault splays by dating and correlating Late-Pleistocene paleosols found (1) outcropping in the footwall of one of the inner fault splay and (2) in a borehole located just at the hangingwall of the outermost splay.

Our results show that the fault splays exhibit different and variable activity rates, suggesting that fault activity is localized on specific fault splays through space and time with the potential to rupture simultaneously during large earthquakes. Our findings have strong implications on fault-based seismic hazard assessments, as they imply that data collected on one splay may not be representative of the behaviour of the entire fault.

How to cite: Iezzi, F., Francescone, M., Pizzi, A., Blumetti, A. M., Boncio, P., Di Manna, P., Pace, B., Piacentini, T., Papasodaro, F., Morelli, F., Caciagli, M., Chiappini, M., D’Ajello Caracciolo, F., Materni, V., Nicolosi, I., Sapia, V., and Urbini, S.: Slip localization on multiple fault splays accommodating distributed deformation across normal fault complexities., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13133, https://doi.org/10.5194/egusphere-egu24-13133, 2024.

Previous studies have constrained the fault slip rates and block geometries of the SoutheasternTibetan Plateau (SETP) with contradictory results due to complex deformation patterns, limited datasets, and subjective choices of block boundaries. In this work, we address the issue of uncertain block geometries by employing an unsupervised machine learning (Euler pole clustering) algorithm that automatically resolves regions that behave as rigid blocks (clusters) using ~1000 GNSS velocity vectors. The optimal clustering results, determined by F-test and Euler-vector overlap analyses, indicate 4 elongated blocks exist in the SETP that are approximately parallel and delineated by a set of arcuate sinistral-slip faults. Our clustering results redefine the kinematicsof the SETP region with new block definitions which elucidate the dominance of sinistral-slipfaults.

How to cite: Xu, R. and Liu, X.: Clustering of GNSS Velocities Using Unsupervised Machine Learning in the Southeastern Tibetan Plateau: Block Identification and the Dominance of Sinistral-slip Faults, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13534, https://doi.org/10.5194/egusphere-egu24-13534, 2024.

EGU24-14326 | Orals | TS3.1

Low-angle normal faulting triggered by fluids 

Carolina Pagli, Alessandro La Rosa, Derek Keir, Gareth Hurman, Hua Wang, Cecile Doubre, Renier Viltres, Martina Raggiunti, and Atalay Ayele

In extensional settings under Andersonian mechanics, low-angle normal faults should not form in favour of steeply dipping normal faults. However, InSAR shows that a seismic sequence including an earthquake with magnitude Mw 5.6 on August 1st, 2023 (NEIC - National Earthquake Information Center) at the northern end of the Afar rift was caused by normal faulting on a low-angle 35° dipping plane. Our best-fit InSAR model shows that the low-angle normal fault occurred on the west margin of the rift axis, it was relatively deep (6.7 km) and it slipped fully seismically, having a geodetic magnitude of Mw 5.66 in agreement with the global seismic recordings (NEIC). Temporally, the faulting occurred at the end of a one-year period (December 2022-December 2023) of increased seismicity in the northern sector of Afar, with swarms of seismicity migrating northward along the rift. The seismic characteristics, fault location and kinematics are consistent with the low-angle normal fault being triggered by fluids that locally could be released by a deep magmatic heat source along the rift axis under high extensional stresses. Our observations show that low-angle normal faults can form in rifting settings, are activated seismically and are likely fluid-induced.

How to cite: Pagli, C., La Rosa, A., Keir, D., Hurman, G., Wang, H., Doubre, C., Viltres, R., Raggiunti, M., and Ayele, A.: Low-angle normal faulting triggered by fluids, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14326, https://doi.org/10.5194/egusphere-egu24-14326, 2024.

EGU24-16153 | ECS | Posters on site | TS3.1

Transient aseismic vertical deformation during the interseismic cycle across the Pisia-Skinos normal fault (Gulf of Corinth, Greece) 

Zoe Mildon, Manuel Diercks, Gerald Roberts, Joanna Faure Walker, Athanassios Ganas, Ioannis Papanikolaou, Vassilis Sakas, Jennifer Robertson, Claudia Sgambato, and Sam Mitchell

Loading and deformation during the interseismic period of the earthquake cycle is often considered to be constant for continental faults, therefore assuming that the short-term (annual-decadal) deformation is representative of longer-term deformation. Based on this assumption, geodetically-derived deformation rates are sometimes used to infer the slip-rates and thus seismic hazard of faults. However geological observations indicate that deformation and slip rates are variable over a range of timescales, and we present an observation of variable deformation across an active normal fault occurring on an annual timescale. The Pisia-Skinos normal fault in the Gulf of Corinth, Greece, is a well-known fault which slipped most recently during a sequence of damaging earthquakes in 1981. Using vertical deformation data, available from the European Ground Motion Service (EGMS), we observe uplift/subsidence of the footwall/hangingwall of the Pisia fault between 2016-2021. Of particular interest is our observation that the deformation is not uniform over the 6 year time period, instead there is an up to 7-fold increase in the vertical deformation rate in mid-2019. We hypothesise that this deformation is aseismic as there is no temporally correlated increase in the earthquake activity (M>1). We explore four possible causative mechanisms  for observed deformation; shallow slip, post-seismic after-slip, deep slip on an underlying shear zone, and post-seismic visco-elastic rebound. Our preferred hypothesis is that the transient deformation is caused by centimetre-scale slip in the upper 5km of the Pisia fault zone, based on the magnitude and spatial extent of the deformation. Our results suggest that continental normal faults can exhibit variable deformation over shorter timescales than previously observed, implying that the interseismic period of the earthquake cycle on continental faults may be more variable than previously hypothesised. This also highlights potential pitfalls of using slip rates measured over short-timescales to infer seismic hazard.

How to cite: Mildon, Z., Diercks, M., Roberts, G., Faure Walker, J., Ganas, A., Papanikolaou, I., Sakas, V., Robertson, J., Sgambato, C., and Mitchell, S.: Transient aseismic vertical deformation during the interseismic cycle across the Pisia-Skinos normal fault (Gulf of Corinth, Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16153, https://doi.org/10.5194/egusphere-egu24-16153, 2024.

EGU24-16171 | Orals | TS3.1

Fast stress-loading and -unloading below the seismogenic zone 

Claudia Trepmann, Lisa Brückner, and Fabian Dellefant

At depth just below the seismogenic zone of the continental crust, i.e. at greenschist facies conditions, stresses increase during seismic rupturing within minutes from differential stresses on the order of a few tens of MPa to several hundreds of MPa. These fast stress-loading rates are manifested in characteristic microfabrics in fault rocks (cataclasites and pseudotachylytes) exhumed from these depths. The microfabrics indicate quasi-instantaneous cataclasis of almost all rock-forming minerals including garnet and quartz, as well as mechanical twinning of pyroxenes, amphiboles and titanite. In combination with experiments, the microfabrics can be used as paleo-stress gauges, i.e., paleopiezometers. The characteristic microstructures can occur distributed over the whole width of large-scale thrust faults, as the Silvretta basal thrust in the Central European Alps. There, twinned amphiboles record transient differential stresses of more than 400 MPa in a rock volume to about 300 m above the basal thrust exposed at the contact to the Penninic units of the Engadine window over several tens of km. Fast stress-unloading is indicated by growth of new undeformed quartz grains along cleavage cracks in host quartz generated coeval with seismic rupturing and missing evidence of quartz dislocation creep after pseudotachylyte formation. This fast stress-loading and unloading is recorded in pseudotachylytes, i.e., close to the seismic rupture, whereas at larger distance to the seismic rupture accelerated creep at hundreds of MPa occurs on a longer time scale. 

How to cite: Trepmann, C., Brückner, L., and Dellefant, F.: Fast stress-loading and -unloading below the seismogenic zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16171, https://doi.org/10.5194/egusphere-egu24-16171, 2024.

EGU24-16276 | ECS | Orals | TS3.1

Triggered and recurrent slow slip in North Sulawesi, Indonesia 

Nicolai Nijholt, Wim Simons, Taco Broerse, and Riccardo Riva

Nearby faults interact with each other through the exchange of stress. However, the extent of fault interaction is poorly understood. In particular, closely tied tectonic systems like crustal-scale faults that are right next to subduction zone interfaces are likely to express such interactions. Interactions may lead to slow-slip activity, resulting in episodes of transient surface motion.

Our study concentrates on Northwest Sulawesi (Indonesia), which hosts two fault zones with potential for major earthquakes and tsunamis: the strike-slip Palu-Koro fault and the Minahassa subduction zone. Both fault zones accommodate 4 cm/yr of interseismic relative motion. Thanks to a 20-year-long effort in geodetic monitoring, we are able to identify multiple periods during which surface velocities deviate from their interseismic trend. The most recent episode followed the 2018 Mw7.5 Palu earthquake.

We use a Bayesian methodology with forward predictions of slip on the two fault interfaces to match the observations following the 2018 Mw7.5 Palu earthquake, and infer that both deep afterslip on the Palu-Koro fault and slow slip on the Minahassa subduction interface have caused the observed transient surface motion. This finding represents the first recording of a slow slip event on the Minahassa subduction interface. We also speculate that the subduction interface and the strike-slip fault are likely interacting on a regular basis, affecting the seismogenic potential of both parts of this tectonic system.

How to cite: Nijholt, N., Simons, W., Broerse, T., and Riva, R.: Triggered and recurrent slow slip in North Sulawesi, Indonesia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16276, https://doi.org/10.5194/egusphere-egu24-16276, 2024.

EGU24-16670 | Orals | TS3.1

Bayesian Inference of Rheological Parameters from Observations Before and After the Tohoku Earthquake 

Rob Govers, Celine Marsman, Femke Vossepoel, Ylona van Dinther, and Mario D'Acquisto

Geodetic data covering different phases of the earthquake cycle provide a great opportunity to improve our understanding of the processes and parameters governing the dynamics at subduction margins. However, quantifying the individual contributions of physical processes such as viscoelastic relaxation, afterslip, and (re)locking throughout the earthquake cycle remains challenging. Moreover, it is relevant to account for these processes within a rheological framework that is consistent over the entire earthquake cycle. We address this using Bayesian inference in the form of an ensemble smoother, a Monte Carlo approach that represents the probability density distribution of model states with a finite number of realizations, to estimate geodynamic model parameters. Prior estimates of the imperfect physical model are combined with the likelihood of noisy observations to estimate the posterior probability density distribution of model parameters.

 

We construct a 2D finite element seismic cycle model with a power-law rheology in the mantle. A priori information, such as a realistic temperature field and a coseismic slip distribution, is integrated into the model. Model pre-stresses are initialized during repeated earthquake cycles wherein the accumulated slip deficit is released entirely. We tailor the last earthquake to match the observed co-seismic slip of the 2011 Tohoku earthquake. The heterogeneous rheology structure is derived from the temperature field and experimental flow laws. Additionally, we simulate afterslip using a thin, low-viscosity shear zone with a Newtonian rheology. We focus on constraining power-law flow parameters for the mantle, and the shear zone viscosity.

 

We assimilate 3D GEONET GNSS displacement time series acquired before and after the 2011 Tohoku earthquake. The data require separate viscoelastic domains in the mantle wedge above and below ~50 km depth, and in the sub-slab mantle. Power-law viscosity parameters are successfully retrieved for all three domains. The trade-off between the power-law activation energy and water fugacity hinders their individual estimation. The wedge viscosity is >1019 Pa·s during the interseismic phase. Postseismic afterslip and bulk viscoelastic relaxation can be individually resolved from the surface deformation data. Afterslip is substantial between 40-50 km depth and extends to 80 km depth. Bulk viscoelastic relaxation in the wedge concentrates above 150 km depth with viscosities <1018 Pa·s. Landward motion of the near-trench region occurs during the early postseismic period without the need for a separate low-viscosity channel below the slab.

How to cite: Govers, R., Marsman, C., Vossepoel, F., van Dinther, Y., and D'Acquisto, M.: Bayesian Inference of Rheological Parameters from Observations Before and After the Tohoku Earthquake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16670, https://doi.org/10.5194/egusphere-egu24-16670, 2024.

Shallow creep, as a widespread phenomenon in the earthquake cycle, plays an important role in understanding the behavior of faults and seismic hazards. However, it is still under debate whether creeping is an inherent behavior of fault or is a form of afterslip following large earthquakes. The East Anatolian Fault was recently ruptured by the 2020 Mw6.8 Elazig, and 2023 Mw7.8/Mw7.6 Kahramanmaras earthquake sequence, providing a unique opportunity to investigate the relation between shallow creep and earthquakes along strike-slip fault. Here, we show the spatial distribution and temporal evolution of creeping segments along the EAF using the InSAR phase-gradient stacking method. We derive the shear-strain rates in three periods – before the 2020 earthquake, between the 2020 and 2023 earthquakes, and after the 2023 earthquake sequence. By comparing the spatial distribution of the interseismic strain rates, the coseismic slip, and the post-seismic strain rates, we document a tight connection between creeping and coseismic slip on the two recent earthquakes. We also investigate the temporal behavior of faults following the two earthquakes using time-series shear strain analysis. The results reveal behaviors of shallow creep on different segments of the EAF with different statuses before the earthquakes. Our results shed new light on understanding the mechanism of creeping and its relation with large earthquakes during the earthquake cycle.

How to cite: Liu, Z. and Wang, T.: Shear-strain rates across the East Anatolian Fault (EAF) response to the 2020 Mw6.8 Elazig, and 2023 Mw7.8/Mw7.6 Kahramanmaras earthquake sequence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18092, https://doi.org/10.5194/egusphere-egu24-18092, 2024.

EGU24-18562 | Posters on site | TS3.1

Insights into the site-to-site correlation of paleoseismic data  

Nicolás Pinzon and Yann Klinger

Integration of paleoseismic data from multiple sites is important to assess the past fault rupture scenarios and determine an earthquake chronology for the entire fault system. However, the current methods used to combine paleoseismic data are diverse and lack theoretical foundations from a mathematical perspective. We present a method to evaluate and integrate paleoseismic event data from multiple sites into a single earthquake time history. We apply this method to the central-eastern fault sections of the Altyn Tagh Fault using data from ten fault trenches. Applying a Bayesian approach we constructed time-stratigraphic models that yield the probability density functions corresponding to the age of individual earthquakes at each site. Then, our method to integrate these data consists of two main steps: 1) we constructed a rupture pool with all the modeled event ages, and we evaluated the overlapping degree between the site PDFs; 2) For sufficiently contemporary PDFs we combine them by computing the weighted-mean method which emphasizes the overlap in the site earthquake times. The weighted-mean method yields smaller earthquake-time uncertainties compared to the rupture-mean approach and is consistent with the earthquake rupture assumptions behind the integration of paleoseismic data and the probability theory of density functions. This approach helps to clarify the timing and rupture extent of past earthquakes along central-eastern ATF and is essential to improve the earthquake probability assessment for the region.

How to cite: Pinzon, N. and Klinger, Y.: Insights into the site-to-site correlation of paleoseismic data , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18562, https://doi.org/10.5194/egusphere-egu24-18562, 2024.

Following large earthquakes, postseismic crustal deformations are often observed. They include the afterslip and the viscoelastic deformation of the crust and the upper mantle, activated by the coseismic stress change. In order to predict the future deformations, and the stress change distributions, it is important to divide each deformation. The physical parameters; frictional properties of the fault and the rheological properties are the key to determining the slip behavior, but they are generally unknown.

Data assimilation (DA) studies have attempted to estimate the frictional properties directly from the observational data. DA incorporates the observed data into the physics-based model to construct a more plausible model. When DA works well, we can obtain the physics-based model, including the physical properties, that can quantitatively explain the observed data. The constructed physics-based model can be used to simulate the slip evolution beyond the data period, i.e., prediction of the deformation.

There are two types of DA technique applying to nonlinear system, the sequential method called as Ensemble Kalman filter method (EnKF) and the variational method called as 4DVAR. For the fault system, EnKF is applied to the deformation data to estimate the physical variables (van Dinther et al., 2019, Hirahara and Nishikiori, 2019). 4DVAR is also applied to the afterslip assuming elastic medium to estimate the fault frictional properties (Kano et al., 2015; 2020). If the physics-based model under consideration is linear, the sequential and the variational methods are consistent, but this is not the case for fault systems.

In this presentation, I construct a simple model that include the fault slip that follows the rate- an state- friction law and the viscoelastic deformation. Then I apply both EnKF and 4DVAR, and compare the results to discuss the characteristics of the methods.

How to cite: Ohtani, M.: Numerical experiments on estimating the fault frictional properties and the viscosity from the postseismic deformation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19405, https://doi.org/10.5194/egusphere-egu24-19405, 2024.

EGU24-20077 | ECS | Orals | TS3.1

Co-seismic fault offsets of the 2023 Türkiye earthquake ruptures using Sentinel-2 satellite imagery and field observations 

Floriane Provost, Volkan Karabacak, Jean-Philippe Malet, Jérôme Van Der Woerd, Mustapha Meghraoui, Frédéric Masson, Matthieu Ferry, David Michéa, and Elisabeth Pointal

On February 6, 2023, southern Türkiye was hit by two major earthquakes at 01:17 UTC (Mw 7.8, Pazarcık, Kahramanmaraş) and at 10:30 UTC (Mw 7.6, Elbistan, Kahramanmaraş) leading to severe damages at the complex junction of the Dead Sea Fault (DSF), the Cyprus arc and the East Anatolian fault zone (EAFZ). The ruptures propagated along several known strands of the southwestern termination of the EAFZ, the main Pazarcık and Karasu valley faults and the Çardac-Sürgü fault. The spatial extent of the impacted zone (300 x 300 km) supports the use of satellite images to map ruptures and damages and measure the co-seismic displacement over the whole region. Among the different satellite constellation available nowadays, Sentinel-2 presents the advantages of offering high-resolution images (10 m), global coverage with frequent revisit time and open access policy to the images. We here present the high-resolution mapping of the entire coseismic surface ruptures derived from image correlation of optical Sentinel-2 satellite acquisitions. We further estimated the rupture width, the total and on-fault offset, and of the diffuse deformation obtained a few days after the two mainshocks along the two main ruptures at 50 m resolution along the rupture. The mapping and the estimation of the offset are validated with the location of the rupture and the offset measurements collected on the ground. We found that the ruptures extend over lengths of 310 km and 140 km, with maximum offsets reaching 7.5±0.8 m and 8.7±0.8 m near the epicenters, for the Mw 7.8 and Mw 7.6 mainshocks, respectively. We propose a segmentation of the two ruptures based on these observations, and further discuss the location of potential supershear rupture. The use of optical image correlation complemented by field investigations along earthquake faults provides new insights into seismic hazard assessment.

How to cite: Provost, F., Karabacak, V., Malet, J.-P., Van Der Woerd, J., Meghraoui, M., Masson, F., Ferry, M., Michéa, D., and Pointal, E.: Co-seismic fault offsets of the 2023 Türkiye earthquake ruptures using Sentinel-2 satellite imagery and field observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20077, https://doi.org/10.5194/egusphere-egu24-20077, 2024.

EGU24-20361 | ECS | Posters on site | TS3.1

3D discrete element modeling for the simulation of seismic cycles on a strike-slip fault 

Adélaïde Allemand, Liqing Jiao, and Yann Klinger

Knowing about the geometry of both (i) ruptured zones during seismic events, and (ii) faults throughout seismic cycles, as well as the evolution of this geometry, is important to understand what is controlling the start and the ending of large earthquakes. In this study, we use 3D Discrete Element Modeling (DEM) in order to simulate a strike-slip fault, formed from an initially homogeneous, intact medium representing brittle rock that is submitted to tectonic loading. Indeed, this numerical method models the crust as an assembly of rigid spheres which are linked by user-defined interactions and reconfigurate very naturally when subjected to loading. Therefore, such approach is adapted to study the evolution of fault geometry through earthquake cycles, since it permits to simulate large displacements of the particles, while avoiding prescribing fault location and geometry, and letting such geometry evolve freely.

A 3D parallelepipedic model is designed and then indefinitely sheared by assigning periodic boundary conditions. The particular feature of our model is the implementation of a healing phenomenon, a key process which allows fractured zones to restrengthen after a slip event. During the simulation, the position of particles and the state of their bonds are recorded at regular time intervals; consequently, the shape and dimension of deformation are evaluated, the evolution of fault geometry is monitored, and the stresses in the domain can be measured. Results show a stick-slip behaviour which can be identified as earthquakes separated by locking periods. In addition, the amount of displacement and the rupture surface can be estimated and enable the computation of a magnitude-like quantity. Thus, earthquake-like events seem to follow a magnitude-frequency relationship, and earthquake-like surface deformations are comparable to observations of ground deformation after real size earthquakes. Eventually, the evolution of the fault geometry during the simulation is also scrutinized.

How to cite: Allemand, A., Jiao, L., and Klinger, Y.: 3D discrete element modeling for the simulation of seismic cycles on a strike-slip fault, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20361, https://doi.org/10.5194/egusphere-egu24-20361, 2024.

G4 – Satellite Gravimetry, Gravity and Magnetic Field Modeling

EGU24-680 | ECS | Orals | G4.1

Role of catchment morphometrics in addressing the spatial resolution of GRACE-derived total water storage changes 

Komali Bharath Narayana Reddy and Balaji Devaraju

The spatial resolution of the total water storage changes from GRACE data is a conundrum, but also the most sought after quantity. The availability of various solutions exacerbates the situation -- unconstrained spherical harmonics, constrained spherical harmonics, mascons and different data processing centers. Some attempts have been made previously to arrive at an answer, and some numbers have been proposed. Notably, in the context of hydrologic applications, the spatial resolution morphs into a question of the catchment sizes and shapes, thereby rendering some of these numbers deficient. This study uses ideas from leakage analysis to arrive at answers for the spatial resolution issue. Care is taken to incorporate the morphometric characteristics of catchments in the answers being arrived at.

How to cite: Bharath Narayana Reddy, K. and Devaraju, B.: Role of catchment morphometrics in addressing the spatial resolution of GRACE-derived total water storage changes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-680, https://doi.org/10.5194/egusphere-egu24-680, 2024.

EGU24-1914 | ECS | Posters on site | G4.1

On the analysis of geodetic height changes obtained using different observation techniques at proposed IHRF sites 

Samuel Milki Yadeta, Walyeldeen Godah, Malgorzata Szelachowska, Wojciech Jarmołowski, and Paweł Wielgosz

The determination of geodetic heights with high accuracy is one of the main tasks in geodesy. In 2015, a resolution for definition of International Height Reference System (IHRS) and its realization by International Height Reference Frame (IHRF) was released by the International Association of Geodesy (IAG). In the recent few years, intensive efforts have been devoted to develop the IHRF and its temporal changes. The main goal of the proposed study is to analyze temporal variations of geodetic height changes at the locations of proposed IHRF sites using data from Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions, tide gauges, and space geodetic techniques, i.e. GNSS, SLR, VLBI, and DORIS.

Monthly GRACE/GRACE-FO-based Global Geopotential Models were utilized to estimate temporal variations of ellipsoidal height at proposed IHRF sites. Moreover, geodetic height changes were obtained from the aforementioned space geodetic techniques and tide gauge stations that co-located with the proposed IHRF sites. Then, the seasonal decomposition method and Discrete Fourier Transform were implemented to analyze time series of obtained geodetic height change. Based on the results, seasonal and long-term components of geodetic height variations at the proposed IHRF sites were determined, analyzed, and discussed according to the contemporary requirements for the definition of the IHRF, as well as the precise levelling measurements.

Keywords: GRACE/GRACE-FO satellite missions, space geodetic techniques, tide gauge, reference system/frame, geodetic height

How to cite: Yadeta, S. M., Godah, W., Szelachowska, M., Jarmołowski, W., and Wielgosz, P.: On the analysis of geodetic height changes obtained using different observation techniques at proposed IHRF sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1914, https://doi.org/10.5194/egusphere-egu24-1914, 2024.

EGU24-2909 | Posters on site | G4.1

The “NGGM-MAGIC: A breakthrough in the understanding of the dynamics of the Earth” project 

Anna Maria Marotta, Riccardo Barzaghi, Carla Braitenberg, Luca Brocca, Gabriele Cambiotti, Stefania Camici, Stefano Casotto, Carlo Iapige De Gaetani, Angelo De Min, Maurizio Fedi, Alberto Pastorutti, Tommaso Pivetta, Mirko Reguzzoni, Umberto Riccardi, Lorenzo Rossi, Roberto Sabadini, Simona Zoffoli, Giovanni Paolo Blasone, and Francesco Longo

The substantial improvement in spatio-temporal accuracy that will be provided by the ESA NGGM/MAGIC mission will make it possible to take a decisive step forward in our knowledge of the dynamics of the main physical processes involving the different compartments of the Earth.

Since every physical process that occurs within each terrestrial compartment involves a redistribution of mass and therefore a signal of gravity, the project intends to provide results of impact and breakthroughs in the modeling and understanding of the dynamics of Solid Earth and Fluid Earth processes, the latter including the water stored in continents and oceans, as well as in geodesy.

Methodologies will be developed that link gravity signals from the various compartments of the Earth to the MAGIC raw data, finally linking each terrestrial compartment with the two pairs of satellites, the core of MAGIC.

The partnership proposing the project includes researchers from different Universities and Research Institutions and has all the skills in the various sectors mentioned above, from its assets in basic science to the application ones.

The following activities are planned:

- Modeling of the gravitational effects of slow tectonics and seismic cycle

- Modeling of the gravitational effects from volcanic processes

- Development of methodologies of compact imaging/inversion for the estimation of mass changes

- Tidal and ocean circulation models for gravity signal and generation of L2 data

- Precipitation and river flow models, hydrological models for the TWSA

- High resolution background gravity and gravity anomaly error determination and E2E simulations for geophysical processes detectability.

Among the objectives of these activities, common to all partners, there will be in particular that of verifying that the spatio-temporal resolution of MAGIC allows to satisfy the requirements necessary to extract from the mission data the gravity signal that allows a significant advance in the basic research and related applications in the various geophysical and geodetic components.

The project is funded by the Italian Space Agency - ASI.

How to cite: Marotta, A. M., Barzaghi, R., Braitenberg, C., Brocca, L., Cambiotti, G., Camici, S., Casotto, S., De Gaetani, C. I., De Min, A., Fedi, M., Pastorutti, A., Pivetta, T., Reguzzoni, M., Riccardi, U., Rossi, L., Sabadini, R., Zoffoli, S., Blasone, G. P., and Longo, F.: The “NGGM-MAGIC: A breakthrough in the understanding of the dynamics of the Earth” project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2909, https://doi.org/10.5194/egusphere-egu24-2909, 2024.

EGU24-3215 | ECS | Orals | G4.1

A Quantitative Analysis of the Contributions of High-Low Satellite-to-Satellite Tracking (SST) Observations used for Gravity Field Estimation 

Niusha Saadat, Srinivas Bettadpur, Christopher McCullough, and Peter Nagel

Satellite gravimetry missions continue to provide data to produce high resolution gravity models of the Earth for over 20 years. The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) exemplifies the current state-of-the-art mission architecture. GRACE-FO consists of a pair of twin satellites flying in the same orbit with an onboard laser ranging interferometer (LRI) system and GNSS receivers. The LRI is used for accurately tracking low-low satellite range change. The GNSS receivers are used for high-low SST to GNSS satellites, contributing information for satellite positioning, timing, and long-wavelength gravity field information.

We present results from a numerical simulation study to characterize the contributions of various high low SST observation architectures relative to the GRACE-FO configuration. These include gravity fields estimated with only high-low SST observations as well as fields with combined high-low and low-low SST observations. Other aspects of the setup such as measurement observables, bias parameterization, and noise characteristics are evaluated to better understand how high-low SST and its errors impact gravity field estimation. We anticipate the results to be useful in the architecture and science data analysis algorithms for future mass change missions.

How to cite: Saadat, N., Bettadpur, S., McCullough, C., and Nagel, P.: A Quantitative Analysis of the Contributions of High-Low Satellite-to-Satellite Tracking (SST) Observations used for Gravity Field Estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3215, https://doi.org/10.5194/egusphere-egu24-3215, 2024.

EGU24-3692 | ECS | Orals | G4.1

Enhancing GRACE-FO Gravity Field Solutions: A Comparative Assessment and Novel Combination of ACT Products 

Yufeng Nie, Jianli Chen, Yunzhong Shen, and Qiujie Chen

The performance degradation of one onboard accelerometer of the GRACE-FO mission presents a significant challenge to the scientific community. This issue has been largely mitigated by transplanting data from the other fully functional accelerometer. Various accelerometer data transplant (ACT) products have been developed using distinct methodologies, each showing different performances in gravity field recovery. In this study, we conduct a systematic evaluation of three available ACT products—JPL-ACT and JPL-ACH from NASA's Jet Propulsion Laboratory, and TUG-ACT from Graz University of Technology—utilizing a uniform Level-1B data processing approach. Our analysis reveals that these ACT products exhibit inconsistent quality across different time periods. Consequently, we introduce a novel approach combining these ACT products at the normal equation level to enhance gravity field solution accuracy. Compared to solutions using the JPL-ACT, the combined solution gives a notable noise reduction of 5% to 12% depending on the choice of post-processing filters and the replacement of C20/C30 coefficients, which doubles the noise reduction achieved by the next best individual ACT product, JPL-ACH. Furthermore, the C20 coefficient derived from the combined solution agrees better with the Satellite Laser Ranging (SLR) benchmark, compared to those derived from individual ACT products. This advancement largely reduces the spurious 161-day signal observed in polar regions. Regarding the C30 coefficient, while JPL-ACT solutions exhibit suboptimal estimates, the JPL-ACH, TUG-ACT, and combined solutions all contribute to substantial improvements.

How to cite: Nie, Y., Chen, J., Shen, Y., and Chen, Q.: Enhancing GRACE-FO Gravity Field Solutions: A Comparative Assessment and Novel Combination of ACT Products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3692, https://doi.org/10.5194/egusphere-egu24-3692, 2024.

The Gravity Recovery and Climate Experiment (GRACE) has played an important role in sea level observations over the last few decades. However, regional-scale studies of this phenomenon are still challenging due to the potential land-to-ocean leakage along coastlines. In this study, we utilized the Spherical Slepian Functions (SSF) to inverse the regional sea level signal within the South China Sea by incorporating an optimal coastal buffering zone into transform procedures of the original GRACE spherical harmonics (SH). By synthesizing the time series of oceanic and coastal areas with different trends, annual amplitudes and phases, the SSF-inversed signal with a 1° buffering zone was found to be more consistent with synthesized time series than traditional SH-inversed results. Then, the spatiotemporal characteristics of seasonal and residual sea level variations were further analyzed and compared with results from traditional GRACE SH product, GRACE Mascon resolution, the Estimating the Ocean Circulation and Climate (ECCO) model, and the difference between altimetry and a steric sea level model (i.e., Altimetry-Steric data). Temporal analysis shows that the trend and the phase of regional sea level signal within the South China Sea with the 1° buffering zone using the GRACE SSF was 0.28 cm/yr and 108° respectively, which generally agrees with other sea level solutions. However, the SSF-inversed mass sea level amplitude of 4.63 cm was larger (smaller) than that obtained from the SH (Mascon) method by approximately 0.7 cm (0.6 cm), showing relatively better consistency with the 4.47 cm from the ECCO model and 4.23 cm from the Altimetry-Steric data. For the spatial analysis, an extremely high amplitude of sea level signal at the centre of the Gulf of Thailand due to seasonal alternating circulations was observed in all data, except for the GRACE SH solution, which significantly underestimated the signal due to a smoothing effect of filtering. Besides, the SFF-inversed GRACE exceptionally observed an apparent seasonality of sea level signal near the mouth of the Pearl River with an amplitude of ~ 8 cm. Furthermore, the sea level signal along the eastern coasts and the Sunda Shelf was out-of-phase for SSF GRACE and Altimetry-steric data, probably due to the interaction of active tropical eddies nearby. The potential inter-annual sea level variability was also analyzed by decomposing the residual time series through the Multivariate Singular Spectrum Analysis (MSSA) method. Results show that the highest cross-correlation between the decomposed modes of GRACE Mascon mass sea level and Southern Oscillation Index (SOI) reached 0.52 with a time lag of 2 months, considerably larger than 0.14 from GRACE SSF. This finding can be explained by the fact that most of the truncated Spherical Slepian functions capture short-term signals that are mainly attributed to seasonal changes. Consequently, it is difficult to distinguish between a relatively small long-term signal and noise. This may also explain the irregular spatial distribution in the GRACE SSF sea level trends. Nevertheless, this study demonstrates a feasibility of using the Spherical Slepian functions in modelling of mass sea level signal over a medium-sized sea.

How to cite: Ma, Z., Tenzer, R., and Fok, H.-S.: Estimating spatio-temporal characteristics of sea level variations of the South China Sea using the Spherical Slepian functions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4465, https://doi.org/10.5194/egusphere-egu24-4465, 2024.

EGU24-5322 | ECS | Orals | G4.1

Improving the spatial resolution of global mass changes observed by GRACE(-FO) using deep learning — from terrestrial water to the ocean 

Junyang Gou, Lara Börger, Michael Schindelegger, and Benedikt Soja

Gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) and its follow-on (GRACE-FO) satellite mission provide an essential way to monitor mass changes in the climate system, comprising terrestrial water storage (TWS) anomalies and ocean bottom pressure (OBP) fluctuations. However, the coarse spatial resolution of the GRACE fields blurs important spatial detail, such as OBP gradients or mass fluxes in individual catchments. By contrast, classical hydrological or ocean models provide small-scale mass change information but of doubtful accuracy, especially for trends. To combine the strengths of both data sources, we develop a self-supervised data assimilation algorithm based on deep learning concepts and apply it successfully to global TWS and OBP anomalies. The specific design of the loss function allows the model to be optimised without requiring a high-resolution ground truth. Instead, the model parameters are optimised by weighing monthly GRACE(-FO) and numerical model inputs according to their respective advantages (i.e., spatial scales where their fidelity is highest). We obtain downscaled TWS and OBP anomaly maps with grid spacings of 0.5° and 0.25°, respectively, preserving reasonable large-scale agreement with monthly GRACE(-FO) fields. We validate our downscaled products on various time scales against satellite altimetry-measured water levels, tide gauge data, and in-situ bottom pressure measurements. The downscaled products facilitate analyses beyond the nominal GRACE(-FO) resolution, including closing the water balance equation in small basins or monitoring coastal ocean mass changes. Over the terrestrial water, our downscaled product provides an average improvement of 0.79 in terms of Nash–Sutcliffe efficiency (w.r.t. ERA5-Land water budget components) for the basins smaller than the effective resolution of GRACE(-FO) missions. Over the ocean, our downscaled product agrees better with coastal tide gauge measurements at more than 78% of studied stations. We anticipate our approach to be generally applicable to other GRACE(-FO) level-3 products and other gridded Earth observation data.

How to cite: Gou, J., Börger, L., Schindelegger, M., and Soja, B.: Improving the spatial resolution of global mass changes observed by GRACE(-FO) using deep learning — from terrestrial water to the ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5322, https://doi.org/10.5194/egusphere-egu24-5322, 2024.

EGU24-5715 | Posters on site | G4.1

Impact of new Earth’s time-variable gravity field models on orbits of altimetry satellites 

Sergei Rudenko, Denise Dettmering, Mathis Bloßfeld, and Julian Zeitlhöfler

Gravitational forces are the major forces acting on near-Earth orbiting (e.g., altimetry) satellites. Recently published Earth’s gravity field models used within the satellite precise orbit determination (POD) comprise observations of GRACE (Gravity Recovery And Climate Experiment) and GRACE-FO (GRACE-Follow-On), gravity field satellite missions between 2002 until 2017 and since 2018, respectively. In this presentation, we perform a review of selected Earth’s time-variable gravity field models developed in the past ten years (2014-2023). We analyze also the POD results obtained for selected altimetry satellites, namely, TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 at the time interval from 1992 to 2023 using various Earth’s gravity field models. A special focus is put on the CNES/GRGS mean gravity field models of releases 2 to 5, including the latest CNES_GRGS.RL05MF_COMBINED_GRACE_SLR_DORIS model. The impact of these models is assessed for different orbit parameters as well as the root-mean-square and mean values of Satellite Laser Ranging observation residuals and orbit differences. Furthermore, the impact of these models on altimetry (single- and multi-satellite) sea surface height crossover differences is investigated. From these crossover differences, radial errors and geographically-correlated mean errors are derived and analyzed. The results are used to conclude on the accuracy of current Earth’s time-variable gravity field models when used for the POD of altimetry satellites.

How to cite: Rudenko, S., Dettmering, D., Bloßfeld, M., and Zeitlhöfler, J.: Impact of new Earth’s time-variable gravity field models on orbits of altimetry satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5715, https://doi.org/10.5194/egusphere-egu24-5715, 2024.

EGU24-6951 | Orals | G4.1

Analysis challenges for spaceborne multi-technique mass-change measurement: Mechanisms and mitigation 

Srinivas Bettadpur, Furun Wang, NIcholas Childress, Ben Krichman, and Geethu Jacob

Considerable research is underway in the satellite geodesy, spaceflight engineering, and high-precision metrology community that brings to bear modern technology to next generation mass-change estimation. This is motivated by a consensus community desire for ever increasing resolution and accuracy of global mass change - an essential climate variable - for understanding and inference of the Earth system at all spatio-temporal scales.

The infusion of high-precision modern technology brings with it additional challenges in the data analysis including fundamental enabling analyses such as attitude and orbit determination, modeling of the observation and its connection to the gravity field parameters, and estimation techniques to maximize the fidelity of spatial patterns and signal amplitudes in estimated mass-change fields.

In this paper, we report on our investigations into the mechanisms of aliasing - one of the most visible challenges in mass-change estimation from satellite gravity observations. In prior work, we have presented symptomatic assessments of how aliasing can have orthogonal impacts on gravity field estimated from low-low satellite-to-satellite (SST) tracking and from gravity gradiometry (GG), and shown how a combination of the two in a hybrid configuration can offer the best of both techniques. In this follow-up paper, we present results of closer investigations into the mechanisms of aliasing and their differential impacts on SST and GG, and what this suggests for mitigation in future multi-technique mass-change measurement environment. These results form the basis for recommendations of analysis techniques such as appropriate modifications to the variational methods, scoping the requirements on prior knowledge of rapid mass variability that is the principal cause of aliasing errors, and their mitigation in estimation techniques.

How to cite: Bettadpur, S., Wang, F., Childress, N., Krichman, B., and Jacob, G.: Analysis challenges for spaceborne multi-technique mass-change measurement: Mechanisms and mitigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6951, https://doi.org/10.5194/egusphere-egu24-6951, 2024.

EGU24-6953 | ECS | Orals | G4.1

A multiple-parameter regularization approach for filtering monthly GRACE/GRACE-FO gravity models 

Kunpu Ji, Yunzhong Shen, Lin Zhang, Qiujie Chen, Lizhi Lou, and Lianbi Yao

The Gravity Recovery and Climate Experiment (GRACE) and its subsequent GRACE Follow-On (GRACE-FO) missions have been instrumental in monitoring Earth’s mass changes through time-variable gravity field models. However, these models suffer from high-frequency noise and significant north-south striping (NSS) noise. The most widely used spectral filter for addressing these issues is the decorrelation and denoising kernel (DDK) filter, utilized by official processing agencies. The key operation of DDK filtering is to regularize the normal equation built by the Level-1b data. However, the regularization parameter used in original DDK filters is empirically determined by the signal-to-noise ratios and remains unchanged across all months. This is improper due to the heterogeneity of the monthly covariance matrix. Additionally, a single regularization parameter may not effectively address the ill-posedness of the inversion equation. For this reason, we propose a multiple-parameter regularization approach for filtering GRACE gravity field models, with regularization parameters determined by minimizing the mean squared error (MSE) for each month. The proposed method is used to process the ITSG-Grace2018 and ITSG-Grace_operational Level-2 spherical harmonic coefficients with degree/order 96 from April 2002 to December 2022. The results show that our method produces the filtered mass anomalies, global trend, and annual signal amplitudes that align better with three mascon solutions (CSR, JPL, and GSFC) compared to DDK filters and ordinary Tikhonov regularization with a single regularization parameter. In some typical areas with significant signals, our approach retains more detailed characteristics in filtered signals compared to DDK filters and ordinary Tikhonov regularization. Repeated simulations demonstrate that the filtered signals by our approach are closer to the simulated true signals than those by other methods.

How to cite: Ji, K., Shen, Y., Zhang, L., Chen, Q., Lou, L., and Yao, L.: A multiple-parameter regularization approach for filtering monthly GRACE/GRACE-FO gravity models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6953, https://doi.org/10.5194/egusphere-egu24-6953, 2024.

Despite the increasing accuracies of GRACE/GRACE-FO gravity field models through worldwide endeavors, the temporal aliasing effect caused by the imperfect background models used in gravity field modelling is still a crucial factor that degrades the quality of gravity field solutions. Recognizing the significant impact of temporal resolution in atmospheric de-aliasing models, this study specifically explores its influence on gravity field modeling across frequency, spectral, and spatial domains. Analysis indicates that elevating the temporal resolution from 3 hours to 1 hour has a negligible impact on gravity solutions in both frequency and spectral domains, and this effect is smaller than the variations caused by employing different atmospheric datasets. Nevertheless, in the spatial domain, increasing temporal resolution proves effective in mitigating LRI range-rate residuals, particularly in specific regions of the Southern Hemisphere at mid- and high-latitudes. Mass changes, expressed in Equivalent Water Height (EWH) and derived through P4M6 filtering, reveal that the maximum RMS value of spatial differences resulting from enhanced temporal resolution in atmospheric de-aliasing models can reach ~13.4mm in the sub-region of the Congo River Basin. However, using different atmospheric datasets can lead to a maximum difference of ~16.5mm. For the Amazon River Basin, the corresponding maximum discrepancy is ~18.1mm, and that caused by improving temporal resolution is ~9.4mm. Subsequently, the Congo River Basin is divided into several sub-regions using a lat-lon regular grid with a spatial resolution of 3 degrees. The subsequent time series results of mass changes reveal that the maximum contribution of temporal resolution and changes in the atmospheric datasets can reach 11.09% and 21.24%, respectively. These findings underscore the importance of accounting for temporal resolution in de-aliasing products when investigating mass changes at a regional scale.

How to cite: Bai, Y., Chen, Q., and Shen, Y.: Comparisons of Temporal Resolution of Atmospheric De-aliasing Products for the Analysis of Gravity Field Estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7181, https://doi.org/10.5194/egusphere-egu24-7181, 2024.

EGU24-7389 | ECS | Posters on site | G4.1

Contribution Analysis of the SGG Observation from Different GOCE Orbital Altitudes to Static Gravity Field Solution 

Jianhua Chen, Qiujie Chen, Yunzhong Shen, Xingfu Zhang, and Yufeng Nie

The Satellite Gravity Gradiometry (SGG) data from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite demonstrated unprecedented accuracy in estimating the gravity field model across medium and long wavelengths. However, the GOCE satellite re-entered Earth’s atmosphere in Nov. 2013. Leveraging SGG data for gravity field estimation will be a prominent research focus within the Next-Generation Gravity Mission (NGGM) to enhance further the spatial resolution and accuracy of solved gravity field models. During the final 15 months of the GOCE mission, there was a notable reduction in orbital altitude from 259.5 to 229 km. This decline provides essential data for assessing how different orbital altitudes affect static gravity field estimation. Based on Tongji-GMMG2021S (Gravity field Model from Multi-Gravity observation [Satellites]), this paper conducts a quantitative analysis, leading to the following conclusions: (1) The Tongji-GMMG2021S model derived from reprocessed Level-1b SGG data and the normal equation of Tongji-Grace02s, exhibits spatial and accuracy levels comparable to those of the GOCO06s model. (2) The contribution analysis at the normal matrix level shows that SGG data primarily contributes between 95 and 260 degrees to the Tongji-GMMG2021S normal matrix. (3) In terms of the geoid grid height difference to the Tongji-GMMG2021S model in the spatial domain, the period of Low Orbital Altitude from Aug. 2012 to Oct. 2013 significantly contributes to reducing residuals compared to the period of Higher Orbital Altitude from Nov. 2009 to Jul. 2012. These findings also provide a valuable reference for balancing the orbital altitude of NGGMs, the lifespan of NGGMs operational and the accuracy of the gravity field models.

How to cite: Chen, J., Chen, Q., Shen, Y., Zhang, X., and Nie, Y.: Contribution Analysis of the SGG Observation from Different GOCE Orbital Altitudes to Static Gravity Field Solution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7389, https://doi.org/10.5194/egusphere-egu24-7389, 2024.

EGU24-7426 | Orals | G4.1 | Highlight

GRACE-FO: science results, project status and further plans  

Frank Flechtner, Felix Landerer, Himanshu Save, Christopher Mccullough, Christoph Dahle, Srinivas Bettadpur, Robert Gaston, and Krzysztof Snopek

The GRACE Follow-On satellite mission, a partnership between NASA (US) and GFZ (Germany), successfully completed its nominal five-year prime mission phase in May 2023, and has already entered its extended mission phase. GRACE-FO continues the unique essential climate data record of mass change in the Earth system initiated in 2002 by the GRACE mission (2002-2017). The combined GRACE & GRACE-FO data records now span over 22 years and provide foundational observations of monthly to decadal global mass changes and transports in the Earth system derived from temporal variations in the Earth’s gravity field. These observations have become indispensable for climate-related studies that enable process understanding of the evolving global water cycle, including ocean dynamics, polar ice mass changes, and near-surface and global ground water changes.

In this presentation, we will present recent GRACE/GRACE-FO science and applications highlights, review key data processing and calibration approaches for GRACE-FO and lessons learned during the recent years, and discuss the GRACE-FO mission plan to operate and collect high-quality science data through the intensifying solar cycle 25, aiming for continuity with the upcoming NASA/DLR Continuation mission GRACE-C, targeted to launch in 2028.

How to cite: Flechtner, F., Landerer, F., Save, H., Mccullough, C., Dahle, C., Bettadpur, S., Gaston, R., and Snopek, K.: GRACE-FO: science results, project status and further plans , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7426, https://doi.org/10.5194/egusphere-egu24-7426, 2024.

EGU24-7548 | Posters on site | G4.1

The COST-G GRACE RL02 

Adrian Jaeggi, Ulrich Meyer, Martin Lasser, Frank Flechtner, Christoph Dahle, Eva Boergens, Torsten Mayer-Gürr, Felix Öhlinger, Jean-Michel Lemoine, Stéphane Bourgogne, Thorben Döhne, Hao Zhou, Jianjun Ran, Qiujie Chen, Changqing Wang, and Wei Feng

In 2019 the Combination Service for Time-variable Gravity fields (COST-G) started its operation with the first release of combined monthly GRACE gravity field models. Meanwhile almost five years have passed, while new experience was gained with the operational combination of the monthly gravity field models of the successor mission GRACE-FO, which has triggered a review of the weighting scheme and consequently a second release of GRACE-FO models in 2023. Moreover, the COST-G consortium has been in close cooperation with new GRACE/GRACE-FO analysis centers from China since spring 2020, which recently provided time-series of unconstrained models, covering the whole GRACE period, as it is requested by the COST-G processing standards. After careful evaluation of all individual time-series the whole GRACE time-series has now been recombined based on the new weighting scheme and also taking into account the contributions of the new COST-G analysis centers APM-SYSU, HUST, SUSTech and Tongji. We present the COST-G GRACE RL02 and also show latest results of the operational GRACE-FO combination.

How to cite: Jaeggi, A., Meyer, U., Lasser, M., Flechtner, F., Dahle, C., Boergens, E., Mayer-Gürr, T., Öhlinger, F., Lemoine, J.-M., Bourgogne, S., Döhne, T., Zhou, H., Ran, J., Chen, Q., Wang, C., and Feng, W.: The COST-G GRACE RL02, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7548, https://doi.org/10.5194/egusphere-egu24-7548, 2024.

EGU24-8268 | ECS | Orals | G4.1

Investigations on the Scale Factor Readout of the Laser Interferometer aboard NGGM 

Malte Misfeldt, Vitali Mueller, and Gerhard Heinzel

The GRACE-FO mission was launched in 2018 and has been providing valuable data since then. However, developments for future missions have been initiated: the US-German GRACE-C Mission with a planned launch in 2028 and the ESA-led Next Generation Gravity Mission (NGGM) with a launch window around 2031. Both use laser interferometers as their primary and only inter-satellite ranging instruments. Accurate knowledge of the laser wavelength, or equivalently the laser frequency, is required to convert the measured phase to a range with a unit of meters.

In GRACE-FO, this conversion (or scale) factor can be determined with the main microwave ranging instrument. However, future missions will require a dedicated wavelength or scale factor readout. Additional phase modulations to be applied to the laser light, in parallel with the conventional cavity locking scheme, have been proposed by the Australian National University (ANU) to achieve such a readout. This technique is now being implemented as a novel Scale Factor Unit (SFU) for the Laser Ranging Interferometer (LRI) onboard the GRACE-C mission, and is also being investigated for the European Laser Tracking Instrument (LTI) of NGGM.

In this talk we will explain the measurement principle, show first results from a breadboard setup of our Scale Factor Measurement System (SFMS) and give an outlook on the next steps towards an implementation for the NGGM LTI.

How to cite: Misfeldt, M., Mueller, V., and Heinzel, G.: Investigations on the Scale Factor Readout of the Laser Interferometer aboard NGGM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8268, https://doi.org/10.5194/egusphere-egu24-8268, 2024.

EGU24-8356 | ECS | Posters on site | G4.1

Sensitivity analysis on gravity change data in order to observe mantle convection 

Bart Root and Cedric Thieulot

With the GRACE-FO mission well underway and the plans of the MAGIC/NGGM mission in the future, there will be several decades of satellite gravity change data available. Both periodic and secular mass changes are studied with this data, mostly surface mass changes like hydrology, ice melt, Glacial Isostatic Adjustment, and large Earthquakes. With the increasing time period of the gravity data set, smaller variation in the signal can be detected, especially linear secular changes. One of the processes that would result in small secular gravity rate is the mass change due to mantle convection.

We perform various sensitivity analysis studies to understand the added benefit of detecting mantle convection with satellite gravity change observations. A fast stoke solver (FLAPS) is developed that is based on an axisymmetric half annulus geometry. A density and viscosity structure can inserted as well as test anomalies to understand the effect of the mantle flow on the gravity change observations. The model evolves over 50 years after which the difference between the initial and final state is computed. This will also give the rate of change information. Realistic Earth models (PREM) as well as synthetic models are tested to better understand the sensitivity of the gravity change data.

The gravity change observations are sensitive to the absolute viscosity state of the mantle. This is contrary to dynamic topography and geoid data, which do not have this sensitivity and studies using these data always have an ambiguity wrt. viscosity state. Moreover, it seems that the gravity change data is more sensitive to the lower mantle of the Earth. This sensitivity can be very helpful in further exploration of Core-Mantle Boundary structures. The modelled magnitude of the gravity change linked to global mantle convection seems to be larger then the formal error estimates of the GRACE and GRACE-FO instrumentation. A longer acquisition period will reduce the secular errors in the ocean, atmosphere and tidal correction models, such that eventually mantle convection can be studied directly by satellite gravimetry.

How to cite: Root, B. and Thieulot, C.: Sensitivity analysis on gravity change data in order to observe mantle convection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8356, https://doi.org/10.5194/egusphere-egu24-8356, 2024.

EGU24-8595 | ECS | Orals | G4.1

GRACE Follow-On gravity-field results incorporating the ZARM ACC transplant based on high-precision environment modeling 

Moritz Huckfeldt, Florian Wöske, Benny Rievers, and Meike List

We have developed a GRACE-D accelerometer product that relies more heavily on modeled acceleration data instead of a transplant. Here we present our approach and a performance evaluation of our data products with different models, processing options and compared to transplant products from other institutes.

Comparisons of the artificial acceleration data to the real ACT1B data for GRACE-C show that models related to the atmospheric drag (especially density and drag coefficient) are the limiting factors in the high precision environment modeling approach. Even though it is still possible to generate monthly gravity field solutions with a combination of ACT1B data for GRACE-C and artificial data for GRACE-D that show all prominent hydrological signals, we also implemented a minimalistic transplant where we estimate the atmospheric density from GRACE-C and transplanted it to GRACE-D.

We compare our transplant data by incorporation of the GROOPS software to generate monthly gravity field solutions. This enables us to compare the results with other monthly solutions and the ITSG solutions, without getting differences due to the GFR processing tool.

We publish the ZARM GRACE-D data product, all modeled non-gravitational accelerations and additional data on a publicly accessible server.

How to cite: Huckfeldt, M., Wöske, F., Rievers, B., and List, M.: GRACE Follow-On gravity-field results incorporating the ZARM ACC transplant based on high-precision environment modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8595, https://doi.org/10.5194/egusphere-egu24-8595, 2024.

EGU24-10401 | ECS | Posters on site | G4.1

Improved alternative GRACE-FO accelerometer transplant product computed at Graz University of Technology (TUG) 

Felix Öhlinger and Torsten Mayer-Gürr

Gravity field recovery using GRACE-FO observations requires the reduction of non-conservative forces usually measured by the onboard accelerometer in the center of mass of each spacecraft. The accelerometer of GRACE-D degraded significantly in June 2018 showing increased noise levels by orders of magnitude and common mode errors on all acceleration components. However, the quality of the accelerometer measurements is vital for accurately estimating the Earth’s gravity field. The standard approach to account for the degraded data of GRACE-D is to replace the measurements with synthetic data, the so-called transplant data. At Graz University of Technology (TUG) a very effective procedure to estimate such an accelerometer transplant was developed adopting a remove-restore approach (Behzadpour, 2021). Hereby, data from GRACE-C and non-conservative force models are used to substitute GRACE-D data. Since then the effort was made to further improve the TUG transplant product.

Effects that need to be considered are on the one hand the increased solar activity as we are approaching the peak of solar cycle 25 which makes it harder to estimate an accurate transplant product by using force models and on the other hand influences such as thruster leakage which occurs on both GRACE-C and GRACE-D. Investigations that were carried out comprise the adaption of the physical properties of the satellite’s surface elements and the consideration of bias jumps at each thruster firing. The bias jumps for GRACE-C were corrected before the transplant process and with the use of actual GRACE-D data thruster leakage and some residual drag acceleration was restored for GRACE-D.

How to cite: Öhlinger, F. and Mayer-Gürr, T.: Improved alternative GRACE-FO accelerometer transplant product computed at Graz University of Technology (TUG), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10401, https://doi.org/10.5194/egusphere-egu24-10401, 2024.

EGU24-10995 | ECS | Orals | G4.1

Future satellite gravity field missions – Impact of a direct time-variable parametrization 

Philipp Zingerle, Roland Pail, Thomas Gruber, and Ilias Daras

The limited achievable temporal resolution poses one of the main limitations of current satellite gravity field missions such as GRACE and GRACE-FO and is, eventually, responsible for temporal aliasing. Increasing the temporal resolution is thus one of the most important tasks for future satellite gravity field missions. This, however, can only be achieved by means of larger satellite constellations since the temporal resolution can basically be defined as the time needed to achieve a global observation coverage. This needed (retrieval) time scales linearly with the number of satellites: e.g., a two-pair mission such as the upcoming joint ESA/NASA MAGIC mission can easily achieve global coverage with sufficient spatial resolution within less than a week. For a hypothetical 6-pair mission, even an independent daily retrieval is feasible. Future missions will hence allow to sample the gravity field in much shorter intervals. However, up until now, the parametrization of the gravity field within these intervals usually only accounts for a static behavior, resembling a step function in the time domain. Obviously, such a behavior is unnatural and does not follow the actual progression of the gravity field. So, even if sufficient temporal resolution would be available, temporal aliasing will not be fully mitigated due to this mis-parametrization. In this contribution we will thus investigate the impact of a direct time-variable parametrization through continuous spline-functions. On the example of a fictive 6-pair mission, we show how such a spline parametrization with daily support points can be applied: firstly, we prove that the spline parametrization allows numerically stable and correct solution based on a closed loop scenario without residual (sub-daily) temporal aliasing. Secondly, based on a more realistic scenario with sub-daily temporal gravity signal, we also highlight the (theoretical) limitations of a 6-pair mission due to the still very dominant temporal aliasing (from sub-daily signal sources). This work is supported by the ESA QSG4EMT study in collaboration with Politecnico di Milano, Delft University of Technology, HafenCity University Hamburg, University of Bonn and University of Trieste.

How to cite: Zingerle, P., Pail, R., Gruber, T., and Daras, I.: Future satellite gravity field missions – Impact of a direct time-variable parametrization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10995, https://doi.org/10.5194/egusphere-egu24-10995, 2024.

EGU24-11024 | ECS | Posters on site | G4.1

Recovering North Atlantic meridional transport variability from bottom pressure anomalies – a revisit 

Le Liu and Michael Schindelegger

Significant resources have been and are continuing to be devoted to monitor variability in the North Atlantic Meridional Overturning Circulation (AMOC), an essential component of the climate system. Transport mooring arrays are one means of choice, but given their confinement to individual latitudes, complementary large-scale observations are desirable. Here we follow lines of previous research and explore whether ocean bottom pressure (OBP) estimates from present and future satellite gravimetry missions can add useful constraints on interannual AMOC variability between 25°N and 55°N. Central to these considerations are OBP signals along the continental slope of the basin’s western boundary, which—in principle—allow for recovery of geostrophic AMOC variability above 1000 m, between 1000–3000 m, and in some latitudes also below 3000 m. We apply the geostrophic calculation to latest GRACE (Gravity Recovery and Climate Experiment) monthly OBP solutions, in part to document current system capabilities and highlight known shortcomings (e.g., coarse horizontal resolution and data noise). Despite these issues, there are tentative signs of robust and meridionally connected transport variations at latitudes of the New England continental slope (between 35°N and 42°N), including a positive anomaly of ~2 Sverdrup between 2006 and 2012 below 1000 m. We further assess the feasibility of recovering AMOC variability from boundary pressures in high-resolution coupled climate models. These datasets provide useful information on the variance of the involved quantities as well as locations (i.e., depths and latitudes) where accurate knowledge of OBP changes is most important. Insights gained here will be used in upcoming closed-loop orbit simulations that will make special allowance for mass change recovery on the continental slope through dedicated parameterizations in the gravity field estimation.

How to cite: Liu, L. and Schindelegger, M.: Recovering North Atlantic meridional transport variability from bottom pressure anomalies – a revisit, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11024, https://doi.org/10.5194/egusphere-egu24-11024, 2024.

EGU24-11271 | Orals | G4.1 | Highlight

Next Generation Gravity Mission (NGGM) status overview and scientific outlook 

Ilias Daras, Luca Massotti, Philip Willemsen, Guenther March, Michael Francois, and Bernardo Carnicero Dominguez

The Next Generation Gravity Mission (NGGM) is European Space Agency’s (ESA) next Mission of Opportunity.  It aims to extend and improve time series of satellite gravity missions by providing enhanced spatial and temporal resolution time-varying gravity field measurements with reduced uncertainty and latency to address the international user needs as expressed by the International Union of Geodesy and Geophysics (IUGG[1]) and the Global Climate Observing System (GCOS[2]) and demonstrate the critical capabilities for a potential future operational gravity mission.

The NGGM principal observable is the variation of the range (distance) and range rates between two satellites measured by a laser interferometer; ultra-precise accelerometers measure the non-gravitational accelerations to correct the gravity signal retrieval in the on-ground data processing. The current baseline NGGM mission concept comprises a pair of satellites on a 397km-altitude circular orbit, at 220 km separation with an inclination of 70°. The satellite-to-satellite tracking technique for detecting the temporal variations of gravity was established by GRACE (300-400 km spatial resolution at monthly intervals) using tracking in the microwave band. Today, GRACE is being continued by GRACE-Follow-On, with similar objectives, where the laser interferometry has improved the measurement resolution by a factor of 100 (upper Measurement Bandwidth.

MAss Change and Geosciences International Constellation (MAGIC) is the European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) jointly developed concept for collaboration on future satellite gravity constellation that addresses the needs of the international user community. MAGIC will consist of the GRACE-C (NASA and German Aerospace Center (DLR)) and NGGM (ESA) staggered deployment of 2 satellite pairs, with progressively improving measurement performance, to form a Bender-type constellation. It builds on the success of previous missions such as GOCE, GRACE and GRACE-FO therefore is considered a mature system architecture, that maximises the scientific benefit and enables new applications.

This presentation provides a status overview of the NGGM system and technology development activities resulting from NGGM Phase A, entering NGGM Phase B1 as currently implemented by the European Space Agency and the scientific outlook of NGGM and MAGIC. In preparation for the MAGIC constellation, ESA and NASA have established a joint science and application plan on MAGIC, with the priority to identify and resolve the challenges in the development of the new MAGIC constellation products. We will present ESA’s plans on the development of the MAGIC higher-level products which involves the optimal combination of GRACE-C and NGGM data. We will also highlight the expected impact of NGGM and MAGIC on dedicated scientific research fields and applications.


[1] Pail, R., Bingham, R., Braitenberg, C. et al. Science and User Needs for Observing Global Mass Transport to Understand Global Change and to Benefit Society. Surv Geophys 36, 743–772 (2015). https://doi.org/10.1007/s10712-015-9348-9

[2] Terrestrial Water Storage ECV Requirements: The 2022 GCOS ECVs Requirements (GCOS 245)

How to cite: Daras, I., Massotti, L., Willemsen, P., March, G., Francois, M., and Carnicero Dominguez, B.: Next Generation Gravity Mission (NGGM) status overview and scientific outlook, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11271, https://doi.org/10.5194/egusphere-egu24-11271, 2024.

EGU24-11987 | ECS | Orals | G4.1

Patterns in GRACE-FO LRI Post-Fit Range Rate Residuals 

Mathias Duwe, Igor Koch, and Jakob Flury

The LRI on GRACE Follow-On (GRACE-FO) provided range and range rate measurements for more than 4 years. At our institute we produce monthly gravity field coefficients from these observation data. We apply different techniques to analyse the post-fit range rate residuals and the post-fit range acceleration residuals to identify unknown characteristics and systematic effects within the LRI measurement system. We identified several effect: the range rate effect, the panel effect, the CNR effect and the polar effect. All these effects have not been detected in the KBR residuals. Beside the current status of GRACE/GRACE-FO processing standards at our institute, the focus lies on the characterisation of the range rate effect as well as the panel effect. The range rate effect occurs when the range rate observation is around 0 m/s and shows a very specific butterfly pattern. The panel effect is induced by the interaction of the spacecraft body panels and the sun. There is also an interaction of the LRI steering mirrors observable when the LRI laser beam is aligned with the sun.

How to cite: Duwe, M., Koch, I., and Flury, J.: Patterns in GRACE-FO LRI Post-Fit Range Rate Residuals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11987, https://doi.org/10.5194/egusphere-egu24-11987, 2024.

EGU24-12435 | ECS | Posters on site | G4.1

What can we expect from angular velocity sensing for future gravity missions? 

Yihao Yan, Vitali Müller, Gerhard Heinzel, Changqing Wang, and Zitong Zhu

The GRACE-like gravity satellites are designed to provide accurate measurements of the global time-varying gravity field, allowing to monitor the changes in the distribution of the Earth's mass caused, for example, by climate change. The gravity information is encoded in the line-of-sight vector, which is given by the position difference between the satellites. The key observable of GRACE and GRACE follow-on is the change in length of the LOS vector, measured by dedicated ranging instruments (K-band ranging system (KBR) or laser ranging interferometer (LRI)). However, the orientation of the LOS vector is measured with some precision using GNSS/GPS, which limits the accuracy of the gravity field maps. To overcome this problem, we propose the use of a dedicated angular velocity sensing (AVS) system that tracks the changes in the orientation of the line of sight with respect to the inertial frame. The angular velocity vector of the LOS has two independent components, yaw and pitch, which we introduce as additional observations in the gravity field recovery process. We firstly show how the AVS and range observables can be used to reconstruct the 3-dimensional differential acceleration vector. Then we find that the inversion results with AVS and regular ranging can mitigate the effect of AOD errors and significantly improve the accuracy of the gravity fields if more accurate AVS observations are available than currently provided by GNSS/GPS orbits. One potential way to achieve more accurate AVS observations is to use differential wavefront sensing (DWS) to accurately measure the orientation of the accelerometer test masses with respect to the platform, giving lower noise than the conventional star cameras, and combine these measurements with the DWS measurements from the inter-satellite laser interferometer to obtain the orientation of the LOS with respect to the inertial frame. With a DWS noise level of 0.1 nrad/√Hz, a single pair of GRACE satellites can achieve the same accuracy as a four-satellite Bender configuration. This study provides a promising alternative to the development of multiple satellite pairs to improve the accuracy of gravity missions.

How to cite: Yan, Y., Müller, V., Heinzel, G., Wang, C., and Zhu, Z.: What can we expect from angular velocity sensing for future gravity missions?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12435, https://doi.org/10.5194/egusphere-egu24-12435, 2024.

EGU24-12539 | ECS | Posters on site | G4.1

Preliminary CSR GRACE RL07 re-processing results  

Chaoyang Zhang, Byron Tapley, Himanshu Save, Peter Nagel, Zhigui Kang, Steven Poole, Mark Tamisiea, and Furun Wang

The fifteen and half years long GRACE temporal gravity data has greatly contributed to interdisciplinary studies especially in climate and solid Earth sciences. To further improve the noise level and error characteristic of the GRACE temporal gravity solutions, as well as provide an archival record for supporting a multidecade mass change measurement based on measurement continuity between the GRACE and GRACE Follow-On mission, the GRACE RL07 re-processing has been carried out at CSR. We will use an initial version of the GRACE Level1B  data (i.e. version 04P), updated background models, new GPS observation strategy and improved observation noise model for the RL07 re-processing. In this poster, we will present preliminary results from the GRACE RL07 re-processing and compare them with the GRACE RL06 solutions using different metrics.       

How to cite: Zhang, C., Tapley, B., Save, H., Nagel, P., Kang, Z., Poole, S., Tamisiea, M., and Wang, F.: Preliminary CSR GRACE RL07 re-processing results , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12539, https://doi.org/10.5194/egusphere-egu24-12539, 2024.

EGU24-12760 | ECS | Posters virtual | G4.1

An iterative method combining GRACE/GRACE- FO, ICESat/ICESat-2, GPS, and SMB from climate model outputs to improve Antarctic mass balance and GIA 

Chiachun angela Liang, Isabella Velicogna, Geruo Aa, and Tyler Sutterley

Consensus from mass balance studies published in the past decade revealed an increase in mass loss from the Antarctic Ice Sheet. However, independent methods (e.g., gravity, altimetry, and mass budget) for determining the rate of mass loss disagree about the magnitude and uncertainty of estimates for East Antarctica. This discrepancy is largely due to the size of East Antarctica, the low signal-to-noise ratios of existing sensors, and the confluence of uncertainties for each method. As a result, ice sheet models may not be well-constrained to make future projections of ice mass change and sea level change. Here, we combine GRACE/GRACE-FO, ICESat/ICESat-2, and GPS observations and extend Velicogna et al. (2002) iterative algorithm to improve the estimate of the Antarctic mass balance. We add outputs from surface mass balance (SMB) and firn models to satellite altimetry, time-variable gravity, and GPS measurements. We evaluate the sensitivity of the approach to realistic ice mass spatial and time distributions using an effective density map derived from ICESat-2 data, and reconstructions of SMB and firn depth from climate model outputs. Our result provides information on how the GPS network could be completed to resolve major uncertainties, obtain a better glacial isostatic adjustment (GIA), and a better estimate of ice mass balance.

How to cite: Liang, C. A., Velicogna, I., Aa, G., and Sutterley, T.: An iterative method combining GRACE/GRACE- FO, ICESat/ICESat-2, GPS, and SMB from climate model outputs to improve Antarctic mass balance and GIA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12760, https://doi.org/10.5194/egusphere-egu24-12760, 2024.

The publicly available SLR-derived monthly Earth’s oblateness C20 (or J2) time series exhibits varying levels of noise or systematic errors depending on the processing strategies used during estimation. We propose the use of two strategies, variance component estimate (VCE) and equal weighting (EW), to combine the SLR-derived J2 time series from four internationally renowned institutions. The resulting combined J2 time series is theoretically expected to demonstrate enhanced quality by reducing noise and systematic errors compared to individual contributions. These two combined solutions alongside four individual solutions are then discussed by analyzing their effects on global and local mass changes, thus exploring the potential for an optimized J2 time series in GRACE applications. The two combined SLR-derived J2 time series can assess the accuracy of the GRACE-derived J2 time series, which has shown poor but progressively improving accuracy. Results indicate that the RL06 version model of GRACE-derived J2 significantly outperforms the RL05 version, thus rendering the 160-day ocean tide effect in RL06 negligible. Moreover, significant discrepancies and lower quality among the various institutions' GRACE-derived J2 lead to Antarctic/Greenland ice sheet mass change estimates notably deviating from SLR-derived results. Therefore, upon replacing the GRACE-derived J2 time series with the VCE-combined SLR-J2 time series, the difference between the calculated mass change of the Antarctic/Greenland ice sheet and the RACMO2.3p2 model is theoretically the smallest, displaying the highest correlation coefficient between them.

How to cite: Yu, H., Zhang, L., and Zhang, Y.: Combination and analysis of the SLR monthly Earth’s oblateness variation solutions from different processing strategies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14290, https://doi.org/10.5194/egusphere-egu24-14290, 2024.

EGU24-15115 | ECS | Orals | G4.1

Integration of laser ranging range-rate observations into the GRACE Follow-On processing at the AIUB 

Martin Lasser, Ulrich Meyer, Daniel Arnold, and Adrian Jäggi

We study temporal gravity field determination from GRACE Follow-On satellite-to-satellite tracking data using the inter-satellite link of the K-Band Ranging System (KBR) and kinematic positions of the satellites as observations and pseudo-observations, respectively. In addition, we introduce the range-rate observations collected by the Laser Ranging System (LRI) as further observation group. We compute our solutions with the Celestial Mechanics Approach using next to the kinematic positions either only LRI range-rate observations or combining them with the KBR derived range-rate data by the means of Variance Component Estimation (VCE).

The stochastic noise of the KBR and LRI data is modelled with an empirical description of the noise based on the post-fit residuals between the final GRACE Follow-On orbits, that are co-estimated together with the gravity field, and the observations, expressed in position residuals to the kinematic positions and in KBR and/or LRI range-rate residuals. We validate the LRI-only and KBR+LRI monthly solutions by comparing them with the KBR-only derived models from the operational GRACE Follow-On processing at the AIUB, by examining the stochastic behaviour of respective post-fit residuals and by inspecting  areas where a low noise is expected. Last but not least, we investigate the influence of LRI-only and KBR+LRI monthly gravity field solutions in a  combination of monthly gravity fields based on other approaches as it is done by the Combination Service for Time-variable Gravity fields (COST-G) and make use of noise and signal assessment applying the quality control tools routinely used in the frame of COST-G.

How to cite: Lasser, M., Meyer, U., Arnold, D., and Jäggi, A.: Integration of laser ranging range-rate observations into the GRACE Follow-On processing at the AIUB, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15115, https://doi.org/10.5194/egusphere-egu24-15115, 2024.

EGU24-15143 | Orals | G4.1

Statistical assessment of temporal aliasing in GRACE/-FO and NGGM induced by hydrometeorological extremes 

Christian Mielke, Anne Springer, and Jürgen Kusche

Hydrometeorological extreme events, such as heavy rainfall, can cause a rapid increase in local water storage over a short period of time. The duration, magnitude, and area of the event, as well as the runoff of the affected region, determine the life span of these water mass changes. This leads to temporal aliasing, which, along with instrument noise, poses a significant challenge to improving the accuracy and resolution of satellite gravimetry products from GRACE, GRACE Follow-On, and next-generation gravity missions (NGGM). The current Atmospheric Ocean Dealiasing (AOD) products can remove tidal and sub-monthly non-tidal mass variations in the ocean and atmosphere from the level-1 GRACE/-FO data. However, the reanalysis and forecast datasets underlying these AOD products only have a limited temporal and spatial resolution and do not include high-frequency hydrological mass variations and liquid cloud water content of atmospheric mass, that can significantly increase during hydrometeorological extreme events.

The research group New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV), funded by the German Research Foundation (DFG), aims at improving GRACE/-FO data products by developing new analysis methods and modeling approaches. This includes a revision of existing geophysical background models as well as their spatial-temporal parameterization. Within this research group we investigate how hydrometeorological extreme events are mapping into GRACE/-FO level-1 data. In this study, we provide statistics on events that may affect GRACE/-FO/NGGM observations and are not accounted for in current AOD products. Using a 3D connected component algorithm, we determine the duration, magnitude, and area of these events for multiple test years over the entire GRACE/-FO observation time span from 2002 to 2023. As expected, the majority of hydrometeorological extreme events take place in tropical regions and areas that are frequently impacted by typhoons, hurricanes, and monsoon rains such as Japan, northern India, and around the Gulf of Mexico. Additionally, we found an increasing number of events over Europe that could significantly impact GRACE/-FO/NGGM observations. Overall, the number of events per year more than doubles from the start to the end of the observation period, which is likely due to climate change. We suspect that the GRACE-FO LRI measurement is sensitive to instantaneous precipitation and liquid cloud water content during overfly for a significant number of these extreme events. Hence, we anticipate an increased probability of NGGM observations being affected by such events, particularly in the context of ongoing climate change. Therefore, we recommend that upcoming dealiasing procedures carefully consider these events.

How to cite: Mielke, C., Springer, A., and Kusche, J.: Statistical assessment of temporal aliasing in GRACE/-FO and NGGM induced by hydrometeorological extremes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15143, https://doi.org/10.5194/egusphere-egu24-15143, 2024.

EGU24-16530 | Posters on site | G4.1

Gravity field recovery using co-estimation of background model errors to improve de-aliasing capabilities of the MAGIC double-pair constellation 

Josefine Wilms, Markus Hauk, Christoph Dahle, Michael Murboeck, Natalia Panafidina, and Frank Flechtner

GFZ has performed various full-scale simulations within the ESA NGGM/MAGIC Science Support Study, including instrument noise and background model error assumptions. The focus was set on developing and applying extended parameterization techniques for improved de-aliasing of short-term mass variations.

The impact of using model uncertainties was investigated for ocean tide and non-tidal atmospheric and oceanic background models. As part of the DFG Research Unit NEROGRAV covariances of model uncertainties were computed and during gravity field retrieval model corrections were co-estimated using this prior covariance information. In principle, model errors are absorbed by the additional co-estimated parameters, and gravity field estimation is thereby improved.

First, simulations with only ocean tide errors and only non-tidal background model errors were performed separately for one month to assess the error reduction obtained for each. Finally, ocean tide and non-tidal errors were included together in a full noise simulation and compared to the processing strategy that did not include co-estimation of background model errors.

The novel optimized method was then also applied for monthly gravity field retrieval over one year, showing improvements for each month. The estimated residual ocean tides from this 1-year simulation were then used to calculate an improved ocean tide model optimized for gravity field recovery.

In addition, monthly solutions, obtained with co-estimation of background model errors, have been calculated for the inclined pair alone using regularization for the not-covered polar regions and compared to double pair solutions for latitudes lower than +/- 70 degrees.

How to cite: Wilms, J., Hauk, M., Dahle, C., Murboeck, M., Panafidina, N., and Flechtner, F.: Gravity field recovery using co-estimation of background model errors to improve de-aliasing capabilities of the MAGIC double-pair constellation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16530, https://doi.org/10.5194/egusphere-egu24-16530, 2024.

EGU24-16789 | Orals | G4.1

Advanced processing strategies for a future GFZ GRACE/GRACE-FO Level-2 data release 

Michael Murböck, Christoph Dahle, Natalia Panafidina, Markus Hauk, Josefine Wilms, Karl-Hans Neumayer, and Frank Flechtner

Being part of the GRACE/GRACE-FO Science Data System, the GFZ German Research Centre for Geosciences is one of the official Level-2 processing centers routinely providing monthly gravity field models. These models are used by a wide variety of geoscientists to infer mass changes mainly at the Earth’s surface. Currently, the operationally processed monthly gravity fields are still based on release 6 (RL06) standards, but developments in view of a reprocessed and improved GFZ RL07 time series are already ongoing. Most of these improvements have been developed within the Research Unit “New Refined Observations of Climate Change from Spaceborne Gravity Missions” (NEROGRAV) funded by the German Research Foundation DFG. After a successful first phase, the second three years phase of NEROGRAV has started last year.

At present, we primarily work towards the completion of an optimized stochastic modeling for GRACE and GRACE-FO gravity field determination. This includes the extension of the stochastic instrument error models, the optimization of the combination of the different observations, and the inclusion of tidal and temporally changing non-tidal background model error variance-covariance matrices in the adjustment process.

This presentation provides an overview of the main outcomes of these advanced processing strategies. We discuss details on stochastic modeling of non-tidal atmospheric-oceanic background models including the assessment of temporal correlations and will present preliminary RL07 Level-2 results in the spectral and spatial domain in comparison with the standard GFZ GRACE/GRACE-FO RL06 time series.

How to cite: Murböck, M., Dahle, C., Panafidina, N., Hauk, M., Wilms, J., Neumayer, K.-H., and Flechtner, F.: Advanced processing strategies for a future GFZ GRACE/GRACE-FO Level-2 data release, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16789, https://doi.org/10.5194/egusphere-egu24-16789, 2024.

EGU24-17286 | ECS | Posters on site | G4.1

Momentum Transfer Events and Other Disturbances in LRI Data 

Pallavi Bekal, Malte Misfeldt, Laura Müller, Vitali Müller, and Gerhard Heinzel

The Laser Ranging Interferometer (LRI) is a technology demonstrator instrument on board the GRACE-FO twin-satellite mission that has been in orbit since 2018. It uses laser interferometry to measure the range between the two satellites (GF1 and GF2) with a nanometer level of accuracy. The gravity field measurements using the ranging data quantify the spatial and temporal variation in the Earth's mass distribution.

The change in the range measured by the LRI has gravitational and non-gravitational origins. Many non-gravitational effects, like atmospheric drag and thruster firings, are known and can be delineated from the LRI data. However, other sporadic instantaneous changes in the range are described as possible momentum transfer events (MTEs) candidates. Some potential sources are meteoroids and space debris's physical impacts on the spacecraft. 

To analyze MTE candidates, we first present the process of detecting them by correlating the LRI ∆v with that of the accelerometer (ACC) for both GRACE-FO spacecraft. Through this, 129 events were found on GF1 and 138 in GF2 between mid-2018 and the end of 2022. Some events show a better correlation between LRI and ACC data than others. Hence, further analysis is conducted by categorizing them accordingly and studying their spatial distribution and periodicity. The occurrence of many events coincides with the period of the beta angle of the sun. Structural changes in the spacecraft could cause these events upon exposure to solar radiation. However, many events have ∆v < 5 × 10 −8 m/s, which is too low to be considered an MTE. They are instead categorized as disturbances to the spacecraft. The origin of these remains unknown.

Furthermore, simulations are performed using the ESA MASTER v8.0.3 to render the number of events per year that cause MTEs via physical impact during the same observation period. The observed events are consistent with the simulation for ∆v ≥ 5 × 10 −8 m/s. 

This analysis is beneficial in creating a repository of known effects in the first-ever space laser interferometer. In future missions, the knowledge of these occurrences in the LRI and ACC data will be helpful during post-processing.

How to cite: Bekal, P., Misfeldt, M., Müller, L., Müller, V., and Heinzel, G.: Momentum Transfer Events and Other Disturbances in LRI Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17286, https://doi.org/10.5194/egusphere-egu24-17286, 2024.

EGU24-17380 | ECS | Orals | G4.1

Novel LRI Level 0/1A Data Simulator 

Laura Müller, Vitali Müller, Malte Misfeldt, and Gerhard Heinzel

GRACE-FO was launched almost six years ago, following the successful GRACE mission. Measuring changes in the Earth's mass distribution is useful for climate research, such as monitoring melting ice caps or changes in groundwater storage. The Earth's gravitational field causes distance variations between the two twin satellites, which are measured by a Microwave Instrument (MWI) and a Laser Ranging Interferometer (LRI). This first inter-satellite laser interferometer provides reliable measurements with lower noise than the MWI and has therefore been selected as the main science instrument for future gravity missions.

Here we present the current status and results of a novel LRI Level 0/1A data simulator developed to support studies for future missions and to verify and improve the current LRI1B processing chain. The main inputs to the simulator are satellite orbit files with position and velocity and attitude data sets, which are transformed into LRI Level 0/1A data files, taking into account relativistic effects, phase wrapping, tilt-to-length coupling and many other noise sources. The output data format is equivalent to the raw phase or ranging data from GRACE-FO. The Level 1A data can then be further processed to Level 1B using the same software used for the GRACE-FO LRI flight data processing. We explain our strategy to validate the results and to identify and address limitations in the Level-1A simulator and in our Level-1B flight data processing chain, e.g. by using specially tailored orbit sets.

We conclude that the simulator is capable of deriving realistic LRI Level 0/1A data that can be further processed to Level 1B, and that the simulator has led to improvements in our GRACE-FO LRI Level 1B processing.

How to cite: Müller, L., Müller, V., Misfeldt, M., and Heinzel, G.: Novel LRI Level 0/1A Data Simulator, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17380, https://doi.org/10.5194/egusphere-egu24-17380, 2024.

EGU24-17911 | ECS | Posters on site | G4.1

Development of a calculation method for viscoelastic relaxation incorporating nonlinear rheology in a self-gravitating spherical Earth model 

Kazuma Nakakoji, Yoshiyuki Tanaka, Volker Klemann, and Zdeněk Martinec

Space geodetic techniques such as GNSS have been used to observe co- and post-seismic crustal deformation in subduction zones with high spatio-temporal resolution. However, it is difficult to observe such crustal deformations in oceanic regions. Satellite gravimetry, on the other hand, can detect co- and post-seismic mass changes both over land and ocean. However, the spatio-temporal resolution of these satellites is insufficient to distinguish co- and post-seismic effects. The planned MAGIC mission aims to achieve a 3-day, 100 km resolution, enabling their separation. This advancement is expected to provide a more precise understanding of the mechanisms of post-seismic deformations following major earthquakes.

 

Geodetic observations have so far shown that there are three mechanisms of post-seismic deformations: afterslip, poroelastic rebound, and viscoelastic relaxation. The last one, viscoelastic relaxation has not been considered to contribute to short-term deformations unlike other two mechanisms. However, seafloor geodetic observations after the 2011 Tohoku earthquake captured the characteristic deformation even one year after the earthquake, which cannot be interpreted without a contribution of viscoelastic relaxation. Geophysical models that reproduce such viscoelastic relaxation have been proposed considering surface topography and 3D viscoelastic and density structure including a subducting oceanic slab. However, there are only a few models incorporating a nonlinear rheology to calculate post-seismic gravity changes. In the nonlinear case, the effective viscosity changes in space and time with stress evolution. In particular, co-seismic high stress changes lead to low effective viscosity, which promotes short-term viscoelastic relaxation after an earthquake. Hence, it is essential to discuss the extent to which this mechanism can be constrained when satellite gravity data with high spatio-temporal resolution become available by MAGIC.

 

Previous physical models to calculate post-seismic deformation have often treated the self-gravitation effects only approximately or ignored it. To represent the effects naturally, we have developed a spectral finite-element method based on a spherical earth model with a 3D viscosity distribution for a linear rheology. In this study, we extend this method to a nonlinear rheology. This method computes the deformation in the time domain. Therefore, one can easily obtain the deformation for the nonlinear case by evaluating effective viscosity at each time step without major changes in the algorithm for the linear case. In the presentation, the spectral finite element method will be introduced, and numerical results will be shown, including viscosity distributions corresponding to co-seismic stress changes and their time evolution, and gravity signals reflecting a nonlinear rheology.

How to cite: Nakakoji, K., Tanaka, Y., Klemann, V., and Martinec, Z.: Development of a calculation method for viscoelastic relaxation incorporating nonlinear rheology in a self-gravitating spherical Earth model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17911, https://doi.org/10.5194/egusphere-egu24-17911, 2024.

It is common to convert GRACE-based level-2 data product (spherical harmonic coefficients) into mass anomalies at the Earth’s surface using spherical harmonic synthesis. We claim that it is more appropriate to use for that purpose a least-squares adjustment (which can be understood in this context as a variant of mascon approach). Among other, this allows one to take into account the stochastic model of errors in the spherical harmonic coefficients, as well as a various physical constraints, such as geometry of coastal lines, geometry of deserts, etc. The latter constraints can be implemented, e.g., by introducing a spatially-varying first-order Tikhonov regularization. We apply such an approach to make a state-of-the-art estimate of Greenland Ice Sheet (GrIS) mass losses.


First, a numerical study is carried out to optimize the spatially-varying regularization and demonstrate the performance of the developed approach. We show, among other, that the optimal regularization parameters strongly depend on the region and the spatial scale of interest. For instance, a substantially different regularization is recommended for the best global estimates of mass anomalies, for the best estimates of mass anomalies with Greenland only (pointwise), and for the best estimates of total mass anomalies per GrIS drainage system. This suggests that an optimal estimate of mass anomalies produced by a regularized least-squares adjustment tailored for a particular application is, in general, superior to an off-the-shelf mascon-type data product.


Second, the mass trends in 2002–2023 per drainage system and over entire Greenland are estimated from actual GRACE/GRACE-FO level-2 data products. We show, among other, that the average rate of total mass loss in Greenland in the considered time interval is of the order of 270 Gt/yr. Furthermore, we analyze the factors that affect the estimated trends and quantify the uncertainties of the obtained estimates.

 

How to cite: Ditmar, P.: Optimization of GRACE-based mass anomaly estimates using the first-order Tikhonov regularization, with application to the Greenland Ice Sheet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18889, https://doi.org/10.5194/egusphere-egu24-18889, 2024.

EGU24-19340 | Orals | G4.1

Innovative solid Earth applications of future gravity field missions 

Carla Braitenberg, Anna Fantoni, Gerardo Maurizio, and Alberto Pastorutti

The upcoming gravity missions anticipated in the next decade are expected to significantly reduce noise levels compared to current data acquisitions from GRACE and GRACE Follow On. Our objective is to proactively prepare for these future datasets and develop scientific processing tools that can yield innovative applications in solid earth research. These applications have the potential to evolve into community-relevant ser-vices for earth monitoring and exploration.

We specifically focus on key categories such as earthquakes, crustal uplift and subsidence, seamounts, and lithospheric structure. Accurately estimating the gravity field necessitates the formulation of realistic 3D models of density and their temporal changes.

Uplift and subsidence is considered for the Alpine mountain arc, where a lithosphere density model has been formulated (Tadiello & Braitenberg, 2021) imposing vertical movements from measured GNSS rates. The exploration of the lithosphere is tested on a recent 3D density model of Iran (Maurizio et al., 2023) which was inverted from the presently available gravity field integrated with a seismic tomography model. We distinguish crustal and mantle signals and evaluate prospective improvements to detect structures in crust and mantle.

In the context of earthquakes, our focus lies in improving the minimum detectable magnitude, depending on fault plane mechanisms, and detecting post-seismic relaxation. Seamounts pose a unique challenge with limited alternatives for detection, placing gravity detection in a primary role, provided the associated mass changes are sufficiently significant. Therefore, we conduct a review of documented seamount eruptions, estimating the associated mass changes. Particularly intriguing are 'silent' seamounts that grow several hundred meters high without breaking the ocean surface, remaining invisible.

We compare the signals against noise levels of the future gravity missions, including the polar and inclined satellite couples with inter satellite distance measurement, the MAGIC proposal (Daras et al., 2024) and proposals with the payload of quantum technology gradiometers presently under discussion at ESA and NASA.

 

References

Daras, I., March, G., Pail, R., Hughes, C. W., Braitenberg, C., Güntner, A., Eicker, A., Wouters, B., Heller-Kaikov, B., Pivetta, T., & Pastorutti, A. (2024). Mass-change And Geosciences International Constellation (MAGIC) expected impact on science and applications. Geophysical Journal International, 236(3), 1288–1308. https://doi.org/10.1093/gji/ggad472

Maurizio, G., Braitenberg, C., Sampietro, D., & Capponi, M. (2023). A New Lithospheric Density and Magnetic Susceptibility Model of Iran, Starting From High‐Resolution Seismic Tomography. Journal of Geophysical Research: Solid Earth, 128(12), e2023JB027383. https://doi.org/10.1029/2023JB027383

Tadiello, D., & Braitenberg, C. (2021). Gravity modeling of the Alpine lithosphere affected by magmatism based on seismic tomography. Solid Earth, 12(2), 539–561. https://doi.org/10.5194/se-12-539-2021

How to cite: Braitenberg, C., Fantoni, A., Maurizio, G., and Pastorutti, A.: Innovative solid Earth applications of future gravity field missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19340, https://doi.org/10.5194/egusphere-egu24-19340, 2024.

EGU24-2746 | Posters on site | G4.2

YeMiGO: Data Processing and Analysis of Underground Superconducting Gravity Data in South Korea 

John J. Oh, Mohammad Javad Dehghan, Ik Woo, Hwansun Kim, Edwin J. Son, SeungMi You, and Jeong Woo Kim

We present the status of the Yemi micro-gravity observatory (YeMiGO), including the installation, operation, and initial analysis of the gravity data. In October 2022, we installed GWR Instruments Inc,’s iGrav (serial #001) superconducting gravimeter (SG) at Yemi underground laboratory (YemiLab) in South Korea. YemiLab is located approximately 1,008 and 118 meters below the Earth's surface and mean sea level, respectively. The noise characteristics were assessed using one month of raw data collected in September 2023 and compared to those of other seismometer stations. The results show the noise level at the SG station, especially in the seismic band, is significantly low and proves the stability of the Lab.  The research findings also indicate that blasting during mining operations at a distance between ~700 and ~900 meters (please confirm this) from the SG impacted the dewar and barometer pressures as well as the tilt balance data. However, no discernible effects were observed in the raw SG data, leading to the hypothesis that the SG tilt system was able to compensate for the resulting vibrations. After 6 months of continuous data recording from 16th November 2022 to 18th May 2023, a calibration factor of -92.17 μGal∙V-1 was estimated using tidal analysis. In November 2023, a new calibration factor of -94.15 μGal∙V-1 was estimated using parallel measurements with FG5-231 provided by the Ministry of Interior, R.O.C. (Taiwan). Having accounted for various environmental effects, including Earth tide, atmospheric pressure, groundwater level, and polar motion, during the initial six months of data, the residual gravity was obtained. Spectral analysis revealed several unidentified residual gravity power spectrum density frequencies, necessitating further investigation. Co-seismic gravity changes resulting from four earthquakes in May 2023 with different magnitudes and within various distances from the SG station were examined. The M6.2 earthquake that occurred 765 km away was linked to the most notable co-seismic gravity alteration, which recorded a value of 0.561 μGal. The mentioned changes decreased gradually and faded away entirely within half an hour after the SG's first arrival.

How to cite: Oh, J. J., Dehghan, M. J., Woo, I., Kim, H., Son, E. J., You, S., and Kim, J. W.: YeMiGO: Data Processing and Analysis of Underground Superconducting Gravity Data in South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2746, https://doi.org/10.5194/egusphere-egu24-2746, 2024.

EGU24-3305 | Posters on site | G4.2

ENIGMA: East-Asian Network Initiative for Gravity Measurement Alliance: A Proposal and Science Cases 

Edwin J. Son, Jeong Woo Kim, John J. Oh, Hwansun Kim, Cheinway Hwang, Ching-Chung Cheng, Yoshihiro Ito, Yoshiyuki Tanaka, Wenbin Shen, Wei Luan, Minzhang Hu, Ziwei Liu, Heping Sun, Xiaodong Chen, Sangwook Bae, and Heejun Yoon

We propose the establishment of an observational network comprising micro gravitometers across East Asia including, but not limited to Republic of Korea, Japan, Taiwan, and the Chinese mainland. The network will generate a parallel observation belt within the seismogenic zone that connects the Japan Trench, Ryuku Trenches, and Nankai Through, both constituent components of the Ring of Fire, for the detection of slight changes in micro-gravity for analyzing earthquakes of different magnitudes with different sources and depths. We will establish a data hub for sharing data, managing combined data format, and distributing computing resources for conducting collaborative research. In addition, the network measurement of micro-gravity can be used for searching the dark matter candidate inside Earth. The presentation demonstrates various science cases that could be undertaken by implementing a network of GWR Instruments Inc.’s superconducting gravimeters and a data hub within the East Asian region.

How to cite: Son, E. J., Kim, J. W., Oh, J. J., Kim, H., Hwang, C., Cheng, C.-C., Ito, Y., Tanaka, Y., Shen, W., Luan, W., Hu, M., Liu, Z., Sun, H., Chen, X., Bae, S., and Yoon, H.: ENIGMA: East-Asian Network Initiative for Gravity Measurement Alliance: A Proposal and Science Cases, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3305, https://doi.org/10.5194/egusphere-egu24-3305, 2024.

EGU24-3560 | Orals | G4.2

Absolute Quantum Gravimeter for Field Applications 

Jérémie Richard, Laura Antoni-Micollier, Pierre Vermeulen, Maxime Arnal, Romain Gautier, Camille Janvier, Vincent Ménoret, Cédric Majek, Bruno Desruelle, and Peter Rosenbusch

Absolute gravity measurements at the level of 1 µGal using cold atom quantum technology have been demonstrated in the laboratory in 1992 and have ever since received an increasing interest from the geophysics community [1]. In 2015, Exail launched on the marketplace the Absolute Quantum Gravimeter (AQG) [2]. Cutting-edge technology developments brought the necessary easy-of-use, autonomy, and robustness for field deployment. More than 15 units have since been produced for various geophysical applications, including hydrology and volcanology.

Designed for field applications with autonomous or remote-controlled operation, the AQG does not require heavy vibration isolation equipment thanks to an integrated real time vibration compensation module which hybridizes the quantum measurement with a built-in classical accelerometer. As a result, all units reproducibly achieve a resolution of 10-9 g after < 2 hours of measurement at our inner-city factory site or after < 40 minutes at a quiet site, as we will demonstrate in this talk [2,4]. Moreover, we will present recent progress on the AQG including a gravity measurement campaign that has been on-going for 3 years now near the summit of Mt Etna [3,4]. Finally, we will detail our study of systematic effects affecting the instrument, whose evaluation is required to build a rigorous accuracy (or trueness) budget.

[1] M. Kasevich, S. Chu. Measurement of the gravitational acceleration of an atom with a light-pulse atom interferometer. Applied Physics B, 1992, vol. 54, p. 321-332.
[2] V. Ménoret et al, Gravity measurements below 10-9 g with a transportable absolute quantum gravimeter. Scientific Reports, 2018, 8, pp.12300.
[3] L. Antoni-Micollier et al Detecting volcano-related underground mass changes with a quantum gravimeter. Geophysical Research Letters, vol. 49, issue 13, e2022GL097814 (2022).
[4] L. Antoni-Micollier et al, Absolute quantum gravimeters and gradiometers for field measurements. IEEE Instrumentation & Measurement Magazine (submitted).

How to cite: Richard, J., Antoni-Micollier, L., Vermeulen, P., Arnal, M., Gautier, R., Janvier, C., Ménoret, V., Majek, C., Desruelle, B., and Rosenbusch, P.: Absolute Quantum Gravimeter for Field Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3560, https://doi.org/10.5194/egusphere-egu24-3560, 2024.

EGU24-5316 | ECS | Orals | G4.2

Airborne Gravimetry with Quantum Technology 

Tim Jensen, René Forsberg, Andreas Stokholm, Bjørnar Dale, Yannick Bidel, Nassim Zahzam, Alexandre Bresson, and Alexis Bonnin

In summer 2023 an airborne gravity survey was carried out utilizing the GIRAFE quantum gravimeter from ONERA and the iMAR classical strapdown gravimeter from DTU. The survey consisted of two parts: (1) In Iceland targeting the Vatnajökull ice cap and some active volcanoes, all expected to have some source of mass variation; (2) A regular survey grid around the Nuuk fjord system as input for Geoid computation, along with a strapdown test of the cold-atom sensor, which is currently operated on a stabilized platform.

Results from both instruments will be presented and compared with external information. An intercomparison of the two instruments will be presented along with plans for a new cold-atom sensor designed for airborne applications.

How to cite: Jensen, T., Forsberg, R., Stokholm, A., Dale, B., Bidel, Y., Zahzam, N., Bresson, A., and Bonnin, A.: Airborne Gravimetry with Quantum Technology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5316, https://doi.org/10.5194/egusphere-egu24-5316, 2024.

EGU24-6235 | Posters on site | G4.2

Monitoring aquifers and subsidence with the chronometric leveling 

Guillaume Lion, Kristel chanard, Gwendoline Pajot, Michel Diament, and Olivier Jamet

Subsidence poses a significant global threat to the viability and economic development of approximately one-fifth of the world's population, especially in coastal or heavily urbanized regions experiencing ground settlements ranging from centimeters per month to meters per decade. This phenomenon, driven by natural or anthropogenic factors, is intricately linked to hydrology, geology, tectonics, and the geotechnical properties of underlying formations. Multiple triggers, including underground cave collapses, organic soil oxidation, natural gas and oil extraction, and aquifer consolidation, contribute to subsidence, disrupting vital water reserves crucial for societal needs. Spatial and temporal limitations of conventional techniques like gravimetry, positioning, and spatial imaging in resolving the effects of extreme weather events and resource exploitation on subsidence prompt an exploration of their complementarity and the emergence of quantum sensors—specifically, atomic clocks sensitive to gravitational potential variations.
Since 2021, the SYRTE, IPGP, IGN, and SHOM participate in the ANR ROYMAGE project (Optical Ytterbium Mobile Atomic Clock Applied to Geodetic Exploration). The project aims to develop a transportable atomic clock prototype with sufficient performance to determine altitude differences within the T-REFIMEVE fiber network, achieving a centimeter-level uncertainty in just a few hours across points separated by hundreds of kilometers for geodetic applications. As optical atomic clocks become integral to fieldwork, their sensitivity to mass anomalies and vertical displacement becomes a crucial consideration.

Within the ANR framework, we have initiated digital tool implementation to model the signal generated by remote clock comparisons, mainly gravitationally and geometrically influenced by mass and altitude variations. The challenge lies in identifying and decorrelating signal sources to reveal the studied phenomenon. Geopotential differences, a novel geodetic observable, necessitate modeling considering gravitational signatures at the Earth's surface from buried mass anomalies (e.g., aquifers), the (in)elastic medium response to pressure changes causing vertical crust displacement, and other effects like solid Earth tides, ocean tide loading, polar motion, etc. Preliminary results suggest that clock comparisons with centimeter-level uncertainties could detect variations in regional groundwater levels.

This work proposes to assess whether chronometric leveling, in France, can complement gravimetric, spatial imaging and levelling techniques to study vertical soil displacements resulting from disturbances in underground water resources due to climatic or anthropogenic origins.

The authors acknowledge the support of the French Agence Nationale de la Recherche (ANR) under reference ANR-20-CE47-0006.

How to cite: Lion, G., chanard, K., Pajot, G., Diament, M., and Jamet, O.: Monitoring aquifers and subsidence with the chronometric leveling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6235, https://doi.org/10.5194/egusphere-egu24-6235, 2024.

EGU24-7350 | ECS | Posters on site | G4.2

Cold Atom Interferometry Accelerometers for Future Satellite Gravity Missions 

Annike Knabe, Manuel Schilling, Mohsen Romeshkani, Alireza HosseiniArani, Nina Fletling, Alexey Kupriyanov, Jürgen Müller, Quentin Beaufils, and Franck Pereira dos Santos

Satellite gravity missions are a powerful tool to measure the global Earth’s gravity field and consequently provide important information for geosciences. However, improvements in spatial and temporal resolution are required for many applications. Simulation studies are performed to quantify the influence of improved sensors, orbit parameters and measurement concepts on the recovered gravity field solution. The investigations focus primarily on accelerometers by evaluating the concept of Cold Atom Interferometry (CAI) accelerometers and their combination with electrostatic accelerometers for future satellite gravity missions.

The CAI noise behavior is mainly estimated based on the quantum projection noise, but also challenges due to the longer duration of the measurement cycle are investigated. The results of the low-low Satellite-to-Satellite Tracking (ll-SST) closed-loop simulations indicate, on the one hand, benefits from the addition of CAI and reveal, on the other hand, the dominance of background modeling errors. Furthermore, the combination of ll-SST and cross-track gradiometry is studied. In order to significantly benefit from an additional cross-track gradiometer, it has to achieve a low noise level of 1 mE and the angular velocity measurements have to ensure high accuracies.

We acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434617780 – SFB 1464 and under Germany’s Excellence Strategy – EXC-2123 Quantum-Frontiers – 390837967, the support by Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) for the project Q-BAGS and the European Union for the project CARIOQA-PMP (Project-ID 101081775).

How to cite: Knabe, A., Schilling, M., Romeshkani, M., HosseiniArani, A., Fletling, N., Kupriyanov, A., Müller, J., Beaufils, Q., and Pereira dos Santos, F.: Cold Atom Interferometry Accelerometers for Future Satellite Gravity Missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7350, https://doi.org/10.5194/egusphere-egu24-7350, 2024.

EGU24-8912 | Posters on site | G4.2

Laser Ranging Interferometry for the next gravity missions 

Vitali Müller, Pallavi Bekal, Malte Misfeldt, Laura Müller, Reshma Sudha, Martin Weberpals, Kolja Nicklaus, Kai Voss, and Gerhard Heinzel

The Laser Ranging Interferometer (LRI) on board the GRACE Follow-On spacecraft has successfully demonstrated for the first time interferometric laser ranging between satellites with a noise level below 1 nm/rtHz. In addition, the LRI’s steering mirror information provides attitude information that enable inter-comparisons with the conventional star cameras. Two new twin-satellite missions are now under development: the Next Generation Gravity Mission (NGGM) by ESA and the GRACE-C mission by a US-German partnership. Both missions rely on laser interferometry as the primary and only means of measuring the distance variations between the spacecraft.

In this presentation, we introduce the measurement concept and design principles, report on the current status of the ranging instruments and explain the changes to be implemented with respect to GRACE-FO, mainly related to redundancy and lessons learned.

How to cite: Müller, V., Bekal, P., Misfeldt, M., Müller, L., Sudha, R., Weberpals, M., Nicklaus, K., Voss, K., and Heinzel, G.: Laser Ranging Interferometry for the next gravity missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8912, https://doi.org/10.5194/egusphere-egu24-8912, 2024.

EGU24-8931 | ECS | Posters on site | G4.2

Improvement of ONERA Electrostatically suspended torsion pendulum 

Nolwenn Portier, Bruno Christophe, Marine Dalin, Vincent Lebat, Françoise Liorzou, and Manuel Rodrigues

In order to meet the objectives of the Next Generation Gravity Mission (NGGM), the French Aerospace Lab ONERA is developing a new accelerometer concept MicroSTAR with three sensitive linear and three true angular acceleration measurements (Dalin et al., session G4). This instrument benefits from previous developed accelerometers which flew in the well-known gravity space missions: CHAMP, GRACE, GOCE, GRACE-FO.

The principle of operation of these accelerometers is to maintain motionless a proof-mass with respect to the surrounding electrodes using a control loop. The applied electrostatic forces needed for this control, are proportional to the accelerations suffered by the proof-mass. The proof-mass is polarized with a very thin (few micrometer) wire in order to measure precisely its position by capacitive detection with the electrodes and to avoid charging in orbit. The stiffness and damping induced by the polarization wire impact the performance of the accelerometer at low frequencies. To quantify on-ground the performance limitation due to the wire, an electrostatically suspended torsion pendulum (PTSE) is used (Willemenot 1997, Willemenot and Touboul 2000).

The PTSE is a six-axes servo-controlled accelerometer, optimized for the measurement of angular accelerations about the vertical axis. The torque noise spectral density is 1.3 10-14 Nm/√Hz  around 0.05 Hz with a 1/√f increase at lower frequency, corresponding to 10-8 rad/s²/√Hz , and 2 10-10 ms-2/√Hz with a lever arm of 2cm. For instance, regarding a gold wire of 7.5µm diameter and 1.7cm length, we use it to measure theoretical stiffness of 2.5 10-5 N/m i.e. a torsion of 10-8 Nm/rad. In our presentation, this instrument will be described before sharing ideas for its improvement.

 

Willemenot, P. Touboul; Electrostatically suspended torsion pendulum. Rev Sci Instrum 1 January 2000a; 71 (1): 310–314. https://doi.org/10.1063/1.1150198

Willemenot, P. Touboul; On-ground investigation of space accelerometers noise with an electrostatic torsion pendulum. Rev Sci Instrum 1 January 2000b ; 71 (1): 302–309. https://doi.org/10.1063/1.1150197

Willemenot, Pendule de torsion à suspension électrostatique, très hautes résolutions des accéléromètres spatiaux pour la physique fondamentale. Ph.D. thesis, Université Paris 11, France, 1997

How to cite: Portier, N., Christophe, B., Dalin, M., Lebat, V., Liorzou, F., and Rodrigues, M.: Improvement of ONERA Electrostatically suspended torsion pendulum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8931, https://doi.org/10.5194/egusphere-egu24-8931, 2024.

EGU24-9463 | ECS | Orals | G4.2

Quantum-based Accelerometers for Satellite Gravimetry Missions 

Nina Fletling, Annike Knabe, Jürgen Müller, Matthias Weigelt, and Manuel Schilling

Accelerometers are an essential component of satellite gravimetry missions, as the non-gravitational forces acting on the satellites must be known in order to determine the Earth's gravity field. However, the accelerometers currently in use are one of the limiting factors regarding the accuracy of the determined gravity field, which opens up room for improvement. Among other techniques, quantum-based accelerometers are promising candidates to be applied in the future.

In order to achieve the required technology readiness level for operation in space, a pathfinder mission is planned to demonstrate the technology. This mission is being prepared in the framework of the Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometer - Pathfinder Mission Preparation (CARIOQA-PMP) project funded by the European Union. In addition to designing the pathfinder mission and instrument to achieve a specific performance, simulations are carried out based on the expectable performance not only for the pathfinder mission but also beyond on the utilisation of quantum-based accelerometers in future satellite gravimetry missions. This includes a broad study on different mission types, such as a single satellite with high-low satellite-to-satellite tracking, as foreseen in the pathfinder mission, or a satellite constellation with GRACE-FO-like conditions utilising low-low satellite-to-satellite tracking. Here, closed-loop simulations are used to investigate under which conditions the determined gravity field solution benefits from a quantum-based accelerometer compared to a classical electrostatic one and which challenges still need to be addressed in order to improve resolution and accuracy.

How to cite: Fletling, N., Knabe, A., Müller, J., Weigelt, M., and Schilling, M.: Quantum-based Accelerometers for Satellite Gravimetry Missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9463, https://doi.org/10.5194/egusphere-egu24-9463, 2024.

EGU24-10007 | ECS | Posters on site | G4.2

General Relativistic Chronometry from Ground and in Space 

Dennis Philipp, Eva Hackmann, Jan Hackstein, and Claus Laemmerzahl

Geodesy's primary objective lies in the determination of Earth's gravity field through ground and space-based measurements. General relativity and, thus, relativistic geodesy, introduce a novel perspective, leveraging high-precision clock comparisons to potentially unveil a new tool for globally determining Earth's gravito-electric potential based on the gravitational redshift.

In the pursuit of clock-based gravimetry, which involves chronometry in stationary spacetimes, precise expressions for the relativistic redshift and timing among observers in different configurations are presented. These observers, equipped with standard clocks, move on arbitrary worldlines. The analysis reveals how redshift measurements, employing clocks on the ground and/or in space, can be harnessed to deduce the (mass) multipole moments of the underlying spacetime geometry. Importantly, our findings align with the Newtonian potential determination via conventional methods such as the energy approach.

The framework of chronometric geodesy is introduced and demonstrated across various exact vacuum spacetimes for clarity. The study extends to gravity degrees of freedom, encompassing gravito-magnetic contributions, with investigations into potential experiments for their determination. Looking ahead, upcoming gravity field recovery missions might incorporate clock comparisons as an additional resource for advanced data fusion.

How to cite: Philipp, D., Hackmann, E., Hackstein, J., and Laemmerzahl, C.: General Relativistic Chronometry from Ground and in Space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10007, https://doi.org/10.5194/egusphere-egu24-10007, 2024.

Gravity sensors for high-precision monitoring or mapping can be grouped into 1) Relative spring, 2) Absolute free-fall, 3) Absolute cold atom, and 4) Superconducting. While all can provide valuable data, few comparisons of performance or cost have been published. Here we report on performance of CG-6 relative gravimeters and discuss how it relates to other sensors.

The Scintrex CG-6 sensor has weight of 5.5 kg and volume of 10,8 litre, which is less than previous quartz sensors. While the manufacturer specifies 5 µGal repeatability, Francis (2021) reported better performance and improved drift, noise level, tilt susceptibility and temperature influence. Mao et al., (2022) reported uncertainty down to 0.1 µGal in the laboratory. We have analysed more than 2000 survey records from as diverse environments as the desert and the seafloor. Station repeatability is a robust measure of the precision for surveys with multiple station visits and sensors. Data redundancy allows in-situ calibration of scale factors and parameters for tilt and temperature corrections. Up to 10oC temperature difference between night and day gave no remaining correlation between sensor temperature and gravity residuals, but some diurnal drift periodicity, and repeatabilities <1.5 µGal were achieved. For more stable external temperatures, the scatter of residuals were well below 1 µGal. Both merits are significantly better than for the older CG-5 sensors in similar survey setups.

More instruments and measurements will improve the precision – and increase the cost. Most microgravity surveys have so far been done in R&D settings, and the costs have been baked into a wider project. The relation between cost and precision can be predicted and the optimal choice of survey parameters made in an industrial setting. The absolute free-fall A-10 gravimeter had in our case inferior precision compared to CG-6 for the same acquisition effort. The benefits of absolute measurements for monitoring surveys remain to be demonstrated, and it is too early to judge the performance of cold atom gravimeter developments. Superconducting sensors give time-series of superior resolution, but their limited mobility reduces the spatial resolution – or drive the cost. They can give control points with a lower detection threshold, but arial surveys are required for fair coverage of a subsurface target.

Obtaining <1 µGal precision with relative gravimeters requires good instruments, multiple sensors/repeats, and comprehensive data processing. Recent improvements by CG-6 gravimeters increase technical and economic opportunities for providing valuable gravity monitoring data. Future sensor developments by e.g. cold atom or MEMS should be benchmarked against the CG-6, not the older and less precise CG-5 sensors.

 

References

Francis, O. 2021: Performance assessment of the relative gravimeter Scintrex CG-6. Journal of Geodesy 95: 116.

Mao, Q., Xu, H., Cheng ,Y., Huang, T., Huang, J. And Li, Q. [2022] Apparatuses for verifying the precision of gravimeters with lifting spherical source masses. Recv. Sci. Instrum. 93, 124503.

How to cite: Eiken, O.: Recent improvements in gravity precision from CG-6 sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10880, https://doi.org/10.5194/egusphere-egu24-10880, 2024.

EGU24-11059 | Posters on site | G4.2

ONERA accelerometers for future gravity mission 

Marine Dalin, Bruno Christophe, Vincent Lebat, Damien Boulanger, Francoise Liorzou, Manuel Rodrigues, Nassim Zahzam, Yannick Bidel, and Alexandre Bresson

The 2017-2027 Decadal Survey for Earth Science and Applications from Space has identified the Targeted Mass Change Observable as one of 5 Designated Mission. In Europe, ESA has confirmed at Ministerial Counsel of November 2022 to continue the development on the Next Generation Gravity Mission with a Phase B.

These missions will continue the observation provided by GRACE and GRACE-FO. In these missions and the future concepts, the accelerometer provides either the gravity signal in a gradiometer configuration (GOCE type mission), or the non-gravitational acceleration to be suppressed to the ranging measurement between two satellites (GRACE-type mission).

ONERA has procured the accelerometer for all the previous gravity missions (GRACE, GOCE, GRACE-FO) and works to improve the scientific return of the instruments for the future missions.

In a frame of a contract with ESA, ONERA is developing its new accelerometer MicroSTAR, a high accuracy accelerometer with 3 sensitive linear acceleration measurements as well as 3 angular acceleration measurements for the attitude control or reconstruction.

In parallel, a miniaturized version of MicroSTAR with low accuracy, CubeSTAR accelerometer, is developed with internal funding. CubeSTAR is adapted for constellation or nanosat.

Another way is to improve the low-frequency noise of the accelerometer, by hybridization of electrostatic accelerometer with cold atom interferometer.

The presentation will detail these developments.

How to cite: Dalin, M., Christophe, B., Lebat, V., Boulanger, D., Liorzou, F., Rodrigues, M., Zahzam, N., Bidel, Y., and Bresson, A.: ONERA accelerometers for future gravity mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11059, https://doi.org/10.5194/egusphere-egu24-11059, 2024.

EGU24-11177 | ECS | Orals | G4.2

Assessment of a quantum gravity mission by the space-wise approach in the framework of the QSG4EMT project 

Lorenzo Rossi, Mirko Reguzzoni, Öykü Koç, and Federica Migliaccio

Quantum technology is becoming more and more popular in science and applications. For some years now the possibility of equipping a future satellite mission with quantum instrumentation has been investigated to improve the current knowledge of the Earth’s gravity field. In this framework the QSG4EMT project, which is funded by ESA, aims at investigating different mission principles (low-low satellite-to-satellite tracking with one or more pairs, gradiometry, etc.) especially with the aim of retrieving the time variations of the gravity field. One of the processing strategies that are used for this assessment is the so-called space-wise approach, which is mainly based on a least-squares collocation scheme passing through the estimation of gridded values to adapt the noise filtering level to the local characteristics of the static and time-variable gravity field. This approach is naturally used for local/regional solutions, but it can be also applied for global modelling by patching overlapped regional solutions all over the world and then performing a spherical harmonic analysis. In this work, the space-wise approach is used to assess the performances of different mission scenarios of future missions having on board purely quantum or quantum-electrostatic hybrid accelerometers. The focus is both on the estimation of the total water storage and on the comparison of the information retrieved from global and local solutions.

How to cite: Rossi, L., Reguzzoni, M., Koç, Ö., and Migliaccio, F.: Assessment of a quantum gravity mission by the space-wise approach in the framework of the QSG4EMT project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11177, https://doi.org/10.5194/egusphere-egu24-11177, 2024.

EGU24-14607 | Posters on site | G4.2

The Study of Quantum Phenomena with the Cold Atom Lab in Microgravity  

Jason Williams, Kamal Oudrhiri, David Aveline, Sofia Botsi, Ethan Elliott, James Kellogg, James Kohel, Norman Lay, Matteo Sbroscia, Christian Schneider, and Robert Thompson

The Cold Atom Lab (CAL) launched to the International Space Station (ISS) in May 2018 and has been entirely remotely operated from NASA's Jet Propulsion Laboratory since then as the world's first multi-user facility for studying ultra-cold atoms in space. CAL uses lasers and magnetic traps to cool atoms down to less than a degree above absolute zero. When clouds of atoms reach these ultracold temperatures, they form a fifth state of matter called a Bose-Einstein Condensate (BEC). Distinct from gasses, liquids, solids, and plasmas, a BEC makes the quantum properties of atoms macroscopic, so scientists can more easily observe and interact with them in the essentially limitless free-fall of ISS. An on-orbit upgrade to CAL in 2021 enabled the study of atom interferometry (AI) in space, which uses the interference of atomic matter waves as exquisitely precise sensors for fundamental forces, including gravity, accelerations, and rotations. Relevant to Earth and planetary sciences, these quantum sensors are expected to serve as precision gravity sensors for geodesy, seismology, and subsurface mapping in the near future. We will discuss our efforts to provide pioneering, microgravity-enabled quantum gas research capabilities with CAL, to demonstrate AI for the first time in Earth's orbit, to realize simultaneous, dual-species atom interferometry in space, and to mature this technology for future mission opportunities.

 © 2024 California Institute of Technology. Government sponsorship acknowledged.

How to cite: Williams, J., Oudrhiri, K., Aveline, D., Botsi, S., Elliott, E., Kellogg, J., Kohel, J., Lay, N., Sbroscia, M., Schneider, C., and Thompson, R.: The Study of Quantum Phenomena with the Cold Atom Lab in Microgravity , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14607, https://doi.org/10.5194/egusphere-egu24-14607, 2024.

EGU24-14722 | Posters on site | G4.2 | Highlight

Community assessment on user requirements for future satellite gravity missions 

Annette Eicker, Christina Strohmenger, Carla Braitenberg, Jürgen Kusche, Roland Pail, and Ilias Daras

Since 2002, the GRACE and GRACE-FO satellite gravity missions have been observing changes in the Earth’s gravity field. ESA and NASA are currently planning a double-pair satellite constellation MAGIC, which promises an enhanced spatial and temporal resolution compared to GRACE/-FO. After MAGIC, in the long-term post-2040-time frame, a gravity mission constellation with multiple satellite pairs equipped with novel quantum sensor instrumentation is considered as a promising candidate concept to improve the observation time series even further. It has the potential to acquire unprecedented data on key Earth processes and is expected to significantly expand the potential range of applications.

Within the ongoing ESA project “Quantum Space Gravimetry for monitoring Earth’s Mass Transport Processes” (QSG4EMT) an online questionnaire was created to assess user requirements for such a future quantum mission concept. We will present the results of this community assessment based on 135 answers from various user groups (hydrology, oceanography, glaciology, atmospheric and climate sciences, solid earth sciences, and geodesy). In addition to application-driven demands of the different disciplines regarding the required spatial and temporal resolution, accuracy, and latency, we discuss the expected added benefits of hypothetical future mission scenarios and outline possible new application fields.

How to cite: Eicker, A., Strohmenger, C., Braitenberg, C., Kusche, J., Pail, R., and Daras, I.: Community assessment on user requirements for future satellite gravity missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14722, https://doi.org/10.5194/egusphere-egu24-14722, 2024.

EGU24-14996 | ECS | Posters on site | G4.2

CARIOQA-PMP quantum accelerometer simulation 

Manuel Schilling, René Forsberg, Naceur Gaaloul, Thomas Gruber, Thomas Lévèque, Federica Migliaccio, Jürgen Müller, Franck Pereira Dos Santos, and Nassim Zahzam and the CARIOQA-PMP Consortium

Satellite gravimetry missions have been providing a global measure of Earth's mass transport for more than 20 years. This provides insights into the solid Earth, cryosphere, ocean dynamics and hydrology. Planned NASA and ESA missions will continue this observation well into the 2030s. They are likely to be based on the technology currently used on the GRACE-FO mission, with some further developments, e.g. in laser ranging technology. A higher temporal and spatial resolution of these gravity field products, currently limited to a few hundred km for 1 cm equivalent water height, is required to meet future user need.

One of the limitations is related to instrumental effects, of which the accelerometer is a major aspect. Quantum-based accelerometers are a potential improvement for future missions, but the required technology readiness level (TRL) for key technologies currently precludes deployment. A European pathfinder mission is planned to increase the TRL and demonstrate the technology in space.

Under the Horizon Europe funding programme, technology development and maturation are being promoted and "the [Quantum Space Gravimetry] Pathfinder mission shall be launched within this decade, paving the way for the deployment of an EU [Quantum Space Gravimetry] mission within the next decade". Within this framework, the Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometer - Pathfinder Mission Preparation (CARIOQA-PMP) project is the first step in the design and preparation of the Pathfinder mission. It identifies user needs, prepares simulation tools and develops an engineering model of the quantum accelerometer.

This presentation will give an overview of the scientific activities within CARIOQA-PMP, including the link between hardware design and specification, as well as the planning for the Pathfinder mission and a future gravimetry mission. The focus will be on the elements and workflow of the simulation of the quantum sensor on a satellite platform, combining the efforts of the physics and geodesy partners.

CARIOQA-PMP is a joint European project, including experts in satellite instrument development (Airbus, Exail SAS, TELETEL, LEONARDO), quantum sensing (LUH, SYRTE, LP2N, LCAR, ONERA, FORTH), space geodesy, Earth sciences and users of gravity field data (LUH, TUM, POLIMI, DTU), as well as in impact maximisation and assessment (PRAXI Network/FORTH, G.A.C. Group), coordinated by the French and German space agencies CNES and DLR under CNES lead. Funded by the European Union

How to cite: Schilling, M., Forsberg, R., Gaaloul, N., Gruber, T., Lévèque, T., Migliaccio, F., Müller, J., Pereira Dos Santos, F., and Zahzam, N. and the CARIOQA-PMP Consortium: CARIOQA-PMP quantum accelerometer simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14996, https://doi.org/10.5194/egusphere-egu24-14996, 2024.

EGU24-16325 | Posters on site | G4.2

Towards a realistic modelling of gravimetric errors in future missions equipped with quantum sensors 

Joao de Teixeira da Encarnacao, Christian Siemes, Ilias Daras, Aaron Strangfeld, Philipp Zingerle, and Roland Pail

Cold Atom Interferometry (CAI) stands poised as a groundbreaking technique in satellite gravimetry, offering unparalleled precision and unbiased measurements. Despite the numerous studies on CAI's conceptual measurement techniques, attitude reconstruction accuracy poses a critical challenge. This submission seeks to bridge this gap by conducting an analysis of state-of-the-art attitude sensors and their suitability for upcoming quantum low-low satellite-to-satellite and gravity gradiometry missions utilizing CAI instruments.

Acknowledging the immense promise of Cold Atom Interferometry, we emphasise the need to put this conceptual potential in the context of the accuracy of attitude reconstruction, a factor that significantly influences the feasibility of Quantum Space Gravimetric (QSG) missions. We examine the specifications, strengths, and limitations of attitude, acceleration, position and inter-satellite distance sensors to combine them realistically in scenarios specific to quantum low-low satellite-to-satellite and gravity gradiometry missions relying on CAI instruments. We also analyse the classic counterparts, offering valuable insights into the conceptual mission configurations that benefit the most from CAI-based observations. Our findings contribute not only to the advancement of the use of CAI technology in future graviemtric missions but also to the broader understanding of the intricate interplay between cutting-edge measurement techniques and the supporting instrumentation required for their successful implementation.

This work is supported by the European Space Agency, under the project Quantum Space Gravimetry for monitoring Earth’s Mass Transport Processes (QSG4EMT), which has the general objectives to analyse future QSG mission architectures with ultimate goal to optimally exploit the performance of quantum sensors for retrieving temporal variations of Earth’s gravity field, evaluate the impact of mission configurations on the quality of the retrieved gravity field models and support the evolution of user requirements for future QSG missions.

How to cite: de Teixeira da Encarnacao, J., Siemes, C., Daras, I., Strangfeld, A., Zingerle, P., and Pail, R.: Towards a realistic modelling of gravimetric errors in future missions equipped with quantum sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16325, https://doi.org/10.5194/egusphere-egu24-16325, 2024.

EGU24-17336 | ECS | Posters on site | G4.2

Updating the ESA Earth System Model for Future Gravity Missions Simulation Studies 

Linus Shihora, Kyriakos Balidakis, Robert Dill, and Henryk Dobslaw

The ESA Earth System Model (ESA ESM) provides a synthetic data-set of the time-variable global gravity field that includes realistic mass variations in atmosphere, oceans, terrestrial water storage, continental ice-sheets, and the solid Earth on a wide set of spatial and temporal frequencies. It was widely applied as a source model in simulations of for gravity missions, but has been also applied to study novel gravity observing concepts on the ground. For that purpose, the ESM needs to include a wide range of signals even at very small spatial scales which might not yet have been reliably observed by any active mission.

In this contribution, we present first steps towards an update to the current ESA ESM. We focus in particular on an evolved oceanic component which will newly include (a) deep oceanic transport variations in the Atlantic Overturning Circulation and the associated variation in oceanic bottom pressure along the shelf slope of the Western boundary; (b) an update to the realistically perturbed de-aliasing model and (c) the inclusion of the Sea-Level Equation for spatially variable barystatic sea-level variations and global mass conservation.

How to cite: Shihora, L., Balidakis, K., Dill, R., and Dobslaw, H.: Updating the ESA Earth System Model for Future Gravity Missions Simulation Studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17336, https://doi.org/10.5194/egusphere-egu24-17336, 2024.

EGU24-17378 | ECS | Orals | G4.2

Gravitational field recovery via inter-satellite redshift measurements 

Jan Patrick Hackstein, Dennis Philipp, and Eva Hackmann

Satellite gravimetry is a common tool to monitor global changes in the Earth system, generally utilising accelerometers aboard satellites to measure acting forces along the orbits. In contrast, high-precision atomic clocks are used in first experiments in terrestrial gravimetry to measure physical heights. In relativistic gravity, a comparison of two clocks is sensitive to their relative positions and velocity, making clocks ideal tools to investigate Earth’s gravity field. However, one important obstacle for Earth-satellite chronometry is the low measurement accuracy of satellite velocities, which enter into the redshift via the Doppler effect.
We present an alternative approach based on the framework of general relativity without velocity measurements from ground stations, instead measuring redshift between satellite pairs equipped with clocks via laser ranging. This method promises higher accuracy for gravity field recovery by improving control of the Doppler effect. We investigate this problem in analytically given spacetimes as well as in the general first post-Newtonian approximation of Earth’s gravity field, and discuss the prospects for gravity field recovery.

How to cite: Hackstein, J. P., Philipp, D., and Hackmann, E.: Gravitational field recovery via inter-satellite redshift measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17378, https://doi.org/10.5194/egusphere-egu24-17378, 2024.

EGU24-19218 | ECS | Orals | G4.2

Revisiting non-tidal atmospheric and oceanic gravity corrections for terrestrial gravimetry 

Kyriakos Balidakis, Ezequiel Antokoletz, Roman Sulzbach, Henryk Dobslaw, Hartmut Wziontek, Christian Voigt, Robert Dill, and Ludger Timmen

Mass redistribution within Earth’s atmosphere and oceans affects gravity time series recorded by precise superconducting and quantum gravimeters at a multitude of temporal scales. While the largest component of the systematic disturbances is attributed to tides mainly in the oceans, the solid Earth, and to a smaller extent also the atmosphere, synoptic weather features also cause non-negligible gravity anomalies. The accurate description of these effects requires a high-resolution representation of certain components of the instantaneous Earth system state, namely the 3D atmospheric density and the ocean bottom pressure distribution. In this contribution, we calculate gravity anomalies induced by the Newtonian attraction of the mass anomalies and the loading effect they exert on Earth’s crust, employing the state-of-the-art meso-beta scale numerical weather model ERA5 reanalysis from ECMWF. We compare the ERA5-derived gravity anomalies to those provided by ATMACS, a service that features weather-driven gravity anomaly corrections for most superconducting gravimeter sites based on the operational model ICON-global, from the German Weather Service. In this work, we place our focus on non-tidal contributions only, while tidal signatures are estimated based on the gravity anomaly time series. The ocean state is based on a recent MPIOM simulations forced consistently from ERA5 which is also the basis of the latest GRACE/GRACE-FO non-tidal atmosphere-ocean dealiasing product AOD1B RL07. To assess the effectiveness of the modelling strategy as well as the quality of the mass anomaly fields, we apply the ERA5 and ATMACS-retrieved models to a few selected superconducting gravimeter time series with a focus on sites with unusual orography such as on the small island of Helgoland located in the North Sea, and assess the band-pass filtered residuals to assess the quality of the various correction models available.

How to cite: Balidakis, K., Antokoletz, E., Sulzbach, R., Dobslaw, H., Wziontek, H., Voigt, C., Dill, R., and Timmen, L.: Revisiting non-tidal atmospheric and oceanic gravity corrections for terrestrial gravimetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19218, https://doi.org/10.5194/egusphere-egu24-19218, 2024.

Co-seismic dislocation and post-seismic relaxation are mass transport processes that can be sensed by a broad array of seismological and/or geodetic techniques. Gravity observations through time have the potential of improving the amount of available information on these processes, especially when the dislocation is a-seismic and when its surface expression occurs mostly in areas that are difficult or impossible to sense with space geodesy (such as GNSS, DInSAR), as is the case for off shore areas. New  mission concepts, such as those proposed for the Mass change And Geosciences International Constellation (MAGIC), have been recently assessed as capable of providing significant enhancements in the spatial and temporal resolution of gravity field products, resulting in turn in unprecedented impact on the scientific applications, including earthquake gravimetry [1]. The evolution of sensors beyond classic electrostatic accelerometers, such as future applications of Cold Atom Interferometry (CAI) on space borne platforms, has the potential to allow further steps forward in sensing the mass transport in the Earth’s system.

In this context, we aim at assessing the impact of Quantum Space Gravimetry (QSG) to earthquake detectability, by modelling a database of synthetic earthquake gravity signal, including the effect of post-seismic viscoelastic relaxation, and setting up a strategy do assess their detectability in simulated time-varying gravity field products. We compute the gravity change in time using the QSSPSTATIC [2] code and a workflow we developed to obtain the spherical harmonics (SH) expansion of the geopotential change through time. We designed the structure of this synthetic earthquake data to be easily included as part of time-varying signals used in simulations, improving the solid-Earth component of models such as AOHIS [3]. In this contribution we present the detection threshold of different events, real earthquakes ranging from Mw 9.2 to 7.6 with an assortment of depths, locations and focal mechanisms, using an SNR assessment in the spectral domain, between the modelled signal and retrieval errors (residuals) obtained from mission simulations.

This work is supported by the ESA QSG4EMT study, a collaboration between Technical University of Munich, Politecnico di Milano, Delft University of Technology, HafenCity University Hamburg, University of Bonn and University of Trieste.

[1] Daras I., March G., Pail R., Hughes C. W., Braitenberg C., Güntner A., Eicker A., Wouters B., Heller-Kaikov B., Pivetta T., & Pastorutti, A. (2023). Mass-change And Geosciences International Constellation (MAGIC) expected impact on science and applications. Geophysical Journal International, 1288–1308. https://doi.org/10.1093/gji/ggad472

[2] Wang, R., Heimann, S., Zhang, Y., Wang, H., & Dahm, T. (2017). Complete synthetic seismograms based on a spherical self-gravitating Earth model with an atmosphere-ocean-mantle-core structure. Geophysical Journal International, 210(3), 1739–1764. https://doi.org/10.1093/gji/ggx259

[3] Dobslaw, H., Bergmann-Wolf, I., Dill, R., Forootan, E., Klemann, V., Kusche, J., & Sasgen, I. (2015). The updated ESA Earth System Model for future gravity mission simulation studies. Journal of Geodesy, 89(5), 505–513. https://doi.org/10.1007/s00190-014-0787-8

How to cite: Pastorutti, A. and Braitenberg, C.: Detecting the co-seismic and post-seismic gravity signal of large thrust earthquakes with Quantum Space Gravimetry mission concepts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19344, https://doi.org/10.5194/egusphere-egu24-19344, 2024.

EGU24-19937 | Orals | G4.2 | Highlight

CARIOQA-PMP: developing quantum sensors for earth observation 

Christian Schubert

For the CARIOQA-PMP Consortium

Due to their performance especially at low frequencies, quantum sensors based on atom interferometry are expected to enhance the capabilities of future missions for earth observation. Atom interferometers, e.g. in a configuration as an accelerometer / gravimeter are routinely operated in laboratories and commercial versions exist. Additionally, payloads with demonstration experiments on cold atoms and atom interferometry were implemented on microgravity platforms including parabola flights, a drop tower, and sounding rockets, significant steps towards a future deployment on a satellite, but each limited in microgravity time.

Both the specific environment of a satellite and the desired performance of a future, space-borne quantum accelerometer imply strict requirements and consequently the need for further technology developments in comparison to the current state of the art. This context sets the scope for the project CARIOQA-PMP (Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry – Pathfinder Mission Preparation). Supported by scientists, the main task is the development of an engineering model of a quantum accelerometer for a dedicated pathfinder mission in space. Additionally, the project considers the scientific background, especially in the context of a possible future space mission.

This contribution will present the motivation and the approach of CARIOQA-PMP for enabling future quantum-sensor-enhanced missions for earth observation.

CARIOQA-PMP is a joint European project, including experts in satellite instrument development (Airbus, Exail SAS, TELETEL, LEONARDO), quantum sensing (LUH, SYRTE, LP2N, LCAR, ONERA, FORTH), space geodesy, Earth sciences and users of gravity field data (LUH, TUM, POLIMI, DTU), as well as in impact maximisation and assessment (PRAXI Network/FORTH, G.A.C. Group), coordinated by the French and German space agencies CNES and DLR under CNES lead. Funded by the European Union.

How to cite: Schubert, C.: CARIOQA-PMP: developing quantum sensors for earth observation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19937, https://doi.org/10.5194/egusphere-egu24-19937, 2024.

EGU24-20659 | Orals | G4.2

Absolute Quantum Gravimeter as a promising field sensor for volcano monitoring 

Michel Diament, Guillaume Lion, Gwendoline Pajot-Métivier, Sébastien Merlet, and Sébastien Déroussi

Soufrière, an active volcano in Guadeloupe (French West Indies) monitored by the Volcanological and Seismological Observatory of Guadeloupe (OVSG), requires a comprehensive understanding of mass transfers, including water movements. To address this, a gravity repetition network was established in the 1980s following the volcano's last major eruption in 1976. In 2011, initial absolute measurements were conducted using a Micro-g Lacoste portable absolute gravity meter A10 #14.

 

As part of the EQUIPEX RESIF program, aimed at meeting the scientific community's seismic and gravimetric instrument needs in France, the first absolute quantum field gravimeter (AQG-B01) was acquired. This advanced instrument, designed for diverse applications, including volcano gravity monitoring, utilizes atom interferometry with lasers to measure gravity by manipulating 'atomic waves' with a cloud of free-falling cold atoms at a cycling rate of 2 Hz.

 

In March 2023, a fieldwork was undertaken with the AQG-B01 as an initial step toward modern gravity monitoring of Soufrière. The specific goals included reoccupying stations within the microgravity network and identifying new sites for expanding the network, selecting an appropriate location for a permanent station near the summit based on a Lacoste&Romberg D meter, testing the AQG-B01 under challenging tropical conditions (humidity up to 85%, mean temperature of 24°C), assessing the use of an external power supply for the AQG, and evaluating the ease of installation and accuracy of measurements with the AQG, as specified by the manufacturer.

This work primarily focuses on the latter three objectives.

How to cite: Diament, M., Lion, G., Pajot-Métivier, G., Merlet, S., and Déroussi, S.: Absolute Quantum Gravimeter as a promising field sensor for volcano monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20659, https://doi.org/10.5194/egusphere-egu24-20659, 2024.

This study employs gravity modelling to investigate the subsurface geometry of a pull-apart basin located in Elazığ, Turkey. The study area is situated along the East Anatolian Fault Zone—a major active system that recently produced two devastating M7.0+ earthquakes at Kahramanmaraş in February 6, 2023.

Recently collected gravity data, comprising approximately 600 data points from Sivrice and Gezin provinces, form the basis of our investigation. Preliminary examinations show that the gravity anomalies in Gezin are notably lower than those in Sivrice, suggesting a deeper basement for the former. We aimed to estimate the subsurface model using a proprietary computer program. Given the known different geological units with constant density contrasts, the program was employed to deduce their geometry up to a maximum depth of 350 meters in 2D. A total of 16 sections were modeled—8 each for Sivrice and Gezin provinces—yielding RMS values consistently below 0.1 mGals. Next, quasi-3D and 3D models were prepared for Talwani models at Sivrice and Gezin. We assumed the geometry beneath Lake Hazar to be similar to the bathymetry of the lake, assigning sediment thickness to estimate the basement in this part. The individual models were then integrated into a full 3D representation of the geometry of the basin.

Our findings suggest that the pull-apart basin situated here is in its extinction phase, with pull-apart tectonics no longer active, and only strike-slip movement along main East Anatolian Fault is observed. Notably, slips along the main fault have impacted the basement geometry. This study contributes valuable insights into the current state of the basin, emphasizing the importance of 3D modelling in unraveling the complexities of pull-apart basins.

How to cite: Aydın, N. G. and İşseven, T.: Gravity Modelling of a Pull-Apart Basin in Elazığ, Turkey: Unraveling the 3D Basement Geometry (Preliminary Results), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-397, https://doi.org/10.5194/egusphere-egu24-397, 2024.

EGU24-1294 | Posters on site | G4.3

Voxel-based Density Models for Accurate Gravitational Field Computation 

Benjamin Haser, Thomas Andert, and Roger Förstner

Asteroids and moons are promising targets for physical space exploration. The use of physically-based simulations within a virtual environment for (deep) space missions can significantly benefit the testing and validation of guidance, navigation, and control algorithms. This approach offers advantages in terms of cost and time efficiency. Especially for orbit propagation and landing maneuvers, information about the gravitational field is crucial. However, several factors contribute to the complexity of this task, such as limited information available about the inner structure of celestial bodies. The lack of detailed knowledge about their shapes further adds to the challenge.

This study presents a voxel-based mass concentration (MASCON) method to model detailed and realistic density distributions, enabling accurate gravity field determinations. We chose a cube with constant density as first case due to the perfect shape reconstruction and the availability of an analytical solution for its gravity field. To validate our results, we calculated the surface gravity and compared it with the analytical solution, ensuring the accuracy of our calculations. Furthermore, the surface gravity is derived for different resolutions and compared against other state-of-the-art methods like the polyhedral method that provides a closed-form analytical solution of the gravity field for homogeneous density. The other two methods for validation also use a MASCON approach, one utilizing polydisperse sphere packing and another with MASCON represented in spherical coordinates. The relative errors of the gravitational acceleration between the four methods will be evaluated for a cube and sphere, with homogeneous density.

The second aspect of this study was to create a tool that generates realistic density distributions. We are able to successfully reproduce natural environments by placing body-specific restrictions on three-dimensional Perlin noise with additional normalization. The simulator can add the following structural features to the density distribution: an arbitrary number of centralized or decentralized shells, with varying thickness and densities, anomalies of arbitrary size and shape, only restricted by its maximum permille of the body's volume. Furthermore, we implemented different normalization techniques to keep the mass of all generated bodies fixed. Our results show that the tool can generate realistic density distributions and calculate the corresponding gravitational field correctly. The data generated here is used to train Machine Learning and Deep Learning algorithms for gravity inversion.

 

How to cite: Haser, B., Andert, T., and Förstner, R.: Voxel-based Density Models for Accurate Gravitational Field Computation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1294, https://doi.org/10.5194/egusphere-egu24-1294, 2024.

Precise determination of Moho topography holds paramount importance in advancing our comprehension of Earth's structural characteristics, geodynamic phenomena, and the exploration of resources. This study introduces an innovative methodology employing conditional Generative Adversarial Networks (cGAN) to unveil Moho topographies from observed gravity anomalies. To address the scarcity of real Moho datasets for training the cGAN model, we meticulously generated a comprehensive set of quasi-realistic synthetic training data using the FFT filtering technique. The forward estimation of gravity anomalies, arising from synthetic Moho topographies, was assessed through spherical prism-based gravity modeling. These estimated anomalies served as input data for the training of the cGAN model. For evaluating the efficacy of our developed cGAN algorithm in deriving Moho architecture, we conducted a comparative analysis against a conventional inversion scheme. This assessment utilized various synthetic datasets and a real case study in Southern Peninsular India, renowned for its geological diversity and ancient continental tectonic blocks. The established Bott's inversion scheme was employed as a benchmark to validate the Moho surface estimation obtained through the Deep Learning approach. To mitigate the impact of diverse factors such as topography, bathymetry, sediments, crustal and mantle heterogeneities, observed gravity anomalies underwent meticulous corrections using spherical prism-based forward gravity modeling for real case studies. The gravity contribution exclusively associated with the pure Moho was subsequently inverted using both the cGAN and traditional Bott's inversion schemes. Crucial hyperparameters, including the mean Moho depth and density contrast between the crust and mantle, were determined by utilizing seismic constraints. Our results underscore the potential of the cGAN and spherical prism-based gravity modeling approach in accurately predicting Moho topography. This study provides valuable insights into high-resolution Earth's Moho architecture and contributes to advancing our understanding of geodynamic processes, facilitating resource exploration endeavours with reduced computational demands.

How to cite: Roy, A., Sharma, R. K., Jash, D., and Kallukalam, T. J.: Innovative Insights into Earth's Interior: Moho Topography Estimation using Conditional Generative Adversarial Networks from Observed Gravity Anomalies , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1405, https://doi.org/10.5194/egusphere-egu24-1405, 2024.

EGU24-2837 | ECS | Orals | G4.3

Joint inversion of airborne gravity and magnetic data for the crustal structure in central Dronning Maud Land 

Mikhail Ginga, Jörg Ebbing, Antonia Stefanie Ruppel, Andreas Läufer, and Graeme Eagles

Topography and physical conditions at the base of the Antarctic ice sheet are critical inputs for studies of its present and future ice discharge, and of subglacial geology and hydrology. Airborne gravity and magnetic data, especially when interpreted jointly can help us to link the geology from outcrops towards the coastal areas to unknown subglacial regions further inland. Here we use airborne geophysical data obtained during the joint AWI-BGR campaign WEGAS/GEA between 2015 and 2017 in central Dronning Maud Land (DML) as input for a novel joint inversion scheme. With regard to Gondwana reconstruction, this region is critical because it hosts the ice-covered Forster Magnetic Anomaly, a prominent lineament crossing central DML for some 100s of kilometers south of the main mountain chain. This lineament, originally interpreted as the main pan-African suture of East and West Gondwana, likely represents the eastern margin of Kalahari and its boundary to the Tonian Oceanic Arc Super Terrane (TOAST). In the inversion using the software jif3D, sources of the gravity and magnetic field are combined through a coupling method which decreases the variation of information (VI), so data misfit and model dissimilarity are minimized simultaneously. The model results can be classified in geologically meaningful provinces by applying cluster analysis based on machine learning. Our joint inversion approach improves previous interpretations and sheds light on the crustal architecture of the study area, contributing to further studies on the interaction between the ice sheet and the underlying solid earth.

How to cite: Ginga, M., Ebbing, J., Ruppel, A. S., Läufer, A., and Eagles, G.: Joint inversion of airborne gravity and magnetic data for the crustal structure in central Dronning Maud Land, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2837, https://doi.org/10.5194/egusphere-egu24-2837, 2024.

In Western Europe, the Variscan belt contacts Avalonia along the Rhenohercynian Suture, a result of Early Carboniferous continental collision. Moving east of the Harz Mts., the Rhenohercynian suture disappears beneath a thick sedimentary sequence of the Permian-Mesozoic basin. Its extension is either truncated by major NW-SE strike-slip faults like the Elbe, Odra, or Dolsk faults or bends under the cover of a thick sedimentary succession. The extension of Avalonia into Poland is challenging to determine, with the thinned margin of Baltica considered the substratum of the Permian-Mesozoic basin. Deep seismic soundings show that the thinned margin of Baltica reaches the NW-SE oriented Dolsk or Odra fault, potentially bringing the crust of Baltica into direct contact with the crust of the Variscan internides of the Bohemian Massif. Along the Dolsk fault, there is the two-layered, low-velocity Variscan crust in the SW that contacts the three-layered Baltica crust. The geometry of this contact remains unknown, but the lower, high-velocity crust of Baltica may extend southwest to the Odra fault. In the basement of the sedimentary sequence between the Dolsk and Odra faults, low-grade metamorphosed phyllites with a metamorphic age of approximately 360 Ma are found. They apparently represent a fragment of Variscan metamorphic nappes.

The Variscan front is oriented NE-SW in Western Europe, but in Poland, it bends by 90° to the NW-SE direction, continuing to the border of Ukraine. In southeastern Poland, the front enters the slope of the East European Platform, constituting an undisputed example of a direct contact between the Variscan belt and Baltica. If the geometry of the Variscan front reflects the structure of the orogen, the edge of Baltica must have initially played the role of a transform margin with a right-lateral displacement. NW-SE strike-slip faults, parallel to this margin, truncated the Rhenohercynian and other Variscan sutures from the NE. The following accretion event resulted in NE-SW shortening, either thin-skinned, leading to folding of the external fold-and-thrust belt, or thick-skinned, resulting in the emplacement of the Variscan nappe stack on the Baltica margin.

The last folding of external Variscides in Poland occurred around 305 Ma and was immediately followed by the emplacement of a large igneous province at the Carboniferous to Permian transition. The centre of magmatism was in NE Germany, the area of greatest crustal thinning. The origin of the igneous province was linked to plate boundary forces leading to extension and continental rifting. The latter produced the Mid-Polish trough, an elongated continental rift running NW-SE parallel to the Teisseyre-Tornquist zone. Permian rifting further attenuated the Baltica margin and, jointly with coeval magmatism, reshaped the margin of Baltica masking its contact with the Variscan belt. Toward the east, the continuity of the Variscan internides was disrupted by early Mesozoic rifting in the area of the present-day Carpathians.

How to cite: Mazur, S.: From Carboniferous convergence to Permian continental rifting – the interaction of Baltica with the Variscan belt of Europe at the time of the Pangaea assembly, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4560, https://doi.org/10.5194/egusphere-egu24-4560, 2024.

The South China Sea, situated at the convergence of the Tethys and Pacific tectonic domains, holds immense geological significance due to its interaction with multiple tectonic plates (Hall 2002; Hayes and Nissen 2005; Metcalfe 2011). With its abundant sedimentary basins, the region is of paramount importance for geological and structural studies, particularly in relation to its potential for oil and gas resources. In this study, we propose the utilization of satellite gravity data to analyze the tectonic structure of the South China Sea, focusing on three key areas:

1. High-resolution construction of gravity gradient anomalies and fault identification: By integrating Fast Fourier Transform algorithms with satellite gravity anomalies and high-resolution terrain elevation data, we obtaina comprehensive dataset of full tensor gravity gradient information. Through spatial analysis of this data, we successfully identify 17 significant and deep faults, as well as partition the study area into 9 distinct tectonic units characterized by well-defined geological structures.

2. Moho Depth Determination and Interpretation: Employing an improved regularization Bott's method, we determine the Moho depth using information obtained from sonar-buoy detection and submarine seismograph detection profiles. Regularization parameters are introduced to ensure the smoothness of the inversion results. By analyzing the distribution characteristics of the Moho and its relationship with tectonic units, we conduct a comprehensive analysis to comprehend the coupling between shallow and deep structures. The resultsreveal distinct regional characteristics in the depth distribution of the Moho surface in the South China Sea, shedding light on the distribution of continental crust, oceanic crust, and the ocean-continent transition zone.

3. Comprehensive Geophysical Analysis: We employ a combination of seismically constrained Moho undulation, gravity data, gravity gradient anomalies, and unconstrained 3D correlation imaging to investigate the crustal structure of the South China Sea. Integrating various geophysical datasets, we gain a deeper understanding of the distribution of continental crust, oceanic crust, and transitional crust within the region. Notably, the results shows that the trench-island arc-back arc basin systemplays a pivotal role in the active continental margin of the Western Pacific. This comprehensive analysis provides valuable insights into the tectonic dynamics and geological processes occurring in the South China Sea region.

*This study was supported by y the Basic Frontier Science Research Program of the Chinese Academy of Sciences (No. ZDBS-LY-DQC028).

Reference:

Hall, R. (2002). Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations, J. Asian Earth Sci. 20:353–431.

Hayes, D.E., Nissen, S.S. (2005). The South China Sea margins: implications for rifting contrasts, Earth Planet Sci. Lett., 237: 601–616.

Metcalfe, I. (2011). Tectonic framework and phanerozoic evolution of Sundaland, Gondwana Res., 19 (1): 3–21.

How to cite: Guo, D.: Constrained Gravity Inversion for the Moho Depth and Tectonic Patterns in South China Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4845, https://doi.org/10.5194/egusphere-egu24-4845, 2024.

EGU24-6228 | Posters on site | G4.3

Harnessing Modern 3D Gravity Analysis Techniques: A Study of the Ligurian Offshore Area 

Hans-Jürgen Götze, Ronja Strehlau, Denis Anikiev, Anke Dannowski, and Magdalena Scheck-Wenderoth

This interdisciplinary study describes the integration of gravity field analysis, curvature techniques and various spatial applications. The data are based on land-based Free Air and Bouguer gravity data from the AlpArray Gravity Research Group, complemented by recent satellite missions. New seismic and seismological data from the AlpArray initiative and the German MB-4D Priority Program were used as independent boundary conditions for the 3D modeling and inversion of the gravity data. Prior to this modeling, Euler deconvolution, terracing/clustering techniques, and advanced filtering methods were employed to reveal intricate details of the region's gravitational signatures. For example, a distinct zoning of gravity is observed in the central part of the Ligurian Sea, pointing to traces of past rifting processes. Analysis of various curvature parameters (e.g., dip-, min-, max- and shape-curvature) of the processed gravity fields, in particular gradients and residual fields support the identified zonation of the gravity fields, which reflect the geological structures in the crust. The final 3D modeling of the Ligurian Sea area is based on a previous density model of the entire Alpine region and includes density distribution of the upper mantle. These densities were derived from tomographic velocity models, accounting for petrology, temperature, and pressure. Additional information of the upper crust was obtained from the refraction seismic results of the LOBSTER project, offering a comprehensive understanding of spatial phenomena. Calculations of the gravitational potential energy (GPE) provide additional information on local stresses, facilitating a deeper understanding of the flexural rigidity in the area. By elucidating the relationship between processing techniques and 3D modeling, this work advances interdisciplinary interpretation crucial for geological studies in the Ligurian offshore area.

How to cite: Götze, H.-J., Strehlau, R., Anikiev, D., Dannowski, A., and Scheck-Wenderoth, M.: Harnessing Modern 3D Gravity Analysis Techniques: A Study of the Ligurian Offshore Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6228, https://doi.org/10.5194/egusphere-egu24-6228, 2024.

EGU24-6402 | Posters on site | G4.3

Participative gravity-modelling challenge to constrain the Balmuccia peridotite body (Ivrea-Verbano Zone, Italy) 

György Hetényi, Ludovic Baron, Matteo Scarponi, Shiba Subedi, Konstantinos Michailos, Fergus Dal, Anna Gerle, Benoît Petri, Jodok Zwahlen, Antonio Langone, Andrew Greenwood, Luca Ziberna, Mattia Pistone, Alberto Zanetti, and Othmar Müntener

The Balmuccia peridotite exposes relatively fresh mantle rocks at the Earth’s surface, and as such it is of interest for geologists and geophysicists. The outcrop is a kilometre-scale feature, yet its extent at depth is insufficiently imaged. Our aim is to provide new constraints on the shape of the density anomaly this body represents, through 3D gravity modelling. In an effort to avoid personal or methodology bias, we hereby launch an invitation and call for participative modelling. We openly provide all the necessary input data: pre-processed gravity data, geological map, in situ rock densities, and digital elevation model. The expected inversion results will be compared and jointly analysed with all participants. This approach should allow us to conclude on the shape of the Balmuccia peridotite body and the associated uncertainty. This crowd effort will contribute to the site surveys preparing a scientific borehole in the area in frame of project DIVE. The full description, the dataset, as well as the tentative timeline can be found at https://zenodo.org/records/10390437

How to cite: Hetényi, G., Baron, L., Scarponi, M., Subedi, S., Michailos, K., Dal, F., Gerle, A., Petri, B., Zwahlen, J., Langone, A., Greenwood, A., Ziberna, L., Pistone, M., Zanetti, A., and Müntener, O.: Participative gravity-modelling challenge to constrain the Balmuccia peridotite body (Ivrea-Verbano Zone, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6402, https://doi.org/10.5194/egusphere-egu24-6402, 2024.

Coseismic gravity changes provide significant information for the study of the mechanisms of large earthquakes and for developing fault models (Sun, 2012). In this research,  coseismic gravity changes of the 2008 Ms8.0 Wenchuan earthquake in China were studied by using gravity observation data and simulation based on a fault model.

Firstly, a fine processing of relative and absolute gravity data from the Longmenshan Gravimetric Network was carried out and observed gravity change of 22 stations near this earthquake were obtained; Secondly ,simulation of coseismic gravity changes was conducted based on half-space dislocation theory using the fault model obtained by Wang et al(2008) through inversion with multiple types of geodetic survey data, including GPS, INSAR, and leveling, and the results were compared with the observations..

It was found that the observed and simulated results are basically consistent, showing that the significant changes are mainly concentrated in the near-rupture zone in the hanging wall of the Yingxiu–Beichuan fault and that the changes decrease rapidly away from the rupture zone. The changes exhibit a positive to negative trend from east to west in the footwall of the Yingxiu–Beichuan fault and have a distribution characterized by alternate positive and negative changes in the hanging wall of the fault. This demonstrates the reliability of the observed results and the reasonableness of the fault model used in this paper.

In the near-rupture zone on the west and east sides of the Yingxiu–Beichuan fault, there are still some differences between the observed and simulated results. The trends in the spatial distribution of these differences exhibit a deviation similar to “phase delay”; in other words, an observed result deviates from the corresponding simulated result in terms of spatial position, which is speculated to be caused by errors in the geometric parameters and in the slip distribution of the fault model. After the slip distribution of  the Pengguan fault model was modified based on the actual surface rupture distribution, the simulated result at the Hongjiawan station near the eastern boundary of the fault model showed greater consistency with the observed result. This indicates that the observed gravity change results in this paper can provide an important reference for further detailed study of the fault model.         

            Fig1.Schematic of the Chengdu Gravimetric Network                        Fig2.Spatial distribution of observed gravity changes and simulated results

 

 

How to cite: Hao, H. and Hu, M.: Coseismic gravity changes of the 2008 Wenchuan earthquake in China observed by surface gravimetric data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7561, https://doi.org/10.5194/egusphere-egu24-7561, 2024.

EGU24-8059 | Posters on site | G4.3

Enhancing sub-ice geology in East Antarctica with Self-Organizing maps based on gravity, magnetic and radar data 

Jörg Ebbing, Jonas Liebsch, and Kenichi Matsuoka

Sub-ice geology significantly influences the dynamics and future evolution of the Antarctic Ice Sheet, but largely inaccessible for direct sampling. Here, we present an approach, where we use a Self-Organizing Map (SOM) to describe sub-glacial properties. Based on attributes derived from gravity, magnetics and radar data from the NASA Operation Ice Bridge dataset in East Antarctica, we train a SOM, where attributes are selected to best represent sub-glacial conditions. Therefore, we study the trade-offs between these data sets helping to identify for which properties these are most sensitive.
The trained SOM identifies the outlines of the main geological structures beneath the ice and supplements models based on inverse and forward modelling. In contrast to such often regional interpretations, the SOM captures small-scale structures at the ice bed, as we illustrate with case examples, and highlights areas with inconsistencies in existing geological interpretations. The SOM can furthermore be used as input for inverse modelling of the physical properties of the sub-glacial geology in Antarctica.

How to cite: Ebbing, J., Liebsch, J., and Matsuoka, K.: Enhancing sub-ice geology in East Antarctica with Self-Organizing maps based on gravity, magnetic and radar data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8059, https://doi.org/10.5194/egusphere-egu24-8059, 2024.

EGU24-8934 | Posters on site | G4.3

What can we learn from magnetic surveys at different scales? Geological insight from mineral to airborne surveys in the Bjerkreim-Sokndal Layer Intrusion, Norway 

Suzanne McEnroe, Madeline Lee, Yuleika Madriz, Richard Gloaguen, Zeudia Pastore, Peter Lelièvre, and Nathan Church

Multiple magnetic surveys, including fixed-wing, helicopter-borne, uncrewed aerial vehicle (UAV), and ground magnetics have been acquired over parts of the Bjerkreim-Sokndal layered intrusion (BKS) in Rogaland, Norway. The Proterozoic 230 km2 Bjerkreim-Sokndal layered complex intrudes into anorthosites and hosts recurrent megacyclic units (MCU) with varying cumulus and critical minerals. Some MCUs are associated with strong magnetic remanence, resulting in Koenignsberger ratios (Q ratio) over 5 and anomalies of 12 000 nT below background.  A comparative analysis of these surveys over the Bjerkreim Lobe provide insights into what features can be mapped at different scales. Here we focus on new geological details provided by UAV, ground, and mineral scale surveys.  A UAV can typically operate at a maximum altitude of 150 m above terrain to a minimum of tens- of centimeters in ideal conditions. Thus, UAV magnetic surveys are optimal for understanding the change of a magnetic anomaly with varying source-separation through multiple flight altitudes. Survey altitudes by UAVs overlap with the source-sensor separation of ground and low-altitude crewed flights, therefore allowing a comparative analysis.

In 2023, the Norwegian University of Science and Technology and Helmholtz Institute Freiberg acquired coincident magnetic survey grids by UAV and ground magnetometer over key sites in the Bjerkreim lobe. Here we compare results of crewed-, uncrewed-, and ground-based data collected over the eastern margin of the Bjerkreim lobe and assess how these impact subsequent geologic interpretations. The petrophysical database for the survey area also contains > 1500 previously collected samples in combination with surface geometry information. This database in combination with the extensive lateral magnetic survey data at various sensor heights and other available complementary geophysics, including gravity, provide excellent parameters and constraints for forward modelling and inversions.

In the Bjerkreim lobe two MCU have significant magnetic remanence where anomalies are several thousand nT below background due to natural remanent magnetizations that are typically > 15 A/m. Therefore, an additional focus is on understanding the nature of the magnetic mineralogy using high-resolution scanning magnetic microscopy. These large amplitude magnetic anomalies may also cause logistical challenges for both airborne- and ground magnetic surveying. UAVs employ onboard magnetometer for navigation and attitude corrections which can be impacted by these large magnetic gradients. Similarly, significant noise or sensor drop-outs when the sensor’s dead zone is aligned with these large, often steep, magnetic gradients.

How to cite: McEnroe, S., Lee, M., Madriz, Y., Gloaguen, R., Pastore, Z., Lelièvre, P., and Church, N.: What can we learn from magnetic surveys at different scales? Geological insight from mineral to airborne surveys in the Bjerkreim-Sokndal Layer Intrusion, Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8934, https://doi.org/10.5194/egusphere-egu24-8934, 2024.

EGU24-9258 | ECS | Orals | G4.3

Moho Depth Model and Structural Characteristics of China and Adjacent Regions 

Zhixin Xue, Dongmei Guo, Jian Fang, and Huiyou He

The Moho interface is an important parameter for describing the structure and morphology of the Earth's crust, and it is of significant importance in the study of the formation and evolution of the crust and mantle, as well as deep-seated dynamic processes (Stern et al., 2018). Existing Moho models derived from seismic data often suffer from inaccuracies due to irregular distribution and regional imbalances of seismic data. However, with the development of gravity satellite technology, high-precision satellite gravity data has injected new vitality into the study of lithospheric tectonic features and crustal evolution. In this study, constrained by seismic data (Li et al., 2013; Zhang et al., 2021), we utilized an improved regularized Bott method (Uieda et al., 2017) to invert high-precision satellite gravity data and obtained a high-precision unified Moho depth model for the East Asian region, encompassing both land and sea areas. The research results show that the Moho depth model exhibits a continuous increase in depth from east to west, and its overall distribution in the horizontal direction is non-uniform, displaying distinct regional block features. This paper provides a high-resolution and high-precision Moho model for studying the evolution of the East Asian continental tectonics and plate interactions, and further discusses the macrostructural framework and geological implications of East Asia.

References

Li Y Gao M, Wu Q. Crustal Thickness Map of the Chinese Mainland from Teleseismic Receiver Functions [J]. Tectonophysics, 2013, 611.

Stern, Robert, J, et al. Continental crust of China: A brief guide for the perplexed [J]. Earth Science Reviews the International Geological Journal Bridging the Gap Between Research Articles & Textbooks, 2018.

Uieda L, Barbosa V. Fast nonlinear gravity inversion in spherical coordinates with application to the South American Moho [J]. Geophysical Journal International, 2016.

Zhang J , Yang G , Tan H , et al. Mapping the Moho depth and ocean-continent transition in the South China Sea using gravity inversion [J]. Journal of Asian Earth Sciences, 2021, 218(3–4):104864.

How to cite: Xue, Z., Guo, D., Fang, J., and He, H.: Moho Depth Model and Structural Characteristics of China and Adjacent Regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9258, https://doi.org/10.5194/egusphere-egu24-9258, 2024.

EGU24-10299 | ECS | Orals | G4.3

Satellite gravity validation by new airborne gravimetry in coastal regions of Antarctica and Norway 

Bjørnar Dale, Sebastian Bjerregaard Simonsen, Ove Christian Dahl Omang, Tim Enzlberger Jensen, and René Forsberg

Airborne gravimetry provides gravity observations of higher spatial resolution than what can be obtained from satellite gravity field measurements, and together with terrestrial measurements they augment the satellite observations to determine high-resolution geoid models. Satellite altimetry in coastal and ice-covered regions is known to have significant errors. We use modern strapdown gravimetry for the surveys and compare the indirect method, using Kalman filtering, and the direct filtering method for the processing. We present the result of strapdown gravimetry for two airborne campaigns conducted in Antarctica 2022 and Norway 2023. During both campaigns the sensors used were an iMAR navigation-grade inertial measurement unit together with a geodetic GNSS receiver.

The 2022 campaign covered part of the sea-ice covered Weddell Sea and was surveyed as a piggyback activity as part of the ESA CRYO2ICE and NERC DEFIANT 2022 Antractica campaign. The 2023 airborne campaign was carried out in the coastal region of Norway near Trondheim. In both areas the data were compared to satellite altimetry and other gravity data from ship or airborne surveys. Both campaigns show improvements in spatial resolution and accuracy of the new mGal-level airborne gravimetry data when compared to satellite altimetry and older marine gravity observations.

How to cite: Dale, B., Bjerregaard Simonsen, S., Christian Dahl Omang, O., Enzlberger Jensen, T., and Forsberg, R.: Satellite gravity validation by new airborne gravimetry in coastal regions of Antarctica and Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10299, https://doi.org/10.5194/egusphere-egu24-10299, 2024.

EGU24-11380 | ECS | Orals | G4.3

Gravity inversion of sub-ice shelf bathymetry in West Antarctica using a geostatistical Markov Chain Monte Carlo approach 

Michael Field, Emma MacKie, Lijing Wang, and Atsuhiro Muto

Sub-ice-shelf bathymetry controls the delivery of warm water to the ice-shelf bottom in West Antarctica, making the bathymetry beneath ice shelves in the Amundsen Sea critical inputs to ice-sheet and ocean models. Previous estimates of the bathymetry have often used deterministic inversion frameworks or do not account for the non-uniqueness of the inverse problem, and ultimately lack robust uncertainty quantification. To provide more robust and reproducible bathymetry models, we implement a random walk Metropolis-Hastings Markov Chain Monte Carlo (MCMC) inversion approach, which iteratively generates model perturbations using random Gaussian fields and forward models the gravity disturbance of proposed bathymetry models. After convergence, our approach samples the posterior distribution allowing for estimation of the mean and variance of the bathymetry while providing realistic models of the sub-ice-shelf bathymetry. An ensemble of bathymetry models can then be used in ice-sheet and ocean simulations to propagate the uncertainty in bathymetry to dynamic ice processes, resulting in better uncertainty quantification of future sea-level rise. In addition to providing more robust bathymetry models, this work provides a step forward in the reproducibility of geophysical inversions by leveraging the growing open-access geoscientific computing ecosystem of Python.

How to cite: Field, M., MacKie, E., Wang, L., and Muto, A.: Gravity inversion of sub-ice shelf bathymetry in West Antarctica using a geostatistical Markov Chain Monte Carlo approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11380, https://doi.org/10.5194/egusphere-egu24-11380, 2024.

EGU24-12072 | Posters on site | G4.3

3D joint inversion of regional magnetotelluric, seismic, gravity and magnetic datasets to image lithospheric structure of Ireland 

Dmitry Molodtsov, Duygu Kiyan, and Christopher Bean

Regional gravity and magnetic surveys are essential sources of information about the structure and geodynamics of the lithosphere. However, geologically meaningful inversion of gravity and magnetic data usually requires integration with other geophysical methods. We have developed a 3-D joint inversion framework that has the flexibility of using independent inversion codes and model discretizations for each of the included methods, is easily expandable and supports a wide range of the coupling constraints. Here we show its application to the regional geophysical datasets available in Ireland. We present the results of joint inversion of long-period magnetotelluric data, seismic traveltimes, and land gravity – a multiparameter geophysical model of the crust and uppermost mantle of the whole Ireland. On a smaller scale, we present the results of joint inversion of gravity, airborne magnetic and magnetotelluric data for the Limerick Basin, focusing on imaging of a Carboniferous volcanic structure.  The main aim is to better understand the Pb-Zn mineral systems which are controlled by the tectonics of the basement and lower crust. Exploration-scale geophysical surveys and geothermal exploration will also benefit from the regional 3-D geophysical models.

How to cite: Molodtsov, D., Kiyan, D., and Bean, C.: 3D joint inversion of regional magnetotelluric, seismic, gravity and magnetic datasets to image lithospheric structure of Ireland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12072, https://doi.org/10.5194/egusphere-egu24-12072, 2024.

EGU24-12510 | ECS | Orals | G4.3 | Highlight

Are there thick sediments within South Pole Basin? Investigating the lithology of SPB using COLDEX airborne geophysics  

Megan Kerr, Duncan Young, Weisen Shen, Gregory Ng, Shivangini Singh, Dillon Buhl, Jamin Greenbaum, Shuai Yan, and Donald Blankenship

Because sedimentary basins may exert considerable control over ice sheet dynamics and basal heat flow, it is vital to constrain the extent, thickness, and level of consolidation of sediments throughout the continent and at local scales. Until recently, the South Pole Basin (SPB), situated between the Gamburtsev Subglacial Mountains, the Transantarctic Mountains, and Recovery Subglacial Highlands, has been one of Antarctica's least-explored regions. Previous studies based on seismic and machine learning models, including those by Baranov & Morelli (2023) and Li et al. (2022), have characterized SPB as a sedimentary basin with sediment thicknesses exceeding 1 km. Conversely, a seismic study conducted by Zhou et al. (2022) identifies SPB as a region with little to no sedimentary rock. A lack of dense geophysical data as well as the inherent difficulty of studying geology beneath the Antarctic Ice Sheet introduced a large amount of uncertainty into these assessments. Recent airborne radar, gravity, and magnetics data collected by the Center for Oldest Ice Exploration (COLDEX) has revealed two distinct geomorphological provinces within South Pole Basin: the southern portion of SPB which exhibits relatively smooth, reflective bedrock, while the northern SBP manifests as much rougher terrain. The abrupt boundary between Inner and Outer SPB is associated with the onset of subglacial melting, inferred from a rapid thinning of the basal layer, decreased ice sheet surface slope, and presence of subglacial lake-like features. In addition to surficial differences, these provinces are marked by distinct free-air, Bouguer, and isostatic gravity signatures. A large, arc-shaped magnetic high parallel to Recovery Subglacial Highlands cuts across SBP, facilitating a robust depth to basement analysis and providing constraints for gravity inversions. By integrating COLDEX data with previous airborne surveys and newly collected seismic data, we offer a revised geological interpretation of the South Pole Basin and discuss its tectonic history, potential for groundwater storage, and the preservation of ancient ice in this region.

How to cite: Kerr, M., Young, D., Shen, W., Ng, G., Singh, S., Buhl, D., Greenbaum, J., Yan, S., and Blankenship, D.: Are there thick sediments within South Pole Basin? Investigating the lithology of SPB using COLDEX airborne geophysics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12510, https://doi.org/10.5194/egusphere-egu24-12510, 2024.

Joint inversion can utilize multiple geophysical datasets to supplement or enhance the information on subsurface structures, improve the resolution and certainty of recovered subsurface structures, and provide broad prospects for various geophysical application scenarios. Model coupling is crucial in joint inversion, and there are two main coupling methods based on structural similarity and petrophysical information. These two coupling methods have their own advantages and disadvantages. The structural similarity-based coupling method can obtain structurally similar models without prior information, but the assumption of structural similarity between models is not always valid. The petrophysics-based coupling method provides finer constraints on physical property values, and its difficulty lies in acquiring petrophysical information, which is usually imprecise and incomplete in the inversion region. Joint inversion using a single model coupling approach is insufficient to face complex joint inversion situations. Combining the two coupling methods can complement the structural similarity of the model in the inversion of incomplete petrophysical information.

We develop a novel joint inversion method based on the extended alternating direction method of multipliers (eADMM), which is compatible with multiple model coupling methods and reduces non-uniqueness and uncertainty more effectively. Multiple model coupling methods are contained in an indicator function, which requires the model to satisfy specific mathematical sets, allowing the various models to satisfy arbitrary relationships and ranges. The inequality constraints and linear and nonlinear relational equations extracted from the petrophysical information are expressed directly in mathematical sets, and the structural similarity coupling is implemented by a constraint set that requires a cross-gradient of zero between models. The solution of the indicator function in the eADMM framework is converted into a projection function, and we develop corresponding projection algorithms for multiple constraint sets of both model coupling strategies. The constraint sets are also spatially flexible. Regions with complete petrophysical information and regions requiring increased structural similarity can be constrained by the corresponding sets, respectively.

We apply the method to gravity and magnetic data to test its performance. We compare the performance of our method with that of the joint inversion using a single coupling method for incomplete petrophysical information, including petrophysical information for partial regions and partial geologic units. Synthetic examples show that regions and geologic units with known petrophysical information are recovered with accurate geometric boundaries and physical property values closer to the true values, and structural similarity coupling provides structural information for unknown regions or geologic units, recovers more accurate geometric structures and reduces model uncertainty. The new joint inversion method provides higher resolution models than the traditional joint inversion method, and the inversion results are closer to the true model.

How to cite: Wang, K. and Yang, D.: joint inversion of gravity and magnetic data with petrophysical and structural coupling constraints using indicator functions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14351, https://doi.org/10.5194/egusphere-egu24-14351, 2024.

EGU24-14771 | ECS | Orals | G4.3

Joint inversion of potential field data to unmask sub-ice geology, from a case study in Scandinavia to application in NE Greenland 

Agnes Dakota Wansing, Jörg Ebbing, Max Moorkamp, and Björn Heincke

The surface geology of Greenland is only known along the ice-free coast. The remaining 80% of Earth's largest island are covered by ice that masks the surface geology and makes direct observation nearly impossible. Interpolation of the known coastal geology over the inland ice, combined with expert knowledge, can provide a first, but not well-constrained picture. In contrast, the surface geology in Scandinavia is well-studied. The formerly adjacent northeastern part of Greenland belongs to the same Caledonian orogeny and is expected to be somewhat similar to Scandinavia. Therefore, we use Scandinavia as a case study to set up a workflow of joint inversion of potential field data to find physical relations for the known geological structure and apply this workflow to NE Greenland.

Results from individual inversion of potential field data are non-unique and have limited depth resolution. Combining gravity and magnetic data in a joint inversion can minimise the non-uniqueness and improve the depth resolution. The coupling furthermore creates comparable anomaly patterns for both inverted parameters. As coupling method, a variation of information (VI) constraint is used in the inversion. The VI creates representative parameter relationships where different branches reflect the numerous combinations of density and susceptibility for various rock types. Thus, the inverted parameter relationship can be used to map the surface geology.

Crucial parts in the workflow setup are how deeper sources are handled for the gravity data and at which resolution and height the magnetic data are required.  The simultaneous analysis of the well-studied surface geology in Scandinavia helps to verify the analysis, providing higher confidence in the resulting sub-ice geology for NE Greenland.

How to cite: Wansing, A. D., Ebbing, J., Moorkamp, M., and Heincke, B.: Joint inversion of potential field data to unmask sub-ice geology, from a case study in Scandinavia to application in NE Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14771, https://doi.org/10.5194/egusphere-egu24-14771, 2024.

EGU24-15133 | ECS | Posters on site | G4.3

Investigating the feasibility of resolving hydrological processes with a Differential Quantum Gravimeter by hydrological scenario modeling 

Marvin Reich, Camille Janvier, and Andreas Güntner

Quantum sensors have gained increased attention in the last years, both from the applied but also from the manufacturer perspective. Most instruments are still limited to operation within a dedicated lab. With the Absolute Quantum Gravimeter (AQG), one device has already proven mobile capabilities and was used in several research studies. This application perspective is an important topic for new instruments, in order to meet scientific requirements in terms of usability and usefulness for various research interests.

One of these research interests is hydrology. From the monitoring perspective, hydrological observations in the field traditionally rely on point measurements, often in form of invasive sensor installations. These spatially-limited observations sometimes complicate natural hydrological process investigations. An advantage is provided when using the hydrogravimetric method, with its integral nature of monitoring water mass changes as a whole.

In this contribution, we address the above-mentioned important topics for a first feasibility study of an emerging instrument: the Differential Quantum Gravimeter (DQG). Developed by Exail Quantum Sensors, the DQG measures the acceleration due to gravity and the vertical gravity gradient simultaneously. It is an industry-grade demonstrator that has been operational for three years now and has achieved state-of-the-art sensitivity on the gradient of about 60E/sqrt(tau) and a long-term stability on the gradient around 1E. For gravity measurements the performances are on par or better than the AQG with a sensitivity of 600nm/s²/sqrt(tau) and a stability down to 5nm/s².

In preparation for first field measurements, we were interested in its performance for resolving hydrological dynamics and processes. We set up different hydrological modeling scenarios to forward model gravity responses and their DQG-related gravity gradients from water mass changes. Scenarios for obtaining these water mass changes consisted of vertical 1D models using the software Hydrus. Developing scenarios from very simple to more complex soil layer setups, we tested different forcing types (precipitation, evapotranspiration) with varying magnitudes and durations. The overall objective was to simulate resulting gravity gradients at different locations as the DQG would monitor them. Varying the theoretical placement of the DQG within the model domain enabled us to investigate its sensitivity to the simulated hydrological processes with respect to its location and distance to different magnitudes of water mass changes. Forward modeled data was averaged at different time periods and combined with realistically expected noise of the instrument. The study helps to evaluate the capabilities of the instrument as a tool to observe water fluxes in the soil, as well as optimal implementation of the DQG for planning first field measurements.

How to cite: Reich, M., Janvier, C., and Güntner, A.: Investigating the feasibility of resolving hydrological processes with a Differential Quantum Gravimeter by hydrological scenario modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15133, https://doi.org/10.5194/egusphere-egu24-15133, 2024.

EGU24-16919 | ECS | Posters on site | G4.3

Unravelling Deep Aquifer Communication in the Coastal Sahel Region: Insights from Geophysical Methods in the Tunisian Oriental Atlas 

Khaoula Charrek, Kristine Walraevens, Thomas Hermans, and Hakim Gabtni

Understanding the communication pathways of deep aquifers in the Tunisian Oriental Atlas along the southern Mediterranean margin, particularly within the coastal Sahel region, is of utmost importance for designing effective well drilling strategies and reducing risks for groundwater drilling.

In this study, we employed Gravity, Time Domain Electromagnetic (TDEM) methods and the variation of the piezometric level to investigate the structural setting and aquifer characteristic. Gravity and TDEM are two geophysical methods that provide insights into the density variation of underground bodies and reveal resistivity distribution at different depths, respectively. By integrating these methods, we aim to unravel the intricate hydrogeological system in the study area.

Our findings highlight a major fault line with a significant water level discrepancy, which is crucial information for groundwater exploration and exploitation. This study provides insights into the hydrogeological dynamics of the coastal Sahel region, facilitating the design of new drilling strategies. The gained knowledge supports informed decision-making in selecting optimal target production zones, ultimately minimizing drilling risks and promoting sustainable groundwater management in the Tunisian Oriental Atlas.

How to cite: Charrek, K., Walraevens, K., Hermans, T., and Gabtni, H.: Unravelling Deep Aquifer Communication in the Coastal Sahel Region: Insights from Geophysical Methods in the Tunisian Oriental Atlas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16919, https://doi.org/10.5194/egusphere-egu24-16919, 2024.

EGU24-17112 | ECS | Posters on site | G4.3

Application of numerical integration and CUDA parallel in the calculation of ocean gravity gradient 

Zhourun Ye, Jingyu Bu, and Nico Sneeuw

Through Stokes kernel function and gravity anomaly, it is possible to calculate the gravity gradient disturbance on the geoid and its external space. For this Stokes’ integral expression, we apply Laguerre wavelet numerical integration to improve the accuracy of its computational results. Meanwhile, compute unified device architecture (CUDA) is used to implement parallel computing on the Graphic Processing Unit (GPU) for speeding up. The full tensors of gravity gradient in the experimental ocean area with 3°×2°are computed. Compared to serial computing, its computing acceleration ratio can be more than 10 times faster. The results of the vertical gravity gradient are compared and validated from the public model from the University of California San Diego.

How to cite: Ye, Z., Bu, J., and Sneeuw, N.: Application of numerical integration and CUDA parallel in the calculation of ocean gravity gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17112, https://doi.org/10.5194/egusphere-egu24-17112, 2024.

EGU24-17176 | ECS | Posters on site | G4.3

Bayesian Joint Inversion of Bouguer Gravity and Surface Wave data: application to the Western Alps 

Matteo Scarponi and Thomas Bodin

The Western Alps constitute a complex and heterogeneous orogenic system, generated by the continental collision between the European and Adriatic tectonic plates. Three main tectonic domains can be identified across local to regional scales, based on geophysical and geological observations: the European and Adriatic domains, and the high-density, high-velocity anomaly known as Ivrea geophysical body (IGB). Despite being one of the best-studied collisional systems in the world, the 3D Western Alpine lithosphere and its along-arc compositional and structural variations are still subjects of investigations.

 

In this framework, we exploit the inherently-3D information provided by gravity data. In particular, we set up a 3D Bayesian joint inversion of Bouguer gravity anomaly and surface wave dispersion data, to obtain a new 3D ρ-vS model of the Western Alpine lithosphere. We benefit from the Bouguer anomaly map by Zahorec et al. (2021), obtained by homogeneous processing of gravity data across the Alpine domain, and from seismic data recorded by permanent and temporary seismic networks: e.g. IvreaArray, AlpArray (Hetényi et al. 2017, 2018), CIFALPS I and II (e.g. Paul et al. 2022).

 

We perform 3D forward gravity modeling by discretizing the study area in unitary volumes of constant density (voxels), accounting for spherical Earth structure and surface topography. The gravity effect of each voxel is pre-computed, and then only needs to be scaled with density during the inversion. This significantly decreases the computational cost of the forward model, and thus allows us to explore the parameter space with Monte Carlo sampling. We use a Bayesian framework and implement a Markov chain Monte Carlo (McMC) algorithm. We test different types of  parameterizations to reduce the non-uniqueness of gravity inversion. We plan to jointly invert gravity with surface wave dispersion data, providing complementary information on vS. Finally, existing receiver function studies (e.g. Monna et al. 2022, Paul et al. 2022, Michailos et al. 2023) provide prior information on crustal and lithospheric geometry.


We expect to obtain a new 3D ρ-vS model for the Western Alpine crust and lithosphere. This will provide new information on the European-Adriatic collision boundary, together with the IGB structure, and their three-dimensional variation along the orogen. The new model will be also useful to constrain rock composition, upon comparison with the geological observations at the surface.

How to cite: Scarponi, M. and Bodin, T.: Bayesian Joint Inversion of Bouguer Gravity and Surface Wave data: application to the Western Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17176, https://doi.org/10.5194/egusphere-egu24-17176, 2024.

EGU24-17476 | Posters on site | G4.3

A year-long gravity record at Astroni, Campi Flegrei (Southern Italy): some considerations on data processing for volcano monitoring and precise gravity tides 

Alessandro Fedele, Umberto Riccardi, Tommaso Pivetta, Stefano Carlino, and Giuseppe Ricciardi

High-precision observations of gravity plays a central role in modern approaches for active volcano monitoring. Time-lapse observations over a network of benchmarks are frequently used to detect underground mass redistribution in the plumbing system of active volcanoes. Such approach however does not allow to retrieve small mass variations occurring over short terms (i.e. few hours or days). To fill this gap, continuous gravity monitoring at a fixed station may be employed. In January 2023 the relative gravimeter gPhoneX#116 was installed at the WWF Nature Reserve of Astroni volcano, in the Campi Flegrei caldera, to further complement time-lapse observations periodically performed over a network of benchmarks. During the 1-year of recordings, the gPhone has continuously recorded the relative gravity changes, only shortly interrupted by a few technical issues. The purpose of the observations is to monitor continuously the short-term gravity signals in one of the world's highest-risk volcanoes; to pursue this objective targeted and meticulous corrections need to be applied to remove the effect of several other geophysical effects, such as tides and atmospheric effects, which may superpose on the signals of interest. Special effort was devoted to the study of instrumental drift, which can mask actual gravity changes due to mass variations occurring in the volcanic and geothermal systems. In this contribution we report the various processing steps and analysis performed to obtain reliable parameters of the Earth tides, non-tidal corrections and gravity residuals. The retrieved Earth tide model is then used to properly reduce tidal effects in high-precision relative and absolute gravity measurements.

How to cite: Fedele, A., Riccardi, U., Pivetta, T., Carlino, S., and Ricciardi, G.: A year-long gravity record at Astroni, Campi Flegrei (Southern Italy): some considerations on data processing for volcano monitoring and precise gravity tides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17476, https://doi.org/10.5194/egusphere-egu24-17476, 2024.

EGU24-18969 | ECS | Posters on site | G4.3

GRAVHEDRAL: a novel gravity inversion method to unravel planets’ interior 

Alessandro Ghirotto, Andrea Zunino, Egidio Armadillo, Anna Mittelholz, and Andreas Fichtner

Suitable modelling capabilities paired with planetary-scale datasets provide fundamental information to unravel planets’ interior and evolution. Despite the key role and tremendous effort of decades of scientific missions in advancing the understanding of planets’ subsurface, knowledge about their crustal structures and processes shaping them is still limited. This is mainly due to a sparse record of return samples or meteorites, in addition to the scarcity of surface geophysical measurements. Planets’ crust is however a recorder of ancient geological events leading to nonhomogeneous 3D density distributions, expressed in the form of gravity anomalies. While on Earth combined geophysical data can inform on subsurface properties, for other planets such datasets are sparser, and orbiter-based gravity data is one of few or even the only global-scale source of information related to their interior. Developing an innovative modelling methodology suitable to exploit such orbiter-based data can help infer the 3D density distribution in planets’ crusts, providing key insights to reconstruct their geological history. Here we present GRAVHEDRAL, a fully non-linear 3D inversion methodology of gravity anomaly data suitable for both local- and planetary-scale studies and capable of addressing limitations of existing modelling strategies. Such limitations are related to the challenge of i) characterizing complex 3D density distributions, which are expected in actual geological scenarios, and ii) mitigating the non-uniqueness of the solution. Using GRAVHEDRAL, planets’ interiors (e.g., crust, mantle, etc.) are parameterized in terms of polyhedra with density contrasts expressed as high-order polynomial functions, whose gravity responses can be computed thanks to recently derived analytical formulae. The inversion scheme relies on the Hamiltonian Monte Carlo (HMC) method, a probabilistic approach that is currently gaining momentum in the geophysical community. Compared to other probabilistic approaches, the HMC strategy allows the model space to be explored more efficiently thanks to the gradient calculation of the posterior probability density of the model parameters (i.e., polyhedra node positions and/or density contrasts). Statistical analysis and uncertainty estimation on the model parameters can be performed from the collection of posterior models, enabling the appraisal of different probable geological scenarios to address the non-uniqueness of the solution. GRAVHEDRAL aims to provide the space science community with a flexible tool to help image the still poorly known 3D crustal density distribution of other celestial bodies of our solar system, allowing researchers to test the occurrence of Earth-like geological structures on other terrestrial planets and thus to decipher the reasons behind their different geological evolution.

How to cite: Ghirotto, A., Zunino, A., Armadillo, E., Mittelholz, A., and Fichtner, A.: GRAVHEDRAL: a novel gravity inversion method to unravel planets’ interior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18969, https://doi.org/10.5194/egusphere-egu24-18969, 2024.

G5 – Geodetic Monitoring of the Atmosphere

Precipitable water vapor (PWV), an essential climate variable enlisted by the Global Climate Observing System (GCOS), can be efficiently mapped using popular Earth Observation techniques like Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR). When used in a combination, these techniques complement each other in terms of temporal and spatial resolution for producing high-resolution PWV. Tropospheric water vapor (measured as wet delay) can be perceived in two components: non-turbulent (ZWD_NT) as well as turbulent information (ZWD_T). Wet delays from InSAR acquisitions are able to capture only the turbulent information, hence need to be enhanced. The non-turbulent component further can be spatially classified into shortwave and longwave components. In this study, GNSS observations from a dense network of twelve GNSS CORS for 2021, from the newly established CORS network by Survey of India with a homogeneous spread over Uttarakhand (UK) state, is used to establish the ZWD_NT model. We develop an exponential elevation-dependent model for shortwave components, incorporating seasonal variations and a location-dependent model for long wave components. Model assessment shows the performance of the developed model when a satisfactory mean RMSE of 8.32 mm is obtained through internal checks, which shows the efficacy of the developed model in capturing elevation dependency and seasonal variations. Further, a geodetic framework is conceptualized wherein the values derived from developed ZWD_NT model are appended to non-differential ZWD_T estimated after Small BAseline Subset InSAR (SBAS-InSAR) processing at measurements points density of about 50 million points from 30 ascending pass Sentinel 1A acquisitions, to arrive at full atmospheric information (ZWD_total). A previously developed weighted mean temperature (Tm) model for the highly undulating himalayan foothills region in the UK, is incorporated in the conversion of ZWD_total to PWV, for better accuracy and further assessment. A high resolution combination of PWV derived from complementary GNSS and InSAR techniques can be efficiently utilized in improving the numerical weather prediction (NWP) skill as well as monitoring extreme weather event since the spatial variations in local tropospheric conditions of a hilly terrain are quite frequent. When validated against PWV from ERA5 reanalysis data, a mean RMSE of 9.5 mm is obtained, except for the monsoon period, when RMSE falls in the range of 10-20mm. This may be due to the fact that InSAR partial non differential PWV captures the spatially correlated artifacts especially in the temporal vicinity of a rainy event. The results show that the proposed approach can effectively enhance the InSAR derived non-differential PWV and provide useful information at a high spatial resolution in a varied topography in lesser Himalayan.These high-resolution PWV maps hold great promise for enhancing meteorological understanding and quantitative analysis, specially during heavy rainfall in a complex terrain like UK. With the upcoming NISAR mission for the Indian subcontinent, spatio-temporal analysis of tropospheric parameters can be further enhanced for weather forecasting.

How to cite: saxena, S., ojha, C., and dwivedi, R.: Establishing Zenith Wet Delay model (ZWD) and developing a framework for generating high resolution PWV for extreme weather monitoring using MT-InSAR and GNSS for Indian Himalayan region , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1091, https://doi.org/10.5194/egusphere-egu24-1091, 2024.

Integrated Water Vapor (IWV) stands as a pivotal parameter in contemporary environmental research, offering crucial insights into atmospheric dynamics. Due to the inherent challenges in direct measurement, IWV necessitates estimation through various methods. Current approaches, including Global Navigation Satellite System (GNSS), radiosondes, radiometers, and satellite remote sensing, have inherent limitations, resulting in a scarcity of high spatial resolution data. While GNSS technology, radiosondes, and radiometers provide precision, they are confined to specific locations, imposing spatial coverage constraints. On the other hand, satellite remote sensing offers expansive, high spatial resolution IWV data, yet its accuracy is hindered under cloudy conditions and limited by satellite ground tracks.

This study addresses these challenges by introducing a regional IWV prediction model based on Machine Learning. Leveraging IWV data from diverse GNSS stations within a specified region, the study establishes a regional IWV prediction model utilizing an adaptive least squares support vector machine (ALSSVM). This predictive model enables accurate IWV estimation at any designated location within the region, incorporating inputs such as latitude, longitude, height, and temperature. Significantly, the model attains remarkable predictive accuracy, with an overall average root mean square error (RMSE) of 2 millimeters.

The model's performance exhibits variability across different seasons and terrains, illustrating its adaptability to diverse environmental conditions. The study further evaluates the reliability of the conventional ERA5 IWV calculation method in the specified region by comparing it against the predicted results from the proposed IWV prediction model. In conclusion, the developed model is applied to conduct a climate analysis, demonstrating its practical utility in environmental research for the transnational Upper Rhine Graben region.

Keywords:

Global Navigation Satellite System (GNSS), Integrated Water Vapor (IWV), least squares support vector machine (LSSVM), Climate Analysis

How to cite: Wang, L. and Kutterer, H.: Advancing Integrated Water Vapor Estimation: Introducing an Enhanced Regional Prediction Model Utilizing Improved Least Squares Support Vector Machine for the Upper Rhine Graben Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2068, https://doi.org/10.5194/egusphere-egu24-2068, 2024.

EGU24-2522 | ECS | Posters virtual | G5.1

First results about height correction of tropospheric delay mapping function in GNSS applications 

Miaomiao Wang, Ping Li, Ruyu Lu, Shuheng Wang, and Fangyu Zhang

One of the dominant error sources for Global Navigation Satellite System (GNSS) measurements is the correction for delay of an electromagnetic wave as it traverses the neutral atmosphere, which is usually shorted as tropospheric delay. Generally, tropospheric delay must be calculated or estimated since refractivity along ray path is not easily or economically measured. Empirically, the line of sight delay for either hydrostatic or wet component is modeled as product of zenith delay and a mapping function. The accuracy of estimated geodetic parameters for GNSS could be limited due to the indeterminacy of mapping function, when observations are typically made to low elevation angles. Nowadays, there are many different empirical tropospheric delay mapping functions are generated and used in GNSS applications, the sensitivity of mapping functions to height above the geoid of point of observations are mostly corrected with method and formulas proposed in Niell (1996), in which the height corrections are only concerned in hydrostatic delay mapping function. In Niell (1996), the adopted form of height correction for hydrostatic delay mapping function is linearly dependent on height, and the linear coefficient is empirically chosen for fitting precision purpose. In this work, similar to many current works about modelling mapping factors to operational mapping functions, with the help of ERA-Interim reanalysis data set from the European Centre for Medium-range Weather Forecasts (ECMWF), the sensitivity of both hydrostatic and wet delay mapping factors to height are calculated and preliminary analyzed. As an important part of the work, the needed data set sources, i.e., the tropospheric delays at some ground-based stations along some previously set ray paths with different elevation angles, azimuth angles, heights and time epochs, are generated with a self-generated tropospheric delay ray-tracing package named GTRATS (Gnss Tropospheric delay RAy Tracing Software). The first results show that for a specific not low elevation angle, the variations of both hydrostatic and wet mapping factors to the height are not too obvious; the hydrostatic mapping factors change linearly to height with different performances, while wet mapping factors are not with linearly change, especially for low elevation angles; height corrections with method in Niell (1996) for hydrostatic mapping factors actually perform well in some cases, while maybe correct too much or too less in some stations at some time epochs, thus maybe new correction strategy can be accounted; the height correction should also be concerned for wet delay mapping functions, while there is no obvious, regular and reliable relation or appearance can be observed according to our first results, and more efforts should be made for the examination and investigation of this problem.

How to cite: Wang, M., Li, P., Lu, R., Wang, S., and Zhang, F.: First results about height correction of tropospheric delay mapping function in GNSS applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2522, https://doi.org/10.5194/egusphere-egu24-2522, 2024.

EGU24-5628 | ECS | Orals | G5.1

Worldwide Small-Scale Land Surface Roughness Retrieval at L-band Using Space-born GNSS-R Observations  

Mina Rahmani, Jamal Asgari, and Jens Wickert

    Soil moisture (SM) is a crucial factor influencing the exchange of energy between the soil and the atmosphere, playing a key role in hydrological processes. GNSS Reflectometry (GNSS-R) has recently become an innovative method for remotely monitoring various geophysical and hydrological parameters, including soil moisture. GNSS-R operates by utilizing signals from Global Navigation Satellite Systems (GNSS) that are reflected off the Earth's surface. In addition to the quantity of soil moisture content, the features of vegetation, such as vegetation water content, and the soil surface roughness influence GNSS-R observations. Consequently, accurately parameterizing these effects is essential for achieving precise and high-quality estimates of soil moisture. Nevertheless, separating the influences of surface roughness and vegetation on reflected signals is often challenging.

     In this context, we employed a methodology aimed at assessing and mapping the sensitivity of GNSS-R observations to soil roughness effects. This analysis is based on observations collected by NASA's GNSS-R mission, CYGNSS, on a global scale in 2021. Initially, we endeavored to explore the responsiveness of CYGNSS observations to soil effects across a regular 0.2-degree global grid. The results revealed that CYGNSS observations exhibit sensitivity to soil effects over around 90% of the Earth's land surface covered by CYGNSS, spanning latitudes from 37° in the Northern Hemisphere to 37° in the Southern Hemisphere for all longitude values. Nevertheless, they show low sensitivity in the remaining 10% of land areas, primarily attributed to the impact of dense vegetation covers, particularly in the Amazon and Congo forests. In the second step, over regions where CYGNSS observations are sensitive to soil effects, we attempted to compute a map of the roughness parameter (Hr). To achieve this goal, we suggested integrating the effects of both vegetation and roughness into a single parameter, referred to as VR in this study. Initially, VR values were retrieved on a global scale from CYGNSS by inverting the L-MEB model. The L-MEB (Land Microwave Emission Model with Briggs approach) is a radiative transfer model used to simulate microwave emissions from land surfaces for remote sensing applications. Then, the effects of vegetation and soil roughness included in the VR parameter were decoupled by assuming a linear relationship between VR and Leaf Area Index (LAI) (~0.5 in this research) for the purpose of mapping the roughness parameter, Hr.

    In this study, the obtained Hr values range from 3.2 to 4.6. The spatial distribution of Hr values is observed to be influenced by predominant vegetation types, where forests demonstrate higher roughness values (Hr = 4-4.6), whereas deserts, shrubs, crops, and bare soils exhibit lower values (Hr = 3.2-3.4). We also inferred vegetation optical depth (VOD) using CYGNSS observations in conjunction with estimated Hr values as an ancillary dataset. The evaluation of the obtained VOD in comparison with Vegetation Water Content (VWC) and LAI produced correlation coefficients of 0.57 and 0.71, confirming the effectiveness of the recently introduced Hr dataset in our research and highlighting its promising potential for future applications in GNSS-R.

How to cite: Rahmani, M., Asgari, J., and Wickert, J.: Worldwide Small-Scale Land Surface Roughness Retrieval at L-band Using Space-born GNSS-R Observations , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5628, https://doi.org/10.5194/egusphere-egu24-5628, 2024.

EGU24-5929 | ECS | Posters virtual | G5.1

Probing the Dynamics of Extreme Weather Events in the Azores, Portugal 

Dhiman R. Mondal, Pedro Elosegui, Lucy Brock, Scott Paine, Pedro Mateus, and Virgilio Mendes

The rapidly changing climate is escalating the frequency and intensity of extreme weather events in the Azores, Portugal. It is crucial to comprehend the dynamics of these events to mitigate them. Atmospheric water vapor data from the Global Navigation Satellite System (GNSS) and reanalysis products from an atmospheric general circulation model can be utilized to investigate the dynamics of weather fronts in the Azores Islands. A primary goal of our study is to conduct a comprehensive comparison between GNSS and MERRA2-based atmospheric reanalysis data and derive small-scale atmospheric structures with high-temporal resolution. Using statistical analysis, we will unveil the similarities and discrepancies between the two approaches in capturing atmospheric water vapor patterns. Emphasizing an exploratory methodology, we will showcase our findings using a restricted dataset that centers on specific instances of extreme precipitation witnessed in the Azores Islands.

How to cite: Mondal, D. R., Elosegui, P., Brock, L., Paine, S., Mateus, P., and Mendes, V.: Probing the Dynamics of Extreme Weather Events in the Azores, Portugal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5929, https://doi.org/10.5194/egusphere-egu24-5929, 2024.

EGU24-6211 | Posters on site | G5.1

Novel Real-time Observation of High-resolution Water Vapor Behavior for Detection of Precursors of Cumulonimbus Clouds and Investigation of Their Evolution: - Preliminary Results - 

Ryuichi Ichikawa, Yusaku Ohta, Kentaro Araki, Takuya Tajiri, Mikiko Fujita, Hideki Ujihara, Takayoshi Yamada, Takaaki Jike, Hiroshi Imai, Masahiro Minowa, and Yuya Takashima

We have initiated a new research project to analyze the behaviors of precipitable water vapor with high spatial and temporal resolutions using a dense global navigation satellite system (GNSS) network and next-generation microwave radiometers. Recently, line-shaped rainbands with extreme and hazardous characteristics have been occurring frequently in Japan, leading to disasters such as severe flooding and landslides. However, there is insufficient knowledge regarding the generation mechanism of cumulonimbus clouds within these rainbands. Our project has four research subobjectives: (1) to develop a novel microwave radiometer for use in millimeter-wave spectroscopy, enabling high-resolution and high-precision monitoring of water vapor behavior, and conduct field measurements using this radiometer for proof of concept; (2) to conduct high-resolution water vapor measurements using a dense network of low-cost GNSS receivers; (3) to conduct GNSS water vapor tomography for estimating precise temporal and spatial variations; and (4) to numerically predict weather precisely using dense-measurement water vapor datasets and fine GNSS tomography results. Our project is aimed at not only the advancement of mesoscale meteorology but also application to space geodetic techniques such as very long baseline interferometry (VLBI) and GNSS. Regarding the first subobjective, significant progress has been achieved in the development of a next-generation microwave radiometer utilizing millimeter-wave spectroscopy since 2018. To date, we have successfully engineered a new front-end module equipped with an orthomode transducer (OMT) and a wideband feed. The prototype of the complete receiver system has a wide bandwidth feed spanning from 16 to 58 GHz, facilitating the measurement of two frequency bands: 16-28 GHz (H2O) and 50-58 GHz (O2). We plan to integrate this system into a 40-meter-class dish telescope to assess its performance in detecting water vapor variability this summer. For the observation of GNSS precipitable water vapor, we first installed a low-cost GNSS receiver and a commercial-based microwave radiometer at Kagoshima University in early November 2023 as a preliminary observation to understand the variability of water vapor in the southern Kyushu area. In addition to the precipitable water vapor information obtained from this observation, we plan to investigate the variability of water vapor in this area based on the information obtained from the GNSS Earth observation network (GEONET) system of the Geospatial Information Authority of Japan (GSI) and a commercial-based GNSS observation network. Our presentation will include preliminary results and an outlook on future developments. This work received support through JSPS KAKENHI Grant Numbers JP21H04524 and 23H00221.

How to cite: Ichikawa, R., Ohta, Y., Araki, K., Tajiri, T., Fujita, M., Ujihara, H., Yamada, T., Jike, T., Imai, H., Minowa, M., and Takashima, Y.: Novel Real-time Observation of High-resolution Water Vapor Behavior for Detection of Precursors of Cumulonimbus Clouds and Investigation of Their Evolution: - Preliminary Results -, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6211, https://doi.org/10.5194/egusphere-egu24-6211, 2024.

EGU24-8726 | Posters on site | G5.1

Near real-time water vapour monitoring with shipborne GNSS for numerical weather prediction 

Pierre Bosser and Pierre Tulet

MAP-IO (Marion Dufresne Atmospheric Program Indian Ocean) is a research project that aims to collect long-term atmospheric, biological and marine observations to document the under-instrumented areas of the Indian and Southern Oceans. To achieve this, the French Research Vessel (R/V) Marion-Dufresne, based in Réunion Island in the Indian Ocean, has been equipped with around twenty autonomous instruments to take measurements along its route.

Among the instruments deployed on this R/V, a GNSS antenna has been in operation since autumn 2020, providing unique and continuous measurements of atmospheric water vapour in this part of the world. The data were initially transmitted daily to shore for ultra-rapid (day +1) and rapid (day +3) routine analysis. The quality of the retrieved tropospheric delays and integrated water vapour contents was highlighted in a previous study. With more reliable transmission facilities, raw GNSS data are now transmitted hourly and can be analysed with a latency of less than 30 minutes.

In this study, we provide an initial assessment of the near real-time (h+20min) processing performed as part of this project. This evaluation is based on GNSS raw data collected in August 2023 during a rotation of the R/V Marion-Dufresne in the French Austral Islands (Crozet, Kerguelen, Saint-Paul and Amsterdam Islands). Processing is performed every hour over a 24-hour window, using the raw hourly data transmitted by the R/V and the cumulative real-time ephemerides and clocks provided by JPL / GDGPS. Only the last hour of each analysis is then considered. Over this period, the estimated tropospheric delays are in good agreement with the rapid routine solution, with differences of less than 1 cm RMS. The comparison with the analysis and the 6h forecast of the Météo-France's global numerical weather prediction model Arpège highlight the benefits of these shipborne GNSS measurements for numerical weather prediction.

The medium-term objective of this work is to establish an operational procedure for the assimilation of these near real-time GNSS tropopheric solutions into numerical weather prediction models.

How to cite: Bosser, P. and Tulet, P.: Near real-time water vapour monitoring with shipborne GNSS for numerical weather prediction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8726, https://doi.org/10.5194/egusphere-egu24-8726, 2024.

EGU24-8792 | Posters on site | G5.1

Validation of GNSS-based Integrated Water Vapor for the Swabian MOSES 2023 field campaign 

Florian Zus, Annika Oertel, Rohith Muraleedharan Thundathil, Galina Dick, Peter Knippertz, and Jens Wickert

The Swabian MOSES (Modular Observation Solutions for Earth Systems) field campaign was conducted between June and September 2023 in the southeastern Black Forest, the Neckar Valley and the Swabian Alb in southwestern Germany. It focused on hydro-meteorological extreme events, including the initiation and intensification of convective events which are accompanied by heavy rain and can lead to local flooding. As a part of the observing system the GFZ installed eight additional GNSS stations in the region of interest and operated them in near real time during the measurement campaign. The precise point positioning technique was utilized to provide Integrated Water Vapor (IWV) estimates with a temporal resolution of 15 min. In this contribution we provide a first comparison of these IWV estimates with those derived from atmospheric (re-) analysis datasets. We utilize the atmospheric reanalysis ERA5 (horizontal resolution 31 km) and the operational analysis ICON-D2 (horizontal resolution 2 km) provided by the German Weather Service. Ground-based GNSS data are not assimilated into ERA5 and ICON-D2. In general, we find good agreement between GNSS and (re-)analysis estimates: the root mean square error is 1-2 kg/m2. Our goal is to better understand the remaining station specific systematic and random deviations. For example, for all stations, the random deviations are smaller for the high compared to the low resolution model data. We attribute this to smaller representative errors and smaller forward model (interpolation) errors. However, for the systematic deviations the result is not too obvious. Comparisons with measurements from instruments which are collocated with the GNSS stations are envisaged to better understand the issue.  

How to cite: Zus, F., Oertel, A., Muraleedharan Thundathil, R., Dick, G., Knippertz, P., and Wickert, J.: Validation of GNSS-based Integrated Water Vapor for the Swabian MOSES 2023 field campaign, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8792, https://doi.org/10.5194/egusphere-egu24-8792, 2024.

EGU24-10250 | ECS | Orals | G5.1

Assimilating UAV-based GNSS ZTDs for Numerical Weather Predictions 

Zhenyi Zhang, Mengjie Liu, Valeria Huber, Gregor Möller, Jan Henneberger, Philipp Kryenbühl, Lukas Hammerschmidt, Grzegorz Kłopotek, and Benedikt Soja

In recent decades, various studies have demonstrated that assimilating tropospheric parameters from ground-based GNSS receivers benefits numerical weather predictions (NWPs). However, the achieved performance is limited by the spatial resolution of GNSS, especially in the vertical direction. With the rapidly developing and growing market of unmanned aerial vehicles (UAVs) and the facilitates of integrating low-cost GNSS hardware into various autonomous systems over the last years, there is a potential to address this problem by utilizing UAVs to collect airborne GNSS data and generate zenith total delays (ZTDs). The airborne GNSS ZTDs can act as a potential complementary source to radiosonde data for obtaining vertical profiles of the troposphere, making it promising to investigate the impact of assimilating GNSS ZTDs of high spatio-temporal resolution in NWPs.

In this study, we explored the use of GNSS data collected by a vertically ascending UAV, with ZTDs processed using the software CamaliotGNSS. Based on the airborne GNSS ZTDs, we conducted not only data assimilation but also weather predictions using the Weather Research and Forecasting Model (WRF). With the onboard meteorology observations as references, we found that assimilating airborne GNSS ZTDs positively impacted humidity and temperature forecasts, with their forecasting root-mean-square errors decreasing by about 19% and 29%, respectively. Moreover, by selecting and comparing different subsets of data, we found that better forecasts can be obtained with airborne GNSS ZTDs of higher spatio-temporal resolution. The positive results invite further exploration of applications of airborne platforms such as UAVs in the field of GNSS meteorology. 

How to cite: Zhang, Z., Liu, M., Huber, V., Möller, G., Henneberger, J., Kryenbühl, P., Hammerschmidt, L., Kłopotek, G., and Soja, B.: Assimilating UAV-based GNSS ZTDs for Numerical Weather Predictions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10250, https://doi.org/10.5194/egusphere-egu24-10250, 2024.

EGU24-10463 | ECS | Orals | G5.1

Tropospheric slant delays interpolating multiple mapping functions 

Angel Navarro Trastoy, Ghodsiyeh Motlagh Zadeh, Maksym Vasiuta, Patrick Dumitraschkewitz, Torsten Mayer-Gürr, and Heikki Jarvinen

Representing the tropospheric slant delays in geodesy can get complicated due to the inhomogeneity and fast variations of the weather. Mapping functions are the most common used tool for this task, but due to the lack of information when calculating the parameters of the mapping functions, relevant errors could appear. The errors in the zenithal direction come from the limitations of the mapping functions, and in the azimuthal direction come from the asymmetries in the sight-field of the receiver. New representations, as the full skyviews representation made by University of Helsinki, have proven to lead to better results in the computation of GNSS products using orbit processing softwares, but these are expensive, both computationally and in size. In this study, we apply the mapping functions approach using the Least Travel Time ray-tracer with larger amounts of mapping functions per receiver, and a 1-hour update of all the parameters. We believe that a more precise use of the slant delays would lead to a better computaiton of GNSS products, along with a important data assimilation to the weather forecast from the residuals obtained in the Least Squares Adjustment used in the processing. The results show that the error induced when using mapping functions converges quickly to a minimum when we increase the amount of mapping functions used per receiver. The most efficient number of mapping functions is 10, being equidistant (one mapping functions every 36 degrees in azimuth).

How to cite: Navarro Trastoy, A., Motlagh Zadeh, G., Vasiuta, M., Dumitraschkewitz, P., Mayer-Gürr, T., and Jarvinen, H.: Tropospheric slant delays interpolating multiple mapping functions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10463, https://doi.org/10.5194/egusphere-egu24-10463, 2024.

EGU24-10874 | ECS | Orals | G5.1

A machine learning model for the vertical correction of tropospheric zenith delays 

Peng Yuan, Kyriakos Balidakis, Jungang Wang, and Zhiguo Deng

Tropospheric delay is one of the most important error sources for space geodetic techniques, such as the Global Navigation Satellite Systems (GNSS). A priori tropospheric Zenith Hydrostatic and Wet Delays (ZHD and ZWD) should be obtained properly in advance to the GNSS data processing. Numerical Weather Model (NWM) is capable to provide accurate tropospheric zenith delays at any specific location with sophisticated calculation. As a more convenient alternative, the tropospheric zenith delays can be first modeled with NWM as a 2-D grid on the Earth surface and then corrected to the height of the specific location. In this case, accurate vertical correction algorithm is crucial. However, though empirical analytical models have been developed for the vertical correction of tropospheric zenith delays, their accuracies are limited due to the large spatiotemporal variability of the delays. In this work, we propose a Machine Learning (ML) model based on neural network for the vertical corrections of both ZHD and ZWD. The training data is obtained from the state-of-the-art NWM, the fifth-generation global reanalysis of European Centre for Medium-Range Weather Forecasts (ERA5). The proposed ML model is capable to reconstruct the tropospheric delays at any height from the Earth surface to up to 14 km. The precision of the ML model is superior to the analytical models with global average RMS values less than 2 and 3 mm for ZHD and ZWD, respectively. Therefore, it provides a convenient alternative to the sophisticated vertical integration of NWM for ordinary users with slight precision loss.

How to cite: Yuan, P., Balidakis, K., Wang, J., and Deng, Z.: A machine learning model for the vertical correction of tropospheric zenith delays, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10874, https://doi.org/10.5194/egusphere-egu24-10874, 2024.

EGU24-13449 | Posters on site | G5.1

The tropospheric delay of the GPS signal and its correlation with the solar cycle 

Umberto Tammaro, Vincenzo Carbone, Vincenzo Capparelli, Fabio Lepreti, and Claudio Martino

The INGV operates a network of about 60 permanent GNSS stations to monitor the Neapolitan volcanic area (southern Italy), which includes three active volcanoes: Somma Vesuvio, Campi Flegrei and the island of Ischia. In this study we consider only the GPS constellation, whose signals are transmitted in the microwave band. Therefore, they suffer a delay while propagating in the troposphere. Bearing in mind that the refractive index in the atmosphere is a function of the water vapour content, pressure and temperature, tropospheric delay can be assimilated into short-term weather forecast models and used in long-term climate studies. We analyse a data set ranged about 14 years (2006-2019) of continuous GPS data, to evaluate the tropospheric delay to be used as a probe tool to quantify precipitable water and track its spatial-temporal evolution. We limit the analysis to the area of Somma Vesuvio, a strato-vulcano that covers an area of 165 km2 and is about 1200 meters high, to study also the effect of the steep topography on the spatial distribution of the precipitable water content. The data are analysed in terms of empirical functions (IMF), organised in ascending order with a parameter ranging from 0 to 15, plus the trend. The trend found is not a linear growth, but grows to a maximum that is in the middle of the time range of about 11 years and then decreases. It is very interesting that the correlation with the solar cycle is high. Therefore, the next developments will be to analyze other data sets to verify the generality of this result.

How to cite: Tammaro, U., Carbone, V., Capparelli, V., Lepreti, F., and Martino, C.: The tropospheric delay of the GPS signal and its correlation with the solar cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13449, https://doi.org/10.5194/egusphere-egu24-13449, 2024.

EGU24-14710 | ECS | Posters on site | G5.1

Improved Least Travel Time ray-tracing operator for GNSS tropospheric delays 

Maksym Vasiuta, Angel Navarro Trastoy, Lauri Tuppi, Sanam Motlaghzadeh, and Heikki Järvinen

Modelling of the microwave signal delay in the neutral atmosphere (i.e., the tropospheric delay) is a crucial part of GNSS observations processing. The design of observation-modelling algorithms is based on signal ray tracing. Considering advancements in modern Numerical Weather Prediction (NWP) models and high standards of GNSS product quality, it is necessary to revise the existing ray-tracing algorithms. We developed an improved least-travel time (LTT) ray-tracer with robust physics assumptions, based on the original LTT algorithm. Both new and original LTT implementations, along with the state-of-the-art VieVS Ray-tracer (RADIATE), are supplied with numerical weather data by the Open Integrated Forecasting System model (OpenIFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). These three ray tracers are justly compared in the setup of modelling the skyview delays for 256 GNSS stations during one month (December 2016). The skill of these delay products is assessed as the quality of GNSS precise orbit determination (POD) products of the GPS constellation made by the orbit solver GROOPS (Gravity Recovery Object Oriented Programming System) software toolkit of the Graz University of Technology. The GNSS POD metrics which have been analysed are orbit midnight discontinuities (MD) and precise point positioning (PPP) error. In the context of these metrics, the usage of the new LTT algorithm leads to better orbit products, compared to the original LTT and the RADIATE ray tracers.

How to cite: Vasiuta, M., Navarro Trastoy, A., Tuppi, L., Motlaghzadeh, S., and Järvinen, H.: Improved Least Travel Time ray-tracing operator for GNSS tropospheric delays, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14710, https://doi.org/10.5194/egusphere-egu24-14710, 2024.

EGU24-14947 | ECS | Posters on site | G5.1

Extended Kalman filtering applied to high-rate GNSS-R sea level measurements 

Aurélien Pira, Alvaro Santamaría-Gómez, and Guy Woppelmann

Coastal water monitoring is of increasing importance for applications such as sea level monitoring and urban planning. Currently, traditional tide gauge by radar measurement remains the most widely used method, but it involves placing a sensor close to the water surface, which can lead to its destruction, particularly in hostile maritime environments.

Sea level measurement by GNSS-R offers a promising alternative to traditional tide gauge methods by enabling continuous and global sea level measurements (e.g., Larson et al., 2013). It has the significant advantage of limiting the constraints linked to the installation of sensors physically close to the water surface, as a GNSS antenna can be placed away from the coast or on a high structure. Furthermore, this technique takes advantage of the high availability of existing GNSS installations around the globe, which would make it possible to considerably extend the scope of tide gauge measurements on a global scale.

Most of the methods used in GNSS-R are based on the analysis of the signal/noise ratio (SNR). They generally use a spectral analysis based on a Lomb-Scargle periodogram and are effective for monitoring mean sea level at the centimeter level (e.g., Larson et al., 2013; Santamaría-Gómez and Watson, 2017; Peng et al., 2021). However, they require a relatively long portion of the SNR series to obtain a precise estimate of the oscillation frequency of the SNR signal. This has the effect of limiting the sampling rate of the measurement series and limits spectral methods to the observation of slow variations in sea level such as the tide. Other approaches use Kalman filtering and show that it is possible to achieve an accuracy of less than 5cm in near real time (e.g., Strandberg, Hobiger and Haas, 2019; Liu et al., 2023). Furthermore, these methods show that it is possible to considerably increase the data sampling rate and thus monitor rapid variations in sea level. This extends the scope of GNSS-R techniques to all applications requiring real-time sea level measurement.

We present a novel approach for measuring sea level by analyzing SNR signals with Kalman filtering. This approach relies on the estimation of the oscillation frequency and amplitude of SNR signals using an extended Kalman filter. It has the advantage of providing sea level height estimates at a sampling rate as high as the SNR measurements. The major constraint linked to the method lies essentially in the estimation of the initial phase of the SNR signals, which particularly affects the fit of the SNR signals from setting satellites.

GNSS-R measurements were carried out with a sampling frequency of 1 second and compared to those of a tide gauge colocated on the Aix Island ILDX site (France). By combining data from different existing GNSS systems (GPS, GLONASS, Galileo, BDS) and considering all available carriers, we estimate that it is possible to obtain an RMS error of less than 5cm on sites with high tidal ranges (± 6m).

How to cite: Pira, A., Santamaría-Gómez, A., and Woppelmann, G.: Extended Kalman filtering applied to high-rate GNSS-R sea level measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14947, https://doi.org/10.5194/egusphere-egu24-14947, 2024.

EGU24-15000 | ECS | Orals | G5.1

Estimating GRACE-FO orbit perturbations with numerical weather prediction models 

Sanam Motlaghzadeh, Maksym Vasiuta, Marja Bister, Angel Navarro Trastoy, Lauri Tuppi, Torsten Mayer-gürr, and Heikki Järvinen

Satellites in Earth orbit are exposed to Earth radiation, consisting of reflected solar and emitted thermal radiation, thereby exerting a radiation pressure force that causes acceleration and affects the orbits. Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission aiming to retrieve the Earth gravity potential is critically dependent on accounting for all non-gravitational forces, including the Earth radiation. Although weather-of-the-day; e.g., clouds and their properties, has a major role in Earth radiation pressure, only climatology has been used so far to represent this force. Using climatological data doesn’t account for orbit perturbations owing to weather-related transient changes in the Earth radiation pressure. We show here that the top-of-atmosphere radiation fluxes computed with a numerical weather prediction model explain most of the measured variations in the radial acceleration of the GRACE-FO satellite. Our physics-based modelling corrects a hitherto unexplained lack of power spectral density in the measured accelerations. For example, we can accurately model the accelerations associated with a tropical storm in Indian Ocean in December 2020, which would not be possible when using climatological data. Our results demonstrate that using a global numerical weather prediction model significantly improves the simulation of non-gravitational effects in the satellites’ orbit. This advancement will allow more precise gravity retrieval and its applications in Earth sciences. 

How to cite: Motlaghzadeh, S., Vasiuta, M., Bister, M., Navarro Trastoy, A., Tuppi, L., Mayer-gürr, T., and Järvinen, H.: Estimating GRACE-FO orbit perturbations with numerical weather prediction models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15000, https://doi.org/10.5194/egusphere-egu24-15000, 2024.

EGU24-15082 | ECS | Posters on site | G5.1

Impact analysis of processing strategies for long-term GPS zenith tropospheric delay (ZTD) 

Jingna Bai, Yidong Lou, Weixing Zhang, Yaozong Zhou, Zhenyi Zhang, Chuang Shi, and Jingnan Liu

Homogenized atmospheric water vapour data is an important prerequisite for climate analysis. Compared with other techniques, GPS has inherent homogeneity advantage, but it still requires reprocessing and homogenization to eliminate impacts of applied strategy and observation environmental changes where a selection of proper processing strategies is critical. Here, we reprocess GPS observations at 44 IGS stations during 1995 to 2014. We focus on the influence of the mapping function, the elevation cut-off angle and homogenization on long-term reprocessing results, in particular for Zenith Tropospheric Delays (ZTD) products. Moreover, for the first time, we include the mapping function (VMF3) and exploit homogenized radiosonde data as a reference for ZTD trend evaluations. Our analysis shows that both site position and ZTD solutions achieved the best accuracy when using VMF3 and 3° elevation cut-off angle. Regarding the long-term ZTD trends, we find that homogenization can reduce the trend inconsistency among different elevation cut-off angles. ZTD trend results show that the impact of mapping functions is very small. On the other hand, the discrepancy can reach 0.60 mm/year by using different elevation cut-off angles. We suggest the low elevation cut-off angles (3° or 7°) for the best estimates of ZTD reprocessing time series when compared to homogenized radiosonde data or ERA5 reference time series.

How to cite: Bai, J., Lou, Y., Zhang, W., Zhou, Y., Zhang, Z., Shi, C., and Liu, J.: Impact analysis of processing strategies for long-term GPS zenith tropospheric delay (ZTD), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15082, https://doi.org/10.5194/egusphere-egu24-15082, 2024.

EGU24-15444 | Orals | G5.1

PRETTY – First experience from a 3U CubeSat In-Orbit Demonstrator for GNSS-Reflectometry under grazing angle geometry 

Andreas Dielacher, Michael Moser-Moritsch, Walter Hoermanseder, Maximilian Semmling, Weiqiang Li, Florian Zus, Mario Moreno, Jens Wickert, Estel Cardellach, Hossein Nahavandchi, and Camille Pirat

The PRETTY CubeSat In-Orbit Demonstrator (IOD) Mission has been finally launched on 9th October 2023 into a Sun-Synchrounous Orbit (SSO) in 560km height. The Launch and Early Orbit Phase (LEOP) was successful, meaning that communication with the CubeSat was possible, solar panels and VHF antennas are deployed. The commissioning phase is started. The 3U CubeSat hosts two scientific payloads, a radiation dosimeter and a novel GNSS-Reflectometry payload. The GNSS-reflectometer will be measuring earth surface under grazing elevation angles at the L5 frequency, in order to obtain altimetric altitude under various surface conditions (e.g., ocean waters or sea ice). The measurements will be done by correlating the direct and reflected signal (the so called interferometric approach), exploiting the full bandwidth of the GNSS signal.

An Algorithm Theoretical Baseline Document (ATBD) has been created within the scientific consortium and first simulation results have been conducted (and the results are analyzed within the consortium). For this presentation we will focus on the status of the satellite and present the first results obtained from space.

How to cite: Dielacher, A., Moser-Moritsch, M., Hoermanseder, W., Semmling, M., Li, W., Zus, F., Moreno, M., Wickert, J., Cardellach, E., Nahavandchi, H., and Pirat, C.: PRETTY – First experience from a 3U CubeSat In-Orbit Demonstrator for GNSS-Reflectometry under grazing angle geometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15444, https://doi.org/10.5194/egusphere-egu24-15444, 2024.

EGU24-16080 | ECS | Orals | G5.1

Performance assessment of GNSS radio occultation measurements from five missions over China  

Zhixiang Mo, Yidong Lou, Weixing Zhang, Yaozong Zhou, Peida Wu, and Zhenyi Zhang

Global Navigation Satellite System (GNSS) radio occultation (RO) is one of the most crucial observations in atmospheric and climate science. GNSS RO globally produces accurate and long-term stable vertical profiles for essential climate variables such as refractivity and temperature at high vertical resolution in all weather conditions. Currently, various RO satellite constellation programs have been developed by nations and companies, and the growing quantity of RO observations can contribute not only globally but also has the potential to benefit specific regions, such as China. To investigate the potential of RO observation in China, the performance of five operational RO measurements from COSMIC-2, MetOp-B/C, FY-3D/E, Spire and PlanetiQ on data coverage capabilities and quality are assessed by comparing with ERA5 and radiosonde over China. The results of data coverage showed that all RO missions can acquire extensive coverage over China with effective low-altitude penetration capability, whereas MetOp-B/C exhibits some gaps in local time coverage. The results of data quality confirmed that commercial Spire and PlanetiQ are comparable to those of national-led COSMIC-2, MetOp-B/C and FY3D/E, even though Spire exhibited a lower signal-to-noise ratio (SNR). The mean bending angle and refractivity relative differences of all RO measurements are within ±2.9% and ±1.5/0.9% (with respect to ERA5/radiosonde) in the altitude range of 5 to 35 km, respectively, and the corresponding relative standard deviations (SD) are less than 6% and 1.8/2.2%, respectively. Mean temperature and specific humidity differences of all RO measurements are within ±0.8/1.0 K and ± 0.7/1.0 g/kg, respectively, from the near surface to 15 km, with SD of less than 2.1/2.0 K and 1.8/1.7 g/kg. These results can help users further understand the strengths and weaknesses of these RO observations and indicate the significant application potential of numerous high-quality RO profiles from various RO measurements, which is anticipated to enhance numerical weather predictions for China.

How to cite: Mo, Z., Lou, Y., Zhang, W., Zhou, Y., Wu, P., and Zhang, Z.: Performance assessment of GNSS radio occultation measurements from five missions over China , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16080, https://doi.org/10.5194/egusphere-egu24-16080, 2024.

EGU24-17013 | Posters on site | G5.1

Tropospheric Parameters Derived From Co-located Instrumentation at the Onsala Space Observatory 

Rüdiger Haas and Gunnar Elgered

Observations performed with ground-based space geodetic and remote sensing techniques are sensitive to the amount of water vapour in the neutral atmosphere. Corresponding parameters that describe the signal delay in the troposphere can be derived for example from the analysis of data collected from geodetic Very Long Baseline Interferometry (VLBI), Global Navigation Satellite System (GNSS), as well as microwave radiometers. The latter instruments are often referred to as water vapour radiometers (WVR).

The Onsala Space Observatory (OSO) operates a number of such instruments for VLBI, GNSS and WVR measurements, all co-located within about 600 m. Among these are the Onsala twin telescopes (OTT), two modern 13.2~m diameter radio telescopes performing observations in the VLBI Global Observing System (VGOS) of the International VLBI Service for Geodesy and Astrometry (IVS). The OTT are the first operational VGOS twin telescopes worldwide and are contributing with observations to the IVS since 2019. OSO also operates eight permanently installed GNSS stations, of which two are official stations in the International GNSS Service (IGS) network. Furthermore, OSO operates ground-based microwave radiometers, which are used for atmospheric research and perform continuous observations of the water vapour content in the neutral atmosphere. Data analysis of all three techniques, VLBI, GNSS and WVR, allows to derive information on the temporal and spatial variations of water vapour in the neutral atmosphere. Using co-located instrumentation within a few hundred metres distance thus offers a perfect opportunity for comparisons and assessments of the results.

We focus on data recorded at OSO during 2022 and compare the parameters describing the signal delay in the neutral atmosphere, i.e. the so-called equivalent zenith total delays and the linear horizontal delay gradients. The temporal resolution of the derived parameters is 15 min or less. Out of more than 40 VGOS experiments in 2022, each of a duration of 24 h, we have WVR data covering at least half of the session in all except one.  We have examples where the equivalent zenith wet delay only varies by 2--3 cm over an experiment during rather stable atmospheres.  When the atmosphere is more variable the zenith wet delay can vary by more than 10 cm over 24 h.

How to cite: Haas, R. and Elgered, G.: Tropospheric Parameters Derived From Co-located Instrumentation at the Onsala Space Observatory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17013, https://doi.org/10.5194/egusphere-egu24-17013, 2024.

EGU24-18019 | ECS | Posters on site | G5.1

Ionospheric Impact on GNSS Reflectometry: A correction approach for the PRETTY satellite data 

Mario Moreno, Maximilian Semmling, Georges Stienne, Mainul Hoque, and Jens Wickert

The ionosphere, spanning 60 to 2000 km above the Earth’s surface, plays a crucial role in Global Navigation Satellite System (GNSS) signal propagation, as signals traverse this layer on their path from the GNSS satellite to the receiver. In GNSS Reflectometry (GNSS-R), coherent observations are prominent in regions with smooth reflecting surfaces and grazing elevation angles (5° - 30°). However, within this elevation range, higher ionospheric effects (e.g., delay biases) are expected due to the longer path signals travel through the atmosphere.

Dual-frequency receivers can mitigate first-order ionospheric effects by using an ionosphere-free linear combination of code or carrier measurements. Single-frequency receivers, on the other hand, rely on a model to compensate for ionospheric refraction. In this study, the Neustrelitz Electron Density Model (NEDM2020) has been employed to estimate the slant total electron content (slant TEC) along the direct, incident, and reflected ray paths. The reflection events have been simulated using the orbit data from the Spire Global CubeSat constellation.

In preparation for the single-frequency GNSS-R ESA “PRETTY” mission data, this study conducts a comprehensive characterization of relative ionospheric delay, Doppler shift, and variations in the heights at which the maximum electron density is found along the ray paths. The investigation spans different elevation angle ranges, latitude-dependent regions, diurnal changes, and solar activity conditions. The results span a wide range of slant TEC values from 10 TECU between the reflection point and receiving satellite at moderate elevations (15°) to 300 TECU between transmitter and receiver (direct path) at very low elevations (5°). These results correspond to periods of low solar activity (March 2021). The ongoing study focuses on identifying and correcting the ionosphere impact in satellite data of the CyGNSS and PRETTY missions based on the developed simulation scheme.

How to cite: Moreno, M., Semmling, M., Stienne, G., Hoque, M., and Wickert, J.: Ionospheric Impact on GNSS Reflectometry: A correction approach for the PRETTY satellite data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18019, https://doi.org/10.5194/egusphere-egu24-18019, 2024.

EGU24-19978 | Posters on site | G5.1

Near real-time GNSS meteorology: a preliminary feasibility demonstration based on the variometric approach  

Alessandra Maria De Pace, Rachele Fratini, Augusto Mazzoni, and Mattia Crespi

The variometric approach has been demonstrated effective in GNSS seismology and GNSS ionospheric seismology to estimate ground shaking (VADASE) and earthquake/tsunami induced ionospheric disturbances (VARION) in real time for years. In this study the same variometric approach has been utilized to appraise the potential for real-time tracking of tropospheric delay (VARTROPO): this investigation holds significance for timely enhancements in weather forecasting, by incorporating this data into numerical weather models.
In contrast to the prevailing method of tracking tropospheric delay, which relies on employing a mapping function and estimating a singular zenith tropospheric delay (ZTD) for all satellites within a specific time interval, the proposed approach is based on the estimation of single-epoch variation of the slant tropospheric delay (VSTD) for individual satellite. The low-pass filtering process and the integration of this variation over time, starting from a known initial value of the STD, allows to estimate the STD in near (due to low-pass filtering) real time for each satellite. It is noteworthy that the proposed approach allows to highlight the azimuthal anisotropy of the troposphere, valuable during periods of intense weather fronts.
The preliminary research focuses on evaluating how the estimates derived from the proposed approach, in near real-time scenario, match with both the official ZTD estimates provided by CDDIS and those obtained through Precise Point Positioning (PPP) technique. In this respect, it has to be underlined that the assessment hereafter illustrated has been developed: (i) using 1-second rate GNSS data; (ii) in both terms of ZTDs and STDs, using a standard 1/sin(elevation) mapping function for conversion; (iii) with fixed position of the GNSS permanent station (only the receiver clock variation has been estimated in the variometric approach); (iv) without multipath mapping and removal. The first presented comparison is between VARTROPO and PPP (MATE station; satellite G03; 1st October 2023) (Figure 1).

Fig. 1

VARTROPO derived VSTD and VZTD exhibits higher noise level; therefore, to mitigate the highfrequency noise, a simple low-pass filter (moving median) with different moving windows (from 5 seconds to 2 minutes) has been applied. Then, the different low-pass filtered VZTDs have been integrated over time, starting from the ZTD at the initial epoch as derived from PPP, and compared to the ZTDs estimated by PPP (Figure 2).

 Fig2

The differences between the reconstructed VARTROPO ZTDs trends and the PPP ZTDs have been represented (Figure 3).

  Fig.3

The second comparison is between VARTROPO and CDDIS, to substantiate the aforementioned findings (Figures 4, 5).

     Fig4

 Fig5

In conclusion, it has been understood that simple moving medians are able to effectively low-pass filter the VARTROPO ZTDs: with 2-minute moving window the agreement with PPP ZTDs and CDDIS ZTDs are at within 1-2 millimeters, what preliminarily demonstrate that near real-time track of the tropospheric delay is feasible. Next research steps will involve: (i) enhancing the VSTDs estimates (e.g. with multipath mitigation); (ii) investigating the possibility to estimate troposphere azimuthal anisotropy in presence of weather fronts.

How to cite: De Pace, A. M., Fratini, R., Mazzoni, A., and Crespi, M.: Near real-time GNSS meteorology: a preliminary feasibility demonstration based on the variometric approach , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19978, https://doi.org/10.5194/egusphere-egu24-19978, 2024.

EGU24-20132 | Orals | G5.1

On the contribution of InSAR Meteorology to a Digital Twin Of The Atmosphere 

Giovanni Nico, Pedro Mateus, and Joao Catalao

In this work, we discuss the potential and perspective use of InSAR meteorology within the Destination Earth (DestineE) initiative. The joined use of high-resolution Numerical Weather Models (NWM),such as the Weather Research and Forecasting (WRF) model, and the next large availability and redundancy of C- and L-band interferometric SAR missions (besides the current Sentinel-1 A&B and SAOCOM missions and the next Sentinel-1 C&D, N.G., ROSE-L, ALOS-4, NISAR), provides an example of the digital model of Earth that could support the complex task of anticipating extreme weather events.

There are two main approaches of applied mathematics to digitalization: Physics-Based and Data Driven. Physics-based models (PBMs) can give useful information on the processes to be described without the need for huge datasets, a first idea of what variables shall be monitored and provide a means for generalization.

Data-driven approaches imply the use of methods from Machine Learning or even Deep Learning to "learn from data collected by sensors". Artificial Intelligence (AI) tools need very high amounts and can be used to find hidden patterns in the data. Such a pattern can be refined whenever new data are collected. NWMs are an example of a physics-based Digital Twin.

We focus on using WRF and InSAR meteorology to continuously update the Digital Twins of the atmosphere. The data lake consists of Sentinel-1 data (high-resolution PWV maps), the output variables of the ERA5 model. The digital twin engine consists of the 3D-Var assimilation of Sentinel-1 PWV maps, which provide a numerical tool to generate replicas of the NWM (e.g., WRF, AROME, COSMO). We want to demonstrate that it is possible to get: 1) Hints to change/modify the assumptions of NWMs; 2) Hints to reduce the extension of approximations; 3) Extend the limits of applications of WRF to better predict extreme weather events.

How to cite: Nico, G., Mateus, P., and Catalao, J.: On the contribution of InSAR Meteorology to a Digital Twin Of The Atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20132, https://doi.org/10.5194/egusphere-egu24-20132, 2024.

EGU24-21040 | Posters on site | G5.1

New Developments in Near Real-Time GNSS Zenith Total Delay Estimates at the University of Luxembourg 

Addisu Hunegnaw, Norma Teferle, and Jonathan Jones

Recently, the University of Luxembourg (UL), in collaboration with the United Kingdom Met Office, has started providing accurate near real-time (NRT) Zenith Total Delays (ZTDs) from networks of GNSS ground stations. This initiative is in alignment with the operational meteorological products from various analysis centers available at the EUMETNET EIG GNSS Water Vapour Programme (E-GVAP) and the team in Luxembourg envisages to re-start its contributions in the near future. Active in Europe, E-GVAP coordinates NRT GNSS-based atmospheric content monitoring to support Numerical Weather Prediction (NWP) modelling with products that are crucial for mesoscale models throughout Europe, for example, for the Met Office. GNSS technology is essential for accurately measuring atmospheric parameters such as ZTD and Integrated Water Vapor (IWV) at high frequencies, regardless of weather conditions. In addition, GNSS data are low-cost when compared to conventional meteorological systems. Ensuring the NRT availability of these data for NWP assimilation systems requires numerous methods in GNSS data handling and processing, quality assurance, and distribution.  The study details the collaborative work between the UK Met Office and the University of Luxembourg in providing accurate and rapidly available meteorological data through GNSS technology. This collaboration has led to the development and update of various systems for the processing of GNSS observations to produce advanced NRT ZTD products at UL and the Met Office. These products are generated at 1-hour intervals on both global and regional scales, and at sub-hourly intervals regionally. This study primarily aims to provide a thorough review and accuracy assessment of NRT ZTD products from the UL, comparing their precision with benchmark data from both post-processed and NRT ZTD estimates from various EGVAP analysis centres. The NRT GNSS processing systems at UL use the Bernese GNSS Software (BSW) versions 5.2 and 5.4 with a double-differencing (DD) approach, and similarly, the post-processed benchmark ZTD estimates employs the DD positioning strategy using the same software packages.

How to cite: Hunegnaw, A., Teferle, N., and Jones, J.: New Developments in Near Real-Time GNSS Zenith Total Delay Estimates at the University of Luxembourg, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21040, https://doi.org/10.5194/egusphere-egu24-21040, 2024.

EGU24-22538 | Posters on site | G5.1

Climate trends derived from long-term ground-based GNSS-derived Zenith Total Delay (ZTD) 

Marcelo C. Santos, Kyriakos Balidakis, Anna Kloss, Rosa Pacione, and Jordan Rees

We present findings from an ongoing investigation into the evaluation of long-term trends in ground-based GNSS-derived Zenith Total Delay (ZTD) for potential integration into climate models, either for assimilation or validation purposes. Our analysis focuses on ZTD time series obtained from six REPRO3 IGS Analysis Centers (ACs) – COD, ESA, GFZ, GRG, JPL, and TUG – spanning 20 years or more. Thirty stations from the IGS global network were selected for this study. The ZTD time series underwent a homogenization process, utilizing ERA-5 derived ZTDs as a reference, followed by daily value averaging to minimize potential discrepancies arising from diverse estimation strategies employed by individual ACs. Similar averaging procedures were applied to ERA-5 ZTDs and the IGS tropo-product if already reprocessed in REPRO3. Two combinations, employing weighted mean and a robust least median of squares, were generated from the six homogenized ACs, serving as quality control measures for each AC. Analysis of trends in each of the nine ZTD time series was conducted in both time and frequency domains, revealing geographical variations in results. For instance, at station ALBH in Canada, the inter-AC scatter was 0.47 mm/decade for trends, 0.11 mm for annual amplitudes, and 0.29 degrees for annual phases.

How to cite: C. Santos, M., Balidakis, K., Kloss, A., Pacione, R., and Rees, J.: Climate trends derived from long-term ground-based GNSS-derived Zenith Total Delay (ZTD), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22538, https://doi.org/10.5194/egusphere-egu24-22538, 2024.

G7 – Short Courses

CC BY 4.0