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Geophysical Applications of GOCE and GRACE Measurements

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A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Environmental Remote Sensing".

Deadline for manuscript submissions: 30 July 2024 | Viewed by 9332

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Prof. Dr. Mehdi Eshagh

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Guest Editor

Department of Applied Geomatics, University of Sherbrooke, Sherbrooke, QC, Canada
Interests: satellite gravimetry and gradiometry; gravity field modelling; isostasy; lithospheric stress and strain modelling

Dr. Carla Braitenberg

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Guest Editor

Dipartimento di Matematica e Geoscienze, Università degli Studi di Trieste, Trieste, Italy
Interests: satellite gravimetry; crustal deformation; future gravity missions; natural resources exploration; remote sensing

Dr. Mirko Reguzzoni

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Guest Editor

Geodesy and Geomatics Division, Department of Civil and Environmental Engineering, Politecnico di Milano, 20133 Milan, Italy
Interests: satellite gravimetry and gradiometry; gravity field modelling; inverse gravimetric problems
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Special Issue Information

Dear Colleagues,

As we all know, GOCE and GRACE have provided wonderful information about the Earth’s gravity field during its lifetime. Numerous theories have been developed and successfully applied to use these valuable data to enhance our understanding and knowledge about the Earth’s interior structures and processes. We believe that the GOCE/GRACE data can be utilised further towards different geophysical purposes. Therefore, in order to create an opportunity for the GOCE/GRACE researchers to communicate further in this subject and develop new knowledge and applications in this field, a Special Issue with the title “Geophysical applications of GOCE and GRACE measurements” in Remote Sensing has been organised. The main goal is to create an excellent source of information with a collection of articles written by experts in the field. This Special Issue will be a reference for many researchers in satellite gravimetry and gradiometry and the connections to the solid Earth’s geophysics, oceanography, and geodesy.

The aim is to provide a valuable source of information and knowledge for the geophysical applications of GOCE and GRACE written by different experts in the field. We encourage submissions of both regular research papers and reviews on topics, including, but not limited to, the following:

Global and local gravity field modelling;
Determination of crustal structure, Moho depth and density contrast;
Elastic thickness modelling;
Ice and sediment thickness;
Lithospheric stress and thermal state;
Oceanographic applications;
Geodetic applications;
Hydrological modelling;
Earthquake monitoring;
Applications in glaciology and post-glacial rebound

Prof. Dr. Mehdi Eshagh
Dr. Carla Braitenberg
Dr. Mirko Reguzzoni
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

GOCE mission
GRACE and GRACE-FO mission
gravity field
moho
lithosphere
inversion
stress modeling
basement determination
thermal state
ocean circulation
height datum unification

Published Papers (7 papers)

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Research

23 pages, 22447 KiB

Open AccessArticle

Assessment of the Added Value of the GOCE GPS Data on the GRACE Monthly Gravity Field Solutions

by Xiang Guo, Yidu Lian, Yu Sun, Hao Zhou and Zhicai Luo

Remote Sens. 2024, 16(9), 1586; https://doi.org/10.3390/rs16091586 - 29 Apr 2024

Viewed by 327

Abstract

The time-varying gravity field models derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission suffer from pronounced longitudinal stripe errors in the spatial domain. A potential way to mitigate such errors is to combine GRACE data with observations from other sources. In this study, we investigate the impacts on GRACE monthly gravity field solutions of incorporating the GPS data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission. To that end, we produce GRACE/GOCE combined monthly gravity field solutions through combination on the normal equation level and compare them with the GRACE-only solutions, for which we have considered the state-of-the-art ITSG-Grace2018 solutions. Analysis in the spectral domain reveals that the combined solutions have a notably lower noise level beyond degree 30, with cumulative errors up to degree 96 being reduced by 31%. A comparison of the formal errors reveals that the addition of GOCE GPS data mainly improves (near-) sectorial coefficients and resonant orders, which cannot be well determined by GRACE alone. In the spatial domain, we also observe a significant reduction by at least 30% in the noise of recovered mass changes after incorporating the GOCE GPS data. Furthermore, the signal-to-noise ratios of mass changes over 180 large river basins were improved by 8–20% (dependent on the applied Gaussian filter radius). These results demonstrate that the GOCE GPS data can augment the GRACE monthly gravity field solutions and support a future GOCE-type mission for tracking more accurate time-varying gravity fields. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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21 pages, 26305 KiB

Open AccessArticle

Comparison of Terrestrial Water Storage Changes in the Tibetan Plateau and Its Surroundings Derived from Gravity Recovery and Climate Experiment (GRACE) Solutions of Different Processing Centers

by Longwei Xiang, Holger Steffen and Hansheng Wang

Remote Sens. 2023, 15(22), 5417; https://doi.org/10.3390/rs15225417 - 18 Nov 2023

Viewed by 1014

Abstract

The GRACE twin satellite gravity mission from 2002 to 2017 has considerably improved investigations on global and regional hydrological changes. However, there are different GRACE solutions and products available which may yield different results for certain regions despite applying the same postprocessing and time span. This is especially the case for the Tibetan Plateau (TP) with its special hydrological conditions represented by localized but strong signals that can overlap or merge with signals inside the plateau, which can falsify the determination of terrestrial water storage (TWS) changes in the TP area. To investigate the effect of GRACE solution selection on inverted TWS changes, we analyze quantitatively the secular and monthly changes for 14 glacier areas and 10 water basins in and around the TP area that have been calculated from 16 different available GRACE solutions. Our analysis provides expectable results. While trend results from different spherical harmonic (SH) GRACE solutions match well, there are significant differences to and between mascon GRACE solutions. This is related to the different processing concepts of mascon solutions and their forced handling in our comparisons. SH solution time series match each other when mass changes are strong with a large amplitude and regular periodicity. However, for regions where small TWS changes are associated with small amplitudes, trends, and/or unstable signal periods, SH solutions can also yield different results. Such behavior is known from a time series analysis. Interestingly though, we find that the COST-G and ITSG SH GRACE solutions are closest to the average of all solutions. Therefore, these solutions appear to be preferable for TWS investigations in regions with highly variable hydrological conditions, such as in the Tibetan Plateau and its surroundings. This also indicates that combined solutions such as COST-G provide a promising pathway for an improved TWS analysis, which should be further elaborated. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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21 pages, 26871 KiB

Open AccessArticle

Tracking Low-Frequency Variations in Land–Sea Water Mass Redistribution during the GRACE/GRACE-FO Era

by Shanshan Deng, Zhenlong Jian, Yuxin Liu, Chushun Yi, Yi Chen and Wenxi Zhang

Remote Sens. 2023, 15(17), 4248; https://doi.org/10.3390/rs15174248 - 29 Aug 2023

Viewed by 1014

Abstract

Climate change has caused a widespread deduction in terrestrial water storage (TWS), leading to ocean water mass gains and sea level rises. A better understanding of how the land–sea water mass has been redistributed can help with the scientific response to climate change. However, there are few studies investigating the roles of the different physical processes involved in low-frequency land–sea water mass redistribution on a global scale. To address this issue, in this study, a comprehensive investigation was carried out with respect to the globally distributed key factors causing low-frequency ocean mass anomalies during the period 2004–2021. Global water mass redistribution data, derived from GRACE/GRACE-FO satellite gravity and surface wind and sea-surface temperature data from ERA5 reanalysis, were employed, and the empirical orthogonal function, maximum covariance analysis, and sea-level equation approaches were used. The results show that the long-term trend and decadal-like fluctuation are two major components of the low-frequency land–sea water mass redistribution. The wind-forcing dynamic processes significantly drive the anomalies near the North Indian Ocean, North Atlantic Ocean, South Pacific Ocean, and some marginal seas, where variance explanations range from 30% to 97%. After removing the ocean dynamics, the residual ocean mass anomaly is mostly explained by sea-level fingerprints (SLFs), especially in the open ocean. The 25th, 50th, and 75th percentiles of the SLF-explained variances in all ocean grids are 59%, 72%, and 82%, respectively. Some non-negligible noise, located in seismic zones, was also found, suggesting the misestimation of seafloor deformation resulting from earthquakes in the GRACE/GRACE-FO data processing. These findings may improve our understanding of the long-term anomalies in regional and global sea levels. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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22 pages, 9332 KiB

Open AccessArticle

Impact of Uncertainty Estimation of Hydrological Models on Spectral Downscaling of GRACE-Based Terrestrial and Groundwater Storage Variation Estimations

by Mehdi Eshagh, Farzam Fatolazadeh and Kalifa Goïta

Remote Sens. 2023, 15(16), 3967; https://doi.org/10.3390/rs15163967 - 10 Aug 2023

Cited by 1 | Viewed by 1290

Abstract

Accurately estimating hydrological parameters is crucial for comprehending global water resources and climate dynamics. This study addresses the challenge of quantifying uncertainties in the global land data assimilation system (GLDAS) model and enhancing the accuracy of downscaled gravity recovery and climate experiment (GRACE) data. Although the GLDAS models provide valuable information on hydrological parameters, they lack uncertainty quantification. To enhance the resolution of GRACE data, a spectral downscaling approach can be employed, leveraging uncertainty estimates. In this study, we propose a novel approach, referred to as method 2, which incorporates parameter magnitudes to estimate uncertainties in the GLDAS model. The proposed method is applied to downscale GRACE data over Alberta, with a specific focus on December 2003. The groundwater storage extracted from the downscaled terrestrial water storage (TWS) are compared with measurements from piezometric wells, demonstrating substantial improvements in accuracy. In approximately 80% of the wells, the root mean square (RMS) and standard deviation (STD) were improved to less than 5 mm. These results underscore the potential of the proposed approach to enhance downscaled GRACE data and improve hydrological models. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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18 pages, 7437 KiB

Open AccessArticle

Antarctic Time-Variable Regional Gravity Field Model Derived from Satellite Line-of-Sight Gravity Differences and Spherical Cap Harmonic Analysis

by Mohsen Feizi, Mehdi Raoofian Naeeni and Jakob Flury

Remote Sens. 2023, 15(11), 2815; https://doi.org/10.3390/rs15112815 - 29 May 2023

Viewed by 1250

Abstract

This study focuses on the development of a time-variable regional geo-potential model for Antarctica using the spherical cap harmonic analysis (SCHA) basis functions. The model is derived from line-of-sight gravity difference (LGD) measurements obtained from the GRACE-Follow-On (GFO) mission. The solution of a Laplace equation for the boundary values over a spherical cap is used to expand the geo-potential coefficients in terms of Legendre functions with a real degree and integer order suitable for regional modelling, which is used to constrain the geo-potential coefficients using LGD measurements. To validate the performance of the SCHA, it is first utilized with LGD data derived from a L2 JPL (Level 2 product of the Jet Propulsion Laboratory). The obtained LGD data are used to compute the local geo-potential model up to K_max = 20, corresponding to the SH degree and order up to 60. The comparison of the radial gravity on the Earth’s surface map across Antarctica with the corresponding radial gravity components of the L2 JPL is carried out using local geo-potential coefficients. The results of this comparison provide evidence that these basis functions for K_max = 20 are valid across the entirety of Antarctica. Subsequently, the analysis proceeds using LGD data obtained from the Level 1B product of GFO by transforming these LGD data into the SCHA coordinate system and applying them to constrain the SCHA harmonic coefficients up to K_max = 20. In this case, several independent LGD profiles along the trajectories of the satellites are devised to verify the accuracy of the local model. These LGD profiles are not employed in the inverse problem of determining harmonic coefficients. The results indicate that using regional harmonic basis functions, specifically spherical cap harmonic analysis (SCHA) functions, leads to a close estimation of LGD compared to the L2 JPL. The regional harmonic basis function exhibits a root mean square error (RMSE) of 3.71 × 10⁻⁴ mGal. This represents a substantial improvement over the RMSE of the L2 JPL, which is 6.36 × 10⁻⁴ mGal. Thus, it can be concluded that the use of local geo-potential coefficients obtained from SCHA is a reliable method for extracting nearly the full gravitational signal within a spherical cap region, after validation of this method. The SCHA model provides significant realistic information as it addresses the mass gain and loss across various regions in Antarctica. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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19 pages, 8073 KiB

Open AccessArticle

Lithospheric Stress Due to Mantle Convection and Mantle Plume over East Africa from GOCE and Seismic Data

by Andenet A. Gedamu, Mehdi Eshagh and Tulu B. Bedada

Remote Sens. 2023, 15(2), 462; https://doi.org/10.3390/rs15020462 - 12 Jan 2023

Viewed by 1743

Abstract

The Afar and Ethiopian plateaus are in a dynamic uplift due to the mantle plume, therefore, considering the plume effect is necessary for any geophysical investigation including the estimation of lithospheric stress in this area. The Earth gravity models of the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) and lithospheric structure models can be applied to estimate the stress tensor inside the Ethiopian lithosphere. To do so, the boundary-value problem of elasticity is solved to derive a general solution for the displacement field in a thin elastic spherical shell representing the lithosphere. After that, general solutions for the elements of the strain tensor are derived from the displacement field, and finally the stress tensor from the strain tensor. The horizontal shear stresses due to mantle convection and the vertical stress due to the mantle plume are taken as the lower boundary value at the base of the lithosphere, and no stress at the upper boundary value of the lithospheric shell. The stress tensor and maximum stress directions are computed at the Moho boundary in three scenarios: considering horizontal shear stresses due to mantle convection, vertical stresses due to mantle plume, and their combination. The estimated maximum horizontal shear stresses’ locations are consistent with tectonics and seismic activities in the study area. In addition, the maximum shear stress directions are highly correlated with the World Stress Map 2016, especially when the effect of the mantle plume is solely considered, indicating the stress in the study area mainly comes from the plume. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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23 pages, 6456 KiB

Open AccessArticle

Global Moho Gravity Inversion from GOCE Data: Updates and Convergence Assessment of the GEMMA Model Algorithm

by Lorenzo Rossi, Biao Lu, Mirko Reguzzoni, Daniele Sampietro, Islam Fadel and Mark van der Meijde

Remote Sens. 2022, 14(22), 5646; https://doi.org/10.3390/rs14225646 - 9 Nov 2022

Cited by 1 | Viewed by 1553

Abstract

Since its discovery in 1909, the Moho was routinely studied by seismological methods. However, from the 1950s, a possible alternative was introduced by gravimetric inversion. Thanks to satellite gravity missions launched from the beginning of the 21st century, a global inversion became feasible, e.g., leading to the computation of the GEMMA model in 2012. This model was computed inverting the GOCE second radial derivatives of the anomalous potential by a Wiener filter, which was applied in the spherical harmonic domain, considering a two-layer model with lateral and vertical density variations. Moreover, seismic information was introduced in the inversion to deal with the joint estimation/correction of both density and geometry of the crustal model. This study aims at revising the GEMMA algorithm from the theoretical point of view, introducing a cleaner formalization and studying the used approximations more thoroughly. The updates are on: (1) the management of the approximations due to the forward operator linearization required for the inversion; (2) the regularization of spherical harmonic coefficients in the inversion by proper modelling the Moho signal and the gravity error covariances; (3) the inclusion of additional parameters and their regularization in the Least Squares adjustment to correct the density model by exploiting seismic information. Thanks to these updates, a significant improvement from the computational point of view is achieved too, thus the convergence of the iterative solution and the differences with respect to the previous algorithm can be assessed by closed-loop tests, showing the algorithm performance in retrieving the simulated “true” Moho. Full article

(This article belongs to the Special Issue Geophysical Applications of GOCE and GRACE Measurements)

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