Improved Estimates of Geocenter Variability from Time-Variable Gravity and Ocean Model Outputs

Geocenter variations relate the motion of the Earth’s center of mass with respect to its center of figure, and represent global-scale redistributions of the Earth’s mass. We investigate different techniques for estimating of geocenter motion from combinations of time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On missions, and bottom pressure outputs from ocean models. Here, we provide self-consistent estimates of geocenter variability incorporating the effects of self-attraction and loading, and investigate the effect of uncertainties in atmospheric and oceanic variation. The effects of self-attraction and loading from changes in land water storage and ice mass change affect both the seasonality and long-term trend in geocenter position. Omitting the redistribution of sea level affects the average annual amplitudes of the x, y, and z components by 0.2, 0.1, and 0.3 mm, respectively, and affects geocenter trend estimates by 0.02, 0.04 and 0.05 mm/yr for the the x, y, and z components, respectively. Geocenter estimates from the GRACE Follow-On mission are consistent with estimates from the original GRACE mission.

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Martian global-scale CO2exchange from time-variable gravity measurements

Journal of Geophysical Research Atmospheres ◽

10.1029/2005je002591 ◽

2006 ◽

Vol 111 (E6) ◽

Cited By ~ 14

Author(s):

Ö. Karatekin ◽

T. Van Hoolst ◽

V. Dehant

Keyword(s):

Global Scale ◽

Time Variable ◽

Time Variable Gravity ◽

Gravity Measurements ◽

Variable Gravity

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Evaluation of GRACE/GRACE Follow-On Time-Variable Gravity Field Models for Earthquake Detection above Mw8.0s in Spectral Domain

Remote Sensing ◽

10.3390/rs13163075 ◽

2021 ◽

Vol 13 (16) ◽

pp. 3075

Author(s):

Ming Xu ◽

Xiaoyun Wan ◽

Runjing Chen ◽

Yunlong Wu ◽

Wenbing Wang

Keyword(s):

Signal To Noise Ratio ◽

Time Variable ◽

Model Errors ◽

Signal To Noise ◽

Time Variable Gravity ◽

Earthquake Detection ◽

Gravity Fields ◽

Variable Gravity ◽

Gravity Recovery ◽

Gravity Field Models

This study compares the Gravity Recovery And Climate Experiment (GRACE)/GRACE Follow-On (GFO) errors with the coseismic gravity variations generated by earthquakes above Mw8.0s that occurred during April 2002~June 2017 and evaluates the influence of monthly model errors on the coseismic signal detection. The results show that the precision of GFO monthly models is approximately 38% higher than that of the GRACE monthly model and all the detected earthquakes have signal-to-noise ratio (SNR) larger than 1.8. The study concludes that the precision of the time-variable gravity fields should be improved by at least one order in order to detect all the coseismic gravity signals of earthquakes with M ≥ 8.0. By comparing the spectral intensity distribution of the GFO stack errors and the 2019 Mw8.0 Peru earthquake, it is found that the precision of the current GFO monthly model meets the requirement to detect the coseismic signal of the earthquake. However, due to the limited time length of the observations and the interference of the hydrological signal, the coseismic signals are, in practice, difficult to extract currently.

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Earth’s Time-Variable Gravity from GRACE Follow-On K-Band Range-Rates and Pseudo-Observed Orbits

Remote Sensing ◽

10.3390/rs13091766 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1766

Author(s):

Igor Koch ◽

Mathias Duwe ◽

Jakob Flury ◽

Akbar Shabanloui

Keyword(s):

Gravity Field ◽

Time Variable ◽

Time Variable Gravity ◽

Gravity Field Recovery ◽

Variable Gravity ◽

Earth’S System ◽

Grace Mission ◽

Insight Into ◽

K Band

During its science phase from 2002–2017, the low-low satellite-to-satellite tracking mission Gravity Field Recovery And Climate Experiment (GRACE) provided an insight into Earth’s time-variable gravity (TVG). The unprecedented quality of gravity field solutions from GRACE sensor data improved the understanding of mass changes in Earth’s system considerably. Monthly gravity field solutions as the main products of the GRACE mission, published by several analysis centers (ACs) from Europe, USA and China, became indispensable products for quantifying terrestrial water storage, ice sheet mass balance and sea level change. The successor mission GRACE Follow-On (GRACE-FO) was launched in May 2018 and proceeds observing Earth’s TVG. The Institute of Geodesy (IfE) at Leibniz University Hannover (LUH) is one of the most recent ACs. The purpose of this article is to give a detailed insight into the gravity field recovery processing strategy applied at LUH; to compare the obtained gravity field results to the gravity field solutions of other established ACs; and to compare the GRACE-FO performance to that of the preceding GRACE mission in terms of post-fit residuals. We use the in-house-developed MATLAB-based GRACE-SIGMA software to compute unconstrained solutions based on the generalized orbit determination of 3 h arcs. K-band range-rates (KBRR) and kinematic orbits are used as (pseudo)-observations. A comparison of the obtained solutions to the results of the GRACE-FO Science Data System (SDS) and Combination Service for Time-variable Gravity Fields (COST-G) ACs, reveals a competitive quality of our solutions. While the spectral and spatial noise levels slightly differ, the signal content of the solutions is similar among all ACs. The carried out comparison of GRACE and GRACE-FO KBRR post-fit residuals highlights an improvement of the GRACE-FO K-band ranging system performance. The overall amplitude of GRACE-FO post-fit residuals is about three times smaller, compared to GRACE. GRACE-FO post-fit residuals show less systematics, compared to GRACE. Nevertheless, the power spectral density of GRACE-FO and GRACE post-fit residuals is dominated by similar spikes located at multiples of the orbital and daily frequencies. To our knowledge, the detailed origin of these spikes and their influence on the gravity field recovery quality were not addressed in any study so far and therefore deserve further attention in the future. Presented results are based on 29 monthly gravity field solutions from June 2018 until December 2020. The regularly updated LUH-GRACE-FO-2020 time series of monthly gravity field solutions can be found on the website of the International Centre for Global Earth Models (ICGEM) and in LUH’s research data repository. These operationally published products complement the time series of the already established ACs and allow for a continuous and independent assessment of mass changes in Earth’s system.

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Evaluation of Release-05 GRACE time-variable gravity coefficients over the ocean

Ocean Science ◽

10.5194/os-8-859-2012 ◽

2012 ◽

Vol 8 (5) ◽

pp. 859-868 ◽

Cited By ~ 109

Author(s):

D. P. Chambers ◽

J. A. Bonin

Keyword(s):

Standard Error ◽

Data Centers ◽

Ocean Model ◽

Time Variable ◽

Science Data ◽

Jet Propulsion ◽

Equivalent Water Thickness ◽

Variable Gravity ◽

Ocean Models ◽

Gravity Recovery

Abstract. The latest release of GRACE (Gravity Recovery and Climate Experiment) gravity field coefficients (Release-05, or RL05) are evaluated for ocean applications. Data have been processed using the current methodology for Release-04 (RL04) coefficients, and have been compared to output from two different ocean models. Results indicate that RL05 data from the three Science Data Centers – the Center for Space Research (CSR), GeoForschungsZentrum (GFZ), and Jet Propulsion Laboratory (JPL) – are more consistent among themselves than the previous RL04 data. Moreover, the variance of residuals with the output of an ocean model is 50–60% lower for RL05 data than for RL04 data. A more optimized destriping algorithm is also tested, which improves the results slightly. By comparing the GRACE maps with two different ocean models, we can better estimate the uncertainty in the RL05 maps. We find the standard error to be about 1 cm (equivalent water thickness) in the low- and mid-latitudes, and between 1.5 and 2 cm in the polar and subpolar oceans, which is comparable to estimated uncertainty for the output from the ocean models.

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Variations of Subpolar Ocean Gyres Observed by the GRACE Time-Variable Gravity: Antarctic Ross/Weddell and Arctic Beaufort Gyres

10.5194/egusphere-egu2020-4022 ◽

2020 ◽

Author(s):

Chunchun Gao ◽

Benjamin Fong Chao

Keyword(s):

Satellite Altimetry ◽

Southern Oscillation ◽

Ocean Model ◽

Time Variable ◽

Empirical Orthogonal Functions ◽

Time Variable Gravity ◽

Grace Data ◽

Short Period ◽

Ocean Gyres ◽

Variable Gravity

<p>The mesoscale ocean gyres within polar oceans, including Ross Gyre (RG), Weddell Gyre (WG) and Beaufort Gyre (BG), are important features of the polar climate and ocean systems. However, they are not well observed by satellite altimetry because of their high latitudes and wintertime sea-ice coverage. We employ the GRACE satellite&#8217;s time-variable gravity (TVG) dataset from the Centre National d'Etudes Spatiales/Groupe de Recherches de G&#233;od&#233;sie Spatiale (CNES/GRGS) Release 03 solutions at nominal 10-day sampling between July 2002 to June 2016, to investigate the non-seasonal and high-frequency variations of the three gyres, a feat demonstrated in a previous work by Yu and Chao (2018) for studying the Argentine Gyre. We solve the empirical orthogonal functions (EOF) and confirm their barotropic structure and find the sea level variations in the RG and WG are strongly correlated with the Antarctic Oscillation (AAO) and the El Nino-Southern Oscillation (ENSO), and that in the BG is correlated with salinity changes and ENSO.&#160;Different from the Argentine Gyre, there are no short-period oscillations of dipole pattern within the three subpolar gyres based on the complex EOF (CEOF) analysis from GRACE data. The fact that&#160;GRACE does observe these signals, while the de-aliasing background ocean model (whose predictions were removed before-hand in the employed GRACE data) fails to, ascertains that GRACE TVG data&#160;can&#160;shed light on the ocean gyre variabilities unavailable by satellite altimetry and&#160;at&#160;spatial and temporal resolutions higher than practiced hitherto.</p>

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