New Approach to Estimate Time Variable Gravity Fields from High-Low Satellite Tracking Data

2014 ◽  
pp. 111-116 ◽  
Author(s):  
N. Zehentner ◽  
T. Mayer-Gürr
Keyword(s):  
Satellite Tracking ◽  
Time Variable ◽  
Tracking Data ◽  
New Approach ◽  
Time Variable Gravity ◽  
Gravity Fields ◽  
Variable Gravity

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

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.

scholarly journals Localized analysis of satellite tracking data for studying time-variable Earth's gravity fields

2008 ◽  
Vol 113 (B6) ◽  
Author(s):  
Shin-Chan Han ◽  
David D. Rowlands ◽  
Scott B. Luthcke ◽  
Frank G. Lemoine
Keyword(s):  
Satellite Tracking ◽  
Time Variable ◽  
Tracking Data ◽  
Gravity Fields ◽  
Localized Analysis

Combination Service for Time-variable Gravity Fields (COST-G): operational GRACE-FO combination and validation of Chinese GRACE time-series

2021 ◽  
Author(s):  
Ulrich Meyer ◽  
Martin Lasser ◽  
Adrian Jäggi ◽  
Christoph Dahle ◽  
Frank Flechtner ◽  
...  
Keyword(s):  
Time Series ◽  
Quality Assessment ◽  
International Association ◽  
Time Variable ◽  
Operational Mode ◽  
Time Variable Gravity ◽  
Gravity Fields ◽  
Variable Gravity ◽  
Processed Products ◽  
The Cost

<p>The Combination Service for Time-variable Gravity Fields (COST-G) of the International Association of Geodesy (IAG) provides combined monthly gravity fields of its associated and partner Analysis Centers (ACs). In November 2020, the combination of monthly GRACE-FO gravity fields started its operational mode, providing consolidated L2 (spherical harmonics) and L3 (gridded and post- processed) products with a latency of currently 3 months. We present an overview and quality assessment of the available products.</p><p>COST-G aims at the extension of its service to include further GRACE and GRACE-FO analysis centers. In January 2020 a collaboration with representatives of five Chinese ACs was initiated, who provided GRACE time-series according to the COST-G requirements. We present the results of a test combination with the Chinese AC models, including comparison and quality assessment of all contributing time-series and validation of the combined gravity fields.</p>

Combination Service for Time-variable Gravity Field Solutions (COST-G) – GRACE-FO operational combination

2020 ◽  
Author(s):  
Ulrich Meyer ◽  
Martin Lasser ◽  
Adrian Jäggi ◽  
Frank Flechtner ◽  
Christoph Dahle ◽  
...  
Keyword(s):  
Time Series ◽  
Quality Control ◽  
International Association ◽  
Time Variable ◽  
Polar Regions ◽  
Time Variable Gravity ◽  
Gravity Fields ◽  
River Hydrology ◽  
Variable Gravity ◽  
Combined Time Series

<p lang="en-US">We present the operational GRACE-FO combined time-series of monthly gravity fields of the Combination Service for Time-variable Gravity fields (COST-G) of the International Association of Geodesy (IAG). COST-G_GRACE-FO_RL01_operational is combined at AIUB and relies on operational monthly solutions of the COST-G Analysis Centers GFZ, GRGS, IfG, LUH and AIUB and the associated Analysis Centers CSR and JPL. All COST-G Analysis Centers have passed a benchmark test to ensure consistency between the different processing approaches and all of the contributing time-series undergo a strict quality control focusing on the signal content in river basins and polar regions with pronounced changes in ice mass to uncover any regularization that may bias the combination.</p> <p lang="en-US">The combination is performed by variance component estimation on the solution level, the relative monthly weights thus providing valuable and independent insight into the consistency and noise levels of the individual monthly contributions. The combined products then are validated internally in terms of noise, approximated by the non-secular, non-seasonal variability over the oceans. Once they have passed this quality control the combined gravity fields are assessed by an external board of experts who evaluate them in terms of orbit predictions, lake altimetry, river hydrology or oceanography.</p>

scholarly journals Simulation of the time-variable gravity field by means of coupled geophysical models

2011 ◽  
Vol 4 (1) ◽  
pp. 27-70 ◽  
Author(s):  
Th. Gruber ◽  
J. L. Bamber ◽  
M. F. P. Bierkens ◽  
H. Dobslaw ◽  
M. Murböck ◽  
...  
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Mass Distribution ◽  
Time Variable ◽  
Data Sets ◽  
Earth System ◽  
Time Variable Gravity ◽  
The Earth ◽  
Gravity Fields ◽  
Variable Gravity

Abstract. Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by redistribution of mass in, on or above the Earth's surface or by geophysical processes in the Earth's interior. The first set of observations of monthly variations of the Earth gravity field was provided by the US/German GRACE satellite mission beginning in 2002. This mission is still providing valuable information to the science community. However, as GRACE has outlived its expected lifetime, the geoscience community is currently seeking successor missions in order to maintain the long time series of climate change that was begun by GRACE. Several studies on science requirements and technical feasibility have been conducted in the recent years. These studies required a realistic model of the time variable gravity field in order to perform simulation studies on sensitivity of satellites and their instrumentation. This was the primary reason for the European Space Agency (ESA) to initiate a study on "Monitoring and Modelling individual Sources of Mass Distribution and Transport in the Earth System by Means of Satellites". The goal of this interdisciplinary study was to create as realistic as possible simulated time variable gravity fields based on coupled geophysical models, which could be used in the simulation processes in a controlled environment. For this purpose global atmosphere, ocean, continental hydrology and ice models were used. The coupling was performed by using consistent forcing throughout the models and by including water flow between the different domains of the Earth system. In addition gravity field changes due to solid Earth processes like continuous glacial isostatic adjustment (GIA) and a sudden earthquake with co-seismic and post-seismic signals were modelled. All individual model results were combined and converted to gravity field spherical harmonic series, which is the quantity commonly used to describe the Earth's global gravity field. The result of this study is a twelve-year time-series of 6-hourly time variable gravity field spherical harmonics up to degree and order 180 corresponding to a global spatial resolution of 1 degree in latitude and longitude. In this paper, we outline the input data sets and the process of combining these data sets into a coherent model of temporal gravity field changes. The resulting time series was used in some follow-on studies and is available to anybody interested via a Website.

scholarly journals Time-variable gravity signal in Greenland revealed by high-low satellite-to-satellite tracking

2013 ◽  
Vol 118 (7) ◽  
pp. 3848-3859 ◽  
Author(s):  
M. Weigelt ◽  
T. van Dam ◽  
A. Jäggi ◽  
L. Prange ◽  
M. J. Tourian ◽  
...  
Keyword(s):  
Satellite Tracking ◽  
Time Variable ◽  
Time Variable Gravity ◽  
Variable Gravity ◽  
Gravity Signal

scholarly journals An Iterative ICA-Based Reconstruction Method to Produce Consistent Time-Variable Total Water Storage Fields Using GRACE and Swarm Satellite Data

2020 ◽  
Vol 12 (10) ◽  
pp. 1639 ◽  
Author(s):  
Ehsan Forootan ◽  
Maike Schumacher ◽  
Nooshin Mehrnegar ◽  
Aleš Bezděk ◽  
Matthieu J. Talpe ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Water Storage ◽  
Time Variable ◽  
Reconstruction Technique ◽  
Reconstruction Method ◽  
Satellite Mission ◽  
Time Variable Gravity ◽  
Gravity Fields ◽  
Terrestrial Water ◽  
Variable Gravity

Observing global terrestrial water storage changes (TWSCs) from (inter-)seasonal to (multi-)decade time-scales is very important to understand the Earth as a system under natural and anthropogenic climate change. The primary goal of the Gravity Recovery And Climate Experiment (GRACE) satellite mission (2002–2017) and its follow-on mission (GRACE-FO, 2018–onward) is to provide time-variable gravity fields, which can be converted to TWSCs with ∼ 300 km spatial resolution; however, the one year data gap between GRACE and GRACE-FO represents a critical discontinuity, which cannot be replaced by alternative data or model with the same quality. To fill this gap, we applied time-variable gravity fields (2013–onward) from the Swarm Earth explorer mission with low spatial resolution of ∼ 1500 km. A novel iterative reconstruction approach was formulated based on the independent component analysis (ICA) that combines the GRACE and Swarm fields. The reconstructed TWSC fields of 2003–2018 were compared with a commonly applied reconstruction technique and GRACE-FO TWSC fields, whose results indicate a considerable noise reduction and long-term consistency improvement of the iterative ICA reconstruction technique. They were applied to evaluate trends and seasonal mass changes (of 2003–2018) within the world’s 33 largest river basins.

One centimeter-level observations of diurnal ocean tides from global monthly mean time-variable gravity fields

2010 ◽  
Vol 84 (12) ◽  
pp. 715-729 ◽  
Author(s):  
Shin-Chan Han ◽  
Richard D. Ray ◽  
Scott B. Luthcke
Keyword(s):  
Time Variable ◽  
Ocean Tides ◽  
Time Variable Gravity ◽  
Gravity Fields ◽  
Variable Gravity ◽  
Mean Time

scholarly journals Time-Variable Gravity Field from the Combination of HLSST and SLR

2021 ◽  
Vol 13 (17) ◽  
pp. 3491
Author(s):  
Luping Zhong ◽  
Krzysztof Sośnica ◽  
Matthias Weigelt ◽  
Bingshi Liu ◽  
Xiancai Zou
Keyword(s):  
Gravity Field ◽  
Spatial Resolution ◽  
Amazon Basin ◽  
Satellite Tracking ◽  
Time Variable ◽  
Earth Gravity Field ◽  
Time Variable Gravity ◽  
Earth Gravity ◽  
The Earth ◽  
Variable Gravity

The Earth’s time-variable gravity field is of great significance to study mass change within the Earth’s system. Since 2002, the NASA-DLR Gravity Recovery and Climate Experiment (GRACE) and its successor GRACE follow-on mission provide observations of monthly changes in the Earth gravity field with unprecedented accuracy and resolution by employing low-low satellite-to-satellite tracking (LLSST) measurements. In addition to LLSST, monthly gravity field models can be acquired from satellite laser ranging (SLR) and high-low satellite-to-satellite tracking (HLSST). The monthly gravity field solutions HLSST+SLR were derived by combining HLSST observations of low earth orbiting (LEO) satellites with SLR observations of geodetic satellites. Bandpass filtering was applied to the harmonic coefficients of HLSST+SLR solutions to reduce noise. In this study, we analyzed the performance of the monthly HLSST+SLR solutions in the spectral and spatial domains. The results show that: (1) the accuracies of HLSST+SLR solutions are comparable to those from GRACE for coefficients below degree 10, and significantly improved compared to those of SLR-only and HLSST-only solutions; (2) the effective spatial resolution could reach 1000 km, corresponding to the spherical harmonic coefficient degree 20, which is higher than that of the HLSST-only solutions. Compared with the GRACE solutions, the global mass redistribution features and magnitudes can be well identified from HLSST+SLR solutions at the spatial resolution of 1000 km, although with much noise. In the applications of regional mass recovery, the seasonal variations over the Amazon Basin and the long-term trend over Greenland derived from HLSST+SLR solutions truncated to degree 20 agree well with those from GRACE solutions without truncation, and the RMS of mass variations is 282 Gt over the Amazon Basin and 192 Gt in Greenland. We conclude that HLSST+SLR can be an alternative option to estimate temporal changes in the Earth gravity field, although with far less spatial resolution and lower accuracy than that offered by GRACE. This approach can monitor the large-scale mass transport during the data gaps between the GRACE and the GRACE follow-on missions.

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