scholarly journals The GFZ GRACE RL06 Monthly Gravity Field Time Series: Processing Details and Quality Assessment

2019 ◽  
Vol 11 (18) ◽  
pp. 2116 ◽  
Author(s):  
Christoph Dahle ◽  
Michael Murböck ◽  
Frank Flechtner ◽  
Henryk Dobslaw ◽  
Grzegorz Michalak ◽  
...  
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Transport Processes ◽  
Research Centre ◽  
Ocean Bottom ◽  
Science Data ◽  
Surface Mass ◽  
Surface Mass Transport ◽  
Grace Mission ◽  
Gravity Field Models

Time-variable gravity field models derived from observations of the Gravity Recovery and Climate Experiment (GRACE) mission, whose science operations phase ended in June 2017 after more than 15 years, enabled a multitude of studies of Earth’s surface mass transport processes and climate change. The German Research Centre for Geosciences (GFZ), routinely processing such monthly gravity fields as part of the GRACE Science Data System, has reprocessed the complete GRACE mission and released an improved GFZ GRACE RL06 monthly gravity field time series. This study provides an insight into the processing strategy of GFZ RL06 which has been considerably changed with respect to previous GFZ GRACE releases, and modifications relative to the precursor GFZ RL05a are described. The quality of the RL06 gravity field models is analyzed and discussed both in the spectral and spatial domain in comparison to the RL05a time series. All results indicate significant improvements of about 40% in terms of reduced noise. It is also shown that the GFZ RL06 time series is a step forward in terms of consistency, and that errors of the gravity field coefficients are more realistic. These findings are confirmed as well by independent validation of the monthly GRACE models, as done in this work by means of ocean bottom pressure in situ observations and orbit tests with the GOCE satellite. Thus, the GFZ GRACE RL06 time series allows for a better quantification of mass changes in the Earth system.

Bridging the gap – linking GRACE and GRACE-Follow On by hlSST and SLR

2020 ◽  
Author(s):  
Matthias Weigelt ◽  
Adrian Jäggi ◽  
Ulrich Meyer
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Driving Dynamic ◽  
Time Step ◽  
Promising Candidate ◽  
Field Service ◽  
Global Gravity ◽  
Variable Gravity ◽  
Grace Mission ◽  
Gravity Field Models

<p>GRACE and GRACE-Follow On are the standard tools for observing the time variable gravity field. Unfortunately, there is no overlap of the two time series of monthly gravity field solutions due to the ending of the GRACE mission in 2017 before the first monthly solutions of GRACE-Follow On became available in June 2018. Thus, there is a need for an intermediate technique that will bridge the gap between the two missions and will allow 1) for a continued and uninterrupted time series of mass observations and 2) to compare, cross-validate and link the two time series. As a bridging technology hlSST/SLR combinations are arguably the most promising candidate. We presented earlier combinations of those based on 41 kinematic orbit products of 27 satellites and 9 SLR satellites. Here, we progress to the next step and present results where we use the combined hlSST/SLR solution within a Kalman environment to link GRACE to GRACE-Follow On via the hlSST/SLR time series. The combination is conducted on coefficient level: after reducing the climatology derived from GRACE, a modified continuous Wiener process acceleration (CWPA) model is employed as the driving dynamic model of the Kalman filter for the prediction step. Subsequently the predicted time step is updated by (residual) observations when available. The resulting time series is thus complete for all months starting from April 2002 till today. We will discuss the benefit and limitations of the approach. The research is conducted within the framework of the International Gravity Field Service (IGFS) product center (COST-G) which is dedicated to the combination of monthly global gravity field models.</p>

Seven years of monthly low-degree gravity field models from Swarm GPS data

2021 ◽  
Author(s):  
Joao de Teixeira da Encarnacao ◽  
Daniel Arnold ◽  
Ales Bezdek ◽  
Christoph Dahle ◽  
Junyi Guo ◽  
...  
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Large Scale ◽  
Signal To Noise Ratio ◽  
Transport Processes ◽  
High Signal ◽  
Gps Data ◽  
Astronomical Institute ◽  
The Individual ◽  
Gravity Field Models

<p>The Swarm satellite constellation provides GPS data with sufficient accuracy to observe the large-scale mass transport processes occurring at the Earth’s surface since 2013. We illustrate the signal content of the time series of monthly gravity field models. The models are published on quarterly basis and are the result of a combination of the individual models produced by different gravity field estimation approaches, by the Astronomical Institute of the University of Bern, the Astronomical Institute of the Czech Academy of Sciences, the Institute of Geodesy of the Graz University of Technology and the School of Earth Sciences of the Ohio State University. We combine the models at the solution level, using weights derived from a Variance Component Estimation, under the framework of the International Combination Service for Time-variable Gravity Fields (COST-G).</p><p> </p><p>We estimate the monthly quality of the models by comparing with GRACE and GRACE-FO products and illustrate the improvement of the combined model as compared to the individual models. We present the high signal-to-noise ratio of this uninterrupted time series of models, smoothed to 750km radius, over large hydrological basins. Finally, we compare the behavior of degree 2 and 3 coefficients with GRACE/GRACE-FO and SLR.</p>

The GravIS Portal: User-friendly Global Mass Variations from GRACE and GRACE-FO

2021 ◽  
Author(s):  
Christoph Dahle ◽  
Eva Boergens ◽  
Henryk Dobslaw ◽  
Andreas Groh ◽  
Ingo Sasgen ◽  
...  
Keyword(s):  
Time Series ◽  
Information Service ◽  
Research Centre ◽  
Data Sets ◽  
Ocean Bottom ◽  
Climatic Regions ◽  
Uncertainty Estimates ◽  
Terrestrial Water ◽  
User Friendly ◽  
Global Mean

<p>The German Research Centre for Geosciences (GFZ) maintains the “Gravity Information Service” (GravIS, gravis.gfz-potsdam.de) portal in collaboration with the Alfred-Wegener-Institute (AWI) and Technische Universität Dresden. Main objective of this portal is the dissemination of data describing mass variations in the Earth system based on observations of the satellite gravimetry missions GRACE and GRACE-FO.</p><p>The provided data sets encompass products of terrestrial water storage (TWS) variations over the continents, ocean bottom pressure (OBP) variations from which global mean barystatic sea-level rise can be estimated, and mass changes of the ice sheets in Greenland and Antarctica. All data sets are provided as time series of regular grids for each area, as well as in the form of regional basin averages. Regarding the latter, for the continental TWS data the user can choose between classical river basins and a novel segmentation based on climatic regions. For the oceans, the segmentation into different regions is derived similarly but based on modelled OBP data. All time series are accompanied by realistic uncertainty estimates.</p><p>All data sets can be interactively displayed at the portal and are freely available for download. This contribution aims to show the features and possibilities of the GravIS portal to researchers without a dedicated geodetic background, working in the fields of hydrology, oceanography, and cryosphere.</p>

Gravity Field Estimation from GRACE Follow-On Data: Results from CSR Analyses

2020 ◽  
Author(s):  
Srinivas Bettadpur ◽  
Himanshu Save ◽  
Peter Nagel ◽  
Nadège Pie ◽  
Steven Poole ◽  
...  
Keyword(s):  
Gravity Field ◽  
Lessons Learned ◽  
System Component ◽  
Science Data ◽  
Orbit Plane ◽  
Flight Data ◽  
University Of Texas ◽  
Earth Gravity ◽  
Grace Data ◽  
Gravity Field Models

<p>At the time of presentation, nearly two years of flight data from the joint NASA/GFZ GRACE Folllow-On mission will have been collected. In this time, gravity field models have been produced using two independent inter-satellite tracking systems - the MWI and the LRI using radio and optical interferometry, respectively. The data have been analyzed over more than two complete cycles of the sun relative to the orbit plane, allowing a characterization of the environmental impacts on the flight data. Extended duration of analyses have also permitted an assessment of the GRACE-FO data relative to the corresponding GRACE data.</p><p>This poster presents the status and lessons learned from two years of estimation of Earth gravity field models from the GRACE-FO data at the science data system component at the University of Texas Center for Space Research.</p>

Recovering climate-related mass transport signals by current and next-generation gravity missions

2020 ◽  
Author(s):  
Roland Pail ◽  
Henryk Dobslaw ◽  
Annette Eicker ◽  
Laura Jensen
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Mass Transport ◽  
Gravity Field ◽  
Transport Processes ◽  
Measuring System ◽  
Climate Projections ◽  
Earth System ◽  
Next Generation ◽  
The Earth

<p>Gravity field missions are a unique geodetic measuring system to directly observe mass transport processes in the Earth system. Past and current gravity missions such as CHAMP, GRACE, GOCE and GRACE-Follow On have improved our understanding of large-scale mass changes, such as the global water cycle, melting of continental ice sheets and mountain glaciers, changes in ocean mass that are closely related to the mass-related component of sea level rise, which are subtle indicators of climate change, on global to regional scale. Therefore, mass transport observations are also very valuable for long-term climate applications. Next Generation Gravity Missions (NGGMs) expected to be launched in the midterm future have set high anticipations for an enhanced monitoring of mass transport in the Earth system with significantly improved spatial and temporal resolution and accuracy. This contribution will present results from numerical satellite mission performance simulations designed to evaluate the usefulness of gravity field missions operating over several decades for climate-related applications. The study is based on modelled of mass transport time series obtained from future climate projections until the year 2100 following the representative emission pathway RCP8.5 Numerical closed-loop simulations will assess the recoverability of mass variability signals by means of different NGGM concepts, e.g. GRACE-type in-line single-pair missions, Bender double-pair mission being composed of a polar and an inclined satellite pair, or high-precision high-low tracking missions following the MOBILE concept, assuming realistic noise levels for the key payload. In the evaluation and interpretation of the results, special emphasis shall be given to the identification of (natural or anthropogenic) climate change signals in dependence of the length of the measurement time series, and the quantification of robustness of derived trends and systematic changes.</p>

Improved multichannel singular spectrum analysis for post-processing GRACE monthly gravity field models

2020 ◽  
Vol 223 (2) ◽  
pp. 825-839
Author(s):  
Fengwei Wang ◽  
Yunzhong Shen ◽  
Tianyi Chen ◽  
Qiujie Chen ◽  
Weiwei Li
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Spectrum Analysis ◽  
Singular Spectrum Analysis ◽  
Linear Interpolation ◽  
Gravity Models ◽  
Total Variance ◽  
Data Interpolation ◽  
Singular Spectrum ◽  
Gravity Field Models

SUMMARY Multichannel singular spectrum analysis (MSSA) is a powerful tool to extract spatiotemporal signals and filter errors from the noisy time-series of monthly gravity field models from the satellite data of gravity recovery and climate experiment (GRACE). Since the GRACE monthly gravity models are missed about 17 months, we develop an improved MSSA approach, which can directly process the incomplete time-series without either data interpolation or iteration. The time-series of 14-yr (2002.04–2016.08) monthly gravity field models of CSR-RL06 up to degree and order 60 are analysed with improved MSSA compared to the MSSA with linear data interpolation and iteration MSSA. By using our improved MSSA approach, the first 11 principal components derived can capture 91.18 per cent of the total variance, higher than 85.80 and 86.44 per cent of the total variance, derived by linear interpolation MSSA and iteration MSSA, respectively. The ratios of the latitude weighted RMS over the land and ocean signals are used to evaluate the efficiency of eliminating noise by the MSSA approach. For improved MSSA, the mean RMS ratio of land and ocean signals of all available months is higher than linear interpolation and iteration MSSA, which indicates that improved MSSA can suppress noise more efficiently and extract more geophysical signals from real GRACE data. Furthermore, the 50 repeated experiments show that all the root mean squared errors and mean absolute errors derived by our improved MSSA are smaller than other MSSA approaches. Moreover, the improved MSSA performs still better than other MSSA based approaches for the cases of large data gaps.

scholarly journals Joint analysis of selected GRACE monthly spherical harmonic solutions and monthly MASCON solutions

2021 ◽  
Vol 51 (1) ◽  
pp. 47-61
Author(s):  
Adam NOVÁK ◽  
Juraj JANÁK ◽  
Barbora KOREKÁČOVÁ
Keyword(s):  
Gravity Field ◽  
Spherical Harmonic ◽  
Statistical Significance ◽  
Detailed Comparison ◽  
Joint Analysis ◽  
Satellite Mission ◽  
Science Data ◽  
Gravity Field Model ◽  
Global Gravity ◽  
Gravity Field Models

Study presented in this paper is focused on comparison and statistical assessment of differences between the selected Level 2 products of the satellite mission Gravity Recovery and Climate Experiment (GRACE). Global monthly gravity field models in terms of spherical harmonic coefficients produced by three institutes of GRACE Science Data System are compared with the partially independent MASCON global gravity field model. Detailed comparison and statistical analysis of differences is performed in 5 selected river basins: Amazon, Congo, Danube, Yenisei and Lena. For each spherical harmonic solution, 8 different filtrations available at International Center for Global Gravity Field Models (ICGEM) are tested over the time span from April 2002 to July 2016. Fischer test at two significance levels 10% and 5% has been performed in order to qualify the statistical significance between the particular solutions.

scholarly journals The International Centre for Global Earth Models (ICGEM)

2020 ◽  
Author(s):  
Christoph Förste ◽  
Elmas Sinem Ince ◽  
Sven Reissland ◽  
Kirsten Elger ◽  
Frank Flechtner ◽  
...  
Keyword(s):  
Gravity Field ◽  
Scientific Community ◽  
Positive Impact ◽  
International Association ◽  
Research Centre ◽  
Global Gravity ◽  
Celestial Bodies ◽  
Governmental Institutions ◽  
Gravity Field Models ◽  
Future Plans

<p>The more than 15-year-old ICGEM is one of the five services coordinated by the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). It is hosted by GFZ German Research Centre for Geosciences in Potsdam, Germany. The aim of the ICGEM service is to provide the scientific community with a state-of-the-art archive of static and time variable global gravity field models of the Earth in a standardized format with a possibility to assign DOI number. Furthermore, ICGEM contains an interactive calculation and visualization service of gravity field functionals. Development and maintenance of such a unique platform is crucial for the scientific community in geodesy, geophysics, oceanography and climatology and has a positive impact in governmental institutions and industrial practice. This poster covers the maintenance, recently established new features and future plans of the ICGEM Service. New features include the calculation of gravity field functionals at a list of user-defined distributed points and new topographic gravity field models, whereas the future plans aim to meet the needs of the scientific community. As an add-on, ICGEM provides also access to the gravity field models of some other celestial bodies (Mars, Venus, and Earth’s moon).</p>

Can daily GRACE gravity field models be used to evaluate short-term hydro-meteorological signals over the continents?

2020 ◽  
Author(s):  
Annette Eicker ◽  
Laura Jensen ◽  
Viviana Wöhnke ◽  
Andreas Kvas ◽  
Henryk Dobslaw ◽  
...  
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Time Scales ◽  
Water Flux ◽  
Water Storage ◽  
Numerical Differentiation ◽  
Data Set ◽  
Grace Data ◽  
Terrestrial Water ◽  
Gravity Field Models

<p>Over the recent years, the computation of temporally high-resolution (daily) GRACE gravity field solutions has advanced as an alternative to the processing of monthly models. In this presentation we will show that recent processing improvements incorporated in the latest version of daily gravity field models (ITSG-Grace2018) now allow for the investigation of water flux signals on the continents down to time scales of a few days.</p><p>Time variations in terrestrial water storage derived from GRACE can be related to atmospheric net-fluxes of precipitation (P), evapotranspiration (E) and lateral runoff (R) via the terrestrial water balance equation, which makes GRACE a new and completely independent data set for constraining hydro-meteorological observations and the output of atmospheric reanalyses.</p><p>In our study, band-pass filtered water fluxes are derived from the daily GRACE water storage time series by first applying a numerical differentiation filter and subsequent high-pass filtering to isolate fluxes at periods between 5 and 30 days. We can show that on these time scales GRACE is able to identify quality differences between different global reanalyses, e.g. the improvements in the latest reanalysis ERA5 of the European Centre for Medium-Range Weather Forecasts (ECWMF) over its direct predecessor ERA-Interim.</p><p>We can further demonstrate that only the very recent progress in GRACE data processing has enabled the use of daily GRACE time series for such an evaluation of high-frequency atmospheric fluxes. The accuracy of the previous daily GRACE time series ITSG-Grace2016 would not have been sufficient to carry out such an assessment.</p>

Status of GFZ's GRACE/GRACE-FO RL06 Level-2 and Level-3 Data Products

2020 ◽  
Author(s):  
Christoph Dahle ◽  
Michael Murböck ◽  
Frank Flechtner ◽  
Rolf König ◽  
Henryk Dobslaw ◽  
...  
Keyword(s):  
Information Service ◽  
Gravity Potential ◽  
Research Centre ◽  
Science Data ◽  
Data Products ◽  
Terrestrial Water ◽  
Level 3 ◽  
User Friendly ◽  
Grace Mission ◽  
Level 2

<p>The GRACE Follow-On (GRACE-FO) mission was successfully launched on May 22<sup>nd</sup>, 2018 and continues the 15-year data record of monthly global mass changes from the GRACE mission (2002-2017). The German Research Centre for Geosciences (GFZ) as part of the GRACE/GRACE-FO Science Data System (SDS) has recently reprocessed the complete GRACE mission data (RL06 in the SDS nomenclature). These RL06 processing standards serve as common baseline for the continuation with GRACE-FO data.</p><p>This presentation provides an overview of the current processing status and the validation of the GFZ GRACE/GRACE-FO RL06 gravity field products. Besides its Level-2 products (monthly sets of spherical harmonic coefficients representing the Earth's gravity potential), GFZ additionally generates user-friendly Level-3 products in collaboration with the Alfred-Wegener-Institut (AWI) and TU Dresden. These Level-3 data products comprise dedicated mass anomaly products of terrestrial water storage over non-glaciated regions, bottom pressure variations in the oceans and ice mass changes in Antarctica and Greenland, available via GFZ's Gravity Information Service (GravIS) portal (http://gravis.gfz-potsdam.de/).</p>

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