22 Oct 2020

22 Oct 2020

Review status: this preprint is currently under review for the journal ESSD.

RECOG RL01: Correcting GRACE total water storage estimates for global lakes/reservoirs and earthquakes

Simon Deggim1, Annette Eicker1, Lennart Schawohl1, Helena Gerdener2, Kerstin Schulze2, Olga Engels2, Jürgen Kusche2, Anita T. Saraswati3, Tonie van Dam4, Laura Ellenbeck5, Denise Dettmering5, Christian Schwatke5, Stefan Mayr6, Igor Klein6, and Laurent Longuevergne7 Simon Deggim et al.
  • 1Geodesy & Geoinformatics, HafenCity University Hamburg, 20457, Germany
  • 2Institute of Geodesy and Geoinformatics, University of Bonn, 53012, Germany
  • 3Department of Engineering, University of Luxembourg, 4364, Luxembourg
  • 4Interdisciplinary Centre for Security, Reliability and Trust, University of Luxembourg, 1359, Luxembourg
  • 5Deutsches Geodätisches Forschungsinstitut, Technical University of Munich (DGFI-TUM), 80333, Germany
  • 6Earth Observation Center, German Aerospace Center (DLR), Oberpfaffenhofen, D-82234, Germany
  • 7CNRS, Geosciences Rennes - UMR 6118, Université de Rennes, 35000, France

Abstract. Observations of changes in terrestrial water storage obtained from the satellite mission GRACE (Gravity Recovery and Climate Experiment) have frequently been used for water cycle studies and for the improvement of hydrological models by means of calibration and data assimilation. However, due to a low spatial resolution of the gravity field models spatially localized water storage changes, such as those occurring in lakes and reservoirs, cannot properly be represented in the GRACE estimates. As surface storage changes can represent a large part of total water storage, this leads to leakage effects and results in surface water signals becoming erroneously assimilated into other water storage compartments of neighboring model grid cells. As a consequence, a simple mass balance at grid/regional scale is not sufficient to deconvolve the impact of surface water on TWS.

Furthermore, non-hydrology related phenomena contained in the GRACE time series, such as the mass redistribution caused by major earthquakes, hamper the use of GRACE for hydrological studies in affected regions. In this paper, we present the first release (RL01) of the global correction product RECOG (REgional COrrections for GRACE), which accounts for both the surface water (lakes & reservoirs, RECOG-LR) and earthquake effects (RECOG-EQ). RECOG-LR is computed from forward-modelling surface water volume estimates derived from satellite altimetry and (optical) remote sensing and allows both a removal of these signals from GRACE and a re-location of the mass change to its origin within the outline of the lakes/reservoirs. The earthquake correction RECOG-EQ includes both the co-seismic and post-seismic signals of two major earthquakes with magnitudes above 9 Mw.

We can show that applying the correction dataset (1) reduces the GRACE signal variability by up to 75 % around major lakes and explains a large part of GRACE seasonal variations and trends, (2) avoids the introduction of spurious trends caused by leakage signals of nearby lakes when calibrating/assimilating hydrological models with GRACE, even in neighboring river basins, and (3) enables a clearer detection of hydrological droughts in areas affected by earthquakes. A first validation of the corrected GRACE time series using GPS-derived vertical station displacements shows a consistent improvement of the fit between GRACE and GNSS after applying the correction. Data are made available as open access via the Pangea database (RECOG-LR: Deggim et al. (2020a); RECOG-EQ: Gerdener et al. (2020b, under revision),

Simon Deggim et al.

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Simon Deggim et al.

Data sets

RECOG-LR RL01: Correcting GRACE total water storage estimates for global lakes and reservoirs Simon Deggim, Annette Eicker, Lennart Schawohl, Laura Ellenbeck, Denise Dettmering, Christian Schwatke, Stefan Mayr, and Igor Klein

RECOG-EQ RL01 Earthquake correction for CSR, GFZ 625 and ITSG solutions of GRACE level 3 total water storage anomalies from 2003-01 to 2016-12 correcting for the Sumatra-Andaman (2004) and Tohoku (2011) earthquakes Helena Gerdener, Kerstin Schulze, Olga Engels, and Jürgen Kusche

Video supplement

Timelapse of RECOG-LR RL01 (removal correction) 2003/01 – 2016/12 Simon Deggim, Annette Eicker, Lennart Schawohl, Laura Ellenbeck, Denise Dettmering, Christian Schwatke, Stefan Mayr, and Igor Klein

Simon Deggim et al.


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Short summary
GRACE provides us with global changes of terrestrial water storage. However, the data has a low spatial resolution and localized storage changes in lakes/reservoirs or mass change due to earthquakes cause leakage effects. The correction product RECOG RL01 presented in this paper accounts for these effects. Its application allows for improving calibration/assimilation of GRACE into hydrological models and better drought detection in earthquake-affected areas.