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  • Review Article
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Water cycle science enabled by the GRACE and GRACE-FO satellite missions

Abstract

Satellite observations of the time-variable gravity field revolutionized the monitoring of large-scale water storage changes, beginning with the 2002 launch of the Gravity Recovery and Climate Experiment (GRACE) mission. Most hydrologists were sceptical of the satellite gravimetry approach at first, but validation studies assuaged their concerns and high-profile, GRACE-based groundwater depletion studies caused an explosion of interest. The importance of GRACE observations for hydrologic and cryospheric science became so great that GRACE Follow-On (GRACE-FO) jumped the National Aeronautics and Space Administration’s Earth science mission queue and launched in 2018. A third mass change mission is currently under development. Here, we review key milestones in satellite gravimetry’s progression from the fringes of hydrology to being a staple of large-scale water cycle and water resources studies and the sole source of observations of what is now an ‘essential climate variable’, terrestrial water storage.

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Fig. 1: Inadequacy of in situ groundwater observation availability.
Fig. 2: TWS depletion in India.
Fig. 3: Growth of GRACE hydrology publications.
Fig. 4: Global trends in TWS.
Fig. 5: Global TWS anomalies over time.
Fig. 6: Global drought and wetness monitoring products.

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Data availability

The well locations mapped in Fig. 1 are available from the US Geological Survey’s Groundwater Water Climate Response Network website and the International Groundwater Resources Assessment Centre’s website. The JPL RL06_v02 gridded monthly mass data used Figs. 2, 4 and 5 is identical to that which is available from the NASA/JPL GRACE Tellus website61. Figure 3 was created from a citation report that searched for journal articles containing ‘GRACE satellite’ or ‘Gravity Recovery and Climate Experiment’ and one of nine hydrology-related terms, performed on the Web of Science website. Figure 6 was constructed from images available on the University of Nebraska-Lincoln National Drought Mitigation Center’s NASA GRACE website10,174.

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Acknowledgements

This work was funded by NASA’s GRACE-FO Science Team. We thank M. M. O’Neill for preparing (Fig. 1)., D. Wiese for providing the data used to create Figs. 4 and 5, and H. Beaudoing for preparing Fig. 6. Portions of this research were conducted at the Jet Propulsion Laboratory, which is operated for NASA under contract with the California Institute of Technology.

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M.R. prepared the Review article outline. M.R. and J.T.R. designed the figures and wrote the manuscript.

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Rodell, M., Reager, J.T. Water cycle science enabled by the GRACE and GRACE-FO satellite missions. Nat Water 1, 47–59 (2023). https://doi.org/10.1038/s44221-022-00005-0

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