16 Dec 2022
 | 16 Dec 2022

Detection of slow changes in terrestrial water storage with GRACE and GRACE-FO satellite gravity missions

Julia Pfeffer, Anny Cazenave, Alejandro Blazquez, Bertrand Decharme, Simon Munier, and Anne Barnoud

Abstract. The GRACE (Gravity Recovery And Climate Experiment) and GRACE Follow-On (FO) satellite gravity missions enable global monitoring of the mass transport within the Earth’s system, leading to unprecedented advances in our understanding of the global water cycle in a changing climate. This study focuses on the quantification of changes in terrestrial water storage based on an ensemble of GRACE and GRACE-FO solutions and two global hydrological models. Significant changes in terrestrial water storage are detected at pluriannual and decadal time -scales in GRACE and GRACE-FO satellite gravity data, that are generally underestimated by global hydrological models. The largest differences (more than 20 cm in equivalent water height) are observed in South America (Amazon, Sao Francisco and Parana river basins) and tropical Africa (Congo, Zambezi and Okavango river basins). Significant differences (a few cm) are observed worldwide at similar timescales, and are generally well correlated with precipitation. While the origin of such differences is unknown, pa rt of it is likely to be climate-related and at least partially due to inaccurate predictions of hydrological models. Slow changes in the terrestrial water cycle may indeed be overlooked in global hydrological models due to inaccurate meteorological forcin g (e.g., precipitation), unresolved groundwater processes, anthropogenic influences, changing vegetation cover and limited calibration/validation datasets. Significant differences between GRACE satellite measurements and hydrological model predictions have been identified, quantified and characterised in the present study. Efforts must be made to better understand the gap between both methods at pluriannual and decadal time-scales, which challenges the use of global hydrological models for the prediction of the evolution of water resources in changing climate conditions.

Julia Pfeffer et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1032', Anonymous Referee #1, 18 Jan 2023
    • AC1: 'Reply on RC1', Julia Pfeffer, 08 Mar 2023
  • RC2: 'Comment on egusphere-2022-1032', Anonymous Referee #2, 21 Jan 2023
    • AC2: 'Reply on RC2', Julia Pfeffer, 08 Mar 2023
    • AC3: 'Reply on RC2', Julia Pfeffer, 08 Mar 2023

Julia Pfeffer et al.

Data sets

supplementary-material-for-egusphere-2022-1032 Julia Pfeffer

Julia Pfeffer et al.


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Short summary
Global hydrological models (GHMs) are essential tools to predict changes in water resources in a changing climate. Compared to satellite gravity observations, GHMs underestimate slow changes in terrestrial water storage occurring over several years to a few decades. GHMs might be improved by systematic calibration and validation with satellite gravity data, conveying more information on long time scales than traditional calibration/validation datasets focusing on surface hydrology.