Integrating GRACE into WaterGAP Global Hydrological Model WGHM

What is it about?

The WaterGAP Global Hydrology Model (WGHM) calculates water storages (e.g. in groundwater and surface water) and its corresponding flows (e.g. discharge, evaporation) for the global land surface. Since 2002, the GRACE (Gravity Recovery and Climate Experiment) satellites are in orbit, which products are used to assess mass changes at the Earth, including changes in the water column. Processed GRACE data are used e.g. to calibrate WGHM water storages in order to improve model results. This paper describes the methodology of this approach and provides first results for the Mississippi basin.

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Why is it important?

This approach is, to our knowledge, the first attempt to i) include GRACE observations as a gridded data product, ii) account for the complex spatial GRACE error correlation pattern by rigorous error propagation from the monthly GRACE solutions, and iii) allow integration of model parameter calibration and data assimilation within a unified framework.

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