GRACE-derived Terrestrial Water Storage Depletion Associated with the 2003 European Heatwave

The GRACE twin satellites have revealed large inter-annual terrestrial water-storage variations for Central Europe. GRACE observes a negative anomaly in regional water storage in 2003 peaking at -7.8 cm in Central Europe with an accuracy of 1 cm. This 2003 excess terrestrial water storage depletion observed from GRACE can be related to the record-breaking heatwave that occurred in Central Europe in 2003. We validate the new measurements from 2002-2005 from GRACE using two independent hydrological estimates and direct gravity observations from superconducting gravimeters in Europe. All datasets agree well with the GRACE measurements despite the disparity of the employed information; the difference between datasets tends to be within GRACE margin of error. The April-to-August terrestrial water storage depletion in 2003 related to the Central European heatwave is found to be significantly larger in 2003 than in 2002 from both models and observations.