Applications of the GRACE Data Assimilation System for Regional Groundwater Monitoring

Since 2003, the Gravity Recovery and Climate Experiment (GRACE) has provided unprecedented observations of water storage dynamics at the basin to continental scale. In order to realize the full potential of GRACE for hydrology, however, GRACE-derived regional-scale, column-integrated, monthly terrestrial water storage (TWS) anomalies must be disaggregated horizontally, vertically, and in time. The GRACE Data Assimilation System (GRACE-DAS) was designed to downscale and to disaggregate GRACE TWS observations by assimilating them into the Catchment Land Surface Model using a novel implementation of an Ensemble Kalman Smoother. As we have reported in the published literature, this system improved model skill in the simulation of hydrological states and fluxes at sub-GRACE resolution in the Mississippi basin. Here we report on new developments in GRACE-DAS, including application of the system to North America, Europe, the Middle East, and North and East Africa, progress and conceptual challenges in improving the assimilation algorithm, and the use of newly available GRACE TWS solutions in GRACE-DAS. Emerging directions in GRACE-DAS development, including multi-sensor assimilation systems and application to coupled regional climate models, will also be discussed.