|KUMAR, S. - National Aeronautics And Space Administration (NASA)|
|ZAITCHIK, B.F. - Johns Hopkins University|
|PETERS-LIDARD, C. - National Aeronautics And Space Administration (NASA)|
|RODELL, M. - National Aeronautics And Space Administration (NASA)|
|REICHLE, R. - National Aeronautics And Space Administration (NASA)|
|LI, B. - Collaborator|
|JASINSKI, M. - National Aeronautics And Space Administration (NASA)|
|MOCKO, DAVID - Science Application International Corporation(SAIC)|
|GETIRANA, A. - Collaborator|
|DE LANNOY, G. - National Aeronautics And Space Administration (NASA)|
|HAIN, C. - University Of Maryland|
Submitted to: Journal of Hydrometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2016
Publication Date: 7/8/2016
Citation: Kumar, S., Zaitchik, B., Peters-Lidard, C., Rodell, M., Reichle, R., Li, B., Jasinski, M., Mocko, D., Getirana, A., De Lannoy, G., Cosh, M.H., Hain, C., Anderson, M.C. 2016. Assimilation of gridded GRACE terrestrial water storage estimates in the North American Land Data Assimilation System. Journal of Hydrometeorology. 17(7):1951-1972. doi:10.1175/jhm-d-15-0157.1.
Interpretive Summary: Groundwater estimates from space provide a valuable tool for water cycle modeling. Data from a satellite which monitors gravity anomalies are used to incorporate ground water change into a national modeling structure. Improvement results are found when compared to in situ ground observations. Comparisons are made to the U.S. Drought Monitor which indicate improvements to the model, especially during severe drought events. Water resource managers and weather and climate forecasters will benefit from this work as it improves the ability to estimate future conditions.
Technical Abstract: The objective of the North American Land Data Assimilation System (NLDAS) is to provide best-available estimates of near surface meteorological conditions and soil hydrological status for the Continental United States. The first two phases of NLDAS, however, have not included the assimilation of remotely sensed datasets. To support the ongoing efforts to develop data assimilation capabilities for NLDAS, we present the results of Gravity Recovery and Climate Experiment (GRACE) data assimilation implemented in a manner consistent with NLDAS development. Following on previous work, we assimilate GRACE terrestrial water storage (TWS) anomaly estimates into the NASA Catchment Land Surface Model (LSM) using an Ensemble Kalman Smoother. In contrast to the previous GRACE Data Assimilation (GRACE DA) studies, we assimilate a gridded GRACE TWS product, account for spatially distributed GRACE error estimates, and evaluate the impact that GRACE scaling factors have on assimilation. Comparisons with quality controlled in situ observations indicate that GRACE DA has a positive impact on the simulation of unconfined groundwater variability across the majority of the eastern U.S. and on the simulation of surface soil moistures across the country. Smaller improvements are seen in the simulation of root zone soil moisture and snow depth, and the impact of GRACE DA on simulated river discharge and evapotranspiration (ET) is regionally variable. The use of GRACE scaling factors during assimilation improved DA results in the western U.S. but led to small degradations in the eastern U.S. Finally, comparisons of GRACE DA results to drought estimates of the U.S. Drought Monitor (USDM) indicate that GRACE DA improves model agreement with USDM during the most severe drought events.