Understanding regional variations in TWS in Eurasia using GRACE time variable gravity data and CLM 4.5 output products

Tuesday, 16 December 2014: 5:00 PM
Meng Zhao, University of California Irvine, Irvine, CA, United States, Isabella Velicogna, University of California Irvine, Department of Earth System Science, Irvine, CA, United States, Sean C Swenson, National Center for Atmospheric Research, Boulder, CO, United States and John S Kimball, The University of Montana, Flathead Lake Biological Station, Polson, MT, United States
The latest Community Land Model (CLM) 4.5 extends terrestrial hydrological modeling into approximately 50 meters below ground and has potentials to be applied to partition water cycle. Uncertainties in CLM 4.5 hydrological outputs are however not well evaluated, which in turn impacts the interpretability of the data. Here, we employ time series of time-variable gravity from the NASA/DLR GRACE mission to calculate total water storage in Eurasia during 2003-2014. We compare TWS from GRACE with CLM 4.5 outputs at the regional and basin scale. At the basin scale we find a good agreement in the amplitude and phase of the seasonal variability, with smaller amplitude in CLM 4.5 derived TWS in the Lena basin. In terms of trends at the basin scale, we find a reasonable agreement for the Ob and Yenisei basins and more significant differences for the Lena basin. When examining the spatial pattern in TWS across Eurasia, the areas of significant decrease or increase in TWS are captured correctly but the amplitude and the spatial extent of the trends do not always agree. To interpret these differences, we compare the CLM 4.5 products to independent observations of precipitation from GPCP, ERA-Interim, MERRA and NCEP CFSR, evapotranspiration from MODIS, and surface hydrology components including snow water equivalent and soil moisture from AMSR-E and SSMI/S satellite products. We evaluate the agreement between these components in terms of seasonal and long-term variability and also determine the dominant control on TWS in each basin.