The terrestrial water storage changes in the continental United States inferred from GRACE data and simulations from land surface models

Measurements of gravity changes by the Gravity Recovery and Climate Experiment (GRACE) satellite mission are used to infer the terrestrial water storage (TWS) variations in the continental United States (US) between 2003 and 2010. The inferred TWS variations from 2003 to 2006 show, significant, continued loss of terrestrial water spreading across the southeastern region of the US and increase of terrestrial water storage in most western region and some northwestern region. Such geographical pattern of the inferred change of terrestrial water storage correlates well with Palmer Hydrological Drought Index (PHDI) changes in the same time periods. The TWS variations inferred from the GRACE data since 2004 to 2010 show water loss in south central region and western region of the US, respectively in 2005-2006 (mainly in the summer and autumn of 2005 and in the summer and winter of 2006) and through all seasons of 2007, and water gain in southwestern region, south central region, central and north central region, eastern region and southwestern region of the US, respectively in 2005, 2007, 2008, 2009 and 2010. The TWS variations inferred from the GRACE data exhibit similar geographic patterns to those simulated from Mosaic land surface model (LSM) and Noah LSM, but differences exist in some regions and the amplitudes of the TWS variations inferred from the GRACE data are smaller than those simulated from LSMs. We will discuss these differences and possible means the GRACE data can be used to improve the monitoring of TWS variations.