Detecting terrestrial water storage variations in northwest China by GRACE

Abstract

The Gravity Recovery and Climate Experiment (GRACE) satellites provide a new quantitative measurement to observe terrestrial water storage (TWS) variations. In this paper, GRACE data were used to detect TWS changes (TWSC) in last decade in the arid region of northwest China. TWSC of the study area were obtained from RL05 Level 2 GRACE data between August 2002 and July 2013. These obtained GRACE based TWSC were thereafter validated against that calculated from global land data assimilation system (GLDAS) data. The validation showed TWSC from two sources were consistent. Together with precipitation, the analyses showed TWSC in this arid region changed over time, and responded sensitively to climate factors. Results indicated that TWSC showed distinct seasonal variation characteristics and the peaks of TWS appeared corresponding to precipitation. The summers of 2005 and 2012 were wet periods with a mean TWS higher than multiple-year average by about 30 mm, while the falls of 2008 and 2009 were dry seasons with a heavily deficit TWS, lower than multiple-year average by about -30 mm. The winter of 2008 was also in deficit but slightly better than the fall of same year. On average, in the last decade, the period of 2008 to 2009 was in the driest condition. Significant decreases in TWS in 2008 and 2009 were successfully detected by GRACE, and corresponded to drought events in the study area. This study showed in the last decade the changes of climate factors resulted in larger TWS variations in the arid region and proved the capability of GRACE in detecting larger-scale and long-term drought events in arid regions.