Terrestrial water storage anomalies of Yangtze River Basin droughts observed by GRACE and connections with ENSO

Two severe drought events occurred in the Yangtze River Basin (YRB) of China in the summer of 2006 and the spring of 2011. We examine terrestrial water storage (TWS) changes in the YRB for these events using time-variable gravity data from the GRACE satellite mission, in combination with observations made by TRMM satellite and in situ river gauges, along with hydrological models GLDAS and WGHM. GRACE TWS deficit estimates clearly quantify these YRB droughts, and a normalized GRACE-based TWS anomaly provides an alternative and useful hydro-climatological index in the YRB. We find that an El Niño (La Niña) event is significantly correlated with high (low) TWS in the YRB with a phase lead of ~ 7–8 months, and the lower YRB is more sensitive to ENSO variability than the upper basin. The possible linkage between TWS anomaly and ENSO is raised in terms of physical mechanisms of influencing the precipitation over the YRB.