Hotspots of recent drought in Asian steppes

Abstract

The present study aims to identify hotspots on the Asian steppe that were vulnerable to widespread drought events in the Northern Hemisphere during 1999-2002, using newly proposed indices of vegetation response (sensitivity and resilience) to drought. Drought sensitivity is defined as vegetation response to decreased precipitation from pre-drought to drought phases, and resilience is defined as response to increased precipitation from drought to post-drought phases. Thus, the sensitivity and resiliency indices SI and RI are similarly expressed as normalized change of vegetation relative to that of precipitation. We also develop new regionally adjusted indices SIr and RIr, to do an interregional comparison of vegetation dynamics. In general, the resilience (RIr or RI) was larger than sensitivity (SIr or SI) over the entire region, whereas they had similar amplitudes over a wetter region (forest steppe). This asymmetric response of SIr