Application of Improved Remotely Sensed Drought Severity Index Based on Soil Moisture Product in Inner Mongolia

Abstract

Based on the drought severity index (DSI), which is derived from the ratio of evapotranspiration (ET) to potential evapotranspiration (PET) and normalized difference vegetation index (NDVI), as measured by remote sensing, we replaced the ET/PET ratio with soil moisture (0-10 cm) to establish an improved index (IDSI) and evaluated the drought situation in Inner Mongolia. The two components in IDSI are independently derived; however, the effects of evapotranspiration are contained in the soil moisture, and even precipitation changes could be reflected. We used monthly IDSI data for Inner Mongolia to evaluate drought throughout the growing season (May-September) during 2001-2010. The IDSI showed that 2001, 2007, and 2009 were years with significant drought. Areas that experienced extreme drought were less extensive than those found by the DSI because we removed the ET/PET component, which already contains the effects of the NDVI. IDSI results not only contained the degree of precipitation change for a given month through soil moisture, but also reflected the influence of water and heat in the previous month through the NDVI. Moreover, IDSI results were generally consistent with agricultural drought disaster records.