Evaluation of using the modified water deficit index derived from MODIS vegetation index and land surface temperature products for monitoring drought

A new version the water deficit index (WDI) is proposed for measuring the dryness of land surface based on the simplification of the assumption of trapezoidal relationship between surface temperature (T_s) and enhanced vegetation index (EVI) using MODIS data. The estimation of WDI is employed to monitor the severe drought in 2009-2010 in Guizhou province in south-western China. The results show that WDI could be a good indicator for dryness monitoring. It is also found that the correlation between WDI and meteorological drought index SPI is generally poor, which implies that droughts indicated by WDI differ from meteorological droughts that indicated by SPI.