Soil moisture and vegetation water content estimation using two drought monitoring index

Abstract

The vegetation supply water index (VSWI) and temperature-vegetation dryness index (TVDI) are modified by normalized difference water index (NDWI), then the soil moisture and vegetation water content are estimated based on VSWI, TVDI, modified VSWI and modified TVDI. Firstly, the vegetation index (VI) including normalized difference vegetation index (NDVI), normalized difference water index (NDWI) and enhanced vegetation index (EVI) are derived using TM and MODIS imagery, secondly, the land surface temperature(Ts) is retrieved for TM imagery and download for MODIS, finally, VSWI and TVDI are evaluated based on VI and Ts. We make use of VSWI and TVDI to estimate soil moisture and vegetation water content, the results show that vegetation water content estimated by VSWI and TVDI is better than VI; soil moisture and vegetation water content estimated by VSWI and TVDI which evaluated based on NDWI are better, EVI takes second place and NDVI comes next; The TM imagery has a better estimation accuracy than MODIS because of the higher resolution. It is useful to soil moisture estimation, vegetation water content estimation and dryness monitor using VSWI and TVDI modified by NDWI.