Assessing the Efficiency of Vegetation Drought Index (VDI) and Temperature Drought Index (TDI) based on Satellite Images in Central Iran

Increasing of temperature and changing in precipitation patterns, leads to extreme climate events such as drought which drastically impact on agricultural, ecological and socio-economic sectores. Knowledge about the timing, severity and extent of drought can aid planning and decision-making. Drought indices derived from in-situ meteorological data have coarse spatial and temporal resolutions. Thus, obtaining a real-time drought condition over a large area is difficult. Therefore, drought indices which is derived from remote-sensing data, has been widely used for drought monitoring. In this study, two new drought indices, Vegetation Drought Index (VDI) and Temperature Drought Index (TDI) derived from remote sensing data are evaluated based on the Standard Precipitation Index (SPI) derived from in-situ meteorological data. The data included the MODIS sensor images from Terra satellite for the 2001 -2004 and rainfalls data from 50 synoptic stations in Central Iran. Accuracy of the two drought indices based on satellite data carried out using evaluation criteria of R and RMSE in 95% confidence levels compared with drought spatial distribution map of the SPI based on rainfalls monthly data. Results indicate significant correlation between VDI (0.69) and TDI (0.66) indices with SPI index. Thus, the drought indices based on remote sensing data could well use in drought early warning systems.