Monitoring Meteorological Drought in Iran Using Remote Sensing and Drought Indices

Drought is a major environmental disaster in many parts of the world. Knowledge about the timing, severity and extentof drought can aid planning and decision-making. Drought indices derived from in-situ meteorological data have coarsespatial and temporal resolutions, thus, obtaining a real-time drought condition over a large area is difficult. This studyused advanced very high resolution radiometer (AVHRR) images to evaluate the efficacy of NOAA-AVHRR data formonitoring drought in Iran for the 1997-2005 (March-July) time period. Ten-day maximum normalized differencevegetation index (NDVI) maps were produced and a vegetation condition index (VCI), vegetation health index (VHI) andtemperature condition index (TCI) for the same period was calculated. Precipitation data from 47 synoptic meteorologicalstations was collected to calculate the standardized precipitation index (SPI) as a meteorological drought index. Analysisand interpretation of these maps revealed that the spatial extent of the satellite-derived drought-indices and SPI generallyconfirm each other. Based on the statistical analysis, higher correlations were found among the satellite-derived indiceswhile lesser or no relationships were found between the satellite-derived indices and SPI. The results revealed that highcorrelations were found among TCI and VHI, VCI and VHI in dry, normal, and wet years (0.662 to 0.813). Iran sufferedfrom severe drought during 1999-2001.The results of remotely-sensed indices and the SPI index for 2002-2005 most ofthe region show that it experienced normal conditions.