Monitoring Meteorological Drought in Iran Using Remote Sensing and Drought Indices

Abstract

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