Drought Monitoring in Southern Coasts of Iran

In this research, SPEI (standardized precipitation and evaporation index) was used as an alternative index to SPI to study drought in warm southern coastal regions of Iran. Drought has a multi-scale nature that can be analyzed in time scales via analysis of precipitation and temperature data. Therefore, data were colected from 105 synoptic stations in Iran in 2015; Respective station SPEI and SPI coding and calculations analyzed in three-month increments.and values of the SPEI and SPI compared against drought zonation patterns in Iran. Comparison of drought zonation patterns reveals that in the three seasons of fall, winter and spring, the SPI and SPEI patterns are nearly the same, but the severity of wet and dry years based on the SPI and SPEI are more pronounced in similar regions, respectively. However, in summer, the SPI and SPEI indices are very different for the central and southern coasts of Iran, specifically, for the Hormozgan and Bushehr provinces. In the central and southern regions, increased precipitation and temperature is encountered, but the SPI and SPEI indices show wet and dry years, respectively. It appears that increased temperature and intensity of evapotranspiration in the southern coastal region of the country (the Persian Gulf and Oman Sea coasts) affects the area severely and that proper precipitation in summer cannot compensate for insufficient rainfall during the previous months or years. Therefore, effects of temperature and evapotranspiration play a major role in determining the severity of dry or wet years in southern coastal regions of Iran; Thus, precipitation is not the only determinant of drought in this region.