Evaluation of Drought Severity Changes in Iran Using Hurst Exponent and Standardized Precipitation Index

Abstract

Drought is a natural hazard that could inflict significant damage to agriculture, society, economy, and ecosystems. The study of drought persistence assists in understanding that droughts could be predictable by constructing the appropriate general climate circulation models. Using the daily precipitation data of 44 synoptic stations in Iran, the relationship between the frequency of drought and the persistence of its risk has been determined with the application of the Hurst Exponent and standardized precipitation index. The results showed that the average drought persistence in Iran is 0.78, but its severity varies because of different climates due to geographical diversification. In regions where the frequency of mild and moderate droughts is more severe, and the intensity of drought persistence has increased in the climate. Also, although the frequency of severe and extreme droughts and the coefficient of rainfall variation is higher, drought persistence is lower in the mountainous areas of the watersheds. However, climate change could be a threat that increases drought persistence in mountainous areas. Drought persistence in non-mountainous regions of Iran has increased the severity of aridity.