Comparison drought severity, frequency and efficiency of five drought index in three climate regions of IRAN

Drought can occur in any climatic region in different severity and frequency. Many indices have been used for drought monitoring to date. In Iran, drought indices are selected arbitrarily for different regions. Due to complexity of drought phenomena, and because of various facets of droughts in any climatic region, determination of representative drought indices is necessary. In this paper compares five different drought indices namely NIZCHE, PN, RAI, SIAP and Z-Score are evaluated. Accordingly, drought severity and frequency for three different regions in Iran were monitored from 1959 to 2003, using climatic data from 20 stations. Finally the best drought index in any region is selected. Drought monitoring showed that severe and frequent drought could occur in all regions. Among all drought indices, SIAP index was pruned to perform best for most of the regions in Iran. RAI and PN indices show to have a relatively high correlation with SIAP index. The correlation of PN and RAI indices with SIAP was higher for arid regions. Results of this can be applicable in future drought monitoring in Iran.