The Comparison of Three Drought Indices in Various Climates in Iran

The identification and monitoring of drought are of great important in the most regions of Iran. Because of a-periodic distribution of precipitation that cause many provinces of Iran are prone to drought. Drought is one of the phenomena that occurred not only in arid & semiarid regions but also in humid climate regions. We have analyzed drought and the data that used in this study are monthly precipitation totals at 8 stations during 1957-2003: Tehran, Shahrekord, Tabriz, Mashhad, Yazd, Bandar Abas, Zahedan and Anzali. Then we used time series that determine 3 indices drought (SPI, CZI and Z-Score) that calculated its intensity, frequency and duration in 3 time scales (1, 3 and 12 Months). The results show that those indices are good tools to define, detect and monitor droughts. In addition the frequencies of 3 indices in time scales of 1 month from humid climate to the dry regions have reduced. The three indices were calculated to investigate the relationship. The results of this paper indicate that the correlation coefficient between the SPI and CZI & the SPI and Z-Score are having acceptable level of significant also the CZI is more responsive to precipitation deficits than of other two indices in extremely dry conditions.