Drought analysis by Standardized Precipitation Index (SPI) for different time scales, Shahrood, Iran

Drought is a threatening global and local problem that has many damages in various ways. It causes huge losses in agriculture and has many negative influences on natural ecosystems. Droughts have been sorted into four types: meteorological, agricultural, hydrological, and social-economic. Several indices in the monitoring and assessment of drought are used : Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI), Palmer Modified Drought Index (PMDI), Palmer Hydrologic Drought Index (PHDI), and Z-Index. SPI is a standardized index that can be computed on different time scales, so as to allow monitoring most of drought types (i.e. meteorological, agricultural, hydrological). Therefore, in this study, SPI is used for meteorological drought analysis of Shahrood meteorological station of Iran. Monthly mean precipitation data of 50 yearly are used. The precipitation values of Shahrood station are investigated for periods of 3, 6, 9, 12, 18, 24 and 48 months according to classification values of the SPI method. The frequencies of drought classes are obtained. Also the drought period, magnitude and standardized precipitation index (SPI) values are presented to depict the relationships between drought duration and magnitude.

Keywords:

Drought , precipitation , Shahrood , Standard Precipitation Index (SPI)