Application and Comparison of Standardized Precipitation and Standardized Precipitation Evapotranspiration Indices for Evaluating Meteorological Drought Condition of Tehran Province

Numerous indicators for drought monitoring in different time scales have been used for monthly and yearly data series. One of the limitations of conventional indicators such as the Standardized Precipitation Index (SPI) is no attention to the water balance based on the amount of evapotranspiration. The Standardized Precipitation Evapotranspiration Index (SPEI) which is based on precipitation and potential evapotranspiration incorporates the water balance in the drought index.The purpose of this study isinvestigating the intensity, duration and frequency of the meteorological droughts in Tehran province using SPI and SPEI in order to determine the relationship between these indices for optimized management of water resources. In this study, the data of monthly precipitation and average monthly temperature for a period of 30 years (1978-2008) in six gauging stations in Tehran province were used. The results indicated that there is a significant correlation between SPI and SPEI while SPEI show a quick response to the meteorological drought.