Assessment of meteorological droughts using SPI index (Case study: Lorestan Province)

In the present study the meteorological drought was analyzed using the Standardized Precipitation Index (SPI). Also the severity, area, and drought frequency data in a network consisting 13 rain gauge stations of Lorestan province during a 46 years period were analyzed in 5 time scales (3, 6, 12, 24 and 48 months). Drought events were characterized using duration-area- frequency (DAF) and severity-area-frequency (SAF) curves. Results showed that for the 12-month time scale, a11-month drought has occurred at all stations (expect for Kahman station) and the most severe droughts with 24.4, 23.4 and 22.1 mm of rainfall were observed in Keshvar, Dorood and Kaka Raza stations. The DAF and SAF curves showed that the largest area of the region have the lowest relative frequency of drought and small magnitude with 45% percentage area. Results indicate that severe drought with 500 month return period (probability of 0.2) would occur in all time scales. The findings of this study may be used for improved drought monitoring across the province.