Analysis The Drought of The Southern Coast of Caspian Sea During The Base and Future Period by Using Downscaling Models (LARSWG and SDSM)

Draught is an event which occurs in all types of climatic conditions. This phenomenon can cause severe damages to thesusceptible areas. Since the drought due to its special features will change the agriculture of the Caspian sea, this phenomenon has been studied in the coastal areas of Caspian sea. The purpose of this study was to evaluate the drought during the base period of 1961-2010 and the future period of 2011-2030 byusing the Standardized Precipitation Index (Z-Value) on five stations of southern coastal of Caspian sea. Daily rainfall data from five stations was obtained to calculate the monthly precipitation and the data from HADCM3 model under B1 and A2 scenario. For downscaling the HADCM3 data, two models of LARS-WG and SDSM were used. Downscaled results Showed that LARS-WG model is better than SDSM for downscaling the precipitation data with less error. LARS _WG Model simulation results has estimated that precipitation will increase for February, November and December and it will decrease for the months of August and September, on each of five stations .We Used GIS to mapping the severity of the drought. 3-month SPI- results showed the greatest frequency and severity of droughts during the observation period on Anzali and Rasht stations. During the future, Rasht and Ramsar stations will have the highest intensity of droughts. 6- Months SPI determine the higher frequency on Babolsar, Gorgan, Ramsar Station and severity on Anzali, Rasht and Ramsar have experienced the highest drought. Ramsar, Rasht and Gorgan stations will have higher drought degrees in future. 12 -months SPI results showed the highest intensity was for the Ramsar and anzali, Ramsar, Rasht Anzali, Babolsar will reveale for future. Results indicated periods of normal SPI is more frequently than in any other period of five stations.