Morteza Akbari - Ph.D. Candidate of Combat Desertification, Department of Watershed and Arid Zone Management, Faculty of Rangeland and Watershed, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Majid Ownegh - Professor, Department of Watershed and Arid Zone Management, Faculty of Range Land and Watershed, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Hamidreza Asgari - Assistant Professor, Department of Watershed and Arid Zone Management, Faculty of Range Land and Watershed, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Amir Sadoddin - Associate Professor, Department of Watershed and Arid Zone Management, Faculty of Range Land and Watershed, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
Hasan Khosravi - Assistant Professor, Department of Arid and Mountainous Regions Reclamation, Faculty of Natural Resources. University of Tehran, Tehran, Iran

Based on SPI and RDI indices, changes in droughts in the semi-arid areas of west Golestan Province was assessed in the GIS environment by incorporating data from Hashemabad synoptic station and ۱۱ climatic stations. After evaluating the ability of LARS-WG۵ in the simulation period (۱۹۸۴-۲۰۱۰), downscaling of HadCM۳, IPCM, and GFC models was done as a group under scenarios of A۱B, A۲ and B۱ to evaluate changes in meteorological values of precipitation, Tmax, Tmin, and evapotranspiration during ۲۰۱۱-۲۰۳۰.Model accuracy was studied using the coefficient of determination, index of agreement (D) and the mean error. The results showed that the highest mean values of Tmax and Tmin were related to the B۱ and A۲scenarios, with an increasing trend of ۰.۸۱and ۰.۹۱°​C, respectively. The highest mean evapotranspiration (۱.۳۴ mm) changes were under group model of B۱ and A۲. For precipitation, these were related to B۱ (۱.۴۹ mm) and A۱B (۱.۳۶ mm) scenarios. Based on the regional interpretation of drought, the central, northern and eastern parts, in spite of the current droughts, are predicted to be hit harder in the upcoming period and for more prolonged period. In this study, performance of group models to simulate climate data and use of drought indices were shown.

Simulation, Downscaling, General Circulation Models, Evapotranspiration