drought monitoring based on the spi and rdi indices under climate change scenarios (case study: semi-arid areas of west golestan province)

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 11 climatic stations. after evaluating the ability of lars-wg5 in the simulation period (1984-2010), downscaling of hadcm3, ipcm, and gfc models was done as a group under scenarios of a1b, a2 and b1 to evaluate changes in meteorological values of precipitation, tmax, tmin, and evapotranspiration during 2011-2030.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 b1 and a2scenarios, with an increasing trend of 0.81and 0.91°​c, respectively. the highest mean evapotranspiration (1.34 mm) changes were under group model of b1 and a2. for precipitation, these were related to b1 (1.49 mm) and a1b (1.36 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.