The effect of climate change on wet and dry spell's characteristics (Case study: Arazkuse and Tamar stations in Golestan Province)

As a result of global warming a significant change in wet and dry spells pattern is expected. These variations would be more significant in regions with diverse climates like Golestan province, Iran. In this research, the impact of climate change on the frequency and intensity of droughts are assessed using Standardized Precipitation Indices (SPI) in two raingauges stations namely Arazkuse and Tamar. The rainfall data for baseline period (1986-2005) for both stations were collected and examined. The projections of rainfall amount for two future periods, 2031–2050 and 2051–2070, obtained from the Coupled Model Intercomparison Project Phase 5 (CMIP5) outputs were downscaled under three representative concentration pathway (RCP2.6, RCP4.5 and RCP8.5), using the statistical downscaling model (SDSM). After evaluation of skill of WG model in simulation of historical rainfall data, SPI and relative SPI values in different time steps were calculated. Then by using first-order Markov chains drought characteristics during baseline and future period were compared. The results showed that probability of droughts in the future in both Tamar and Arazkuse stations, would increase. With increasing SPI time scale, duration of all drought classes is projected to decrease in the future under all three RCP scenarios.