Meteorological drought duration–severity and climate change impact in Iran

This study investigated the effect of climate change on future precipitation and temperature from 2021 to 2050. Three general circulation models (GCMs), namely GFDL-ESM2M, HadGEM2-ES, and IPSL-CM5A-LR, and two greenhouse emission scenarios, RCP2.6 and RCP8.5, were analyzed for this purpose. The CCT model, precipitation data, and minimum and maximum daily temperatures (from 1986 to 2019) were used for downscaling and correcting precipitation and daily temperature bias. According to the results, the weighted annual precipitation recorded in rain-gauge stations was ascending in all scenarios, except for RCP8.5 in the IPSL-CM5A-LR model. The mean weighted precipitation rate of rain-gauge stations in winter did not descend under any climate change conditions, but the precipitation rate decreased or increased in other seasons. The highest increase of 23 mm in the weighted mean precipitation in winter was calculated under the RCP2.6 scenario in the GFDL-ESM2M model. The highest decrease of 10.5 mm in the weighted mean precipitation was observed in autumn. No temperature decline occurred in meteorological stations. The highest increase of 3.1 °C in the weighted mean temperature and the highest seasonal temperature rise of 8.5 °C were observed in summer under the RCP8.5 scenario in the HadGEM2-ES model. According to the standardized precipitation index (SPI), almost 70% of the future 30-year period are dry years, and drought occurs in almost all scenarios in all Iranian watersheds from 2030 to 2040. Given severe long droughts (14 years), Iran needs a comprehensive management plan and a long-term vision of managers and authorities for water resources.