Simulation of Climate Change Impacts on Heat Stress over the Caspian Sea Region

Iran is a large country with a wide climate diversity and up to 80 percent of territory of Iran is located in the arid and semi-arid region with. Numerous observations and various modeling confirm that the Earth's climate is getting warmer. Such condition leads to increase of heat waves and heat stress. Over the last fifty years the average temperature of Iran up to 1.4 degree per decades has increased. The aim of this study is to investigate the heat stress by indicators (pHSI) and physiological pressure (pPhS) in the Caspian Sea region during past (1997-2017) and future (2020-2040) to evaluate the effect of global warming on thermal stresses in this the region of interest. Current study is based on the Regional Climate Modeling System (RegCM – V.4.6). The RegCM is used for downscaling of GFDL-ESM2M general circulation model (GCM). The evaluation is based on three RCP's emission scenarios includes RCP2.6, RCP4.5 and RCP8.5. The observational period is 1997-2017 and future period is 2020-2040. The indexes for evaluation of heat stress is physiological strain (pPhS) and heat stress index (pHSI). The results of this study show that in the winter during the observational period (1997-2017) in the study area, the thermal stress index (pHSI) indicates a slight cold stress, which the maximum is related to Rasht station and the minimum is related to Babolsar station. Such conditions, however, with lower pHSI values ​​for the next period are also observed in all three scenarios of RCP2.6, RCP4.5 and RCP8.5. The Physiological Pressure Index (pPhS) shows that there is a mild cold pressure in all stations studied during the winter in the basic period, and in the future decades this index will increase in all scenarios. In the spring, the physiological pressure index will be neutralized (partial pressure). In the summer, mild heat pressure was observed throughout all station during observational period and the intensity of this heat pressure will increase between 2020 and 2040. In autumn, the results show a mild cold pressure for the observation (base) period, which will be an increase in the physiological pressure index (pPhS) index in Anzali, Ramsar and Rasht stations in the future, and a decrease in the future index value in Gorgan station.