Investigation of changes and prediction of relative humidity of Arak station based on statistical downscaling model

The city of Arak is one of the industrial centers of the country that has been facing population growth in recent decades. Increasing population as well as increasing energy consumption on the one hand and global warming on the other hand have caused changes in climatic elements such as relative humidity. In this paper, the relative humidity behavior of Arak city during the period 1961 to 2017 was investigated using Mann-Kendall statistical test and linear and nonlinear regression. The findings of this study showed that the trend of relative humidity of Arak station is different at different hours during the year and seasons. The most significant changes in the relative humidity of Arak are related to 6.5 and 9.5 hours, which has a downward trend. Using SDSM statistical downscaling model, relative humidity statistics of Arak until 2070 were predicted. The findings of this part of the study showed that the SDSM model can simulate and predict relative humidity. According to two scenarios A2 and B2, the relative humidity of Arak will decrease in the future