The spatiotemporal trend of extreme temperature-humidity variables and assessing the climatic comfort changes in northern Iran

Abstract

Abstract The Earth's climate system is significantly affected by global warming. This study examined the spatiotemporal variations in average and extreme values of relative humidity, temperature, and temperature-humidity index in the northern areas of Iran from 1986 to 2016. The temperature-humidity index was generated for each of the 30 meteorological stations based on relative humidity and temperature data. Previously, trend analysis was calculated in different seasons using ordinary linear and quantile regression methods. For the most part, the results indicate a declining trend in relative humidity and a rising trend in temperature. The highest percentage of decreasing trend slopes for maximum relative humidity (≤-50%) in all seasons, but for maximum temperature, the highest percentage of increasing trend slopes in summer and winter (≥ 30%) identified on the southern coast of the Caspian Sea. However, a decreasing trend (%≤-15) was detected for the maximum temperature in autumn at the northern regions. Average and high values of THI in the summer season (≥ 75) have increased in the western and northern parts with high intensity (≥ 40%). The low values of THI in winter (≤ 30) have increased with a slight slope (20%), which indicates a decline in some of days with cold stress in winter for most regions. The findings of this study are generally useful for identifying changes in weather extremes and their effects on human health.