Vol. 128, No. 4 * Pages 399–496 * October - December 2024

Research on heat waves is greatly important not only due to their effect on social, economic, and ecological systems, but also due to the complexity of the processes that create them. Therefore, this research mainly investigated the trend of long-term changes in various characteristics of heat waves in hot and dry regions of Iran. For this purpose, the daily maximum temperature data of 15 meteorological stations in the central and southeastern parts of Iran were used from 1985 to 2018. Using the excess heat factor (EHF) index,  five different features of heat waves including the number of heat waves (HWN), heat waves duration (HWD), heat waves frequency (HWF), heat waves mean (HWM), and heat waves magnitude (HWA) were extracted for all the studied stations. Then, their trend of long-term changes was analyzed using the Sen’s slope estimator nonparametric method. The results showed that on a regional scale, all five characteristics of heat waves have an increasing trend at a significance level of 95%, so an increase of 0.5 events per decade has been observed for the HWN. The trend of long-term changes in the HWD has also indicated an increase of 0.91 days per decade. The HWF has shown more drastic changes than other characteristics of heat waves, so in every decade 2.61 days have been added to the frequency of days contributing to the occurrence of heat waves. The regional intensity of HWM and HWA also show an increase of 0.1 and 0.4 °C in each decade, respectively. These findings show the importance of choosing a suitable index for monitoring different characteristics of heat waves. The EHF index is a suitable index, which can be one of the efficient indices in this regard.