Trends, Patterns, and Driving Forces of Heat Waves in the Center and Southeast of Iran

In addition to negatively affecting human metabolism and biological activities, heat waves can also affect various social, economic, and industrial aspects. This study mainly investigates trends, patterns, and driving forces affecting heat waves in the center and southeast of Iran. Using the excess heat factor (EHF) index, five different characteristics of heat waves, including the heat wave number (HWN), heat wave duration (HWD), heat wave frequency (HWF), heat wave mean (HWM), and heat wave magnitude (HWA) were extracted for 15 meteorological stations in the center and southeast of Iran. Then, Sen's slope estimator non-parametric method analyzed the long-term changes of the five characteristics of heat waves and atmospheric variables on a synoptic scale. Canonical correlation analysis (CCA) was also used to investigate the relationship between the characteristics of heat waves and the set of atmospheric variables at the synoptic scale. The study of the long-term changes in the five characteristics of heat waves in the center and southeast of Iran showed that all five characteristics have had an increasing trend for this part of Iran. In addition, the sea surface temperature (SST) of the Oman Sea, Arabian Sea, and Persian Gulf Sea have been increasing. Geopotential height at 500 hPa, air temperature at 1000 hPa, and specific humidity at two levels of 1000 and 850 hPa have also had an increasing trend on a synoptic scale. But the only variable whose long-term change trend has decreased is the zonal Wind component at three levels of 1000, 850, and 500 hPa. Therefore, it can be concluded that the long-term changes in sea surface temperature (SST), air temperature at the level of 1000 hPa, specific humidity at the level of 850 hPa, geopotential height at the height of 500 hPa, and the zonal Wind component at the levels of 1000, 850 and 500 hPa can be the most important driving forces in the explanation of long-term changes in the characteristics of heat waves in the center and southeast of Iran.