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چکیده
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This study was conducted to determine the thermal stress and its trend in Iran. The atmospheric variables of 304 synoptic stations including mean temperature, relative humidity, wind speed, and cloudiness were used, during the period 1961 to 2010 to identify the thermal stress conditions in Iran. These data were prepared on a daily basis from Iran Meteorological Organization. Physiologically Equivalent Temperature (PET) and Standard Effective Temperature (SET*) were used to identify thermal stress in Iran. Also, thermal stress in Iran was studied with simple linear regression method and at a 95% confidence level. The results of the study revealed that in Iran, each location can experience different types of environmental conditions throughout the year. At a specified time, thermal stresses of different intensities can be seen in Iran. The other results showed that the mountainous regions, especially the highlands of northwest of Iran, along with the Zagros and Alborz mountains, had the highest coefficient of variability (more than 50%). Also, the southern regions of Iran have both the monthly and the annual scale with the least coefficient of variability (less than 20%) in bioclimatic conditions. In general, a diversity of bioclimatic conditions is evident in Iran both temporally and spatially. In the other part of this study, it was determined that heat and cold stress and heat comfort had a positive trend (less than 60 stations) in parts of Iran, a negative trend in some other parts(more than 50 of stations), and no specific trend in the remaining parts (more than 250 stations). Most of the northern stations, especially on the Caspian coast, have shown a positive trend in the event of cold stress. Indeed, extreme bioclimatic conditions (very cold and hot conditions) have been raising both in the southern and northern latitudes of the country. Even in the southern part of the country, a positive trend of cold and very cold conditions can be observed in some stations.
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