Comparison of selected thermal indices in the northwest of Iran

The present study compared simple thermal indices and the indices derived from energy budget models in the northwest of Iran. For this purpose, the air temperature, solar radiation, relative humidity, cloud, cover and wind speed of 13 meteorological stations in the northwest of Iran during the  the period of 1986 to 2007 were selected for comparison. The results which were extracted using Bioklima and RayMan models, showed that the indices based on human energy balance had  a significant correlation with each other (with R2 above 90%), and the lowest R2 (70%) was related to Subjective temperature index (STI). The indices based on relatively simple formulas had low correlation with Universal Thermal Climate Index (UTCI) and Physiologically Equivalent Temperature (PET). The probable reason for this lack of conformity was the lack of radiation factor in the equations. Furthermore, UTCI was very sensitive to the changes in air temperature, solar radiation, relative humidity and wind speed, especially. In this regard, it represented the response of the human body. The findings of this analysis indicated that UTCI and PET indices were the most suitable indices which could be  used in determining  thermal comfort conditions.