A simple technique for the traditional method to estimate mean radiant temperature

The mean radiant temperature (T_mrt) is the most important meteorological factor influencing human thermal comfort in urban areas. Numerous methods have been implemented for estimating T_mrt using measured radiometer or thermometer data, and exhibit different levels of accuracy. This study presents a simple technique based on the traditional method (T_{mrt_TM}) to estimate T_mrt by utilizing measured radiation data from the radiometers. The estimated T_mrt values from the six-directional method (T_{mrt_SM}) and two black globe thermometer methods (T_{mrt_BG} and T_{mrt_BGv}) at two stations (sky view factor 0.69 and 0.94) in Jeju, Republic of Korea, for 8 days (5 sunny days, 3 (semi-) cloudy days) in spring and summer were used to validate the T_{mrt_TM}. The results showed that the mean differences between T_{mrt_TM} and T_{mrt_SM} were within the required accuracy for comfort in ISO 7726 (± 2 ℃) on sunny days and were reduced to 0.1-0.3 ℃ in high T_mrt conditions such as clear summer days. The T_{mrt_BG} in most sunny and semi-cloudy days and T_{mrt_BGv} on all days resulted in large mean differences from the T_{mrt_TM} that exceeded the required accuracy for thermal stress in ISO 7726 (± 5 ℃). Therefore, both black globe thermometer methods should be used carefully when estimating T_mrt, especially during sunny days. The correlations between T_{mrt_TM} and T_{mrt_SM} were highly significant, 0.93 on all days (p = 0.01). The newly developed regression equations between T_{mrt_TM} and T_{mrt_SM} could reduce mean differences within 0.5 ℃ for all days, and their r² values exceeded 0.87. Therefore, the simple T_{mrt_TM} technique can be used for T_mrt estimation in human thermal comfort studies.