A review of the impacts of climate factors on humans' outdoor thermal perceptions.

Outdoor thermal comfort has been studied globally in recent years to understand thermal perceptions of the local people. It was usually indicated by neutral temperature (NT). However, the findings of studies vary slightly for different areas, a factor which is rarely considered. This article reviewed the results (NTs) of some previous studies with the aim to find the causes of their differences. The calculated NTs (indicated by the physiological equivalent temperature, PET; universal thermal climate index, UTCI; and standard effective temperature*, SET*) in two extreme seasons were associated with the local climate factors (latitude & annual mean temperature, AMT) through linear regression. It was found that NTs decreased with the increase of latitude and the reduction of local AMT, and showed a more significant correlation with latitude than local AMT during summer seasons. This phenomenon occurred for all thermal indices. Increasing the latitude by 10° caused summer NT decreases of 0.23 °C (PET, R = 0.5505), 0.22 °C (UTCI, R = 0.5781), and 0.33 °C (SET*, R = 0.2952), thus proving the impacts of local climatic factors on residents' thermal feelings. This effect may be the result of subjective adaptation towards local permanent thermal conditions. The findings of this study provide directions for further thermal services against people from different climatic zones.