Spatio-temporal Characteristics of Thermal Comfort in the Yangtze River Delta

Based on the hourly reanalysis data of ERA5 from 1981 to 2020, the temporal and spatial variation characteristics of human physiological thermal response in the Yangtze River Delta under climate change were analyzed by using the Universal Thermal Climate Index (UTCI). The results show that the occurrence frequency of climate conditions with no thermal stress is 43.77%, the occurrence frequency of climate conditions with heat stress and cold stress is 22.42% and 33.81%, respectively. The occurrence frequency of climate conditions with intensity heat stress and intensity cold stress is 8.38% and 1.58%, respectively. In terms of spatial distribution, the occurrence frequency of climate conditions with no thermal stress in the Yangtze River Delta shows a zonal distribution of more in the south and less in the north, meanwhile, the characteristics are diagnosed as more in the mountainous areas and less in the plains, more in the coastal areas and less in the inland areas. The intense heat stress mainly occurs in the plains of western and southern Anhui, plan of Jiaxing and Shaoxing, and basin of Jinhua and Quzhou in Zhejiang. Intensity cold stress mainly occurred in the northern Jiangsu, northern Anhui and coastal areas of northern Zhoushan. Under the background of global warming, the interdecadal variation of UTCI value in the Yangtze River Delta shows an upward trend, increasing from 13.83℃ during 1981−1990 to 14.75℃ during 2011−2020. The physiological thermal response of human body indicates a character of the decrease in cold stress, the increase in heat stress, and no thermal stress remains basically unchanged. The increase of periods with no thermal stress in spring basically offset the decrease of periods with no thermal stress in summer.