基于UTCI指数的1980—2019年中国夏季人体舒适度变化特征分析

基于ERA5-HEAT再分析资料中的通用热气候指数（UTCI）数据,利用旋转经验正交函数（REOF）方法将我国划分为8个区,分别为长江、华南、华北、西北、东北、北疆、南疆和西部地区。分析了1980—2019年我国夏季不同地区人体舒适度的变化特征,并初步解释了UTCI变化的原因。主要结论如下：我国夏季UTCI呈不断增加趋势,其中西北地区增速最快（平均增率为0.053℃/a),且西部、西北和南疆地区夜间UTCI相较白天增加更明显,主要表现为这些地区的UTCI最小值增率分别较其最大值增率偏高了112%、34%和33%。随着UTCI的上升,我国大部分地区（西部除外）的热不舒适天数及发生热不舒适持续事件的频次都呈增加趋势,其中增率最大的区域是华北地区,分别为1.7 d/(10 a)和2.4次/(10 a)。从气候影响因子的分析发现,我国夏季UTCI增加的原因是气温、露点温度和平均辐射温度的增加以及风速的减少。其中,气温是UTCI增加的主要气候因子,平均贡献率为49%;辐射是大部分地区（西部和华南除外）的第二大因子,而其他因子对UTCI的贡献率主要与各地区的变率大小有关。

Analysis of the variation characteristics of human thermal comfort in summer of China from 1980 to 2019 based on UTCI

Based on the Universal Thermal Climate Index (UTCI) from the ERA5-HEAT reanalysis data, China was divided into eight regions by using the rotating empirical orthogonal function method (REOF), namely the Yangtze River Valley (YR), the South China (SC), the North China (NC), the Northwest China (NW), the Northeast China (NE), the Northern of Xinjiang (NJ), the Southern of Xinjiang (SJ), and the Western of China (WC). The variation characteristics of human thermal comfort of the eight regions in China in summer during 1980-2019 were analyzed and the variation reason of UTCI was also explained preliminarily. The results are as follows. In summer, UTCI has been increasing in each region of China, with the largest increase rate in NW where the average UTCI increase rate is 0.053℃/a, and in nighttime, the increase of the minimum UTCI is particularly significant in WC, NW, and SJ, respectively augmented by 112%, 34% and 33%, compared with the increase rate of their maximum UTCI. With the increase of UTCI, the days of strong heat stress and the frequency of the events of strong heat stress for lasting in most areas, have been rising in summer, except for WC. The area with the largest increase rate is NC, with the increase rate of 1.7 days per decade and 2.4 times per decade, respectively. From the analysis of influencing factors, it is found that the rise of UTCI in summer of China is caused by the increase of air temperature, dew point temperature and radiation temperature and the decrease of wind speed. Among the four climatic factors, air temperature is the main climatic factor for the rise of UTCI in China, which the average contribution rate is 49%, and except for SC and WC, radiation is the second largest factor in most areas, while the contribution of other climate factors mainly depended on the variable trend of each region in China.