Abstract:

Based on the daily meteorological data from 94 stations in Shaanxi province from 1971 to 2018, the temporal and spatial characteristics of the number of human comfortable days (HCDs) were analyzed using the analytical methods including linear tendency rate, cumulative anomaly, wavelet analysis, and empirical orthogonal function (EOF) analysis.The results indicated that the body feeling status ranges from cold to comfort in most time with the number of days accounting for 85.2 percent of the year.There is a small number of days when the body feels warm and there are no hot and sultry days.The annual mean number of HCDs is 132 d in Shaanxi province from 1971 to 2018 with an increasing linear trend of 0.524 d·a^-1.The number of HCDs in spring and summer increases most significantly.There are two periodic oscillations of quasi 4 years and quasi 8 years for the number of HCDs during the studied period.The results of the sliding-T test show that the number of HCDs in Shaanxi province and the three regions occurs significantly abrupt change over 1997.HCDs appear from March to November, and focus mainly on the period from May to September.There is the largest number of HCDs in northern Shaanxi province from July to August, in Guanzhong from June to August, and in southern Shaanxi province from June to September.The number of annual HCDs is larger in the south than in the north, and is the largest in Hanzhong and Ankang.The EOF analysis results show that the abnormal distribution of annual HCDs is consistent across the province.The spatial distribution of the trend displays that the number of HCDs increases in 80% of regions of the province, but decreases in only 11 districts including north Yulin, north Yan'an, and east Ankang.The number of human uncomfortable days in the province shows a significant decreasing trend with a tendency rate of -0.548 d·a^-1, and the number of cold uncomfortable days decreases significantly.In addition, the discomfort of the human body in Shaanxi province is mainly manifested as cold discomfort which appears mainly in the northwest of northern Shaanxi province, the southern mountainous areas, and the high mountainous areas of Taibai and Huashan in Guanzhong.However, the region of human thermal discomfort is mainly distributed in Hanzhong and Ankang areas in southern Shaanxi province and Xi'an in Guanzhong, and the number of days is small.

Key words: Human comfortable day, Wavelet analysis, Empirical orthogonal function (EOF) analysis