Based on the daily precipitation data at 18 meteorological stations of Hainan Island from 1969 to 2018, the spatio-temporal change characteristics of precipitation randomness were analyzed by using information entropy method, Mann-Kendall trend test and spatial interpolation technique of inverse distance weight. The results show that the uneveness of monthly apportionment of annual precipitation and precipitation days increased from east to west of Hainan Island. In recent 50 years, the monthly apportionment unevenness of annual precipitation and precipitation days showed an increasing trend in northern and western areas and part areas of southern Hainan Island, while it showed a decreasing trend in the rest areas on the whole. The spatial distribution of randomness of daily precipitation was significantly different in the whole year and four seasons in Hainan Island, and they were significantly and positively correlated with the proportion of rainstorm and above rainfall days. In terms of time, the randomness of daily precipitation in the whole year and four seasons increased in most cities (counties) of Hainan Island from 1969 to 2018, especially the probability of strong precipitation increased in four seasons. The rainstorms to torrential rains in central, northwestern, eastern and eastern Hainan Island should be paid enough attention in spring, summer, autumn and winter, respectively.
Based on daily conventional observation data at 19 meteorological stations of Hainan Island from 1980 to 2018, the climatic season in Hainan Island was divided according to China’s meteorological industry standard (QX/T152-2012). Then, the comfortable degree of human body was calculated by using sensible temperature of human body based on ‘golden ratio’ method. And on this basis the comprehensive division of human body comfortable degree was done in each season in Hainan Island by using rotated empirical orthogonal function (REOF), further the optimum comfortable zones of climatotherapy rehabilitation were obtained in Hainan Island. The results are as follows: (1) The climate was mild and moist in Hainan Island, and the annual average temperature was 22.9 to 25.3 ℃, the average annual precipitation was 1157 to 2615 mm, the annual average relative humidity was 74% to 86%, and the annual average specific humidity was 14.8 to 16.4 g·kg-1, which was suitable to rehabilitation. (2) Compared with the conventional climate statistical method, the meteorological industry standard was more in accordance with season division in Hainan Island. According to the climate division, the summer was from mid-March to mid-November in Hainan Island, the autumn and spring were from mid-November to next mid-March, which indicated that there wasn’t winter in Hainan Island, and the optimum period of climatotherapy rehabilitation appeared in spring and autumn. (3) The comfortable region of human body in spring and autumn located in northern Hainan, central Hainan and southern Hainan. Overall, the climate in central Hainan was the most optimal, and the climate in three regions was stable from 1980 to 2018.
