Variety Characteristics of Daily Minimum Air Temperature in China in Recent 50 Years

Based on the data of daily mean minimum air temperature of a year and January, April, July, October (standing for winter, spring, summer and autumn respectively) from 241 stations in 1951-2000, we divided the whole China into eight regions, and studied the characteristics of daily minimum air temperature in different regions and seasons. By the research we found that under the background of the global climate warming, the increase of daily minimum air temperature was remarkable. Especially in the late of the mid 1980s, the increase in the northern China was more conspicuous than that in the southern China and the Qinghai-Xizang Plateau. During the 50 years, the first warming catastrophe of daily minimum air temperature took place around the mid 1970s. The warming trend in this time was not significant, mainly in the form of fluctuation. There was the second warming catastrophe after the mid 1980s, the warming trend in this time was significant. By studying the data of different seasons, we still found that the daily minimum air temperature has a trend of decline in the southern China and the Qinghai-Xizang Plateau.