Changes in Extreme Low Temperature in China in the Winters from 1961 to 2014

Based on the six indices of temperature extreme defined by the World Meteorological Organization (WMO), this study discusses the extreme low temperature change in China in the winters from 1961 to 2014 by analyzing the daily maximum temperature (Tmax) and minimum temperature (Tmin) data at 691 stations that have no missing values and pass the homogeneity processing and quality control checks. The results show that the numbers of cool days, cool nights, frost days, and ice days have decreased in most part of China, particularly in the southern part of Northwest China, North China, the eastern part of Northwest China, East China, central China, Southwest China, and plateau regions with the trends of -0.9 d/10 a, -1.7 d/10 a, -1.5d/10 a, and -1.4 d/10 a, respectively. The maximum Tmin and minimum Tmin in the winter have increased across the country with the trends of 0.4℃/10 a and 0.6℃/10 a, respectively. The number of days of extreme low temperature fluctuated from the 1960s to the mid-1970s, and then exhibited a downward trend from the late 1970s and the early 1980s to the beginning of the 21th century while the declining trend started to slow down since 2006, which is a response to the global warming hiatus. Compared with other periods, the period from the 1960s to the 1970s represented a period with higher occurrence frequency of extreme low temperature events in the winter, which is possibly associated with the frequency and intensity of cold high pressure system over the land.