Changes in Temperature Extremes Based on a 6-Hourly Dataset in China from 1961-2005

Changes in Chinese temperature extremes are presented based on a six-hourly surface air temperature dataset for the period 1961-2005. These temperature series are manually observed at 0200, 0800, 1400, and 2000 Beijing Time （LST）, and percentile based extreme indices of these time series are chosen for analysis. Although there is a difference in time among the different time zones across China, as more than 80% of the stations are located in two adjacent time zones, these indices for all the stations are called warm （cold） nights （0200 LST）, warm （cold） mornings （0800 LST）, warm （cold） days （1400 LST）, and warm （cold） evenings （2000 LST）, respectively for convenience. The frequency of the annual warm extremes has generally increased, while the frequency of the annual cold extremes has decreased, and significant changes are mainly observed in northern China, the Tibetan Plateau, and the southernmost part of China. Based on the national average, annual warm （cold） nights increase （decrease） at a rate of 5.66 （-5.92） d （10 yr）^-1, annual warm （cold） days increase （decrease） at a rate of 3.97 （-2.98） d （10 yr）^-1, and the trends for the annual warm （cold） mornings and evenings are 4.35 （-4.96） and 5.95 （-4.35） d （10 yr）^-1, respectively. For China as a whole, the increasing rates for the occurrence of seasonal warm extremes are larger in the nighttime （0200, 2000 LST） than these in the daytime （0800, 1400 LST）, the maximal increase occurs at 2000 LST except in the summer and the minimal increase occurs at 1400 LST except in autumn; the maximal decrease in the occurrence of seasonal cold extremes occurs at 0200 LST and the minimal decrease occurs at 1400 LST.