Changes of Extreme Temperatures for Heihe River Basin from 1961 to 2010

th , 2012; revised: Aug. 11 th , 2012; accepted: Aug. 26 th , 2012 Abstract: Based on the measured extreme temperatures of 9 stations from 1961 to 2010, the changes of an- nual and seasonal extreme temperatures in Heihe River basin were analyzed by using the trend slope and Mann-Kendall method. The results showed that the generally increasing trends of annual extreme tempera- tures occurred all over the basin and the increase of extreme minimum temperatures were greater than those of extreme maximum temperatures, especially the extreme minimum temperature in Shandan station with an increasing rate of 0.95˚C/10a. The increase of annual extreme minimum temperatures in lower reaches was greater than those in upper and middle reaches of basin. The extreme minimum temperatures began to in- crease at the beginning of 1970's, while the extreme maximum temperatures at the end of 1980's. The sea- sonal differences in trends of extreme temperatures were clear, and the most obvious season was winter in trends of extreme maximum temperatures and autumn in trends of extreme minimum temperatures.