中国大陆1956～2008年极端气温事件变化特征分析

Variation Characteristics of Extreme Temperature Indices in China's Mainland during 1956-2008

利用446个国家级气象站1956～2008年共53年的日最高、最低气温资料,分析了我国大陆地区气温极端事件的变化规律。结果表明,中国大陆地区霜冻日数和结冰日数明显减少,减少显著的区域集中在北方,夏季日数和炎热夜数明显增多,增多显著的区域主要在中东部。日最高(低)气温的极大(小)值整体都有上升趋势,最高(低)气温的极大值在北方上升较明显,而在长江中下游和西南地区有下降的趋势;最高(低)气温的极小值则在全国范围都呈明显上升,极端最低气温上升尤为显著,在北方大部分地区升温速率达1.0℃·(10a)-1以上。冷夜(昼)日数普遍明显减少,53年中减少趋势为7.9d·(10a)-1[2.8d·(10a)-1];暖夜(昼)日数明显增加,增加趋势为7.0d·(10a)-1[4.1d·(10a)-1]。冷夜(昼)日数减少主要发生在冬季,其次是春、秋季,而暖昼和暖夜日数增加最显著的季节分别出现在秋季和夏季。从转折时间上看,绝对指数和极值指数的冷指数是从20世纪80年代中后期开始显著减少的,暖指数显著增加的时间则推迟到20世纪90年代中期。但相对指数的冷指和暖指都是在20世纪80年代中后期开始显著变化的。

The spatial and temporal patterns of changes in the 12 extreme temperature indices in China's Mainland are examined based on the data set of daily maximum and minimum temperature during 1956-2008. Results show that the frost days and ice days have decreased significantly,with stronger decreases in northern China,whereas summer days and tropical nights have largely increased in central and eastern China. There is a trend for the maximum （minimum） value of maximum temperature （TX） （minimum temperature （TN）） to increase in China's Mainland as a whole,with the maximum value of TX （TN） significantly increasing in northern China,but decreasing in the region of the middle and lower reaches of the Yangtze River and southwestern China. Trends of the minimum value of TX （TN） have increased rapidly in the most parts of China's Mainland,especially in northern China reaching more than 1.0 ℃·（10 a）-1. Furthermore,the annual frequency of cool nights （days） has decreased significantly by 7.9 d·（10 a）-1 [2.8 d·（10 a）-1],and the annual frequency of warm nights （days） has increased significantly by 7.0 d·（10 a）-1[4.1 d·（10 a）-1]. The maximum reduction of cold nights/days is found in winter,then in spring and fall. In the meantime,the most significant increase of warm days and nights is found in summer and fall respectively. The absolutely and extremely cold indexes exhibit a notable decreasing trend from the middle-late 1980s,meanwhile the corresponding warm indexes show a pronounced change from the mid-1990s. The relatively cold and warm indexes have significantly changed from the middle-late 1980s.