不同气候背景下新疆冬季极端冷(暖)事件的变化特征

利用1961—2013年新疆89站逐日气温和NCEP再分析高度场资料,分析了不同气候背景下新疆1961年以来冬季(12月—翌年2月)出现的极端冷(暖)事件年代际变化及与其相联系的环流特征。根据对新疆冬季极端冷(暖)事件的气候背景划分,认为新疆冬季极端冷(暖)事件在不同气候背景中都有明显的不同,全疆冬季极端冷事件存在随气候背景转变而发生区域一致变化的特征,但冬季极端暖事件的变化则有南北反相的区域差异。总体而言,新疆极端冷暖事件发生的日数趋于减少,极端冷暖事件强度也具有显著减小的趋势;北疆西部和天山两侧是气候极端性变化最显著的区域。从冷暖期环流特征的差异来看,北疆型极端冷事件减少的主要原因来自于突变后极涡减弱,而南疆型极端冷(暖)事件减少(增加)则主要受欧亚范围内大片正变高区的影响。

Inter-decadal Variability of Extreme Cold(Warm) Events in Winter in Xinjiang with Circulational Character

Inter-decadal variability of Extreme cold(warm) events in winter in Xinjiang since 1961 have been analysized based on the daily air temperature and NCEP reanalysis height field. Extreme cold events in winter in Xinjiang are divided into three types of northern Xinjiang,Southern Xinijang and Eastern Xinjiang according to the REOF result about spatial consistency and major area.In the same way, extreme warm events in winter in Xinjiang are divided into two types of northern Xinjiang and Southern Xinijang.Since 1961, Extreme cold(warm) events in winter in Xinjiang have been appeared remarkable tendency of decrease(increase),and the decrease tendency more severe than increase. Extreme cold events in whole Xinjiang are occurred the decrease mutations in 1978 and extreme warm events in Southern Xinijang have the increase mutation in 1984. Though the decrease tendency of extreme cold events occurred in whole Xinjiang,rangeability in the northern piedmonts of Tianshan mountains are larger than the west of southern Xinjiang.On the other hand,extreme warm events decrease in the west of northern Xinjiang and increase in the southern Xinjiang.Overall,the number of days of extreme cold(warm) events in Xinjiang tends to increase,and the intensity of extreme cold(warm) events also have a trend of significant decrease. The climate have more significant extreme changes in the west of northern Xinjiang and the both side of Tianshan Mountains.The material reason about the decrease of extreme cold events are the polar vortex weakened,and the changes of the extreme warm events in the southern of Xinjiang are affected by the large piece of positive anomalies of height in Eurasian circulation.