拉萨市极端气候变异特征及环流机制分析

利用1961—2014年拉萨市逐日最高和最低气温数据,建立极端温度指标体系;运用统计及小波分析法,分析了拉萨市极端高温、极端低温的变化规律及其与环流的相关性。结果表明,近54年来拉萨市极端高温指数变化幅度不大,增幅为4.778℃/10 a;而极端低温指数逐年增高,增幅为10.622℃/10 a。从发生频次来看,极端高温发生频次呈现出增加趋势,极端低温发生频次总体呈现减少趋势。从年代际来看,极端高温指数在20世纪80年代显著升高,90年代及近10年的极端高温指数一直处于高值区;极端低温指数在20世纪80年代之后显著降低,说明极端低温有增暖趋势。极端气温事件在20世纪70年代存在30年的振荡周期,80年代之后振荡周期均有所减弱。从环流形势看,夏季极端高温指数与副热带高压指数、亚洲极涡指数呈正相关性,与印缅槽呈负相关性;冬季极端低温指数与副热带高压指数、亚洲极涡指数呈正相关性。

Analysis on Variation Characteristics of Extreme Climate in Lhasa City and Its Circulation Mechanism

Using the daily maximal and minimal temperature data in Lhasa station from 1961 to 2014,extremely temperature index system was established,the variation law of extreme high temperature and extreme low temperature in Lhasa City and its correlation with circulation were analyzed by the statistics and wavelet analysis method.The results showed that the variation characteristics of extremely high temperature had no significant change at a rate of 4.778 ℃/10 a.But there had a significant increase for extreme low temperature index at a rate of 10.622 ℃/10 a.From the frequency of occurrence,the frequency of extreme high temperature showed an increasing trend,and the frequency of extreme low temperature showed a decreasing trend.From the interdecadal perspective,the extreme high temperature index increased obviously after 1980s,that had been in the high value area in 1990s and nearly 10 years.Extreme low temperature index reduced significantly after 1980s,it was suggested that the extreme low temperature with the trend of warming.The extremely temperature had quasi oscillation period of 30 years during 1970s,but there had been decreased after 1980s.The extremely high temperature in summer had a significant correlation with the Pacific subtropical high index and Asia polar vortex area index,but it had a negative correlation with India-Burma trough.The extremely low temperature in winter had a significant correlation with Pacific subtropical high index and Asia polar vortex area index.