长江流域夏季极端高温的年代际变化特征及其与大西洋多年代际振荡的关系

本文基于地面观测资料和NCEP/NCAR再分析数据,利用经验正交函数分析、线性回归分析等方法对1960—2016年夏季(6—8月)长江流域的极端高温(Extreme High Temperature,EHT)事件的强度、暖昼、暖夜发生日数的年代际特征及其对应大气环流进行分析,并探讨了EHT事件与大西洋多年代际振荡(Atlantic Multidecadal Oscillation,AMO)的关系。结果表明,中国夏季长江流域的极端高温事件存在明显的年代际变化特征,其中1960—1970年和2002—2016年为暖时期,1971—2001年为冷时期。相较于冷时期,暖时期在高温强度、暖昼和暖夜的发生日数方面均明显偏暖。针对于该极端高温年代际特征的成因,研究结果表明,暖时期位于长江流域北部的对流层中高层异常反气旋和偏北偏西的西太平洋副高有利于该地区下沉运动的增强,进而有利于极端高温的出现。同时,在对流层低层,位于中国东部的异常反气旋将低纬地区的暖湿气流携带至长江流域,这也有利于长江流域EHT事件的发生。此外,进一步分析表明,AMO与长江流域夏季EHT事件在年代际尺度上存在明显的关系,AMO超前中国夏季长江流域的EHT事件6~8 a,这对预测中国长江流域极端高温事件具有一定的指示作用。

Interdecadal Variation of Summer Extreme High Temperature in the Yangtze River and Its Relationship with Atlantic Multidecadal Oscillation

The Yangtze River Basin is one of the most important economic zones in China,and it is also an area with high temperature in summer.Based on the ground observation data and NCEP/NCAR reanalysis data,this paper analyzes the extreme high temperature(EHT)in the Yangtze River Basin during the summer of 1960—2016(June to August)by using empirical orthogonal function analysis and linear regression analysis,The intensity of the event,the decadal characteristics of warm days and warm nights and the corresponding atmospheric circulation are analyzed.The relationship between EHT event and the Atlantic multigenerational oscillation(AMO)is also discussed.The results show that the EHT events over the Yangtze River Basin in summer in China have obvious interdecadal variation characteristics,in which 1960—1970 and 2002—2016 are warm periods,and 1971—2001 are cold periods.Compared with the cold period,the intensity of high temperature,the days of warm day and warm night in the warm period are obviously warmer.According to the cause of the interdecadal characteristics of the extreme high temperature,we find that the anomally anticyclone in the middle and upper troposphere in the northern part of the Yangtze River Basin and the West Pacific subtropical high in the warm period are conducive to the enhancement of the subsidence movement in the region and the emergence of the extreme high temperature.At the same time,in the lower troposphere,the anomalous anticyclone in the east of China carries the warm and humid air from the low latitude region to the Yangtze River Basin,which is also conducive to the occurrence of EHT events in the Yangtze River Basin.In addition,we further found that the interdecadal variation characteristics of summer EHT events in the Yangtze River Basin are obviously related to AMO,which is 6~8 years ahead of the summer EHT events in the Yangtze River Basin of China,which has a certain indicative role in predicting the extreme high temperature events in the Yangtze River Basin of China.