新疆夏季降水年代际转型的归因分析

Possible mechanism for the interdecadal change of Xinjiang summer precipitation

本研究针对我国内陆新疆地区在20世纪80年代末出现由暖干向暖湿的年代际转型,从大气环流因子进行归因分析.结果显示,位于东亚沿海地区的东亚-太平洋型遥相关波列(EAP)的强度和位置的年代际加强和偏移对于新疆地区此次气候的干湿转型具有重要贡献.转型之前EAP强度偏弱,位置相对偏东,对新疆夏季降水变化没有明显贡献,且影响新疆夏季降水发生的主要环流系统是位于中纬度欧亚大陆上空的异常纬向波列.转型后EAP强度偏强,位置相对前期向西偏移,因此从西北太平洋向我国内陆地区的异常水汽输送显著增强,使得新疆地区大气含水量增加,从而导致20世纪80年代末以后新疆夏季降水的增加.

Some studies have indicated that an abrupt climate change of Xinjiang summer precipitation has occurred in the late 1980s, changing from warm-dry to warm-wet condition. This study further investigates the corresponding atmospheric circulation anomalies of this interdecadal change basing on NCEP/NCAR and ERA40 reanalysis datasets. The results demonstrate that the intensified and westward East Asian-Pacific teleconnection （EAP） along the East Asian coast made a great contribution to the increase of Xinjiang summer precipitation after the late 1980 s. Before this transition, the EAP was much weaker at a position relatively to the east and presented no contribution to the variability of summer precipitation. The main system affecting that is the anomalous zonal wave train over the Eurasian continent. After this transition, the EAP pattern is observed to be much stronger and more westward than before. Accordingly, the water vapor flow anomalies associated with this intensified and westward EAP extend from the northwestern Pacific over Xinjiang region, which is partly late 1980 s. resp land China, implying significant onsible for the increased summe increase of water vapor r precipitation after the