西北地区东部夏季降水年际变化特征及其与环流的关系

Interannual Variation of Summer Precipitation in the Eastern of Northwest China and its Relationship with Circulation

利用1961-2012年夏季西北地区东部降水站点资料和NCEP/NCAR同期逐月再分析资料,采用“均一化处理”和合成分析等方法分析了西北地区东部夏季降水的年际变化特征及其对应的环流异常。结果表明:(1)西北地区东部的夏季降水异常主要与南边界的水汽异常输送相联系;(2)西北地区东部夏季降水与西北太平洋副热带高压(简称西太副高)的位置及强度密切相联:当西太副高偏强偏西时,西太副高脊线西伸至我国华南地区,对应的西北地区东部上空表现为西南风异常,将大量的水汽从西北地区东部的南边界输入,有利于该地区夏季降水增多;当西太副高偏东偏弱时,西太副高脊线西伸带来的降水影响无法到达西北地区东部,对应着西北地区东部降水偏少。

Based on the meteorological station precipitation data in the Eastern of northwest China during period 1961-2012 and monthly average reanalysis data from NCEP/NCAR in the same period,using the homogenization and composite analysis methods,the characteristics of summer precipitation in the eastern of northwest China and it’s related circulation anomalies has been investigated.The results show that:(1)The anomalous precipitation in the eastern of northwest China is mainly related to the abnormal transportation of water vapor from the southern boundary.(2)The summer rainfall in the eastern of northwest China is closely related to the location and intensity of the northwest Pacific subtropical high(WPSH):When WPSH is strong and westward,the ridge of WPSH would extend westward and reach the Southern China region,resulting abnormal southwest wind over the eastern of northwest China,bringing more water vapor to the eastern northwest China inputted from its southern boundary,and favoring for more rainfall in this area;When WPSH is weak and eastward,the influence of WPSH can not reach the eastern northwest China,associated with less rainfall.