Abstract:

Based on NCEP/NCAR monthly global reanalysis data from 1961 to 2008，west Pacific subtropical high index information
from National Climate Center and summer precipitation data of Shaanxi，the influence of preceding atmospheric circulation anomalies on
summer rainfall in Shaanxi and its mechanism were discussed． Results showed that there were close relationship between droughts
( floods) in summer of Shaanxi and westerly belt circulation anomalies at low and high latitude in the preceding autumn，winter and
spring． When positive PNA atmospheric teleconnection distribution was appeared in preceding atmospheric circulation，the western Pacific
subtropical high would strengthen and extend westward in summer，and the Balkhash Lake and Okhotsk Sea block high would also
be stronger，which resulted in abnormal southwest wind transporting water vapour over the central and southern Shaanxi，and abnormal
north wind bringing cold air over the northern Shaanxi，there would be flooding in summer of Shaanxi，whereas，it would be drought．
The location of the subtropical high ridge mainly affected the move of rainfall belt in north and south direction in summer of Shaanxi．
When SST in the middle east equatorial Pacific was higher，western Pacific subtropical high was stronger and moved westward in the
coming summer，then there would be more rain in summer of Shaanxi．

Key words: droughts /floods in summer of Shaanxi, the preceding atmospheric circulation anomalies, western Pacific subtropical high index, Pacific － north America teleconnection ( PNA

摘要：

利用NCEP/NCAR 提供的1961 ～ 2008 年500 hPa 位势高度值和风场月平均再分析资料、国家
气候中心提供的西太平洋副高指数资料和陕西夏季降水资料，探讨了前期大气环流异常对陕西夏季
旱涝的影响及机制。结果表明，陕西夏季旱涝与前期秋季、冬季、春季的低纬和中高纬西风带大气环
流异常密切相关，旱涝年对应不同的前期大气环流特征，当前期高度场上从太平洋到北美呈“+ －
+”的距平波列结构，即正的PNA 大气遥相关分布时，夏季西太平洋副高增强、偏西，中高纬度巴尔喀
什湖和鄂霍次克海阻塞高压也随之加强，陕西中南部有异常西南风水汽输送，北部有北风异常，陕西
夏季易涝，反之易旱。副高脊线位置主要影响陕西夏季雨带的南北移动。前期太平洋海温通过影响
西太平洋副高强度、位置变化影响陕西夏季降水，当前期秋、冬赤道中东太平洋海温偏高，海温呈El
Ni珘no 型分布时，夏季副高偏强、偏西，陕西夏季降水偏多。

关键词:  , 陕西夏季旱涝, 前期大气环流异常, 西太平洋副高指数, 太平洋&mdash, 北美遥相关( PNA)