冬春亚洲大气环流与华北中部夏季降水的相关分析

利用1957~2002年的NCEP/NCAR 500 hPa再分析资料以及同期华北地区夏季降水资料,分析了华北中部夏季降水与前期环流的关系。结果表明:夏季华北中部降水的多少与冬季东亚槽强弱、春季巴尔喀什湖到贝加尔湖的蒙古高原地区高度场呈显著相关。20世纪80年代中期以前冬季东亚槽偏强、春季蒙古高原地区高度值偏低;80年代中期之后冬季东亚槽开始转弱、春季蒙古高原地区高度值偏高。这与华北夏季降水的演变趋势相对应。说明冬季东亚槽的减弱以及春季蒙古高原地区高度值偏高是近年来华北夏季降水减少的原因之一。冬季东亚槽强对应夏季西太平洋副高在日本海地区高度呈偏强趋势,有利华北中部夏季降水偏多;春季蒙古高原地区高度值偏高有利于华北夏季出现西高东低形势,华北中部夏季降水易偏少。

Correlation Analysis of General Atmospheric Circulation in Winter and Spring in Asian and Summer Precipitation in Central North China

An analysis is made of the relation between summer precipitation and antecedent circulation by using NCAR/NCEP 500hPa reanalysis data and summer precipitation data from central North China from 1957 to 2002.The results show that there is obvious correlation between summer precipitation,the intensity of winter East Asian Trough and the spring height field over the Mongolia Plateau from Balkhash to Baikal.Winter East Asian Trough was stronger and the height over the Mongolia Plateau in spring was lower than normal before the middle 1980s,but vice versa after 1985.The trend is consistent with the variation of summer precipitation.It is demonstrated that the reasons for summer precipitation decrease include the weakened winter East Asian Trough and higher spring Mongolia Plateau height field.When the winter East Asian Trough is strong,the summer West Pacific Subtropical High is strong over the Japan sea region correspondingly,which is favorable for the increase of summer precipitation over the central North China.When the heights of the spring Mongolia Plateau height field are higher,it is favorable for the occurrence of the circulation pattern "high in the west and low in the east," in which less-than-normal summer precipitation in central North China is likely to happen.