热带对流活动与长江中下游和华北地区夏季旱涝的关系

Relationship between tropical convection and summer rainfall over the mid-lower valleys of the Yangtze and north China

利用 OL R资料 ,结合 NCEP/NCAR再分析资料 ,研究了长江中下游、华北地区旱、涝年热带对流活动特征 ,着重讨论了 ITCZ位置、季节内低频振荡与两地区旱、涝气候异常的联系。结果发现 :1月赤道太平洋上对流活动的异常与夏季两地区旱涝有密切的关系 ,冬季赤道太平洋对流活动东强西弱 (东弱西强 ) ,则对应夏季长江中下游地区易偏涝 (旱 ) ,华北地区易偏旱 (涝 ) ;ITCZ的位置异常偏南 (北 )时 ,夏季长江中下游地区易偏涝 (旱 ) ,华北地区易偏旱 (涝 ) ;两地区旱、涝年 OL R季节内低频振荡存在差别 ,主要表现在低频波的传播方式以及强度 ,这些差异的存在可能是导致两地区夏季降水出现差异的重要原因之一。

In the content of 1975~1995 OLR data and 1 979~1995 NCEP/NCAR reanalysis data,the features of tropical convective activitie s are discussed in wet/dry summers over the mid-lower valleys of the Yangtze an d north China,with focus on the relationship between the position/LFO of ITCZ an d the flood/drought over the two areas.Results show that: 1)there exits a close relationship between the flood/drought over the study areas in summer and the co nvective activities over the tropical Pacific in the preceding January,with stro ng convection in eastern Pacific and weak in western Pacific corresponding to fl ood in the mid-lower valleys of the Yangtze and drought in north China,and v.v. ;2)when ITCZ lies in the south(north) of its mean position,there will be flood(d rought) over the mid-lower valleys of the Yangtze and drought(flood) over north China;3)there are differences in LFO of OLR between wet/dry summers,which is ma inly characterized by its propagation and intensity.Such a differences may serve as one of the important causes for the difference of summer rainfall between th e two areas.