北上变性热带气旋对辽东半岛降水的影响

IMPACTS OF TROPICAL CYCLONE EXTRATROPICAL TRANSITION ON THE RAINFALL OVER LIAODONG PENINSULA

关键词:  变性  热带气旋  辽东半岛  暴雨

Key words:  extratropical transition  tropical cyclone  Liaodong Peninsula  heavy rainfall

摘要:

9711(Winnie)和0509(Matsa)是两个登陆北上影响辽东半岛的变性台风,Matsa直接登陆辽东半岛,但降水量仅为穿过渤海间接影响辽东半岛的Winnie的一半。分析其变性过程与辽东半岛热带气旋降水的关系发现,Winnie和Matsa的降水差异与其北上期间与西风带系统的相互作用密切相关。Winnie变性北上期间被中纬度西风槽"捕获",发生耦合,高层正湿位涡扰动下传,西风带冷空气与热带气旋暖湿气流相互作用,有利于对流云团的生成、发展,在半岛地区产生大暴雨的降水雨带由多个β中尺度云团组成。Matsa在北上变性过程中,只是靠近高空槽底,没有发生耦合,高层正湿位涡扰动不强,没有与低层环流相互作用,冷空气偏南偏弱,变性过程中半岛地区只有1个β中尺度云团生成,降水量较小。

Abstract:

Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET) process when they moved northward after landfall and affected Liaodong Peninsula. However,Winnie produced half as much rainfall as Matsa,although it did not strike Liaodong Peninsula directly as the latter. The relations between ET processes and the precipitation over Liaodong Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa is related to the interactions between the westerly systems and typhoons during their ET processes. Winnie coupled with upper westerly trough when it moved to the mid-latitude,and the positive anomaly of moist potential vorticity (MPV) transported downward from the upper troposphere over the remnant circulation of TC. It was favorable to the activity of warm air and cold air and caused convective cloud clusters to develop. It is found that the rain belt composes of several meso-βcloud clusters over the Liaodong Peninsula resulting in heavy rainfall. On the other hand,Matsa decouples with an upper trough during its ET process and the positive anomaly of MPV on upper troposphere and its downward transportation is weak. It is found that only one meso-βcloud cluster occurred in Matsa's rain belt during its ET process that tended to lessen rainfall over Liaodong Peninsula.