影响辽东半岛两个台风Meari和Muifa暴雨环流特征的对比分析

Meari(1105)和Muifa(1109)是两个路径相似并在辽东半岛产生强降水的热带气旋。但Meari强降水持续时间长,而Muifa时间短。利用中国气象局热带气旋年鉴、FY_2D(0.1°×0.1°)云顶亮温资料、大连地区逐时自动气象站降雨量资料、常规观测资料和NCEP/NCAR再分析资料,对两个台风影响辽东半岛的降水过程进行了对比分析。结果表明:(1)Meari影响辽东半岛时强度较弱,但与低空东南急流相连获得丰富水汽供应,衰减缓慢;Muifa影响时强度较强但与低空急流水汽通道快速断开而衰减迅速。(2)两个台风均进入西风槽区而变性,但两者影响辽东半岛时处于不同的变性阶段。Meari为半冷半暖结构,其北侧中尺度对流活动发展旺盛,非对称结构明显;Muifa低层环流已变性为冷中心,云系结构孤立且无发展。(3)两次过程中辽东半岛位于台风不同的对流发展区域是其降水强度差异的原因之一。辽东半岛位于Meari北侧,低层的水平辐合较强,水平风垂直切变较大,深厚的上升运动维持;Muifa影响下辽东半岛位于其西侧,受偏北风下沉气流控制,不稳定度和动力抬升条件减弱。

Comparison of Synoptic Circulations of Heavy Rain Associated with Typhoons Meari and Muifa over Liaodong Peninsula

Tropical cyclones(TC) Meari(1105) and Muifa(1109) had similar tracks and caused severe rainfall over Liaodong Peninsula. However, Meari produced heavy precipitation with a much longer time period, although with weaker intensity, than that of Muifa. Using the Tropical Cyclone Yearbook, Fengyun(FY_2D) 0.1°×0.1° cloud top brightness temperature data, hourly rainfall observations from Dalian automated weather station, conventional observational data, and National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis data, the two TC cases that affected Liaodong Peninsula were compared and diagnosed. The results showed that(1) Meari had relatively weak intensity when affecting Liaodong Peninsula; however, it decayed slowly due to abundant moisture supply from the low-level southeast jet. Muifa was stronger than Meari, but its strength decreased rapidly due to the cut-off with the low-level moisture jet.(2) Meari and Muifa experienced extratropical transition when approaching westerly troughs. However, they possessed different structures when affecting Liaodong Peninsula:Meari had a hybrid structure with remarkable baroclinic instability, and mesoscale convection developed on its north side; while Muifa transformed into a cold core in low-level circulation and its cloud structure showed isolated features.(3) One of the causes of the difference in precipitation amount over Liaodong Peninsula was their different locations in the typhoon circulation. Liaodong Peninsula was located in the north of Meari, possessing strong low-level convergence, vertical wind shear, and deep and persistent vertical motion. However, its location was in the west of Muifa, where the northerly wind produced downward motion and dynamic lifting was reduced.