双模态风垂直切变对台风结构和强度的作用分析  

Influence of bimodel vertical wind shear on typhoon structure and intensity

作　　者：李启华[1] 陆汉城[1] 钟玮[1] 谭伟才[1] 孙源[1] 

机构地区：[1]中国人民解放军理工大学气象海洋学院,南京211101

出　　处：《地球物理学报》2016年第7期2377-2392,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41175054;41275002);国家自然科学基金重点项目(41230421)资助

摘　　要：本文应用WRF(v 3.4)模式输出资料,揭示了风垂直切变(Vertical Wind Shear:VWS)在垂直方向上的波状变化特征,这种波状变化在台风不同发展时期又有不同形态,其中在持续强盛期呈双模态分布.应用VWS引起的次级垂直环流影响台风对流分布和强度变化的基本原理,用模式资料分析发现:对流层中层具有的VWS是整层VWS的主要部分,台风强度变化滞后VWS的形态突变6h左右;双模态波状变化的VWS产生的次级环流和台风垂直环流的配置不同使台风强对流带结构变得不对称及眼墙区对流强度在垂直分布上变得不均匀,随着持续强盛期涡旋运动的增强,强对流带分布又趋于对称.又根据VWS形成的垂直方向上涡度力分布不均匀引起台风内中尺度滚轴状对流带不稳定发展原理,分析表明:对流层中、低层的涡度力有利于对流不稳定增强,垂直速度的最大值与风垂直廓线的拐点在同一高度上,这与理论模型的结论一致.因此,VWS的波状变化分布特征不仅影响台风强对流带中尺度结构的改变,也对台风持续强盛具有重要作用;同时也是台风内滚轴状对流带不稳定的可能启动机制.Model output data from WRF（v3.4）are used in this study to analyze the influence of the vertical wind shear（VWS）on typhoon structure and intensity.A wave vertically distribution of VWS is revealed.The wave varies with different stage of typhoon development,and exhibits bimodel distribution in the mature stage.Based on the general mechanism of VWS′s influence on typhoon′s intensity and distribution of convection,we found the VWS in the middle troposphere is the major part of the total VWS.The change of the typhoon intensity occurs about 6hours after the abrupt change of VWS′s wave.The secondary circulation induced by bimodel VWS creates an asymmetric deep convection structure and a non-homogeneous vertical distribution of convection in eye wall.With the increased intensity of cyclonic circulation,the distribution of strong convection tends to be symmetric gradually.According to the mechanism that VWS-induced uneven distribution of vorticity can initialize mesoscale convective-rolls associated with convective instability,we also found the vorticity in the lower-to-middle troposphere is favorable for development of convective instability.The maximum vertical velocity is generally at the same altitude with the inflection ofthe vertical wind profile,which is consistent with the results from theoretical models.Therefore,the bimodel VWS not only has influence on the change of the mesoscale structure of strong convection in typhoons,but also is crucial to the maintenance of a strong mature typhoon.Furthermore,the wave distribution of VWS might be the trigger of instability accounting for the convective-rolls in typhoon.

关 键 词：风垂直切变 双模态 热带气旋 中尺度对流带 

分 类 号：P421[天文地球—大气科学及气象学]