垂直切变强度对双眼墙形成前外雨带的影响
刘鑫杭、李青青、戴宇凡
南京信息工程大学，210044
关键字：热带气旋、垂直风切变、双眼墙形成、外雨带
本研究通过理想数值试验以比较不同强度环境垂直风切变对双眼墙形成前热带气旋外雨带特征的影响。五组试验结果表明，在弱环境风切变下没有双眼墙形成，而中强度垂直风切变下，随切变强度增强双眼墙结构更早形成并在其形成前顺风切左侧象限存在SBC结构( Willoughby et al. 1984, Hence and Houze 2012)。对外雨带进行层云-对流分类后显示，垂直风切变强度越大，次眼墙形成前外雨带会存在更宽广有组织化的层云结构，并在层云高层冰相和液态粒子融化蒸发作用下，对流层中低层会有更强的下沉运动和径向入流。以往研究结果显示，外雨带对流层中下层中尺度下沉入流( mesoscale descending inflow, MDI) 引起的非对称动力学有利于次眼墙形成( Qiu and Tan 2013, Yu and Didlake 2019, Wang and Tan 2020)。所以在越强风切变下，其引起的环境非对称风将对流层高层内核区更多高湿空气输送到顺切变左侧象限。通过对内核区粒子追踪模拟( Miller and Zhang 2019) 的结果也表明，强环境风切变会将更多内核区粒子向外输送，有利于形成外雨带组织化层云结构，进而驱动外雨带非对称过程。
参考文献
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