Asymmetric Rainband Processes Leading to Secondary Eyewall Formation in a Model Simulation of Hurricane Matthew (2016)
Asymmetric Rainband Processes Leading to Secondary Eyewall Formation in a Model Simulation of Hurricane Matthew (2016)
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DOI：
10.1175/jas-d-20-0061.1
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发表时间：
2021-01
影响因子：
3.1
通讯作者：
Chau-Lam Yu;A. Didlake;Fuqing Zhang;R. Nystrom
中科院分区：
文献类型：
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作者：
Chau-Lam Yu;A. Didlake;Fuqing Zhang;R. Nystrom
在对飓风马修（2016）的模拟中，研究了导致次级眼壁形成（SEF）的不对称雨带复合体的动力学，特别关注切向风场的演变。在SEF之前，风暴经历了一个轴对称的切向风场的扩大，作为一个稳定的雨带复合体在下切变象限加强。导致这种增宽的轴对称加速度模式是一个向内下降的结构，径向范围接近100公里，在50公里半径附近的低层最大。垂直平流对流上升气流在右下角象限在很大程度上有助于低层加速度最大值，而更广泛的向内下降的模式是由于水平平流层降水在左下角象限。这种广泛的倾斜模式的正加速度是由于中尺度下降流入（MDI），这是由中层冷却驱动的层状区域内，并提请绝对角动量向内。通过检查径向速度的无旋分量进一步揭示了MDI，这表明MDI在顺风方向延伸到左上象限。在这里，MDI连接与边界层，新的对流上升气流被触发沿沿着其内边缘，这些新的上升切变，左上升气流被发现是重要的，随后的轴对称化的低层切向风最大的初始次级眼壁内。
The dynamics of an asymmetric rainband complex leading into secondary eyewall formation (SEF) are examined in a simulation of Hurricane Matthew (2016), with particular focus on the tangential wind field evolution. Prior to SEF, the storm experiences an axisymmetric broadening of the tangential wind field as a stationary rainband complex in the downshear quadrants intensifies. The axisymmetric acceleration pattern that causes this broadening is an inward-descending structure of positive acceleration nearly 100 km wide in radial extent and maximizes in the low levels near 50 km radius. Vertical advection from convective updrafts in the downshear-right quadrant largely contributes to the low-level acceleration maximum, while the broader inward-descending pattern is due to horizontal advection within stratiform precipitation in the downshear-left quadrant. This broad slantwise pattern of positive acceleration is due to a mesoscale descending inflow (MDI) that is driven by midlevel cooling within the stratiform regions and draws absolute angular momentum inward. The MDI is further revealed by examining the irrotational component of the radial velocity, which shows the MDI extending downwind into the upshear-left quadrant. Here, the MDI connects with the boundary layer, where new convective updrafts are triggered along its inner edge; these new upshear-left updrafts are found to be important to the subsequent axisymmetrization of the low-level tangential wind maximum within the incipient secondary eyewall.