广东省气象局/佛山龙卷风研究中心白兰强团队在研究季风期珠江三角洲不规则海岸线对龙卷风中涡旋的影响中取得新突破。相关论文第二部分的数值实验于2023年12月28日发表在《大气科学进展》杂志上。

在中等尺度上，研究人员模拟再现了两个在时间和空间上与现实中涡旋程度接近的中涡旋。结果与观测结果一致，钩状回波之前的指状回波在三相点上也再现。在风暴尺度上，除了模拟的三相点上的中涡旋外，另一个中涡旋源于沿气团边界上、通过剪切不稳定性增强的离散涡旋。敏感性试验结果表明，该地区旋转风暴的模拟对当地环境细节和风暴动力学非常敏感。

来自先前存在的风暴产生的冷池浪涌的强度，影响了指状回波的包裹和中涡旋的形成。虽然模拟并不能完美地模拟在风暴尺度上的观测过程，但该模拟提供了一个更好地理解这个龙卷风热点旋转风暴成因的机会。研究结果强调，喇叭状海岸线是季风活跃期中涡旋形成的重要组成部分。希望本研究能增加预报员对区域非中气旋龙卷风环境的态势感知能力。

据悉，研究第一部分介绍了夏季季风期喇叭形海岸线的海陆对比显示，珠江三角洲西海岸通常形成风移边界。这种独特的地形在改变对涡旋形成的涡度收支中起着重要的调节作用。研究的第二部分通过多重数值模拟，以研究2020年6月1日龙卷风事件期间中涡旋的形成以及喇叭状海岸线的作用。

附：英文原文

Title: Influence of Irregular Coastlines on a Tornadic Mesovortex in the Pearl River Delta during Monsoon Season. Part II: Numerical Experiments

Author: Lanqiang Bai, Dan Yao, Zhiyong Meng, Yu Zhang, Xianxiang Huang, Zhaoming Li

Issue&Volume: 2023-12-28

Abstract: As demonstrated in Part I of this study, wind-shift boundaries routinely form along the west coast of the Pearl River Delta due to the land–sea contrast of trumpet-shaped coastline in summer monsoon season. It is proposed that the unique topography has played essential roles in the modification of vorticity budget of mesovortex formation. Part II aims to examine the mesovortex genesis during the 1 June 2020 tornadic event and the roles of trumpet-shaped coastline through multiple numerical simulations. On mesoscale, the modeling reproduced two mesovortices that were in close proximity in time and space to the realistic mesovortices. In agreement with observations, finger-like echoes preceding hook echoes were also reproduced over the triple point. On storm scale, in addition to the modeled mesovortex over the triple point, another mesovortex originated from an enhanced discrete vortex along airmass boundary via shear instability. Results from sensitivity experiments suggest that simulation of rotating storms in this region is sensitive to local environmental details and storm dynamics.  The strengths of cold pool surges from preexisting storms influence the wrap-up of finger-like echoes and the mesovortex formation. Although the simulations did not perfectly mimic the observed processes on storm scale, they provide an opportunity to better understand the genesis of rotating storms in this tornado hotspot. The findings suggest that the trumpet-shaped coastline is an important component for the mesovortex production during the monsoon active season. It is hoped that this study will increase the situational awareness for forecasters regarding the regional nonmesocyclone tornado environments.

DOI: 10.1007/s00376-023-3096-4

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-023-3096-4viewType=HTML