AGS-PRF: Extreme Near-Surface Wind Speeds Associated with Coherent Small-Scale Vortices within the Boundary Layer of Tropical Cyclones

智慧价值热带气旋拥有地球上最强的一些近地表风速，然而，强烈飓风特有的极端(80-100m/S)局部风速的产生机制仍鲜为人知。初步研究表明，最强风经常出现在强上升气流(10-25m/S)附近，并与连贯的小尺度(1-3公里)涡旋有关。在这个项目中，将研究这些强烈上升气流及其相关涡旋的结构、动力学和影响。这将通过使用天气研究和预报模式(WRF)和布莱恩云模式(CM1)对真实数据和理想化热带气旋的高分辨率模拟进行分析来实现。将与首席调查员以前收集的滴落探空仪观测数据集进行比较。最后，Nolan的线性涡旋模式(3DVPAS)将被用来确定这些涡旋是否是飓风眼壁边界层动力不稳定的结果。这些极端上升气流(在4级和5级飓风中普遍存在)可能会通过它们对边界层中的湍流混合、轴对称和地面通量的影响来影响飓风的整体强度。因此，除了研究涡旋本身，这项研究还将使用大涡模拟(LES)来确定这些特征可能会(也可能不会)对风暴的更大尺度结构产生影响。这项研究将在NCAR进行，理查德·罗通诺博士是赞助科学家，乔治·布莱恩博士是合作科学家。更广泛的影响由于登陆热带气旋中最严重的风灾被观察到是高度局部性的，有可能是这些小尺度涡旋造成的。因此，有必要增加我们在这方面的认识，这个项目可以改进模拟和更好地预报登陆时的地面风场。这些特征也对研究飞机构成了危险，因此正确了解遇到这些上升气流的风险将是有益的。因此，这项工作有可能与热带气旋研究界、风工程界和整个社会高度相关。

Intellectual meritTropical cyclones possess some of the strongest near-surface winds found anywhere on earth, yet the mechanisms by which the extreme (80-100 m/s) local wind speeds characteristic of intense hurricanes are produced remain poorly understood. Preliminary research has shown that the strongest winds are often found in close proximity to intense (10-25 m/s) updrafts and are associated with coherent small scale (1-3 km) vortices. In this project, the structure, dynamics, and impact of these intense updrafts and their associated vortices will be investigated. This will be accomplished through the analysis of high-resolution simulations of both real-data and idealized tropical cyclones, using the Weather Research and Forecasting Model (WRF) and the Bryan Cloud Model (CM1). Comparisons will be made to a dataset of dropsonde observations previously collected by the principal investigator. Finally, the linear vortex model of Nolan (3DVPAS) will be utilized to determine whether these vortices are a consequence of a dynamical instability of the boundary layer in hurricane eyewalls.These extreme updrafts (which are ubiquitous in category 4 and 5 hurricanes) might influence the overall intensity of hurricanes, through their effects on turbulent mixing in the boundary layer, axisymmetrization, and surface fluxes. Therefore, in addition to investigating the vortices themselves, the study will also use Large Eddy Simulations (LES) to determine the impact that these features may (or may not) have on the larger scale structure of the storm.This project will be undertaken at NCAR, with Dr. Richard Rotunno as the sponsoring scientist, and Dr. George Bryan as a collaborating scientist.Broader impacts As the most severe wind-damage in landfalling tropical cyclones has been observed to be highly localized, it is possible that these small-scale vortices are responsible for such occurrences. It is therefore imperative to increase our understanding in this respect, and this project could lead to improved modeling and better forecasts of the surface wind field at landfall. These features also pose a danger to research aircraft, and so a proper understanding of the risk of encountering these updrafts would be beneficial. Therefore, this work has the potential to be highly relevant to the tropical cyclone research community, to the wind engineering community, and to society at large.