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

热带气旋拥有地球上最强的近地表风，但强烈飓风特有的极端风速（80-100米/秒）的产生机制仍然知之甚少。 初步研究表明，最强的风往往出现在强烈（10-25米/秒）的上升气流附近，并与连贯的小尺度（1-3公里）涡旋有关。 在这个项目中，这些强烈的上升气流及其相关的漩涡的结构，动力学和影响将被调查。 这将通过使用天气研究和预报模式（WRF）和布莱恩云模式（CM 1）对真实数据和理想化热带气旋进行高分辨率模拟分析来实现。将与主要研究者先前收集的下投式探空仪观测数据集进行比较。 最后，将利用诺兰的线性涡旋模型（3DVPAS）来确定这些涡旋是否是飓风眼墙边界层动力不稳定的结果。这些极端的上升气流（在4级和5级飓风中普遍存在）可能会影响飓风的整体强度，通过它们对边界层湍流混合、轴对称化和表面通量的影响。 因此，除了调查涡流本身，该研究还将使用大涡模拟（LES）来确定这些特征可能产生的影响。（或可能没有）对风暴的更大规模的结构。这个项目将在NCAR进行，与博士理查德Rotunno作为赞助科学家，和乔治布赖恩博士作为合作科学家。更广泛的影响由于登陆热带气旋造成的最严重的风灾被观察到是高度局部化的，这些小尺度的涡流可能是造成这种情况的原因。 因此，必须增加我们在这方面的理解，该项目可能会导致改进的建模和更好的预报登陆时的地面风场。 这些特征也对研究飞机构成危险，因此正确理解遇到这些上升气流的风险将是有益的。 因此，这项工作有可能是高度相关的热带气旋研究界，风工程界，并在整个社会。

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.