Collaborative Research: Basic Studies in Three-dimensional Tropical Cyclone Intensification

飓风是一种特别具有破坏性的热带天气系统，每年6月至11月期间威胁着美国大西洋沿岸的人口中心。发育良好的飓风在其核心区表现出相对较高的几何组织性，中心无云眼被一个近似的云环包围，称为眼壁，在那里发现了最强烈的地面风。现有的飓风结构理论已经在轴对称环流的框架内利用了这种几何结构，这些方法为研究这种破坏性现象提供了有益的见解。这项资助的项目旨在更好地了解轴不对称或“涡旋”过程在热带气旋增强中的作用。这项研究项目将通过对热带风暴加强阶段的内部涡旋过程进行综合、多管齐下的评估，重点研究飓风涡旋过程的动力学和热力学。具体地说，热带气旋指数将利用传统的欧拉分析和基于拉格朗日相干结构的新分析方法进行诊断分析，以评估涡旋结构对热带风暴轴对称分量的影响。拉格朗日相干结构有助于识别风流中的结构，这些结构往往会将气流分成不同的区域。这些区域将有助于识别涡旋的动量和热量输送。高分辨率计算机模拟将是本研究的基础工具，并将研究在不同计算机分辨率下解析和分析重要涡旋的能力。这项研究对大气科学、流体力学和动力系统领域具有重要意义。确定各种涡旋现象在平均飓风结构中的多种作用具有很高的学术价值。改进旋涡对飓风的风结构和强度的影响的特征，将对今后的参数化发展起到有益的指导作用。由于业务模式不能很好地解决这些细微尺度特征，更好地了解涡旋过程对热带风暴迅速加强的重要性，将有助于进一步提高预测飓风造成的重大危险的技能。

Hurricanes are especially destructive tropical weather systems that threaten population centers of the United States along the Atlantic coast between June and November every year. Well-developed hurricanes display a relatively high degree of geometrical organization in their core region, with a central cloud-free eye surrounded by an approximate ring of clouds, called the eyewall, where the most intense surface winds are found. Existing theories for hurricane structure have exploited this geometric organization in the framework of axial symmetric circulation and these approaches have provided useful insights into this destructive phenomenon. This funded project aims to gain a better understanding of the roles of axial asymmetries or "eddy" processes in the intensification of tropical cyclones. This research project will focus on the dynamics and thermodynamics of eddy processes in hurricanes using an integrated, multi-pronged evaluation of the internal eddy processes during the intensification stage of tropical storms. Specifically, the PIs will conduct diagnostic analyses to evaluate the impact of the eddy structures on the axial symmetric component of tropical storms by employing conventional Eulerian analyses and a new analysis method based on Lagrangian coherent structures. Lagrangian coherent structures help identify structures within the wind flow that tend to separate the flow into distinct regions. These regions will aid in the identification of momentum and heat transport by the eddies. High resolution computer simulation will be the foundational tool in this study, and the ability to resolve and analyze the important eddies at different computer resolutions will be investigated.This research is of interest to atmospheric science, fluid dynamics and dynamical system communities. The determination of the manifold roles of various eddy phenomena on the mean hurricane structure is of high intellectual merit. Improved characterization of the effects of eddies on the wind structure and intensity of hurricanes will serve as useful guidance in the development of future parameterizations. Since operational models do not well resolve these fine-scale features, the improved understanding of the importance of eddy processes for the rapid intensification of tropical storms would help further increase the skill in predicting the substantial hazard posed by hurricanes.