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A Comprehensive Observational Examination of the Physical Processes that Link Tropical Cyclone Vortex Alignment to Future Intensity Change

对将热带气旋涡旋排列与未来强度变化联系起来的物理过程进行全面观测检查

基本信息

批准号：
2241605
负责人：
George Alvey
金额：
$ 54.59万
依托单位：
University of Miami
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2023
资助国家：
美国
起止时间：
2023-04-01 至 2026-03-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2241605&HistoricalAwards=false
关键词：
Comprehensive Observational Examination Physical Processes

项目摘要

The vast societal impacts of rapidly intensifying tropical cyclones, or hurricanes, are exacerbated not only due to poor predictions that create challenges for emergency management decisions, but they also pose a significant threat to coastal populations as these storms quickly become more destructive. Prior to undergoing rapid intensification, which is defined as a quick or sudden increase in the strength of the storm, hurricanes develop from weaker tropical cyclones that initially are more susceptible to detrimental influences from the surrounding environment. A significant environmental influence is vertical wind shear, which is a change in the direction or strength of the wind with increasing height, and can negatively impact the development of hurricanes. Vertical wind shear can cause a displacement of the mid–upper level storm circulation from the low-level circulation. This misalignment of centers allows more unfavorable, dry air in the surrounding environment to enter a storm’s inner core, a deterrent to further intensification. Therefore, previous work strongly supports the notion that a key step for tropical cyclone intensification is achieving an alignment of centers throughout the depth of the atmosphere. However, it is still not well understood how or why some initially misaligned storms transition toward a more vertically-aligned state and rapidly intensify. In some recent, notable U.S. landfalling hurricanes, uncertainty over the processes associated with this structural transition has caused considerable forecast challenges, particularly with intensity change. This project will use a comprehensive radar dataset to provide insights on the processes associated with the alignment of centers prior to and during rapid intensification.Previous observational case studies and idealized modeling simulations have identified multiple pathways through which a misaligned tropical cyclone vortex can transition toward an aligned state. However, it is widely believed that convectively-driven diabatic processes are important in the alignment process, regardless of the pathway. Because all tropical cyclones feature convection to some degree, it is unclear how precisely precipitation structures associated with vortex alignment events differ from storms that remain misaligned. This uncertainty is a key motivator for this study. Furthermore, because these different alignment pathways have only been documented either in idealized modeling systems or in observational case studies of individual storms, robust conclusions as to how precipitation, particularly in weak tropical cyclones, interacts with the surrounding environment and affects the vortex alignment pathway in nature remains ambiguous. Therefore, this project aims to build on previous work by contextualizing the vortex, precipitation, and environmental characteristics associated with a given alignment pathway. The overall goal of this research is to investigate weak tropical cyclones using a novel airborne and ground-based Doppler radar database, which provides the most comprehensive observational database of tropical cyclone structure to date. This assessment of precipitation structure at high resolution will help reveal the three-dimensional structure, from which the physical processes responsible for vortex alignment can be determined.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

迅速增强的热带气旋或飓风的巨大社会影响加剧，这不仅是因为预测不佳，给应急管理决策带来挑战，而且还因为这些风暴迅速变得更具破坏性，对沿海人口构成重大威胁。在经历快速强化（定义为风暴强度的快速或突然增强）之前，飓风是由较弱的热带气旋发展而来的，这些热带气旋最初更容易受到周围环境的不利影响。一个重要的环境影响是垂直风切变，这是风的方向或强度随着高度的增加而变化，并可能对飓风的发展产生负面影响。垂直风切变可使中高层风暴环流从低层环流中位移出来。这种中心的错位使得周围环境中更不利的干燥空气进入风暴的内核，从而阻止风暴进一步增强。因此，以前的工作强烈支持热带气旋强化的关键步骤是在整个大气层深处实现中心对齐的概念。然而，仍然没有很好地理解如何或为什么一些最初错位的风暴过渡到一个更垂直的状态，并迅速加强。在最近一些值得注意的登陆美国的飓风中，与这种结构转变相关的过程的不确定性造成了相当大的预测挑战，特别是强度变化。该项目将使用一个全面的雷达数据集，以提供与快速增强之前和期间的中心对齐相关的过程的见解。以前的观测案例研究和理想化的模式模拟已经确定了多个路径，通过这些路径，一个错位的热带气旋涡旋可以过渡到对齐状态。然而，人们普遍认为，对流驱动的非绝热过程是重要的对齐过程中，无论路径。由于所有的热带气旋都在某种程度上具有对流特征，因此目前还不清楚与涡旋对齐事件相关的降水结构与保持错位的风暴有何不同。这种不确定性是这项研究的关键动机。此外，由于这些不同的对齐路径只记录在理想化的模拟系统或个别风暴的观测案例研究中，关于降水（特别是弱热带气旋）如何与周围环境相互作用并影响自然界中的涡旋对齐路径的可靠结论仍然不明确。因此，该项目旨在通过将与给定对齐路径相关的涡旋、降水和环境特征置于背景中来建立以前的工作。这项研究的总体目标是使用一个新的机载和地基多普勒雷达数据库来研究弱热带气旋，该数据库提供了迄今为止最全面的热带气旋结构观测数据库。这种高分辨率的降水结构评估将有助于揭示三维结构，从而确定造成涡旋排列的物理过程。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。