A Multiscale Diagnostic and Prognostic Investigation of Environmental Influences on Tropical Cyclone Life Cycles

研究的重点将是对热带气旋（TC）生命周期和TC-环境相互作用的多尺度诊断调查。它建立和扩大在完成和正在进行的研究TC，特别是在热带过渡（TT）和热带外过渡（ET）领域。TT过程不太清楚，一直是正在进行的工作的一个重要重点，并将成为这项赠款研究的一个主要重点。TT过程的一个基石是，风暴形成初期发生在以水平温度梯度和相关垂直风切变为特征的环境中，这些环境比热带地区更具有中纬度地区的特征。一个中纬度起源的上层扰动的前兆需要启动TT过程。上升与前兆扰动有助于湿润大气的中层，防止广泛的蒸发冷却与对流下降气流，并促进柱变暖。风暴环流中的多个对流元素随后合并，完成向暖心TC的转变。这种对TT过程的看法源于对飓风戴安娜（1984）、迈克尔（2000）、温贝托（2001）、卡塔里纳（2004）和亚历克斯（2004）的项目相关分析和建模研究。 卡塔里纳（2004年）是一个偶然的事件，值得注意的是它是有记录以来第一个南大西洋飓风。将通过高层扰动对TC生命周期的影响以及TC引起的环境流变化来评估风暴环境相互作用。前者的例子包括通过技术转让进程开发技术合作。后者的例子包括直接和下切TC环境中与TC相关的对流修改的剪切和位涡廓线。PI和他的研究生还将专注于记录登陆TC内中尺度子结构的起源，包括ET风暴。例子包括弗洛伊德（1999），值得注意的是沿海锋相关的洪水产生的降雨，和较弱的风暴，如克里斯（1988），马可（1990）和杰里（1995），值得注意的是异常强降水集中在弱锋边界附近。热带气旋诊断个案研究将用于建立天气动力学背景，以了解热带气旋生命周期的各个方面。设想的多尺度诊断研究将侧重于确定有助于TC演变的先行扰动，并记录与TC-环境相互作用一起发生的大规模流态和流态转换。这项任务的动机已完成和正在进行的研究表明，与ET风暴的降水分布可以理解的基本动力学原理。就更广泛的影响而言，现有的天气预测模型在预测TT过程产生的TC的发展方面做得相对较差。鉴于TT的发展可能发生在人口稠密的美国东南部海岸附近，重要的是要更多地了解这种风暴如何发展和加强。TT风暴也对繁忙的沿海航线的海洋利益构成严重威胁（风和波浪）。登陆和过渡（ET）风暴也可能带来重大的预测挑战。它们可能对海洋利益（风和海浪）、沿海居民/企业（强风、龙卷风和风暴潮造成的洪水）和内陆居民/企业（暴雨造成的淡水洪水）产生不利影响。该项目还提供了与各种政府机构合作的机会（例如，美国国家飓风中心）和其他教育机构（一项正在进行的活动），以帮助促进研究知识转移到业务和学生。研究结果将通过以下方式传播：（1）会议和讲习班报告，（2）参考论文，（3）COMET小型课程、业务预报员讲习班和教育工作者会议上的报告。

The focus of the research will be on multiscale diagnostic investigations of tropical cyclone (TC) life cycles and TC-environmental interactions. It builds and expands upon completed and ongoing research on TCs, particularly in the areas of tropical transition (TT) and extratropical transition (ET). The TT process is less well understood and has been a significant focus of ongoing work, and will be a major focus of this grant research. A cornerstone of the TT process is that incipient storm formation occurs in environments characterized by horizontal temperature gradients and associated vertical wind shear that are more characteristic of mid latitudes than the tropics. A precursor upper-level disturbance of mid latitude origin is needed to initiate the TT process. Ascent associated with the precursor disturbance helps to moisten mid levels of the atmosphere, preventing widespread evaporative cooling associated with convective downdrafts, and facilitating column warming. Multiple convective elements in the storm's circulation then consolidate, completing the transition to a warm-core TC. This view of the TT process has arisen from project-related analysis and modeling studies of Hurricanes Diana (1984), Michael (2000), Humberto (2001), Catarina (2004) and Alex (2004). Catarina (2004), a serendipitous event, was noteworthy for being the first-ever recorded South Atlantic hurricane. Storm environmental interactions will be assessed through the impact of upper-level disturbances on TC life cycles, and through TC-induced changes in the environmental flow. Examples of the former include TC development via the TT process. Examples of the latter include TC-related convectively modified shear and potential vorticity profiles in the immediate and downshear TC environment. The PI and his graduate students will also focus on documenting the origin of mesoscale substructure within landfalling TCs, including ET storms. Examples include Floyd (1999), noteworthy for coastal front-related flood-producing rains, and weaker storms such as Chris (1988), Marco (1990) and Jerry (1995), noteworthy for exceptionally heavy precipitation concentrated near weak frontal boundaries. The diagnostic TC cases studies will be used to establish the synoptic-dynamic context for understanding the various aspects of TC life cycles. The envisioned multiscale diagnostic studies will focus on identifying antecedent disturbances that contribute to TC evolution and document the large-scale flow regimes and regime transitions that occur in conjunction with TC-environmental interactions. This task is motivated by completed and ongoing research that has shown that the precipitation distribution associated with ET storms can be understood in terms of fundamental dynamical principles. In terms of broader impacts, existing weather prediction models do a relatively poor job of predicting the development of TCs that originate by the TT process. Given that TT developments can occur near the populous southeast US coast, it is important to learn more about how such storms develop and intensify. TT storms also pose a serious threat (wind and waves) to marine interests in the heavily traveled coastal shipping lanes. Landfalling and transitioning (ET) storms can also pose significant forecasting challenges. They can adversely impact marine interests (wind and waves), coastal residents/businesses (high winds, tornadoes, and flooding from storm surges), and inland residents/businesses (fresh-water flooding due to heavy rain). This project also presents the opportunity to work with various government agencies (e.g., National Hurricane Center) and other educational institutions (an ongoing activity) to help facilitate the transfer of research knowledge to operations and students. Research findings will be disseminated through: 1) conference and workshop presentations, 2) refereed papers, and 3) presentations at COMET mini-courses, workshops for operational forecasters, and conferences for educators.