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

研究的重点是热带气旋生命周期及其与环境相互作用的多尺度诊断研究。它建立和扩展了关于热带过渡的已完成和正在进行的研究，特别是在热带过渡和温带过渡领域。对TT过程的了解较少，并且一直是正在进行的工作的重要焦点，并且将是本赠款研究的主要焦点。TT过程的一个基础是，早期风暴的形成发生在以水平温度梯度和相关的垂直风切变为特征的环境中，这些环境更具有中纬度地区的特征，而不是热带地区。TT过程需要一个源自中纬度的上层扰动前兆来启动。与前体扰动相关的上升有助于湿润大气中层，防止与对流下降气流相关的广泛蒸发冷却，并促进柱变暖。风暴环流中的多个对流元素随后合并，完成向暖核TC的过渡。这种TT过程的观点源于对戴安娜飓风（1984年）、迈克尔飓风（2000年）、温贝托飓风（2001年）、卡塔琳娜飓风（2004年）和亚历克斯飓风（2004年）的项目相关分析和建模研究。卡塔琳娜（2004）是一个偶然的事件，值得注意的是，它是有史以来第一个有记录的南大西洋飓风。将通过上层扰动对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的相互作用。前者的例子包括通过TT过程进行TC开发。后者的例子包括直接和下切变TC环境中与TC相关的对流修正切变和位涡度剖面。PI和他的研究生也将专注于记录包括ET风暴在内的登陆tc中尺度亚结构的起源。例子包括Floyd(1999)，值得注意的是与沿海锋面相关的产生洪水的降雨，以及Chris（1988）、Marco（1990）和Jerry（1995）等较弱的风暴，值得注意的是集中在弱锋面边界附近的异常强降水。诊断性TC病例研究将用于建立天气动态背景，以了解TC生命周期的各个方面。设想的多尺度诊断研究将侧重于识别有助于TC演变的先前干扰，并记录与TC-环境相互作用相关的大规模流动模式和模式转变。这项任务的动机是完成和正在进行的研究表明，与ET风暴相关的降水分布可以从基本动力学原理来理解。就更广泛的影响而言，现有的天气预报模式在预测由TT过程产生的tc的发展方面做得相对较差。考虑到TT的发展可能发生在人口稠密的美国东南海岸附近，了解更多关于这种风暴如何发展和加强的信息是很重要的。TT风暴还对繁忙的沿海航道的海洋利益构成严重威胁（风和浪）。登陆和过渡（ET）风暴也可能带来重大的预报挑战。它们会对海洋利益（风和海浪）、沿海居民/企业（大风、龙卷风和风暴潮引发的洪水）和内陆居民/企业（大雨导致的淡水洪水）产生不利影响。该项目还提供了与各种政府机构（例如，国家飓风中心）和其他教育机构（一项正在进行的活动）合作的机会，以帮助促进研究知识向业务和学生的转移。研究成果将通过以下方式传播：1)会议和研讨会报告；2)评审论文；3)COMET迷你课程、业务预报员研讨会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.