Thermodynamics of Tropical Cyclone Overland Maintenance and Intensification

热带风暴或飓风的能量通常来自温暖的海水。然而，对于一些热带气旋，观测到陆地上的最大地面风保持甚至增加。一个特别值得注意的例子是俄克拉何马州上空的热带风暴艾琳，当它从西部接近俄克拉何马城时，它出人意料地戏剧性地增强为一场强烈的热带风暴，造成了数百万美元的与风有关的损失。先前对这一现象的少数调查普遍认为，所需的能量来自下伏的陆地表面。然而，对于能量在多大程度上与陆地温暖和湿润有关，以及允许足够数量的能量在地表附近集中从而可以转移到热带气旋的物理过程，他们意见不一。此外，这些先前研究提出的想法通常是使用高度简化的数值天气预报模式模拟来发展的，很少有实例对实际的热带气旋进行测试。因此，该项目旨在显著推进对支持热带气旋在陆地上维持和加强的能量学的基本认识，同时对观测到的大量事件样本进行严格检验。与威斯康星大学密尔沃基分校的Ronald E. McNair后学士学位成就项目合作，将支持来自传统上代表性不足的背景的本科学者的专业发展和学术坚持，帮助增加少数民族个人在大气和相关科学劳动力管道中的代表性。本研究验证了三个指导性假设：远程地表能量交换是陆地上热带气旋强度变化的主要而非唯一控制因素；非沙漠土壤不能充分升温，产生足够的向上焓通量，使热带气旋在陆地上维持或增强；陆地强度变化对地表能量交换和初始有限振幅大气变率同样敏感。将因子分离应用于理想数值模拟中，用于验证前两个假设，而集成初始化的实际数据模拟用于验证理想模拟结果对实际大气的适用性。与陆上热带气旋维持和增强有关的大气和基材特性的扩展气候学，将支持数值模式的模拟，并提高对这些事件发生环境的认识。通过这些活动，本研究将通过量化局地和非局地陆地表面能量交换对陆地上热带气旋强度变化的各自贡献，调和关于支持非斜压或弱斜压热带气旋在陆地上维持和增强所必需的热力学过程的相互竞争的理论。鉴于目前关于允许热带气旋在水面上增强所需的地表潜热通量大小的科学争论，研究结果也将促进对传统的水上热带气旋增强过程的能量学的认识。该奖项反映了美国国家科学基金会的法定使命，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。

The energy that fuels a tropical storm's or a hurricane's winds is typically drawn from warm ocean waters. However, for some tropical cyclones, the maximum surface winds have been observed to be maintained or even increase over land. A particularly noteworthy case is given by Tropical Storm Erin over Oklahoma, which dramatically and unexpectedly intensified into a strong tropical storm as it approached Oklahoma City from the west, resulting in millions of dollars of wind-related damage. The few prior investigations into this phenomenon generally agree that the required energy is drawn from the underlying land surface. However, they disagree on the extent to which the energy is associated with land warmth versus wetness, as well as on the physical processes that allow for a sufficient amount of energy to be concentrated near the surface so that it can be transferred to the tropical cyclones. Furthermore, the ideas advanced by these previous studies have generally been developed using highly simplified numerical weather prediction model simulations, with few instances in which these ideas have been tested for actual tropical cyclones. Consequently, this project seeks to significantly advance basic understanding of the energetics supporting tropical cyclone maintenance and strengthening over land while rigorously testing this understanding for a large sample of observed events. A partnership with the Ronald E. McNair Post-Baccalaureate Achievement Program at University of Wisconsin-Milwaukee will support the professional development and academic persistence of an undergraduate scholar from a traditionally underrepresented background, helping to increase representation of minority individuals within the workforce pipeline in the atmospheric and related sciences.This research tests three guiding hypotheses: remote surface energy exchange is the primary but not exclusive control on tropical cyclone intensity change over land; non-desert soils cannot be sufficiently warmed to result in sufficient upward enthalpy flux for tropical cyclone maintenance or intensification over land; and intensity change over land is equally sensitive to surface energy exchange and initial finite-amplitude atmospheric variability. Factor separation applied to idealized numerical simulations is used to test the first two hypotheses, whereas ensemble-initialized real-data simulations are used to test the applicability of the idealized simulation results to the real atmosphere. An expanded climatology of atmospheric and substrate properties associated with overland tropical cyclone maintenance and intensification is to support the numerical model simulations and advance knowledge of the environments in which these events occur. Through these activities, this research will reconcile competing theories regarding the thermodynamic processes necessary to support non- or weakly baroclinic tropical cyclone maintenance and intensification over land through quantifying the respective contributions of local and non-local land-surface energy exchange to overland tropical cyclone intensity change. Given the ongoing scientific debate regarding the surface latent heat flux magnitudes needed to permit tropical cyclone intensification over water, findings from the research will also advance knowledge of the energetics of the traditional overwater tropical cyclone intensification process.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.