Collaborative Research: Langmuir Turbulence Under Tropical Cyclones

合作研究：热带气旋下的朗缪尔湍流

• 批准号: 1130678
• 负责人: Tobias Kukulka
• 金额: $ 27.49万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1130678&HistoricalAwards=false
• 关键词: Collaborative; Research; Langmuir; Turbulence; Under

Turbulent mixing in the ocean surface layer under tropical cyclones effectively couples the ocean and atmosphere through air-sea fluxes of heat and momentum. Air-sea heat fluxes sustain Tropical Cyclones and strongly depend on near surface temperature, which is determined by mixing with cooler deeper water. Understanding the turbulent processes involved in near-surface layer mixing remains one of the great challenges in modeling the coupled ocean-Tropical Cyclone system. Upper ocean turbulence is driven by the surface wind stress, resulting in sheared subsurface currents. Furthermore, surface gravity waves influence upper ocean turbulence through wave-current interactions that lead to wind-aligned vortices, called Langmuir circulation or Langmuir turbulence. Wave effects on ocean turbulence are particularly complex under Tropical Cyclones, since wind, wave, and current fields are inhomogeneous and may be misaligned. In addition, the surface wave height spectrum can comprise multiple peaks at different wave frequencies and directions. The proposed work is aimed at understanding Langmuir circulation under realistic Tropical Cyclone conditions and at assessing the role of Langmuir circulation on the coupled ocean-wave-atmosphere Tropical Cyclone dynamics. This project addresses the following hypotheses: Langmuir circulation characteristics under Tropical Cyclones critically depend on detailed wind, wave, and current conditions. Specifically, regions under Tropical Cyclones exist where upper ocean mixing is greatly influenced by Langmuir circulation. The use of an ocean mixing scheme with explicit Langmuir circulation effects will lead to significantly modified mixing and sea surface temperature cooling in Langmuir circulation regions. Including explicitly the Langmuir circulation effect will have a significant effect on the three-dimensional Tropical Cyclone dynamics and prediction.These hypotheses will be tested by applying synergistically a coupled atmosphere-wave-ocean model (AWO) and a turbulence resolving large eddy simulation model (LES) that captures Langmuir circulation. Initially, the AWO will provide critical output (wind, waves, and currents) to drive the LES model. LES results, in turn, will aid in characterizing Langmuir circulation under tropical cyclones and in critically assessing the ocean mixing parameterization. Finally, a turbulent mixing scheme with explicit Langmuir circulation and turbulence effects will be implemented in the ocean model component of the AWO model and a sensitivity study by simulating idealized and real case tropical cyclones will be performed. The model results will then be validated against available field observations in collaboration with scientists at the University of Washington. Intellectual Merit: This project investigates ocean and atmosphere dynamics under Tropical Cyclones, which are coupled through turbulent upper ocean mixing. The investigators will examine an insufficiently understood turbulent process, Langmuir circulation, that is not explicitly represented in most ocean models, despite the fact that Langmuir circulation and turbulence may be a principal mixing component. The combination of regional and process-based models is anticipated to significantly advance our understanding of Langmuir circulation under Tropical Cyclones. Broader Impact: While pursuing some fundamental scientific questions related to air-sea interactions, turbulent mixing, and Tropical Cyclone dynamics, the research will aid in addressing an important societal challenge. Tropical Cyclones critically disrupt infrastructure, cause severe flooding, and displace people in coastal regions. The investigator will advance the scientific basis of Tropical Cyclones models and improve their prediction skill, which will ultimately lead to increased reliability of hurricane forecasts and thus confidence in the official hurricane warnings. The resources from the proposed grant will train two doctoral graduate researchers. The outreach effort will educate the public about basic science with its societal impacts through special events (e.g., at the Open House at the University of Delaware). Science material developed in the course of this project will contribute to the University of Rhode Island comprehensive educational website Hurricanes: Science and Society (www.hurricanescience.org). The website provides information on the science of hurricanes, how hurricanes impact society, and how people and communities can prepare for and mitigate the impacts of hurricanes.

在热带气旋下，海面层中的湍流混合通过热和动量有效地将海洋和大气融合在一起。空气热通量维持热带气旋，并强烈依赖于近表面温度，这是通过与较冷的深水混合来确定的。了解近地面层混合中涉及的湍流过程仍然是建模耦合海洋热带气旋系统的巨大挑战之一。上海湍流由表面风应力驱动，导致剪切的地下电流。此外，表面重力波通过波电流相互作用影响上海洋湍流，导致风向涡流，称为Langmuir循环或Langmuir湍流。在热带气旋下，海洋湍流对海洋湍流的影响特别复杂，因为风，波和当前场是不均匀的，并且可能未对准。另外，表面波高光谱可以在不同的波频率和方向上构成多个峰。拟议的工作旨在理解在逼真的热带气旋条件下的Langmuir循环，并评估Langmuir循环在耦合的海浪 - 大气热带热带气旋动力学方面的作用。该项目解决了以下假设：在热带气旋下，Langmuir循环特征严重依赖于详细的风，波浪和当前状况。具体而言，存在热带气旋下的区域，其中上海混合受兰穆尔循环的极大影响。在Langmuir循环区域中，使用具有明确的Langmuir循环效应的海洋混合方案将导致显着修饰的混合和海面温度冷却。 包括明确的Langmuir循环效应将对三维的热带气旋动力学和预测产生重大影响。这些假设将通过在协同上应用协同的大气 - 波西音乐模型（AWO）和解决大型涡流模拟模型（湍流）进行测试（ LES）捕获Langmuir循环。最初，AWO将提供关键的输出（风，波和电流）以驱动LES模型。反过来，LES结果将有助于表征热带气旋下的Langmuir循环，并严格评估海洋混合参数化。最后，将在AWO模型的海洋模型组件中实现具有明确的Langmuir循环和湍流效应的湍流混合方案，并通过模拟理想化和真实情况的热带旋风来进行灵敏度研究。然后，该模型结果将与华盛顿大学的科学家合作，以与可用的现场观察结果进行验证。知识分子的优点：该项目调查了热带气旋下的海洋和大气动态，这些动态通过湍流的上海混合结合。研究人员将检查一个不足以理解的湍流过程，即Langmuir循环，尽管Langmuir循环和湍流可能是主要的混合成分，但在大多数海洋模型中并未明确表示。预计区域模型和基于过程的模型的结合可以显着提高我们对热带气旋下Langmuir循环的理解。更广泛的影响：在提出一些与空气相互作用，动荡的混合和热带气旋动态有关的基本科学问题的同时，该研究将有助于解决重要的社会挑战。热带气旋严重破坏基础设施，造成严重的洪水，并在沿海地区移动人们。研究人员将提高热带气旋模型的科学基础，并提高其预测技能，最终会导致飓风预测的可靠性提高，从而对官方飓风警告的信心。拟议的赠款的资源将培训两名博士研究生研究人员。 外展工作将通过特殊活动（例如，在特拉华大学的开放日）对公众进行基础科学的教育。在该项目过程中开发的科学材料将为罗德岛大学综合教育网站飓风做出贡献：科学与社会（www.hurricanescience.org）。该网站提供有关飓风科学，飓风如何影响社会的信息以及人们和社区如何为飓风的影响做准备和减轻影响。