Air-Sea Momentum Transfer in Extreme Wind Conditions

飓风的发展和加强依靠的是温暖海水的能量。这种海气相互作用是飓风数值模拟中的一个关键因素，但由于在大型飓风中进行测量的困难，这种相互作用在非常高的风速下如何变化尚不清楚。该项目将利用迈阿密大学的一个大型波浪池，它可以产生5级飓风强度的风，以填补目前观测的空白，并研究风和波在海气相互作用中的作用。该项目有可能改进飓风的数值模拟，这直接影响到公共安全和经济。研究小组还计划通过各种外展机制，如社交媒体和设施参观，吸引公众参与。该项目还将有助于培养下一代科学家。研究小组计划在极端风浪条件下建立新的海气动量交换关系，重点是改进飓风模型。该项目的主要目标是确定各种风浪相关过程在控制大风中海气动量转移中的作用，并测量在这种条件下的转移率。研究小组提出的可能的机制是：在陡峭的破碎波的背风处阻挡气流，加强风对波浪的耗散，以及由于喷雾和泡沫夹带而导致垂直密度梯度降低。研究人员假设，在低到中等、高和极端风条件下，海气动量转移经历了控制物理过程的根本变化。为了解决这一假设，提出了四个主要任务：1)在迈阿密大学的巨浪-结构-大气相互作用（SUSTAIN）设施中进行一系列实验室实验；2)建立了海气动量通量与平均风速、波浪状态、喷雾浓度和条纹覆盖率的新关系；3)制定新的风输入源函数；4)在完全耦合的大气-波浪-海洋模式中进行数值模拟，并与现场观测进行验证。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。

Hurricanes develop and intensify by "feeding" off the energy of warm oceanic waters. This air-sea interaction is a key factor in numerical modeling of hurricanes, but how this interaction changes in very high wind speeds is unknown due to the difficulty of making measurements in major hurricanes. This project will make use of a large wave tank at the University of Miami that can generate winds of Category 5 hurricane intensity to fill the current gap in observations and to study the roles of wind and waves in air-sea interactions. The project has the potential to improve numerical modeling of hurricanes, which directly impacts public safety and the economy. The research team also plans to engage the public through a variety of outreach mechanisms, such as social media and facility tours. The project will also help to train the next generation of scientists.The research team plans to establish new relationships for the air-sea momentum exchange in extreme wind and wave conditions with a focus on improving hurricane modeling. The main goal of the project is to identify the roles of various wind and wave related processes in controlling the air-sea momentum transfer in high winds, and to measure the rate of transfer in such conditions. The possible mechanisms cited by the research team are: sheltering of the air flow in the lee of steep breaking waves, enhanced dissipation of waves by wind, and vertical density gradient decrease due to spray and foam entrainment. The researchers hypothesize that the air-sea momentum transfer undergoes a fundamental change of governing physical processes between low-to-moderate, high, and extreme wind conditions. To address this hypothesis, four main tasks are laid out: 1) Conduct a series of laboratory experiments in the SUrge-STructure-Atmosphere INteraction (SUSTAIN) facility at the Univ. of Miami; 2) Derive a new relationship between air-sea momentum flux and mean wind, wave-state, and spray concentration and streak coverage; 3) Formulate a new wind input source function; and 4) Conduct numerical simulations in a fully coupled atmosphere-wave-ocean model and validate against field observations.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.