Collaborative Research: Breaking Wave Effects on Wave Boundary Layer and Air-Sea Momentum Flux

合作研究：破碎波对波浪边界层和海气动量通量的影响

• 批准号: 0526177
• 负责人: Tetsu Hara
• 金额: --
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0526177&HistoricalAwards=false
• 关键词: Collaborative; Research; Breaking; Wave; Effects

0526177Intellectual Merit: Air-sea flux parameterizations are important components of ocean, atmosphere, and coupled ocean atmosphere models. Accurate flux parameterizations are particularly important at high wind conditions as demonstrated by recent hurricane prediction model studies. Yet, ther present air-sea flux parameterizations in the operational models are based on simple bulk formulas and are clearly far from satisfactory. Increasing observational evidences suggest that air-sea fluxes strongly depend on sea states. Recently, the lead investigator and his colleagues have developed a new model of the wave boundary layer (the lower part of the atmospheric boundary layer that is directly influenced by surface waves) based on the fundamental principles of conservation of energy and momentum across the boundary layer. The model has been coupled with surface wave models to predict the equivalent surface roughness and the drag coefficient over mature, growing, and complex seas. In particular, the model predicts reduced levels of the drag coefficient at very high winds under hurricane conditions, consistent with recent field and laboratory observations. One shortcoming of the present model is that it does not include the effect of surface breaking waves on the wave boundary layer.The proposed model of the wave boundary layer and the equilibrium wave spectrum will be based on the following hypotheses: (1) Breaking waves significantly modify the structure of the wave boundary layer and the resulting air-sea momentum flux under strong wind forcing. (2) Breaking wave effects on the air-sea momentum flux can be quantified accurately if the existing wave boundary layer model is extended to incorporate the effect of the form drag due to breaking wave crests and the effect of airflow separation behind breaking wave crests that effectively shelters shorter waves from direct wind forcing (spatial sheltering effect), provided the surface wave spectrum and the breaking wave statistics are known. (3) In the equilibrium range, the surface wave spectrum and the breaking wave statistics may also be predicted together with the air-sea momentum flux. The model will explicitly include the form drag and airflow separation effects and will be used to predict the drag coefficient under high wind conditions. Next, each component of the model will be validated against new laboratory observations carried out at the University of Miami. The experiment is specifically designed for the model validation and provides simultaneous measurements of the total wind stress, the surface viscous stress, the surface wave spectrum, and the breaking wave statistics. The proposed development will be done in close collaboration with Stephen Belcher at the university of Reading, UK. Broader Impacts: The proposed study of the wave boundary layer and the equilibrium wave spectrum will be an important and essential step towards our ultimate goal of developing a new set of parameterizations of air-sea fluxes, which will be valid for the whole range of wind speeds and surface wave conditions and can be used as improved boundary conditions for high-resolution numerical models of ocean, atmosphere, and coupled ocean/atmosphere systems, including the tropical cyclone prediction models. Therefore, this research addresses social needs to improve weather forecast (in particular, tropical cyclone forecast) and to reduce natural hazards caused by extreme wind and wave conditions. The project includes the development of a new experimental technique to estimate the breaking wave statistics. Quantifying surface breaking wave events is extremely important for all aspects of the air-sea interaction studies. The project also involves the education and training of one graduate student. The student will learn both laboratory experimental techniques and theoretical/numerical modeling approaches to study breaking wave effects on air-sea interaction processes. Finally, an existing international collaboration will be fostered.

0526177Intlectual Feerit：空气通量参数化是海洋，大气和耦合海洋大气模型的重要组成部分。正如最近的飓风预测模型研究所证明的那样，在大风条件下，准确的通量参数化尤为重要。然而，操作模型中当前的空气通量参数化基于简单的大体配方，显然远非令人满意。越来越多的观察证据表明，空气通量在很大程度上取决于海州。最近，主要研究者及其同事基于在边界层跨边界层的能量和动量的基本原理开发了波浪边界层（大气边界层的下部）的新模型。该模型已与表面波模型结合在一起，以预测等效的表面粗糙度和拖放系数，超过成熟，生长和复杂的海洋。特别是，该模型预测在飓风条件下非常大风的阻力系数降低，这与最近的现场和实验室观察一致。本模型的一个缺点是，它不包括表面断裂波对波边界层的影响。波浪边界层和平衡波谱的建议模型将基于以下假设：（1）破裂波显着修改波浪边界层的结构以及在强风能下产生的空气微动量通量。 （2）如果扩展现有的波边界层模型，可以准确量化对空气动量通量的破裂波影响，以结合由于断裂波峰而引起的形态阻力的效果，以及在断裂波峰后的气流分离的影响，从而有效地避开了直接风力强迫（空间遮盖效应）的较短波浪（如空间遮挡效应），如果表面波动量大波形和破坏性波浪范围为波浪范围。 （3）在平衡范围内，表面波谱和断裂波统计也可以与空气动量通量一起预测。该模型将明确包含形式的阻力和气流分离效应，并将用于预测在大风条件下的阻力系数。接下来，该模型的每个组成部分都将根据在迈阿密大学进行的新实验室观察结果进行验证。该实验是专门为模型验证设计的，并提供了总风力应力，表面粘应力，表面波频谱和断裂波统计的同时测量。拟议的开发将与英国雷丁大学的Stephen Belcher密切合作。 Broader Impacts: The proposed study of the wave boundary layer and the equilibrium wave spectrum will be an important and essential step towards our ultimate goal of developing a new set of parameterizations of air-sea fluxes, which will be valid for the whole range of wind speeds and surface wave conditions and can be used as improved boundary conditions for high-resolution numerical models of ocean, atmosphere, and coupled ocean/atmosphere systems, including the tropical cyclone prediction models.因此，这项研究解决了社会的需求，以改善天气预报（尤其是热带气旋预测），并减少由极端风和波浪条件引起的自然危害。该项目包括开发一种新的实验技术来估计断裂波统计。量化表面断裂波事件对于空气相互作用研究的各个方面非常重要。该项目还涉及一名研究生的教育和培训。学生将同时学习实验室实验技术和理论/数值建模方法，以研究对空气交互过程的破坏波影响。最后，将培养现有的国际合作。