Collaborative Research: Nonlinear Interactions between Surface and Internal Gravity Waves in the Ocean

合作研究：海洋表面重力波和内部重力波之间的非线性相互作用

• 批准号: 1634939
• 负责人: Wooyoung Choi
• 金额: $ 32.46万
• 依托单位: New Jersey Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634939&HistoricalAwards=false
• 关键词: Collaborative; Research; Nonlinear; Interactions; between

The action of the wind on the ocean surface transfers momentum, serves as a source of kinetic energy for both turbulence and waves and is a controlling factor of the structure of the ocean surface boundary layer. When wind blows over the ocean, the ocean responds in two significant ways. The first is that viscous shear stresses are communicated below the sea surface via transfer of turbulent momentum. The second is that the sea surface acquires an undulatory character as the pressure differences across the leading and trailing faces of surface waves transfer momentum via form drag. While the undulatory character of the ocean surface can be painfully obvious to the ocean scientist onboard a ship, effects such as mixing associated with surface gravity wave breaking, instabilities of the surface wave shear, and coupling of the surface wave?s Stokes drift with wind driven shear to form Langmuir circulations are ignored in standard ocean surface boundary layer models. Missing as well from these models is a representation of relatively high frequency internal waves that could be prone to breaking immediately below the mixed layer. This project seeks to broaden understanding of the connectivity between ocean surface boundary conditions and upper ocean mixing. The highly nonlinear multi-layer model and the numerical and analytical tools to be developed in this project could be useful for a wide range of physical problems in the upper ocean including shear instabilities and coherent features such as Langmuir vortices. It is also important to stress that small changes in the interior mixing coefficients in the tropical oceans can have an immense feedback on Sea Surface Temperature and, therefore, other physical quantities, including convection and precipitation, of climatological significance. This project will provide training in first principles understanding of nonlinear waves and their interactions to a graduate student and a post-doc in applied mathematics. Research training through their active participation in this cross-disciplinary collaboration will provide them a unique opportunity to broaden their research experience in physical oceanography and improve their understanding of the interplay between the two disciplines. Ocean observations and basic physical considerations point towards a paradigm of greatly enhanced transfers at high wind speeds, trapping in the upper ocean at buoyancy frequency turning points that allows a nonlinear equilibration process and interaction with lower frequency shear that promotes enhanced internal wave dissipation. This paradigm demands consideration of something more sophisticated than a resonant analysis. The objective of this project is to understand the role of surface gravity waves resulting in the nonlinear excitation of internal gravity waves and assessing the internal waves propensity for mixing the upper ocean. Three possible parameter regimes are proposed. At low wind speeds, transfers tend to be from the background Internal Gravity Wave (IGW) field to the Surface Gravity Wave (SGW) field. At high wind speeds, current theoretical predictions of SGW-IGW transfer rates are proportional to wind speed, i.e. a very sensitive dependence upon wind speed. Transfers reverse sign and energy is transferred from the SGW field to the IGW field. The change in sign denoting the transition from low-wind to high-wind conditions coincides with gale force wind conditions. Extrapolating such dependencies to gale force, let alone hurricane force, invalidates the validity of the nonlinear theory. A likely third parameter regime coincides with the breakdown of this theory. The proposed research consists of three coordinated efforts. The first is an observational study with the objectives of documenting the vertical structure of upper ocean turbulent dissipation relative to standard mixed-layer schemes and estimates of SGW-IGW transfers rates, and documenting the relationship of high frequency internal wave variability to wind and wave conditions. The second of the three efforts is to develop a highly nonlinear model for a multi-layer system, focusing on the three-layer (well-mixed upper, relatively thin transitional, and deep lower layers) case, without any limitations on wavelength scales, and to perform a numerical study, to investigate both resonant and non-resonant SGW-IGW interactions at finite amplitude. Questions of the onset of internal wave breaking and transition layer mixing will be addressed. The third effort is to construct a self-consistent finite amplitude analytic description of nonlinear SGW-IGW interactions using the proposed layered formulation. The proposed third approach is, by taking advantage of the canonical Hamiltonian structure of the model, to investigate the equilibration of the IGW field with SGW variability and how this equilibration changes at finite amplitude. Then, the numerical and analytic studies will be cross-validated and compared with the ocean observations.

风向海面的作用传递了动量，是湍流和波浪的动能来源，是海面边界层结构的控制因素。当风吹过海洋时，海洋以两种重要的方式做出反应。首先是粘性剪切应力通过湍流动量的转移在海面下方传达。第二个是海面获得波动性特征，因为表面波的压力差异通过形式阻力转移了表面波的转移动量。虽然海洋表面的波动特征对于船上的海洋科学家来说可能很痛苦，但诸如与表面重力波破裂相关的效果，表面波剪切的不稳定性以及表面波的耦合与风能驱动剪切的耦合？在标准海洋表面边界层模型中，忽略了风速剪切的表面波动。这些模型也缺失的是相对较高的频率内波的表示，这些波可能容易在混合层下方打破。该项目旨在扩大对海面边界条件与上海上混合之间的连通性的了解。该项目中高度非线性的多层模型以及要开发的数值和分析工具对于上海中的各种物理问题可能很有用，包括剪切不稳定性和连贯的功能，例如Langmuir涡流。同样重要的是要强调，热带海洋中内部混合系数的小变化可能会对海面温度产生巨大的反馈，因此，其他物理量，包括对流和降水，具有气候意义。 该项目将提供对非线性波及其相互作用的第一原理理解的培训，并向研究生和应用数学后的研究生提供培训。通过积极参与这项跨学科合作的研究培训将为他们提供一个独特的机会，以扩大他们在物理海洋学方面的研究经验，并提高他们对两个学科之间相互作用的理解。海洋观察和基本的物理考虑表明，在高风速下转移的范式大大增强，在浮力转弯点捕获上海洋，这允许非线性平衡过程以及与较低频率剪切的相互作用，从而促进了增强的内部波浪耗散。该范式需要考虑比共鸣分析更复杂的事物。该项目的目的是了解导致内部重力波的非线性激发表面重力波的作用，并评估混合上海的内部波倾向。提出了三个可能的参数制度。在低风速下，转移往往是从背景内部重力波（IGW）场到表面重力波（SGW）场。在高风速下，SGW-IGW传输速率的当前理论预测与风速成正比，即对风速非常敏感。转移符号和能量从SGW场传递到IGW场。符号的变化表示从低风速到高风条件的过渡与大风力条件相吻合。将这种依赖性推断到大风力，更不用说飓风力量使非线性理论的有效性无效。可能的第三个参数制度与该理论的分解相吻合。拟议的研究包括三项协调的努力。第一个是一项观察性研究，其目的是记录相对于标准混合层方案的上海洋湍流耗散的垂直结构以及SGW-IGW传输速率的估计，并记录高频内波变异性与风和波浪条件的关系。这三个努力中的第二个是为多层系统开发高度非线性模型，重点是三层（混合良好的上部，相对较薄的过渡性和深层下层）情况，而没有对波长尺度的任何限制，并且要进行数值研究，以调查有限的互动和非共鸣和非共鸣和非共鸣的互动。内部波破裂和过渡层混合的问题将得到解决。第三个努力是使用拟议的分层公式来构建非线性SGW-IGW相互作用的自洽有限幅度分析描述。提出的第三种方法是利用模型的典型哈密顿结构来研究IGW场与SGW变异性的平衡以及该平衡在有限幅度时如何变化。然后，数值和分析研究将进行交叉验证，并将其与海洋观测结果进行比较。

项目成果

Strongly nonlinear effects on internal solitary waves in three-layer flows

• DOI: 10.1017/jfm.2019.795
• 发表时间: 2020-01-25
• 期刊: JOURNAL OF FLUID MECHANICS
• 影响因子: 3.7
• 作者: Barros, Ricardo;Choi, Wooyoung;Milewski, Paul A.
• 通讯作者: Milewski, Paul A.

On resonant interactions of gravity-capillary waves without energy exchange

关于无能量交换的重力-毛细波的共振相互作用

• DOI: 10.1111/sapm.12249
• 发表时间: 2019
• 期刊: Studies in Applied Mathematics
• 影响因子: 2.7
• 作者: Chabane, Malik;Choi, Wooyoung
• 通讯作者: Choi, Wooyoung