Collaborative Research: Evaluating and parameterizing wind stress over ocean surface waves using integrated high-resolution imaging and numerical simulations

海面上/海面下的小尺度动力学对风浪耦合至关重要，并控制着质量、动量、热量和能量的海气交换。特别是，表面波及其产生的湍流、破碎波和气泡深刻地影响着表面的粗糙度，并决定了给定风速下的风应力。虽然已有许多研究对水波对风应力的影响进行了研究，但目前的参数化与实际需要存在一定的差距。在这个项目中，一个跨学科的研究团队（具有物理海洋学、海气相互作用和大气科学背景）将利用波浪红外成像和高分辨率建模的最新进展，开发一种依赖于海况的数值算法，该算法可以准确地估计无法明确解决波浪上气流的模型的风应力。这些模型用于许多研究、工程和规划应用，包括物理海洋学、气象学、气候学和海岸工程等。该项目是高度跨学科的，将为参与的学生提供与核心学科以外的研究人员互动的宝贵经验。它还将通过已建立的项目，从德州大学达拉斯分校（UT Dallas）和哥伦比亚大学（Columbia University）代表性不足的群体中招募学生，从而扩大对科学的参与。这项研究产生的知识和数据将被纳入两个机构的教育计划。例如，在达拉斯德州大学，PI将在工程课程中引入波浪动力学和海气相互作用的新本科和研究生课程。此外，pi将参加Skype科学家计划，该计划为初高中学生提供谈论基础科学相关主题的机会。作为该项目的一部分，两名研究生将接受湍流海气相互作用的跨学科培训，一名领导该项目的早期职业科学家将获得与两名经验丰富的科学家合作的宝贵经验。海洋表面的风应力是海洋、大气和表面波模式的关键参数。虽然在了解不同海况如何改变海气通量方面取得了进展，但对波浪上方风应力和阻力系数的详细研究仍然很少，而且控制波浪介导的动量转移的具体过程也没有得到很好的理解。大多数可操作的大气模式使用基于等效表面粗糙度的简单整体参数化。利用现有的综合实验室表面应力测量（Co-PI Zappa）和高保真数字孪生模拟海浪之上的湍流（PI Yousefi和Co-PI Giometto），该合作研究项目预计将基于动态降阶建模，实现与海况相关的表面应力参数化。这种综合方法将使pi能够具体地(1)在一系列风浪状态下研究风应力及其分配（即皮肤摩擦和形式阻力）的可变性，(2)检查水波表面阻力的尺度不变性和自一致性参数，以及(3)开发风在海洋波场上的LES的壁层模型，以研究强强迫条件下的海气通量。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 small-scale dynamics above/below the ocean surface are crucial for wind-wave coupling and govern the air-sea exchanges of mass, momentum, heat, and energy. In particular, surface waves and the corresponding generation of turbulence, breaking waves, and bubbles profoundly affect the roughness of the surface and determine the wind stress at a given wind speed. Although many studies have investigated the impact of water waves on wind stress, the present parameterizations lag behind actual needs. In this project, an interdisciplinary team of investigators (with backgrounds in physical oceanography, air-sea interactions, and atmospheric sciences) will leverage recent advances in infrared imaging of waves and high-resolution modeling to develop a sea-state-dependent numerical algorithm that estimates the wind stress accurately for models that cannot explicitly resolve the air flow over waves. Such models are used for many research, engineering, and planning applications, including physical oceanography, meteorology, climatology, and coastal engineering, among others. The project is highly interdisciplinary and will give the participating students valuable experience interacting with researchers outside their core disciplines. It will also broaden participation in science through the recruitment of students from under-represented groups at the University of Texas at Dallas (UT Dallas) and Columbia University through established programs. The knowledge and data generated by this research will be incorporated into the educational programs of both institutions. For example, at UT Dallas, the PI will introduce new under- and graduate-level courses on Wave Dynamics and Air-Sea Interactions into the engineering curricula. Further, PIs will participate in the Skype a Scientist program that provides middle and high school students opportunities to talk about basic science-related topics. As part of this project, two graduate students will receive interdisciplinary training in turbulent air-sea interactions, and an early career scientist who leads the project will gain valuable experience working with two experienced scientists.The wind stress at the ocean surface is a crucial parameter for ocean, atmosphere, and surface wave models. Although progress has been made in understanding how the air-sea fluxes are modified by different sea states, detailed investigations of the wind stress and drag coefficient above waves remain rare, and the specific processes governing wave-mediated transfers of momentum are not well understood. Most operational atmospheric models use a simple bulk parameterization based on the equivalent surface roughness. Using existing integrated laboratory measurements of surface stress (Co-PI Zappa) and high-fidelity digital twin simulations of turbulent flow above ocean waves (PI Yousefi and Co-PI Giometto), this collaborative research project is anticipated to lead to a sea-state-dependent parameterization of surface stress based on a dynamic reduced-order modeling. This integrated approach will allow the PIs to specifically (1) investigate the variability of wind stress and its partitioning (i.e., the skin friction and form drag) over ocean waves under a range of wind-wave regimes, (2) examine the scale-invariance and self-consistency arguments of the surface drag over water waves, and (3) develop a wall-layer model for LES of wind over ocean wavefield to investigate the air-sea fluxes in strongly forced conditions.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.