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

海面上/下的小尺度动力对风浪耦合是至关重要的，并支配着海气质量、动量、热量和能量的交换。特别是，表面波和相应产生的湍流、破碎波和气泡深刻地影响着表面的粗糙度，并决定着给定风速下的风应力。虽然许多研究已经研究了水波对风应力的影响，但目前的参数化方案滞后于实际需要。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的背景)将利用海浪红外成像和高分辨率建模方面的最新进展，开发一种依赖于海况的数值算法，为无法明确解析海浪上的空气流动的模型准确地估计风应力。这些模型被用于许多研究、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其核心学科以外的研究人员互动的宝贵经验。它还将通过现有项目从德克萨斯大学达拉斯分校(UT Dallas)和哥伦比亚大学招收代表不足的群体的学生，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这两个机构的教育计划。例如，在德克萨斯大学达拉斯分校，PI将在工程课程中引入新的关于波浪动力学和海气相互作用的本科生和研究生课程。此外，PI将参与Skype a Science计划，该计划为初中生和高中生提供谈论与基础科学相关的话题的机会。作为该项目的一部分，两名研究生将接受关于湍流海气相互作用的跨学科培训，领导该项目的一名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、大气和表面波模型的关键参数。尽管在理解不同海况如何改变海-气通量方面已经取得了进展，但对海浪上方的风应力和阻力系数的详细研究仍然很少，而且控制海浪介导的动量传输的具体过程也不是很清楚。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总体参数化。利用现有的表面应力综合实验室测量(Co-Pi Zappa)和海浪上方湍流的高保真数字孪生模拟(Pi Yousefi和Co-Pi Giometto)，这一合作研究项目预计将导致基于动态降阶建模的依赖于海况的表面应力参数化。这种综合方法将使PIS能够具体地(1)调查在一定范围的风浪制度下海浪上风应力及其分配(即，表面摩擦和形式阻力)的可变性，(2)检查水波上表面阻力的尺度不变性和自洽论点，以及(3)为海洋波场上的风的LES开发一个墙层模式，以研究强强迫条件下的海气通量。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.