Measuring the turbulent kinetic energy (TKE) budget and momentum flux beneath breaking waves using an autonomous underwater vehicle

表面重力波是大气和海洋之间动量、能量、热量和气体交换的基础。该项目将使用自主水下航行器对表面波下的湍流应力进行详细、全面的测量。这些数据将被分析以量化动量和能量传递，并有望告知湍流如何在数值模型中参数化和计算。推进我们对表面重力波驱动的湍流交换性质的理解，对世界海洋中沿海风力驱动的环流和热交换具有重要而直接的意义。在海岸边缘，自然环境和人造环境经常相互作用，对风和波浪驱动的混合进行现场测量可以为研究和管理工作提供信息，以预测污染物、幼虫、沉积物和营养物质的命运。此外，该研究还增强了高性能自主水下航行器的测量能力。这种对研究基础设施的增强将使研究线能够进入其他感兴趣的领域，包括大陆架上的内波破裂，以及由于珊瑚和水下植被的生物物理相互作用而增强的混合。由于典型观测平台的限制，对海洋表面边界层湍流雷诺应力和全TKE收支的直接测量受到阻碍，因此很少有研究测量破碎波下的湍流动能和耗散。虽然利用固定或浮动平台的观测与数值模拟相结合取得了重大进展，但我们仍然缺乏必要的数据来了解沿海海洋中波浪驱动的湍流的结构和瞬态，其中涌浪和动态风环境有助于不断变化的海况。因此，湍流闭合方案中包含的表面波效应在很大程度上依赖于数值模拟结果而不是直接观测。该项目将使用配备微结构探头和快速测速仪的自主水下航行器测量受波影响的表层湍流雷诺应力和湍流动能收支项。这将提供一幅前所未有的画面：表面重力波如何构造湍流混合，从而在水面下进行动量转移，以及湍流结构如何在涌浪、可变风强迫和风海演变的情况下发生变化。该项目采用的基于auv的新型测量方法将是革命性的，因为这些高分辨率的观测结果对于进一步理解如何同时参数化涡旋应变和湍流注入作为海气界面动量交换机制是必要的，特别是在瞬态条件下。这些结果将通过分析第二时刻关闭方案框架内的动量和能量转移，为未来的建模工作提供信息，并最终提高我们预测沿海海洋中营养物质、沉积物、浮游生物、幼虫和污染物的命运和运输的能力。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。

Surface gravity waves are fundamental to the exchange of momentum, energy, heat, and gases between the atmosphere and the ocean. This project will make detailed, comprehensive measurements of the turbulent stress beneath surface waves using an autonomous underwater vehicle. The data will be analyzed to quantify momentum and energy transfer, and are expected to inform how turbulence is parameterized and accounted for in numerical models. Advancing our understanding of the nature of turbulent exchange driven by surface gravity waves has important and immediate implications for coastal wind-driven circulation and heat exchange within the world's oceans. In coastal margins, where natural and built environments often interact, in situ-measurements of wind- and wave- driven mixing can inform research and management efforts in predicting the fate of pollutants, larvae, sediments, and nutrients. Additionally, this investigation enhances the measurement capabilities of a highly-capable autonomous underwater vehicle. Such enhancements to research infrastructure will enable lines of inquiry into other areas of interest, including internal wave breaking over continental shelves and enhanced mixing due to biophysical interactions of coral and submerged vegetation.Few studies have measured the turbulent kinetic energy and dissipation beneath breaking waves, because direct measurements of turbulent Reynolds stress and the full TKE budget in the oceanic surface boundary layer are hampered by constraints associated with typical observational platforms. While significant advances have been made using observations from stationary or floating platforms in combination with numerical simulations, we still lack the necessary data to understand the structure and transiency of wave-driven turbulence in the coastal ocean, where swell and a dynamic wind environment contribute to an ever-evolving sea state. Consequently, the inclusion of surface wave effects in turbulence closure schemes relies heavily on numerical modeling results rather than direct observations. This project will measure the turbulent Reynolds stress and terms in the turbulent kinetic energy budget of a wave-affected surface layer using an autonomous underwater vehicle equipped with microstructure probes and fast velocimeters. This will provide an unprecedented picture of how surface gravity waves structure turbulent mixing and hence momentum transfer beneath the water surface and how that turbulent structure changes in the presence of swell, variable wind forcing, and with the evolution of a wind sea. The novel AUV-based measurements conducted for this project will be transformative because these high-resolution observations are necessary to advance understanding of how to simultaneously parameterize both vortex straining and turbulent injections as mechanisms of momentum exchange across the air-sea interface, particularly in transient conditions. The results will inform future modeling efforts through analysis of momentum and energy transfer within the framework of second moment closure schemes and ultimately improve our ability to predict the fate and transport of nutrients, sediments, plankton, larvae, and pollutants in the coastal ocean.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.