Collaborative Research: The Heated Wind- and Wave-Driven Ocean Surface Boundary Layer: Synergistic Analyses of Observations and Simulations

与大气接触的海洋表层（或表面边界层- OSBL）通过海气通量将海洋和大气耦合起来，从而控制气候、天气和地球系统动力学。OSBL中的湍流分布着生物地球化学和生态相关的可漂浮（浮力）示踪剂，如浮游生物、气泡、营养物质、油和微塑料。风和海浪以几种关键方式驱动OSBL湍流：风产生的洋流；波流相互作用导致与风对齐的漩涡，称为朗缪尔湍流（LT）；破碎的波浪将湍流动能注入地下。目前波浪驱动OSBL动力学的概念和理论框架在很大程度上是基于假设地表热通量为中性或有利于地表水柱翻转的条件。然而，白天的加热或降雨事件防止了倾覆，并且在世界海洋上无处不在。本项目将利用数值模拟和对现有数据集的分析来探索表面加热条件下表面波对分层OSBL的影响。本研究的目的是：(1)识别波浪效应对传统表面边界假设的限制；(2)在对动量、浮力和湍流动能进行系统分析的基础上，揭示了波浪对加热OSBL的动力学影响；(3)将数据与模拟相结合，建立湍流状态图，揭示了Langmuir湍流（LT）和破碎波效应对OSBL动力学的影响条件；(4)进行湍流统计分析，评估并提出改进的海洋混合参数化。这些新的参数化将用于证明在OSBL日加热过程中波动效应对浮力示踪剂输运的重要性。这项工作将涉及许多海洋学和大气子学科；支持早期职业研究人员；培养研究生；参与外展活动。本研究将验证以下假设：(1)通过观测和模拟，波对加热OSBL动力学的影响显著且可量化；(2)高温对OSBL混合至关重要，但足够强的加热为射流剪切驱动的湍流提供了有利条件；(3)破碎波在强加热条件下防止流动分层；(4)加热OSBLs中波浪驱动的混合可以用改进的湍流混合参数化来精确表示，以捕获加速射流输运和浮力示踪剂的深沉。该团队可以访问几个广泛的观测数据集，从中他们将能够确定地表加热过程中LT的存在，并评估LT对OSBL动力学的影响。数值实验将使用大涡模拟（LES）进行，该模拟通过涡旋强迫和破碎波的影响产生LT。基于综合数据的结果、LES建模分析、加热OSBL的物理动机和实际混合参数化将被开发、评估，并应用于浮力示踪剂的输送，如微塑料、浮游生物或石油。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 ocean's surface layer in contact with the atmosphere (or surface boundary layer -- OSBL) controls climate, weather, and Earth system dynamics by coupling the ocean and atmosphere through air-sea fluxes. Turbulence in the OSBL distributes biogeochemical and ecologically relevant tracers that are floatable (buoyant), such as plankton, bubbles, nutrients, oil, and microplastics. Wind and waves drive OSBL turbulence in several critical ways: Wind-generated ocean currents; wave-current interactions result in wind-aligned vortices, called Langmuir turbulence (LT); and breaking waves inject turbulent kinetic energy to the subsurface . The present conceptual and theoretical framework of wave-driven OSBL dynamics is largely based on conditions for which surface heat fluxes are assumed to be either neutral or conducive to overturn the surface water column. However, diurnal heating or rain events prevent overturning and are omnipresent over the world oceans. This project would use numerical simulations and analysis of existing data sets to explore the effects of surface waves on the stratified OSBL in surface heating conditions. The objectives of this study are to: (1) identify limitations of traditional surface boundary assumptions due to wave effects; (2) reveal the dynamics of wave effects on the heated OSBL, based on a systematic analysis of momentum, buoyancy, and turbulent kinetic energy; (3) integrate data and simulations to establish a turbulence regime diagram that reveals the conditions in which Langmuir turbulence (LT) and breaking wave effects affect OSBL dynamics; (4) perform an analysis of turbulence statistics to assess and proposes improved ocean mixing parameterizations. These new parameterizations will be applied to demonstrate the importance of wave effects on the transport of buoyant tracers during diurnal OSBL heating. The work will be relevant across many oceanographic and atmospheric sub-disciplines; support an early career researcher; train graduate students; and engage in outreach. The proposed research will test specific hypotheses: (1) wave effects on heated OSBL dynamics are significant and quantifiable through observations and simulations; (2) LT is essential for OSBL mixing but sufficiently strong heating generates favorable conditions for shear-driven turbulence due to jets; (3) breaking waves prevent flow laminarization in strong heating conditions; and (4) wave-driven mixing in heated OSBLs can be accurately represented in improved turbulent mixing parameterizations to capture accelerated jet transport and the deep submergence of buoyant tracers. The team has access to several extensive observational data-sets, from which they will be able to determine the presence of LT during surface heating and assess the impact of LT on OSBL dynamics. Numerical experiments will be conducted using Large Eddy Simulations (LES) which produce LT through vortex forcing and include effects from breaking waves. Based on results from a combined data, LES modeling analysis, physics-motivated and practical mixing parameterizations for the heated OSBL will be developed, assessed, and applied to transport of buoyant tracers, such as microplastics, plankton or oil.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.