Wave effects in upper ocean turbulence models

上层海洋湍流模型中的波浪效应

• 批准号: 1558459
• 负责人: Ramsey Harcourt
• 金额: $ 60.5万
• 依托单位: University of Washington
• 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: 2016-04-01 至 2022-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558459&HistoricalAwards=false
• 关键词: Wave; effects; upper; ocean; turbulence; Wave; effects; upper; ocean; turbulence

Wind is the major driving force for the upper ocean. The structure and intensity of turbulent mixing in the surface layer of the ocean vary greatly in the presence of steep wind waves, and existing numerical models are not always very accurate in their predictions. This study seeks to improve the representation of surface wave effects in numerical models of upper-ocean mixing and expand the empirical basis for validating these models against mixed layer turbulence measurements. Existing data from freely drifting instruments that move up and down the well mixed layer of the upper ocean will be analyzed to yield new information about the vertical structure of turbulence under a wide range of wave conditions. Virtual drifters simulated in very high resolution numerical models will be used to develop new analysis methods and to enhance the limited observational data sets. The study will aid comparisons among competing theories on wave-turbulence interaction by expanding and refining the metrics of model-data comparisons. Insights on wave-turbulence interaction will lead to new mixing parameterizations, that can be validated against small-scale turbulence measurements, and ultimately enhance the skill of ocean circulation models. The dissemination of drifter measurements and model code will also benefit other approaches to parameterizing wave effects. The ability of the improved closure models to reproduce the observed anisotropy of mixed layer turbulence, and the homogeneity of momentum and scalar profiles, will be of interest in many physical and biogeochemical oceanographic fields, ranging from climate modeling to coastal sediment transport and oil spill prediction. Implementing the improvements in a widely used modeling framework, the General Ocean Turbulence Model (GOTM) will facilitate usage of these results by a broad range of ocean modelers. This project will promote study at a unique nexus between engineering and geophysics and supports a graduate research associate to work on drifter data analysis and model-data comparisons. The project will contribute new material to the investigators' ongoing individual outreach activities through public school classrooms and science fairs.The second moment closure (SMC) model developments build on recent advances that include Craik-Leibovich (CL) vortex forcing fully in a 'quasi-equilibrium' SMC, adopting a momentum flux closure with a component down the Stokes drift gradient and an inhomogeneous near-surface pressure-strain closure. The CL forcing Reynolds stress terms and new turbulence closures will be applied to modify the larger class of 'weak-equilibrium' SMCs for Langmuir turbulence. These will be implemented and evaluated in the GOTM framework, including the modeled interaction of Langmuir turbulence and surface wave breaking. New analysis of existing high-quality Lagrangian float data will provide profiles of kinetic energy components, turbulent length scales, large-eddy kinetic energy dissipation rates and near-surface Lagrangian statistics that can discriminate between theories for surface -wave forcing of boundary-layer turbulence. New large eddy simulations (LES) will contain embedded virtual floats, and will include forcing by stochastic wave breaking at float- and model-resolved scales. Using this LES, the researchers will develop new data analysis methods and guide SMC modifications for wave forcing. The new near-surface closure for CL forcing will be combined with similar treatments of buoyant production in of turbulent covariance in SMC for convection with nonlocal gradient closures. LES results and float data will be used to verify and tune SMC models. Modified SMC model code and float data test cases will be distributed for public availability via the GOTM framework.

风是上海的主要驱动力。在陡峭的风波存在下，海洋表面层中湍流混合的结构和强度差异很大，并且现有的数值模型在预测中并不总是很准确。这项研究旨在改善上海上混合的数值模型中的表面波效应的表示，并扩展了对这些模型验证混合层湍流测量结果的经验基础。将分析来自上海上良好层的自由漂移仪器的现有数据，以在广泛的波浪条件下产生有关湍流的垂直结构的新信息。在非常高的分辨率数值模型中模拟的虚拟漂流者将用于开发新的分析方法并增强有限的观察数据集。这项研究将通过扩展和完善模型数据比较的指标来帮助对波动扰动相互作用的竞争理论进行比较。 波动扰动相互作用的见解将导致新的混合参数化，可以在小规模的湍流测量中进行验证，并最终增强了海洋循环模型的技能。漂流者测量和模型代码的传播还将有益于其他方法来参数化波浪效应。 改进的闭合模型重现混合层湍流的各向异性以及动量和标量剖面的均匀性，在许多物理和生物地球化学海洋学领域中都会引起人们的关注，从气候建模到沿海沉积物到沿海沉积物到沿海沉积物运输以及溢油预测。一般的海洋湍流模型（GOTM）在广泛使用的建模框架中实施了改进，将促进各种海洋建模者对这些结果的使用。该项目将在工程和地球物理学之间的独特联系中促进研究，并支持研究生研究助理，从事漂流者数据分析和模型数据比较。 The project will contribute new material to the investigators' ongoing individual outreach activities through public school classrooms and science fairs.The second moment closure (SMC) model developments build on recent advances that include Craik-Leibovich (CL) vortex forcing fully in a 'quasi-equilibrium' SMC, adopting a momentum flux closure with a component down the Stokes drift gradient and an inhomogeneous near-surface pressure-strain closure. CL强迫Reynolds应力项和新的湍流闭合将用于修改较大类别的“弱平衡” SMC，以用于Langmuir湍流。这些将在GOTM框架中实现和评估，包括Langmuir湍流和表面波破裂的建模相互作用。对现有高质量Lagrangian Float数据的新分析将提供动能组件，湍流长度尺度，大涡流能量耗散速率和近地表Lagrangian统计数据的概况，这些统计数据可以区分地面 - 边界层湍流强迫的理论。新的大型涡流模拟（LES）将包含嵌入式的虚拟浮子，并包括在浮动和模型分辨的尺度上通过随机波破裂强迫。使用此LE，研究人员将开发新的数据分析方法，并指导SMC修改以进行波强。新的近距离闭合Cl强迫将结合SMC中湍流协方差的浮力产生的类似处理，以与非局部梯度封闭相对。 LES结果和浮点数据将用于验证和调整SMC模型。修改后的SMC型号代码和浮点数据测试用例将通过GOTM框架分发，以供公共可用性。