Collaborative Research: Multiscale modeling of internal tides at topographic generation sites: turbulence and wave energetics:

协作研究：地形生成地点内潮汐的多尺度建模：湍流和波浪能量学：

• 批准号: 1459506
• 负责人: Alberto Scotti
• 金额: $ 31.82万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-02-15 至 2020-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459506&HistoricalAwards=false
• 关键词: Collaborative; Research; Multiscale; modeling; internal

Turbulent processes associated with internal waves occurring at or near the generation sites of internal tides are key ingredients in maintaining and regulating the global ocean circulation which is a crucial component of the climate system affecting simultaneously the uptake of carbon dioxide into the ocean and the meridional transport of heat. Accurate computation of the magnitude and spatial distribution of turbulent dissipation is necessary for the development of physically based parameterizations of conversion and dissipation rates in the near-field. Qualitative changes in turbulence occur when geometry, barotropic forcing and environmental parameters change. The spatial and temporal scales of the physical processes that drive the turbulent energy dissipation during the generation of internal waves span several orders of magnitude. To address these knowledge gaps, a multi-scale approach is necessary to span the disparity between scales: from the scale of the outgoing low-mode internal tide (vertical scale is of order one kilometer, horizontal scale is of order tens of kilometers, time is of order hours) through the nonlinear formation of higher wave number modes to, finally, the turbulence events (spatial scale of meters and time scale of minutes). The integration of models across disparate scales is not only relevant to ocean sciences but also of great interest in many areas of science and engineering, e.g., the representation of turbulent boundary layer processes in medium- and long-term weather forecasting. The broader community interested in developing or applying parameterizations will have access to the simulation data and the numerical model code. Two graduate students will be trained and gain valuable experience in applying cutting edge numerical tools to a complex ocean problem. A numerical investigation of the generation process of internal waves by barotropic tidal flow over an isolated topographic feature scales with the relevant non-dimensional parameters will be conducted. The driving hypothesis is that only the inclusion of turbulence in a realistic way can provide a correct description of the dissipation rates during generation and near-field propagation of internal waves at these sites. The scale-separation will be handled through a novel hierarchical approach that combines Large Eddy Simulation (LES) at small scales with the Stratified Ocean Model with Adaptive Refinement (SOMAR) for the large scales. The LES model, equipped with a sophisticated subgrid-scale model, is capable of providing a faithful description of turbulence, without the need of tunable parameters. The non-hydrostatic SOMAR is specifically optimized to deal with the anisotropy of the internal wave problem. The goal is to implement a two-way nested SOMAR-LES model so that the LES is driven with realistic forcing, and SOMAR receives realistic turbulent feedbacks. We will do so for a model triangular ridge at oceanic scales over a wide range of key non-dimensional parameters: overall Excursion number, obstacle criticality, inner Excursion number and length of critical slope. The simulations will be analyzed to ascertain (i) the dependence of internal wave energetics on the non-dimensional parameters, and (ii) a better understanding of stabilities, turbulence and associated dissipation rates in the near-field.

与内部潮汐发电部位或附近发生的内部波相关的湍流过程是维持和调节全球海洋循环的关键要素，这是气候系统的关键组成部分，对同时影响二氧化碳进入海洋的摄入和子午运输。对于近场中基于物理的转换和耗散率的基于物理的参数化的发展，必须准确计算湍流耗散的大小和空间分布。当几何形状，正压强迫和环境参数发生变化时，湍流的质量变化发生。在内部波的产生过程中驱动湍流能量耗散的物理过程的空间和时间尺度跨越了几个数量级。 To address these knowledge gaps, a multi-scale approach is necessary to span the disparity between scales: from the scale of the outgoing low-mode internal tide (vertical scale is of order one kilometer, horizo​​ntal scale is of order tens of kilometers, time is of order hours) through the nonlinear formation of higher wave number modes to, finally, the turbulence events (spatial scale of meters and time scale of minutes).跨不同量表的模型的整合不仅与海洋科学有关，而且在许多科学和工程领域都引起了极大的兴趣，例如，在中型和长期天气预测中的湍流边界层过程的代表。有兴趣开发或应用参数化的更广泛的社区将可以访问仿真数据和数值模型代码。两名研究生将接受培训，并获得在复杂的海洋问题上应用尖端数值工具方面的宝贵经验。将在隔离的地形特征量表上对内部波的产生过程进行数值研究。驾驶假设是，只有以现实的方式包含湍流才能正确描述这些地点的发电和近场传播期间的耗散率。尺度分离将通过一种新型的分层方法来处理，该方法将大型海洋模型与分层的海洋模型与自适应改进（SOMAR）结合在一起，用于大尺度。配备了复杂的子网格尺度模型的LES模型能够提供对湍流的忠实描述，而无需可调参数。专门优化了非静态SOMAR，以处理内部波问题的各向异性。目的是实现双向嵌套的somar-les模型，以便LES以逼真的强迫驱动，Somar会收到现实的动荡反馈。我们将在多种关键的非二维参数上以海洋尺度处的模型三角脊而做到这一点：总体偏移数量，障碍临界点，内部偏移数量和临界斜率的长度。将分析模拟，以确定（i）内部波能量对非二维参数的依赖性，以及（ii）对近场中的稳定性，湍流和相关耗散率的更好理解。