Submesoscale Instabilities and Turbulence Across Oceans: Connecting Theory and Observations

跨洋的亚尺度不稳定性和湍流：理论与观测的联系

• 批准号: 1736595
• 负责人: Jennifer MacKinnon
• 金额: $ 25.83万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-10-01 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736595&HistoricalAwards=false
• 关键词: Submesoscale; Instabilities; Turbulence; Across; Oceans

Ocean flows at relatively large scales, typically more than tens of miles, are mostly confined to horizontal plane due to the rotation of the Earth. At the smaller submesoscale, this constraint is much reduced, allowing more vigorous vertical motion, which plays a crucial role in mediating upper ocean heat content and air-sea exchange. Improving the representation of these processes in numerical models is therefore important for accurate forecasts of a wide range of directly societally relevant phenomena, from ENSO to tropical monsoons to the rate of Arctic sea ice melt. Due to their intrinsic short lateral scales (order of km) and fast time scales (order of inertial period or faster), submesoscale flows have been difficult to observe directly in the ocean. Numerical and analytical studies, on the other hand, have made substantial progress in describing the dynamics of idealized submesoscale flows. Criteria have been developed for the onset of different submesoscale instabilities. Parametrizations have been made to account for these instabilities in global ocean models where they are not resolved. Yet little of the knowledge gained from these studies has been confirmed by or compared with observations, which makes it difficult to move forward with confidence. This project will address this gap by combining development and application of a comprehensive linear stability model with analysis of several substantial oceanographic datasets already in hand. This project largely written by and will fund an early career scientist.The model, developed by the early career scientist, is novel in that it is forced by observed profiles of density and velocity, unlike many idealized mean states that have been used in the past. Preliminary work demonstrates its capacity to reproduce a vast range of types of submesoscale instabilities, from mixed layer baroclinic instability to symmetric instability to Langmuir circulation, and everything in between. Unlike linear stability models before, it can smoothly transition from one instability class to another; i.e. it produces a broad spectrum of instabilities from a single mean flow state input. The model will be forced by and then compared with amassed datasets from several recent oceanographic expeditions. Two of the data-sets have shown strong evidence of submesoscale activity, both with anecdotal examples and systematic statistics. Model skill will be developed and tested using profiles from several of these examples. In turn, it is anticipated that the model results will help illuminate the nature of the dynamical instabilities present in the observations; because the model is initialized with real gradient profiles and allows a fully complex superposition of a wide range of instabilities, it is uniquely suited for detangling complex observations in a broadband ocean. Comparison of model predictions with available observations that span multiple ocean basins and multiple seasons will help develop understanding of broad patterns of submesoscale variability, the sorts of patterns that can be used to validate new global parametrization development.

由于地球的自转，相对大尺度的海洋流动，通常超过几十英里，大多数被限制在水平面内。在较小的次中尺度上，这种限制大大减少，允许更有力的垂直运动，这在调解海洋上层热含量和海气交换中起着至关重要的作用。因此，改善这些过程在数值模式中的表现，对于准确预测从厄尔尼诺/南方涛动到热带季风到北极海冰融化率等一系列与社会直接相关的现象十分重要。由于其固有的短横向尺度（公里级）和快速的时间尺度（惯性周期或更快），亚中尺度流动一直难以直接在海洋中观测。另一方面，数值和分析研究在描述理想亚中尺度流动的动力学方面取得了实质性进展。不同的亚中尺度不稳定的发病标准已经制定。在全球海洋模型中，参数化已被用来解释这些不稳定性，而这些不稳定性没有得到解决。然而，从这些研究中获得的知识很少得到观测的证实或与观测进行比较，这使得很难有信心地向前迈进。该项目将通过将综合线性稳定性模型的开发和应用与已掌握的几个重要海洋学数据集的分析相结合来解决这一差距。该项目主要由一位早期职业科学家撰写并将资助。该模型由早期职业科学家开发，是新颖的，因为它是由观察到的密度和速度分布所驱动的，不像过去使用的许多理想化的平均状态。初步工作表明，它有能力再现各种类型的亚中尺度不稳定性，从混合层斜压不稳定对称不稳定朗缪尔环流，以及介于两者之间的一切。与以往的线性稳定性模型不同，它可以从一个不稳定性类别平滑地过渡到另一个不稳定性类别，即它从单个平均流状态输入产生宽谱的不稳定性。该模型将通过最近几次海洋学考察收集的数据集进行分析，然后与之进行比较。其中两个数据集显示了中尺度以下活动的有力证据，这两个数据集都有轶事实例和系统统计数据。将使用其中几个示例中的配置文件来开发和测试模型技能。反过来，预计模型结果将有助于阐明观测中存在的动力学不稳定性的性质;由于模型是用真实的梯度剖面初始化的，并允许各种不稳定性的完全复杂叠加，因此它特别适合于在宽带海洋中进行复杂观测。将模式预测与跨越多个海洋盆地和多个季节的现有观测结果进行比较，将有助于了解次中尺度变率的广泛模式，这种模式可用于验证新的全球参数化发展。

项目成果

Lifecycle of a Submesoscale Front Birthed from a Nearshore Internal Bore

近岸内孔产生的亚尺度前缘的生命周期

• DOI: 10.1175/jpo-d-21-0062.1
• 发表时间: 2021
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Haney, Sean R.;Simpson, Alexandra J.;McSweeney, Jacqueline M.;Waterhouse, Amy F.;Haller, Merrick C.;Lerczak, James A.;Barth, John A.;Lenain, Luc;Palóczy, André;Adams, Kate
• 通讯作者: Adams, Kate