Collaborative Research: Lee Waves and Sheared Mean Flow: Interactions and Impacts of Topography

合作研究：李波和剪切平均流：地形的相互作用和影响

• 批准号: 2148405
• 负责人: Eric Kunze
• 金额: $ 28.78万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-15 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2148405&HistoricalAwards=false
• 关键词: Collaborative; Research; Lee; Waves; Sheared

Lee waves are an example of internal gravity waves forced by stably stratified flow over bathymetry. Oceanic internal lee waves have horizontal wavelengths between O(1–10) km that bridge mesoscale currents and smallscale turbulence and play a central role in the ocean’s energy cascade. Their generation exerts wave drag on balanced flow and extracts mesoscale energy, and their propagation transports this energy through wave-fluxes. When they break, they convert energy downscale to turbulent dissipation and mixing, maintaining ocean’s stratification and in turn contributing to the largescale circulation. This project will examine why observed dissipation in the deep ocean downstream from flow-topography interactions is smaller than predicted by the common assumption of equating lee-wave generation with dissipation. This research will determine the role of lee waves in dissipating versus redistributing energy for better parameterizations of wave drag and mixing for oceanic general circulation models. This project will support an early-career lead PI, a graduate and two undergraduate students to be trained on wave dynamics and ocean modeling. Regional numerical modeling with Process Study Ocean Model (PSOM) will simulate the generation, propagation, interaction and dissipation of lee waves in mean shear. PSOM is a non-hydrostatic ocean model that has been widely used to study submesoscale processes. The PIs will extend prior idealized simulations to explore a range of topographic variations to examine mechanisms that may suppress turbulence in the lee of flow-topography interactions. These mechanisms are: (i) nonlinear generation due to topographic blocking and splitting, (ii) reabsorption of lee-wave energy back to the sheared mean flow, (iii) remote dissipation in the form of free waves that escape the localized generating current, and (iv) downstream advection of lee-wave energy from localized generating topography. Among these mechanisms, reabsorption will occur for trapped lee waves in bottom-intensified currents, while nonlinear generation and downstream advection have a strong dependence on specific, as opposed to random, topographies. The primary analysis tool will be energy conservation budgets for different components (mean jet, lee waves, and free waves) to quantify the dissipative and non-dissipative fates of lee waves.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.

李氏波是内部重力波的一个例子，由稳定的分层流在测深上施加压力。海洋内部背风波的水平波长在0 (1-10)km之间，它架起了中尺度流和小尺度湍流的桥梁，在海洋能量级联中起着核心作用。它们的产生对平衡气流施加波浪阻力并提取中尺度能量，而它们的传播通过波通量将这种能量传递出去。当它们破裂时，它们将能量转化为湍流耗散和混合，维持海洋的分层，进而促进大尺度环流。这个项目将研究为什么观测到的深海下游水流-地形相互作用的耗散比将背风波产生与耗散相等的一般假设所预测的要小。这项研究将确定背风波在耗散和再分配能量中的作用，以便更好地参数化海洋环流模式的波浪阻力和混合。该项目将支持一名早期职业生涯的首席PI，一名研究生和两名本科生接受波浪动力学和海洋建模方面的培训。采用过程研究海洋模式（PSOM）进行区域数值模拟，模拟平均切变背风波的产生、传播、相互作用和消散。PSOM是一种非流体静力海洋模式，已被广泛用于研究亚中尺度过程。pi将扩展先前的理想化模拟，以探索一系列地形变化，以检查可能抑制流动-地形相互作用中的湍流的机制。这些机制是：(i)由于地形阻塞和分裂导致的非线性产生，（ii）背风波能量被重新吸收回剪切平均流，（iii）以自由波的形式逃离局部产生电流的远程耗散，以及（iv）局部产生地形的背风波能量的下游平流。在这些机制中，被困的背风波在底部增强的水流中会发生重吸收，而非线性产生和下游平流则强烈依赖于特定的地形，而不是随机的地形。主要的分析工具将是不同分量（平均射流、背风波和自由波）的能量节约预算，以量化背风波的耗散和非耗散命运。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。