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: 2148404
• 负责人: Amit Tandon
• 金额: $ 7.66万
• 依托单位: University of Massachusetts, Dartmouth
• 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=2148404&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.

背风波是由测深稳定分层流推动的内部重力波的一个例子。海洋内部背风波的水平波长在 O(1-10) km 之间，它连接中尺度水流和小尺度湍流，并在海洋能量级联中发挥核心作用。它们的产生对平衡流施加波阻力并提取中尺度能量，它们的传播通过波通量传输该能量。当它们破裂时，它们将能量向下转换为湍流。该项目将研究为什么在流-地形相互作用的下游深海中观测到的耗散小于将背风波产生与耗散等同的常见假设所预测的。这项研究将确定背风波在能量耗散与重新分配方面的作用，以便更好地参数化海洋环流模型的波浪阻力和混合。该项目将支持早期职业生涯的领先。 PI、一名研究生和两名本科生将接受波浪动力学和海洋建模的过程研究海洋模型 (PSOM) 的区域数值模拟，以模拟非平均切变中的背风波的产生、传播、相互作用和消散。 -已广泛用于研究亚中尺度过程的静水海洋模型，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背风处湍流的机制。这些机制是：（i）由于地形阻挡和分裂而产生非线性，（ii）将背风波能量重新吸收回剪切平均流，（iii）以逃离局部生成的自由波形式进行远程耗散。 (iv) 来自局部生成地形的背风波能量的下游平流 在这些机制中，底部强化流中捕获的背风波会发生重吸收，而非线性生成和下游平流则具有这种作用。主要分析工具将是不同成分（平均射流、背风波和自由波）的能量守恒预算，以量化背风波的耗散和非耗散命运。授予 NSF 的法定使命，并通过评估反映使用基金会的智力优点和更广泛的影响审查标准，被认为值得支持。