Scattering of Baroclinic Kelvin Waves by Sills in Straits

海峡基台对斜压开尔文波的散射

• 批准号: 1336752
• 负责人: Theodore Durland
• 金额: $ 57.21万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-15 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1336752&HistoricalAwards=false
• 关键词: Scattering; Baroclinic; Kelvin; Waves; Sills

This project will utilize analytical and numerical modeling to study how shallow sills in channels and straits impact incident coastal Kelvin waves. It is motivated by measurement programs over the past two decades in the passages carrying the Indonesian Throughflow (ITF). Kelvin waves generated in the equatorial Indian Ocean have been shown to penetrate these passages episodically, often reversing branches of the ITF for up to a month at a time. Recent measurements have revealed a vertical structure to these reversals and evidence of vertical phase propagation within the straits associated with passing Kelvin waves. Speculation at present connects the vertical propagation observed within the straits to vertical propagation of the incident waves, but the project will demonstrate that the situation can involve considerable complexity. The work will provide a dynamical foundation for understanding the observations in the ITF passages. A preliminary analytical model has been developed which shows promising results. An incident wave of a single baroclinic mode will be scattered into vertical propagation in the channel and in the basin past the channel. A strait will alter the frequency content of an incident vertically propagating pulse, resulting in vertical propagation characteristics of the transmitted and bypassed pulses that are different from those of the incident pulse. The project will develop the preliminary analytical model, providing justification for the foundational assumptions, error estimates and validity limits. The model predictions will then be analyzed for the most intuitive physical understanding of the various effects. Numerical process models would be used to understand the effects on the model predictions of more realistic dissipation, boundary conditions and bottom topography. Finally, a regional numerical model will be used to attempt to reproduce observations in the ITF passages and explain these in terms of the underlying dynamics revealed by the more idealized models.Intellectual Merit: This study will advance the theory of geophysical fluid dynamics by clarifying the effects that sills in straits and channels have on the baroclinic structures and vertical propagation of incident coastal Kelvin waves.Broader Impacts: The Indonesian Throughflow is a vital link in the upper branch of the global oceanic overturning circulation, which in turn is an important component of Earth's climate system. The Indian Ocean Kelvin waves are known to episodically impact the ITF to the extent of frequently reversing the flow direction, yet the complex vertical and temporal structure of these effects is only now beginning to be understood and they are poorly parameterized in global models. Although this study does not aim at improving the parameterizations of global climate models, its contributions will at least improve the knowledge of what must be parameterized in order to successfully model the global system. The project will provide support for a graduate student and will train the student in analytical and numerical modeling techniques necessary to make further contributions in oceanic dynamics.

该项目将利用分析和数值模拟来研究渠道和海峡中的浅槛如何影响入射的沿海开尔文波。它是由测量计划在过去的二十年中，在通道进行印尼的对流（ITF）的动机。在赤道印度洋产生的开尔文波已经被证明会偶尔穿过这些通道，经常一次扭转ITF的分支长达一个月。最近的测量结果显示，这些逆转的垂直结构和证据的垂直相位传播的海峡内通过开尔文波。目前的推测将海峡内观察到的垂直传播与入射波的垂直传播联系起来，但该项目将证明情况可能相当复杂。这项工作将为理解ITF段落中的观察结果提供动力学基础。初步的分析模型已经开发，显示出可喜的成果。单一斜压模态的入射波在河道和经过河道的盆地中将被散射成垂直传播。海峡将改变入射垂直传播脉冲的频率内容，导致发射和旁路脉冲的垂直传播特性与入射脉冲的垂直传播特性不同。 该项目将开发初步分析模型，为基本假设、误差估计和有效性限度提供理由。然后将对模型预测进行分析，以便对各种效应进行最直观的物理理解。数值过程模型将用于了解更真实的耗散、边界条件和海底地形对模型预测的影响。最后，将使用一个区域数值模式，试图重现ITF通道中的观测结果，并根据更理想化的模式所揭示的基本动力学来解释这些观测结果。智力上的优点：这项研究将通过澄清海峡和航道中的底床对斜压结构和入射海岸开尔文波垂直传播的影响，推进地球物理流体动力学理论。印度尼西亚洋流是全球海洋翻转环流上分支的重要环节，而海洋翻转环流又是地球气候系统的重要组成部分。众所周知，印度洋开尔文波会对ITF产生周期性影响，经常使流动方向发生逆转，但这些影响的复杂垂直和时间结构现在才开始被理解，而且在全球模型中参数化程度很低。虽然这项研究的目的不是为了改善全球气候模型的参数化，其贡献将至少提高什么必须参数化，以成功地模拟全球系统的知识。该项目将为一名研究生提供支助，并将对该学生进行必要的分析和数值建模技术培训，以便在海洋动力学方面作出进一步贡献。