The life cycle of internal waves in the ocean: effects of currents and modulational instabilities

内波是非线性色散波的一个例子，200多年来，对它的研究一直是流体力学中一个引人入胜的重要研究领域。当重力恢复力作用于垂直驱替的流体时，它们存在于密度分层流体的内部。海洋中近一半的内波能量的来源是推动流体在倾斜的水深测量中上下移动的潮流，例如大陆坡和洋脊，近几十年来，人们花费了大量努力来了解这种波源的时空分布以及波传播离开时的命运。内波在将能量从大尺度转移到小尺度以及影响海洋环流和生产力的热量和营养物质的垂直混合方面发挥了基本作用。它们可以在很长的距离内运送液体和颗粒。它们的水流可以使沉积物重新悬浮，并冲击近海结构物。已经观察到鱼类垂直迁移，以响应大的内波的通过，以优化它们的摄食策略。内波可以从其产生地点传播数千公里，因此在一个位置产生的波可以在很远的距离产生影响。内波以多种形式出现，包括垂直和水平传播的内波波束和水平传播的内波模式。波束在接近临界的底部坡度产生，并被假设在塑造大陆架方面发挥作用。水平传播的波包括波长为O(100)公里的内潮，它们可以演化为内孤立波。我的研究目标是(I)确定背景流如何影响潮汐-地形相互作用产生的内波，以及内波如何与洋流和涡流相互作用；(Ii)调查内波的跨陆架传输；以及(Iii)调查水平传播内波包的演变，以确定流氓(异常大的)内波可能形成的条件以及内波包可能如何分解。这项研究将使用二维和三维数值模拟和理论相结合的方法。它将包括理想化的过程研究和基于观测的数值模拟。理论模型将被用来理解由这些模型模拟的复杂波场，并且由于其相对简单和快速，通常需要更全面地探索参数空间。研究地点包括安哥拉和秘鲁的大陆架，这是重要渔业的地点，以及亚马逊大陆架。这项研究将有助于海洋资源的管理和提高我们预测海洋当前和未来状况的能力。我的研究团队成员将获得高性能计算方面的宝贵专业知识，包括数据分析和可视化，以及处理复杂问题的技能。

Internal waves are examples of nonlinear-dispersive waves, the study of which has been a fascinating and important area of research in fluid dynamics for over 200 years. They exist in the interior of density-stratified fluids when gravitational restoring forces act on vertically displaced fluid. The source of close to half of the internal wave energy in the oceans is tidal currents pushing fluid up and down sloping bathymetry such as the continental slopes and ocean ridges and in recent decades a lot of effort has been expended in understanding the spatial and temporal distribution of this wave source and on the fate of the waves as they propagate away. Internal waves play a fundamental role in transferring energy from large to small scales and in the vertical mixing of heat and nutrients impacting ocean circulation and productivity. They can transport fluid and particles over large distances. Their currents can re-suspend sediments and impact offshore structures. Fish have been observed to migrate vertically in response to the passing of large internal waves to optimize their feeding strategy. Internal waves can propagate thousands of kilometers from their generation site so wave generation in one location can have an impact at great distances. Internal waves appear in many forms including vertically and horizontally propagating internal wave beams and horizontally propagating internal wave modes. Beams are generated at near-critical bottom slopes and have been hypothesized to play a role in shaping the continental shelf. Horizontally propagating waves include internal tides with wavelengths of O(100) km which can evolve into internal solitary waves. My research objectives are to (i) determine how background currents affect internal wave generation by tide-topography interactions and how internal waves interact with ocean currents and eddies; (ii) investigate cross-shelf transport by internal waves; and (iii) to investigate the evolution of horizontally propagating internal wave packets to determine the conditions under which rogue (unusually large) internal waves may form and how the packets may break down. The research will use a mixture of two- and three-dimensional numerical modelling and theory. It will include idealized process studies and numerical simulations based on observations. Theoretical models will be used to understand the complex wave field simulated by these models and, because of their relative simplicity and speed, are often required to more fully explore a parameter space. Sites studied include the Angolan and Peruvian Shelves which are locations of important fisheries, and the Amazon Shelf. This research will contribute to the management of ocean resources and the improvement of our ability to predict the current and future state of the ocean. Members of my research team will gain valuable expertise in high-performance computing, including data analysis and visualization, and skills in working on complex problems.