Dynamics of a Rotating, Supercritical Large-River Plume

这个项目分析了从哥伦比亚河口出现的超临界旋转羽流的动力学。由NSF资助的河流影响的陆架生态系统（RISE）项目为世界大型河流的羽流生态系统动力学提供了一个新的视角。羽流的功能主要取决于小尺度过程的联系，如50米宽的非流体静力骤降和羽流产生的非线性内波（NLIW），以及更大尺度的联系，例如，10- 30公里宽的潮汐羽流。该项目结合了分析和数值模型、遥感和船舶数据，以解决多尺度问题，并以传统模型无法实现的方式整合跨尺度问题。将研究以下问题：1）什么是潮汐羽流的动力学和能量学，以及观测到的南北不对称的羽流锋如何影响羽流能量学？拉格朗日锋面方程提供了一个优雅的公式动态的径向扩展羽，但实际的羽是有点深，速度较慢的南侧。这种不对称性影响锋面能量学，主要是因为羽流与底层潮汐涡度场的相互作用。不对称性导致NLIW产生开始的南侧的羽流和顺时针方向的进展。该项目扩展了现有的径向对称，分析和数值锋面模型来描述实际羽流配置的动力学和能量学。使用现有数据验证模型。2)是什么控制了NLIW的产生，以及这一代如何与特定的额叶结构和动力学相关？是否可以产生NLIW的潮汐羽流前端衰减到亚临界状态取决于相对深度的羽流前端和旋转羽流状态的前端衰减。基于羽流前缘、羽流近场和NLIW能量学，定义了一个NLIW生成判据，从而可以用解析和数值模型预测NLIW的生成。3)如何模拟具有显著倾伏和再循环的实际羽流前缘的结构和动力学？现有的拉格朗日锋面理论不能描述实际的锋面结构。与水力控制理论一样，它预测转捩的位置和性质，而不确定其结构，即使垂直混合的能量损失是该理论的一部分。遥感和船舶数据激励和指导新模式的发展，包括非流体静力学的羽流前暴跌。4)潮汐羽流是如何融入近场的？潮汐羽流和近场是如何混合到周围沃茨中的？何时何地营养物从下方进入羽流？CR是贫营养的，但羽是高产的。大多数羽流混合到周围沃茨和几乎所有的营养物输入从下面发生在潮汐羽流和近场。混合机制包括锋面过程、烟羽抬升、风和NLIW-平均切变相互作用。该项目使用精细结构和水团分析，合成孔径雷达数据和波动理论来分析羽流混合的位置，时间和机制。总之，这个项目解释了潮汐羽流的小尺度过程如何影响区域模式再现的大尺度过程。因此，它提供了一个更好的图片如何河流羽流的关键要素的工作和迫切需要的指导浮力羽流建模。浮力羽流在许多情况下都很重要，大型河流及其羽流在全球碳、养分和沉积物收支中发挥着重要作用。RISE表明，哥伦比亚羽流是一个大河流羽流的易处理的例子，羽流与上升流生态系统相互作用，提高了沿海生产。此外，人类和气候驱动的流动季节性变化正在改变羽流与沿海过程的相互作用，可能影响陆地碳和营养物质的命运。羽流和底层沃茨之间的大部分相互作用发生在潮汐羽流中，这是一种新定义的结构，仍然不完全了解，以及它合并的羽流近场。此外，幼鲑（包括濒危种群）广泛地在潮汐羽流及其前沿觅食。因此，本项目进行的分析既有助于了解具有全球意义的进程，又有助于区域管理工作

This project analyzes the dynamics of the supercritical, rotating plume emerging from the mouth of the Columbia River. The River Influenced Shelf Ecosystems (RISE) project, funded by NSF, provides a new view of plume ecosystem dynamics for the world's large rivers. The functioning of the plume depends vitally on the linkage of small-scale processes, like the 50m-wide non-hydro-static plunge and plume-generated non-linear internal waves (NLIW), to larger scales, e.g., the 10-30km wide tidal plume. This project combines analytical and numerical models, remote sensing, and vessel data to address questions on multiple scales and to integrate across scales in a manner that cannot be accomplished using conventional models. The following questions will be investigated: 1) What are the dynamics and energetics of the tidal plume, and how does the observed north-south asymmetry of the plume front influence plume energetics? Langrangian frontal equations provide an elegant formulation of the dynamics of a radially spreading plume, but the actual plume is somewhat deeper and slower on its south side. This asymmetry influences frontal energetics and occurs primarily because of an interaction of the plume with the underlying tidal vorticity field. Asymmetry causes NLIW generation to begin on the south side of the plume and progress clockwise. This project extends existing radially symmetric, analytical and numerical frontal models to describe the dynamics and energetics of the actual plume configuration. Models are verified using existing data. 2) What controls NLIW generation, and how can this generation be related to specific frontal structures and dynamics? Whether NLIW can be generated as the tidal plume front decays to a subcritical state depends on the relative depths of the plume front and rotating plume state to which the front decays. A generation criterion, based on plume front, plume near-field and NLIW energetics, is defined so that the generation of NLIW can be predicted with analytical and numerical models. 3) How can the structure and dynamics of the actual plume front be modeled, with its prominent plunge and recirculation? Existing Lagrangian frontal theory does not describe actual frontal structure ? like hydraulic control theory, it predicts the location and properties of a transition without determining its structure, even though energy loss to vertical mixing is part of the theory. Remote sensing and vessel data motivate and guide development of new models that incorporates the non-hydrostatic plume-front plunge. 4) How does the tidal plume blend into the near-field? How do the tidal plume and near-field mix into ambient waters? When and where does nutrient input to the plume from below occur? The CR is oligotrophic, but the plume is highly productive. Most plume mixing into ambient waters and almost all nutrient input from below occurs in the tidal plume and near-field. Mixing mechanisms include frontal processes, plume lift-off, winds, and NLIW-mean shear interaction. This project uses fine-structure and water mass analyses, SAR data, and wave theory to analyze the location, timing and mechanisms of plume mixing. In summary, this project explains how the small-scale processes of the tidal plume influence larger scale processes that are reproduced by regional models. Thus, it provides a much improved picture of how key elements of a river plume work and urgently needed guidance for modeling of buoyant plumes. Buoyant plumes are important in many contexts, and large rivers and their plumes play a major role in the global carbon, nutrient and sediment budgets. RISE has shown that the Columbia plume is a tractable example of a large-river plume, and that the plume interacts with the upwelling eco-system in a way that enhances coastal production. Human and climate-driven changes in flow seasonality are, moreover, altering the interaction of the plume with coastal processes, likely affecting the fate of carbon and nutrients from land. Much of the interaction between the plume and underlying waters takes place in the tidal plume, a newly defined structure that remains incompletely understood, and the plume-near-field into which it merges. Moreover, juvenile salmonids (including those of endangered stocks) feed extensively in the tidal plume and at its fronts. Thus, the analyses carried out by this project both facilitate understanding of processes with global significance and contribute to regional management efforts