Collaborative Research: Three-Dimensional Surfzone Eddies

合作研究：三维表面区涡流

• 批准号: 1061692
• 负责人: Stephen Henderson
• 金额: $ 43.18万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1061692&HistoricalAwards=false
• 关键词: Collaborative; Research; Three; Dimensional; Surfzone

Surfzone eddies mix pollutants, erode coast- lines, endanger swimmers, and transport marine organisms. Eddies may be directly forced by groups of breaking surface gravity waves, or may develop as shear instabilities of mean alongshore currents ('shear production'). The relative importance of direct forcing and shear production has not yet been determined, but recent numerical simulations suggest that wave group forcing may be an important, yet mostly neglected, factor. Surfzone eddies have often been viewed as two-dimensional and depth-independent, but recent observations indicate that eddies can in fact be strongly three-dimensional. Indeed, observed three-dimensionality can be so strong that total shear production cannot be calculated unless depth-dependence is resolved. This study will examine the dynamics of three-dimensional surfzone eddies using depth-resolving field observations and numerical modeling.A 15-element array of Acoustic Doppler Current Profilers (ADCPs) will be deployed to gather the first synoptic, vertically-resolved observations of surfzone mean currents and eddies. ADCP observations will be used in conjunction with a numerical model that will take advantage of recently developed 3D wave forcing formulations, while also simulating eddy generation by wave groups. Shear production and direct forcing terms in the eddy energy equation will be evaluated in a range of numerical simulations, and in observations, to determine their relative importance under a variety of incident-wave conditions. The project will provide the first horizontally-resolved in-situ observations of near-surface eddy motions. In addition to quantifying magnitudes, phasing, and de-correlation across-shore, the team will test whether alongshore propagation speeds and de-correlation distances vary in the vertical (both vary across-shore). These observations will be compared with simulations. Numerical simulations and observations, especially vertical phasing and coherence with wave groups, will be examined to distinguish vertical shear generated by breaking from shear generated by bottom friction or horizontal advection. Simulations will be used to study the effects of three- dimensionality on mixing, including possible rapid lateral mixing of passive tracers and momentum.This experiment will build on substantial existing resources, including Washington State University experience working with ADCPs, and Oregon State University expertise in three-dimensional circulation modeling. Deployment and recovery will carried out by one of the world's best-equipped field crews at the US Army Corps of Engineers' Field Research Facility. Broader Impacts: This project will improve our understanding of the nearshore eddies that mix pollutants and organisms, transport sediments, and endanger swimmers. A community model for predicting nearshore currents and eddies will be tested and refined and made available to the community, constituting an important step towards the goal of a predictive model for surfzone pollution. Such a model would be valuable to managers, who must currently rely on bacterial cultures that are slow to return actionable results. Field data, constituting the first depth-resolving synoptic measurements of surfzone mean currents, and the first profiling array to extend 1 km from the shore to the inner shelf, will be made available to the oceanographic community. Three graduate students will be funded. To disseminate knowledge beyond universities, students will likely partner with high school teachers (through Washington State University's GK-12 program) and PIs will partner with a community college teacher (facilitated by the COSEE program).

表面涡流混合污染物，侵蚀沿岸线，危害游泳者和运输海洋生物。涡流可以直接被断裂的表面重力波的组直接强制，也可以作为平均沿岸电流的剪切不稳定性（“剪切产生”）形成。直接强迫和剪切产生的相对重要性尚未确定，但是最近的数值模拟表明，波群强迫可能是一个重要但大多被忽略的因素。表面涡流经常被视为二维和独立的涡流，但最近的观察结果表明，涡流实际上可以是强烈的三维。实际上，观察到的三维性能是如此之强，以至于除非解决深度依赖性，否则无法计算总剪切产生。这项研究将使用深度分辨的现场观测和数值建模研究三维表面涡流的动力学。声音多普勒电流剖面（ADCP）的15个元素阵列将部署，以收集第一个Synoptict，垂直垂直，垂直分辨的表面平均电流和涡流的垂直分辨观测。 ADCP观察结果将与数值模型结合使用，该模型将利用最近开发的3D波强制公式，同时还通过波组模拟涡流产生。将在一系列数值模拟和观察中评估涡流方程中的剪切产生和直接强迫术语，以确定它们在各种入射波条件下的相对重要性。该项目将提供第一个水平分辨的近地表涡流的原位观测。除了量化跨越跨越的幅度，相位和去相关​​外，该团队还将测试沿岸的繁殖速度和去相关距离是否在垂直方向有所不同（两者都在跨岸上变化）。这些观察结果将与模拟进行比较。数值模拟和观测值，尤其是与波群的垂直相相位和连贯性，以区分通过底部摩擦或水平对流产生的剪切而产生的垂直剪切。模拟将用于研究三维对混合的影响，包括被动示踪剂和动量的快速横向混合。该实验将基于现有的现有资源，包括华盛顿州立大学与ADCPS合作的经验以及俄勒冈州立大学在三维循环建模中的专业知识。美国陆军工程兵团现场研究设施中，将由世界上装备最完整的现场工作人员之一进行部署和恢复。更广泛的影响：该项目将提高我们对混合污染物和生物体，运输沉积物和危害游泳者的近岸涡流的理解。预测近岸电流和涡流的社区模型将经过测试和完善，并提供给社区，这构成了朝着表面污染的预测模型迈出的重要一步。这样的模型对于经理人来说将是有价值的，他们目前必须依靠缓慢回报可行结果的细菌文化。构成表面平均电流的首次分辨深度分辨的概要测量以及第一个将1公里从海岸扩展到内架1公里的分析阵列的现场数据将提供给海洋学社区。三名研究生将获得资助。为了传播大学以外的知识，学生可能会与高中教师（通过华盛顿州立大学的GK-12计划）合作，PIS将与社区大学老师合作（由Cosee计划促进）。