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Collaborative Research: Characterization of Langmuir Supercells in the Coastal Ocean

合作研究：沿海海洋朗缪尔超级单体的表征

基本信息

批准号：
1756675
负责人：
Clifton Woodson
金额：
$ 29.87万
依托单位：
University of Georgia Research Foundation Inc
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-06-01 至 2023-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756675&HistoricalAwards=false
关键词：
Collaborative Research Characterization Langmuir Supercells

项目摘要

Langmuir circulation (LC) arises from the interplay of wind forcing and wave dynamics, and consists of pairs of parallel counter-rotating vortices (or cells) oriented approximately in the direction of the wind. Over the continental shelf , where the water is shallow and relatively well-mixed, the passage of strong storms can induce large Langmuir cells, the largest of which can span the entire water column and have a strong influence on sediment re-suspension. These so-called Langmuir supercells (LS) play an important role as vectors for the transport of sediment and bioactive material on shallow shelves: their quasi-organized nature makes them more effective than bottom boundary layer shear turbulence at moving material out of the low-speed layer near bottom and into the bulk flow for lateral transport. This study will analyze existing observations from three different sites at 15, 26 and 40m depths as well as high resolution numerical simulations to determine the influence on LS of a number of factors such as large scale flows, tidal currents, less dense surface layers and misalignment between wind and wave direction. Continental shelves are biologically highly productive and LS have direct impact on processes affecting this productivity or distributing its products. Thus, it is essential that shelf models incorporate skillful parameterization of such dominant processes. This study will improve parameterizations used to account for Langmuir circulation in many coastal and regional models where the size of the domain precludes running the model at a high enough resolution to capture Langmuir circulations directly. One post-doctoral researcher, two graduate students and one undergraduate student in each summer will be trained in physical oceanography, turbulence dynamics and closures and numerical techniques. One of the students is from an underrepresented minority group.In the coastal ocean, LS has been observed under tidal and geostrophic flow components, surface heat fluxes and misaligned winds and waves serving to influence LS strength and coherency, as measured through bottom-mounted vertical-beam acoustic Doppler current profilers (VADCPs). Observation sites consist of the Rutgers LEO observatory in 15m of water at the inner shelf off the coast of southern New Jersey, the Navy's R2 tower in 26m of water at mid-shelf off the coast of Georgia, and an additional site north of Cape Hatteras in 40m of water. Analyses of the measurements at LEO and R2 have demonstrated differences in LS characteristics, with more coherent and intense LS occurring at LEO. New analysis of the Cape Hatteras data as well as large eddy simulations (LES) of LS flows closely following the VADCP measurements at the three sites will elucidate the dynamics by which tidal and geostrophic flows, surface buoyancy and misaligned wind and waves combine to affect LS and associated vertical transport. The LES will help provide key information missing from the field data sets, such as detailed velocity structure in the surface and bottom boundarylayers, required to make definite conclusions regarding the roles of the various forcing mechanisms influencing the LS at the different sites. LES will be used to obtain a scaling of vertical velocity fluctuations representative of the strength of non-local vertical mixing induced by LS under the various processes affecting its strength and coherency. The scaling of vertical velocity fluctuations will be used to inform a KPP (K-profile parameterization) developed by the PI accounting for the local transport of the overall Langmuir turbulence and the non-local transport induced by the LS. The updated LS KPP will be implemented in the one-dimensional vertical water column General Ocean Turbulence Model (GOTM) for validation via comparisons with the LES and the field measurements.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.

朗缪尔环流（LC）是由风强迫和波浪动力学的相互作用产生的，由成对的平行反向旋转的涡（或单元）组成，大致沿风向定向。在大陆架上，水较浅，混合相对较好，强风暴的经过可以引起大的朗缪尔池，其中最大的可以跨越整个水柱，对沉积物的重新悬浮有很大的影响。这些所谓的朗缪尔超胞（LS）作为载体的沉积物和生物活性物质的运输浅架上发挥着重要的作用：其准有组织的性质，使他们更有效地比底部边界层剪切湍流在移动材料的低速层附近的底部，并进入大规模流动横向运输。这项研究将分析现有的观测从三个不同的网站在15，26和40米的深度，以及高分辨率的数值模拟，以确定LS的影响的一些因素，如大规模的流动，潮流，不太密集的表面层和风和波浪方向之间的错位。大陆架在生物上具有很高的生产力，土地利用对影响这种生产力或分配其产品的过程有直接影响。因此，至关重要的是，货架模式纳入巧妙的参数化，这种主导进程。这项研究将改善参数化用于占朗缪尔环流在许多沿海和区域模型的域的大小排除运行模型在一个足够高的分辨率直接捕捉朗缪尔环流。每年夏季将有一名博士后研究员、两名研究生和一名本科生接受物理海洋学、湍流动力学和闭合和数值技术方面的培训。在沿海海洋，通过安装在海底的垂直波束声学多普勒海流剖面仪（VADCP）测量，在潮汐和地转流分量、表面热通量和影响LS强度和相干性的错位风和波浪下观测到LS。观测点包括位于新泽西南部海岸内陆架15米深的罗格斯低地轨道天文台，位于格鲁吉亚海岸中陆架26米深的海军R2塔，以及位于哈特拉斯角以北40米深的另一个观测点。对低地球轨道和R2上测量结果的分析表明，LS特征不同，低地球轨道上的LS更为连贯和强烈。新的分析哈特拉斯角的数据以及大涡模拟（LES）的LS流紧接着在三个站点的VADCP测量将阐明潮汐和地转流，表面浮力和错位风和波浪联合收割机相结合，影响LS和相关的垂直运输的动力学。LES将有助于提供现场数据集中缺少的关键信息，如表面和底部边界层中的详细速度结构，这些信息是关于影响LS的各种强迫机制在不同地点的作用得出明确结论所必需的。LES将被用来获得一个缩放的垂直速度波动的强度下的各种过程影响其强度和相干性的LS引起的非本地垂直混合的代表。垂直速度波动的缩放将用于通知由PI开发的KPP（K剖面参数化），该PI考虑了整体朗缪尔湍流的局部传输和LS引起的非局部传输。更新后的LS KPP将在一维垂直水柱通用海洋湍流模型（GOTM）中实施，通过与LES和现场测量结果的比较进行验证。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。