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.

Langmuir循环（LC）来自风强迫和波动动力学的相互作用，由一对平行的反旋转涡旋（或细胞）组成，该涡流（或细胞）大约沿风向。在大陆架上，水是浅且相对混杂的，强风暴的通过可以诱导大型的Langmuir细胞，其中最大的细胞可以跨越整个水柱，并且对沉积物的重新悬浮有很大影响。这些所谓的Langmuir Supercells（LS）是在浅架子上运输沉积物和生物活性材料的向量的重要作用：它们的准本质使它们比底部边界层剪切湍流在从底部移出的低速层移出底部并进入散装流量以进行后期运输时更有效。这项研究将分析15、26和40M深度的三个不同位点的现有观察结果以及高分辨率的数值模拟，以确定对许多因素的影响，例如大规模流动，潮流，密度较低的表面层以及风向和波浪方向之间的错误。大陆货架在生物学上的生产力高，LS对影响这种生产力或分配产品的过程有直接影响。因此，货架模型必须结合此类主要过程的熟练参数化。这项研究将改善用于解释许多沿海和区域模型中Langmuir循环的参数化，在这些模型中，该域的大小排除了以足够高的分辨率运行该模型以直接捕获Langmuir循环。每年夏天，一名博士后研究员，两名研究生和一名本科生将接受体育海洋学，湍流动力学和封闭和数值技术的培训。其中一名学生来自一个人数不足的少数群体。观察地点由新泽西州南部海岸的内架15m的罗格斯狮子座天文台，佐治亚州海岸中部26m水的海军R2塔以及佐治亚州海岸的2600万塔以及40m水中的哈特拉斯角以北的另一个地点。对LEO和R2的测量结果的分析表明，LS特性差异，LEO发生了更连贯和强烈的LS。在三个地点的VADCP测量之后，密切对LS流量的HATTERAS数据以及大型涡流模拟（LE）的新分析将阐明潮汐和地球流动，表面浮力，表面浮力以及模拟的风能和波浪结合LS和相关垂直运输的动态。 LES将有助于提供现场数据集中缺少的关键信息，例如表面和底部边界层中的详细速度结构，以对影响不同站点上LS的各种强迫机制的作用做出明确的结论。 LE将用于获得代表LS在影响其强度和相干性的各个过程中LS引起的非本地垂直混合强度的垂直速度波动的缩放。垂直速度波动的缩放将用于告知由PI核算总体Langmuir湍流的局部运输和LS引起的非局部运输的局部运输而开发的KPP（K-Profile参数化）。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，以通过与LES和LES和现场测量值进行验证。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力和更广泛影响的评估来通过评估来获得支持的值得的。