A Vortex Census from Lagrangian Floats

拉格朗日浮子的涡旋普查

基本信息

批准号：
1235310
负责人：
Jonathan Lilly
金额：
$ 72万
依托单位：
NorthWest Research Associates, Incorporated
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2012
资助国家：
美国
起止时间：
2012-09-01 至 2017-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1235310&HistoricalAwards=false
关键词：
Vortex Census Lagrangian Floats

项目摘要

Three key issues motivate a systematic re-examination of coherent vortex structures in Lagrangian float data: (i) a pressing need for detailed comparison of eddy parameterization schemes, as well as of eddy-resolving numerical models, against in situ observations; (ii) the recent recognition, based on satellite altimetry, that a large swath of variability previously attributed to Rossby waves instead appears due to an energetic nonlinear mesoscale eddy field, the interior signature of which is as yet largely unknown; and (iii) an increasing appreciation of the important but multifaceted role coherent eddies play in fluid transport and mixing, including eddies at scales too small to be accurately resolved by altimetry. These issues all point to the need for a quantitative and integrated study of the coherent eddy field and its large-scale impacts. At the same time, turbulence studies emphasize that the current ability to understand the oceanic vortex field is hampered by the lack of an objective and theoretically compelling avenue for inferring Eulerian "truths" from available Lagrangian data - that is, the inability to currently perform a formal census of vortex properties and populations from the Lagrangian platform. This project will quantify vortex characteristics, populations, and dynamical impacts across a broad range of scales using the historical set of deep Lagrangian acoustically tracked floats. A series of recent advances by the PI and collaborators make such a study possible, providing a new and particularly direct link between Lagrangian observations and vortex dynamics. The starting point for the study is the ability to extract, objectively and with uncertainty estimates, detailed time-varying aspects of coherent eddies from individual Lagrangian trajectories. The first phase of this project utilizes this method to describe vortex currents as they appear in the data. In this second phase, inhomogenous Lagrangian observations will be used to form estimates of underlying Eulerian fields, via statistical inference backed by extensive testing within idealized quasigeostrophic simulations. The goal is to describe the vortex distribution as a geographically-varying random field controlled by a small number of parameters. The third and final phase quantifies impacts of the vortex field on the large-scale flow - by estimating the velocity and vorticity distributions as well as particle and vorticity transport associated with the eddies.Intellectual Merit: This study will substantially extend and refine our understanding of the role of coherent eddies in the ocean. It will be an important step towards the larger goal of understanding and quantifying the impact of small-scale "eddy" processes on the large-scale circulation, by isolating one of the processes that make up the general phenomenon of "eddy fluxes". Addressing the connection to observations from satellite altimetry is particularly timely. The construction and testing of a Lagrangian vortex census statistical methodology is itself an important contribution.Broader Impacts: A primary societal impact of this work is its potential impact on our ability to predict long-term climate variability by immediately increasing our ability to assess the fidelity of both eddy-resolving and non-eddy-resolving numerical models against in situ data. The postdoctoral researcher working on the project will benefit from exposure to novel analysis techniques and an important Lagrangian data set. Value-added versions of the float dataset, and all analysis software developed during this project, will be freely distributed to the community as described in the attached Data Management Plan; these open a new window into ocean dynamics.

三个关键问题促使系统地重新检查拉格朗日浮子数据中的相干涡结构：（i）迫切需要将涡流参数化方案以及涡流解析数值模型与现场观测进行详细比较； (ii) 最近根据卫星测高认识到，先前归因于罗斯贝波的大量变化实际上是由于高能非线性中尺度涡流场而出现，其内部特征目前尚不清楚；（iii）越来越多地认识到相干涡流在流体传输和混合中发挥的重要但多方面的作用，包括尺度太小而无法通过高度测量准确解析的涡流。这些问题都表明需要对相干涡流场及其大尺度影响进行定量和综合研究。与此同时，湍流研究强调，由于缺乏客观且理论上令人信服的途径来从可用的拉格朗日数据中推断欧拉“真理”，目前理解海洋涡流场的能力受到阻碍——也就是说，目前无法执行来自拉格朗日平台的涡旋属性和种群的正式普查。该项目将使用历史上的深拉格朗日声学跟踪浮标集来量化广泛尺度的涡旋特征、数量和动态影响。 PI和合作者最近取得的一系列进展使这样的研究成为可能，在拉格朗日观测和涡动力学之间提供了新的、特别直接的联系。这项研究的出发点是能够通过不确定性估计客观地从各个拉格朗日轨迹中提取相干涡流的详细时变方面。该项目的第一阶段利用这种方法来描述数据中出现的涡流。在第二阶段，非均匀拉格朗日观测将用于通过理想化准地转模拟中广泛测试支持的统计推断来形成对基础欧拉场的估计。目标是将涡旋分布描述为由少量参数控制的地理变化的随机场。第三阶段也是最后阶段，通过估计速度和涡度分布以及与涡流相关的粒子和涡度传输，量化涡场对大规模流动的影响。智力优点：这项研究将大大扩展和完善我们对海洋中相干涡流的作用。通过分离构成“涡流”一般现象的过程之一，这将是朝着理解和量化小尺度“涡流”过程对大尺度环流影响的更大目标迈出的重要一步。解决与卫星测高观测的连接问题尤为及时。拉格朗日涡普查统计方法的构建和测试本身就是一项重要贡献。更广泛的影响：这项工作的主要社会影响是它通过立即提高我们评估保真度的能力来对我们预测长期气候变化的能力产生潜在影响根据现场数据建立涡旋解析和非涡旋解析数值模型。从事该项目的博士后研究员将受益于新颖的分析技术和重要的拉格朗日数据集。浮动数据集的增值版本以及本项目期间开发的所有分析软件将按照所附数据管理计划中的描述免费分发给社区；这些为了解海洋动力学打开了一扇新的窗口。