Collaborative Research: Global eddy-driven transport estimated from in situ Lagrangian observations

该项目将研究全球海洋中长寿命相干中尺度涡旋的流体输送，包括其相干核心内的体积，涡旋外围的瞬时捕获流体，以及由于其中的涡流影响而在周围水团中产生的搅动效应。该项目将依赖于一种新的涡流识别分析技术(由私人投资机构在以前的工作中开发)，适用于对全球地表漂浮物数据集和历史上声学跟踪的地下漂浮物进行现场测量。这与网格卫星产品中涡流探测的通常方法不同，而是依赖于信号处理技术的适应来浮动轨迹数据。以前基于这种网格产品的研究大大低估了涡旋的数量，而高估了涡旋的大小和困在其中的水的传输。数据分析将辅以理论上的理想化和现实化的数值模拟。这项工作将阐述观测到的无处不在的相干涡旋对大尺度流动的影响实际上实现了什么。这是一个具有重要社会意义的问题，因为它与发展用于大气环流模式的准确的次网格尺度参数有关。该项目将推进拉格朗日数据的可行使用范围，从而为社区提供新的涡流检测工具。该项目将为基础和高级海洋学数据分析方面的免费在线课程提供支持和信息，以便下一代研究人员能够广泛接触到这些最先进的方法。该项目支持一位职业生涯早期的拉丁裔科学家，他将开发与该项目相关的本科生水平的教学模块。该项目将以从现场拉格朗日观测到的重大涡旋探测为起点，对相干涡流在驱动流体传输中的作用进行最终研究。这种被称为涡旋信号提取的检测方法从拉格朗日轨迹恢复时变的振荡信号分量，而不要求振荡是严格周期性的。可用的数据包括大约24,000个全球地表漂流轨迹加上来自一组历史涡旋解析浮标的另外3,000个地下轨迹，这两个数据集都是美国国家海洋和大气局的数据集。数据分析将得到理想化和超高分辨率的逼真建模的补充。这些分量将被用来探索从拉格朗日角度观察涡旋场的微妙之处，检查涡流探测方法的理论性质，并研究感兴趣的传输过程的动力学。该项目将分三个分支进行：(1)直接和间接涡动驱动输送的动力学，(2)涡旋可观测性问题，以及(3)全球估计。预期的产品将是通过统计建模对连贯的涡旋特性、种群和边界的新的全球估计，这得益于对长期和暂时捕获的物理学的更好理解。该项目将进一步提供一个校准过程，通过该过程，遥感特征可以更准确地映射到流体结构上，水文分析将把区域交通估计转换为大规模交通。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project will examine fluid transport by long-lived coherent mesoscale eddies in the global ocean, including volumes within their coherent cores, transiently trapped fluids in eddy peripheries, and stirring effects in the ambient watermasses due to eddy influence therein. The project would rely on a novel eddy-identifying analysis technique (developed in prior work by the PIs) applied to in-situ measurements from global surface drifter dataset and the historical set of acoustically-tracked subsurface floats. This is a departure from the usual approach of eddy detection in gridded satellite products, relying instead on the adaptation of signal processing techniques to float trajectory data. Prior studies based on such gridded products significantly underestimate numbers of eddies, and overestimate eddy sizes and transport of water trapped within them. Data analysis will be supplemented by theoretical idealized and realistic numerical modeling. This work will address what observed ubiquitous coherent eddies actually accomplish in terms of their effect on the large-scale flow. This is a question of societal importance because of its relevance for the development of accurate subgrid-scale parameterizations for general circulation models. The project will advance the boundaries of the viable use of Lagrangian data, and thus provide new tools for eddy examination to the community. The project will support and inform free online courses in fundamental and advanced oceanographic data analysis, so that that these state-of-the-art methodologies will be broadly accessible to the next generation of researchers. The project supports an early career latino scientist, who will develop an undergraduate-level teaching module related to this project.This project will produce a definitive study on the role of coherent eddies in driving fluid transport, taking significant eddy detections from in situ Lagrangian observations as the starting point. The detection method, called vortex signal extraction, recovers time-varying oscillatory signal components from Lagrangian trajectories, without a requirement for the oscillations to be strictly periodic. Available data include approximately 24,000 global surface drifter trajectories plus another 3,000 subsurface trajectories from an historical set of eddy-resolving floats, both NOAA datasets. Data analysis will be complemented by idealized and ultra-high-resolution realistic modeling. These components will be used to explore the subtleties of observing the eddy field from the Lagrangian perspective, to examine the theoretical properties of the eddy detection methods, and to investigate the dynamics of the transport processes of interest. The project will proceed in three branches: (i) dynamics of direct and indirect eddy-driven transport, (ii) the vortex observability problem, and (iii) global estimates. Anticipated products will be new global estimates of coherent eddy properties, populations, and boundaries through statistical modeling informed by an improved understanding of the physics of long-term and transitory trapping. The project will further provide a calibration process by which remotely-sensed features can be more accurately mapped onto fluid structures, and a hydrographic analysis will convert areal transport estimates into mass transports.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.