Enhancing the accuracy of automatic eddy detection and the capability of recognizing the multi-core structures from maps of sea level anomaly

Yi, Jiawei; Du, Yanyan; He, Zhongshi; Zhou, Chenghu

doi:10.5194/os-10-39-2014

Cited by 88 publications

(80 citation statements)

References 35 publications

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“…Then, for each detected eddy center, the algorithm searches for the eddy edge that corresponds to the outermost closed SLA contour encircling only the considered center. This eddy detection method detects fewer false eddies than other classically used methods [Chaigneau et al, 2008;Souza et al, 2011;Yi et al, 2014] and is similar to the one used by Chelton et al [2011] to study the main eddy characteristics at global scale.…”

Section: Methodsmentioning

confidence: 82%

Main eddy vertical structures observed in the four major Eastern Boundary Upwelling Systems

2015

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In the four major Eastern Boundary Upwelling Systems (EBUS), mesoscale eddies are known to modulate the biological productivity and transport near‐coastal seawater properties toward the offshore ocean, however little is known about their main characteristics and vertical structure. This study combines 10 years of satellite‐altimetry data and Argo float profiles of temperature and salinity, and our main goals are (i) to describe the main surface characteristics of long‐lived eddies formed in each EBUS and their evolution, and (ii) to depict the main vertical structure of the eddy‐types that coexist in these regions. A clustering analysis of the Argo profiles surfacing within the long‐lived eddies of each EBUS allows us to determine the proportion of surface and subsurface‐intensified eddies in each region, and to describe their vertical structure in terms of temperature, salinity and dynamic height anomalies. In the Peru‐Chile Upwelling System, 55% of the sampled anticyclonic eddies (AEs) have subsurface‐intensified maximum temperature and salinity anomalies below the seasonal pycnocline, whereas 88% of the cyclonic eddies (CEs) are surface‐intensified. In the California Upwelling System, only 30% of the AEs are subsurface‐intensified and all of the CEs show maximum anomalies above the pycnocline. In the Canary Upwelling System, ∼40% of the AEs and ∼60% of the CEs are subsurface‐intensified with maximum anomalies extending down to 800 m depth. Finally, the Benguela Upwelling System tends to generate ∼40–50% of weak surface‐intensified eddies and ∼50–60% of much stronger subsurface‐intensified eddies with a clear geographical distribution. The mechanisms involved in the observed eddy vertical shapes are discussed.

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Section: Methodsmentioning

confidence: 82%

Main eddy vertical structures observed in the four major Eastern Boundary Upwelling Systems

2015

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“…Eddy detection and tracking algorithms based on altimetry data have been widely used to investigate mesoscale structures in both space and time (Isern-Fontanet and E. Garcìa-Ladona, 2003;Chelton et al, 2007Chelton et al, , 2011Escudier et al, 2016;Yi et al, 2014;Schütte et al, 2016;Mason and Pascual, 2013). These algorithms, applied on global and regional scales, have been successful in the characterization of several properties, such as polarity, propagation pathway, lifetime, radius and amplitude.…”

Section: Methodsmentioning

confidence: 99%

Mesoscale Eddies in the Algerian Basin: do they differ as a function of their formation site?

Pessini¹,

Olita²,

Cotroneo³

et al. 2018

Preprint

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Abstract. The circulation of the Western Mediterranean Sea (WMED) is dominated by highly variable and heterogeneous mesoscale circulation, strongly driven by the formation and propagation of eddies (cyclonic and anticyclonic) mainly acting in the Algerian Basin. Anticyclones are characterized by longer life, so potentially contributing to a large extent to the mesoscale characterization of the basin. Hereafter we will take into account only anticyclonic structures.In order to investigate the spatial and temporal distribution of eddy generation and their respective paths in the Algerian Basin, We find that anticyclonic short-life eddies mostly occur in the northern portion of the domain, north of 39•

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“…In general, the automated eddy detection algorithms are categorized into three types: (1) physical parameter-based algorithms, e.g. Okubo-Weiss (Isern-Fontanet et al, 2003;Chaigneau et al, 2008); (2) flow geometry-based algorithms (Fang and Morrow, 2003;Chaigneau et al, 2011;Petersen et al, 2013;Chelton et al, 2011;Xu et al, 2011;Wang et al, 2015); and (3) hybrid methods, which involve physical parameters and flow geometry characteristics (Nencioli et al, 2010, Xiu et al, 2010Dong et al, 2011;Yi et al, 2014). However, each identification method poses a multinuclear eddy identification problem, e.g.…”

Section: Introductionmentioning

confidence: 99%

“…However, their splitting process often resulted in some track problems, and it was finally abandoned. Subsequently, Yi et al (2014) applied a hybrid detection approach by integrating the ideas of the Okubo-Weiss method and the SLA-based method. Li et al (2014), following the approach proposed by Chelton et al (2011), attempted to split multiple eddies according to SLA with two simple strategies and a threshold for strategy choice.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Watershed strategy for oceanic mesoscale eddy splitting

Sun

2015

Ocean Sci.

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Abstract. To identify oceanic mononuclear mesoscale eddies, a threshold-free splitting method was developed based on the watershed. Because oceanic eddies are similar to plateaus and basins in the map of the sea level anomaly (SLA) data, the natural divisions of the basins are the watersheds between them. The splitting algorithm is based on identifying these watersheds by finding the path of steepest descent. Compared to previous splitting methods, the proposed splitting algorithm has some advantages. First, there are no artificial parameters. Second, the algorithm is robust; the splitting strategy is independent of the algorithm and procedure and automatically guarantees that the split mononuclear eddies are simply connected pixel sets. Third, the new method is very fast, and the time complexity is O(N ), where N is the number of multinuclear eddy pixels; each pixel is scanned only once for splitting, regardless of how many extremes there are. Fourth, the algorithm is independent of parameters; the strategy can potentially be applied to any possible physical parameters (e.g. SLA, geostrophic potential vorticity, Okubo-Weiss parameter). Besides, the present strategy can also be applied to automatic identification of troughs and ridges from weather charts. Because this general method can be applied to a variety of eddy parameter fields, we denoted it the Universal Splitting Technology for Circulations (USTC) method.

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Enhancing the accuracy of automatic eddy detection and the capability of recognizing the multi-core structures from maps of sea level anomaly

Cited by 88 publications

References 35 publications

Main eddy vertical structures observed in the four major Eastern Boundary Upwelling Systems

Main eddy vertical structures observed in the four major Eastern Boundary Upwelling Systems

Mesoscale Eddies in the Algerian Basin: do they differ as a function of their formation site?

Technical Note: Watershed strategy for oceanic mesoscale eddy splitting

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