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Ocean Science An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 2 | Copyright
Ocean Sci., 11, 269-273, 2015
https://doi.org/10.5194/os-11-269-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Technical note 20 Mar 2015

Technical note | 20 Mar 2015

Technical Note: Watershed strategy for oceanic mesoscale eddy splitting

Q. Y. Li and L. Sun Q. Y. Li and L. Sun
  • Key Laboratory of Atmospheric Composition and Optical Radiation, CAS, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China

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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This study established a splitting strategy that could separate multinuclear eddies into mononuclear eddies. As the values of eddy parameters (e.g. SLA, geostrophic potential vorticity, Okubo–Weiss parameter) are similar to basins in a map, the natural divisions of the basins are the watersheds between them. It can also be applied to automatic identification of troughs and ridges from weather charts. We denoted it the Universal Splitting Technology for Circulations (USTC) method.
This study established a splitting strategy that could separate multinuclear eddies into...
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