A Scheme to Identify Loops from Trajectories of Oceanic Surface Drifters: An Application in the Kuroshio Extension Region

• DOI: 10.1175/jtech-d-10-05028.1
• Publication Date: 2011-05-10T19:41:44Z
• Authors: Changming Dong; Yu Liu; Rick Lumpkin; Matthias Lankhorst; Dake Chen; James C. McWilliams; Yuping Guan
• Keywords: Drifter; Eddy

Abstract When a drifter is trapped in an eddy, it makes either cycloidal or looping trajectory. The former case takes place when the translating speed larger than eddy spinning speed. background mean velocity removed, trajectories make loops. Thus, eddies can be detected from trajectory by identifying segments. In this paper, automated scheme developed to identify segments Lagrangian trajectories, based on geometric definition of loop, that is, closing curve with its starting point overlapped ending point. find first returning point, if exists, along surface few other criteria. To further increase chance loops are eddies, considered loop identifies only loop’s period longer local inertial and shorter seasonal scale, at least two consecutive same polarity stay sufficiently close found. Five parameters characterize estimated scheme: location (eddy center), time (starting time), period, polarity, intensity. As example, applied drifters Kuroshio Extension region. Results indicate numbers symmetrically distributed for cyclonic anticyclonic sizes 40–50 km, abundance highest path more southern flank.