Articles | Volume 28, issue 1
Nonlin. Processes Geophys., 28, 43–59, 2021
https://doi.org/10.5194/npg-28-43-2021
Nonlin. Processes Geophys., 28, 43–59, 2021
https://doi.org/10.5194/npg-28-43-2021

Research article 19 Jan 2021

Research article | 19 Jan 2021

Ordering of trajectories reveals hierarchical finite-time coherent sets in Lagrangian particle data: detecting Agulhas rings in the South Atlantic Ocean

David Wichmann et al.

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Cited articles

Ankerst, M., Breunig, M. M., Kriegel, H.-P., and Sander, J.: OPTICS: Ordering Points to Identify the Clustering Structure, ACM Sigmod Record, 28, 49–60, https://doi.org/10.1145/304181.304187, 1999. a, b, c, d, e, f, g, h, i, j, k, l
Banisch, R. and Koltai, P.: Understanding the geometry of transport: Diffusion maps for Lagrangian trajectory data unravel coherent sets, Chaos: An Interdisciplinary J. Nonlinear Sci., 27, 035804, https://doi.org/10.1063/1.4971788, 2017. a, b, c, d, e, f, g, h, i, j, k, l, m, n, o
Beron-Vera, F. J., Wang, Y., Olascoaga, M. J., Goni, G. J., and Haller, G.: Objective Detection of Oceanic Eddies and the Agulhas Leakage, J. Phys. Oceanogr., 43, 1426–1438, https://doi.org/10.1175/JPO-D-12-0171.1, 2013. a, b
Bickley, W.: LXXIII. The plane jet, The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 23, 727–731, https://doi.org/10.1080/14786443708561847, 1937. a
Brach, L., Deixonne, P., Bernard, M. F., Durand, E., Desjean, M. C., Perez, E., van Sebille, E., and ter Halle, A.: Anticyclonic eddies increase accumulation of microplastic in the North Atlantic subtropical gyre, Marine Pollution Bulletin, 126, 191–196, https://doi.org/10.1016/j.marpolbul.2017.10.077, 2018. a
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Fluid parcels transported in complicated flows often contain subsets of particles that stay close over finite time intervals. We propose a new method for detecting finite-time coherent sets based on the density-based clustering technique of ordering points to identify the clustering structure (OPTICS). Unlike previous methods, our method has an intrinsic notion of coherent sets at different spatial scales. OPTICS is readily implemented in the SciPy sklearn package, making it easy to use.