Articles | Volume 28, issue 1
Nonlin. Processes Geophys., 28, 43–59, 2021
Nonlin. Processes Geophys., 28, 43–59, 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.

Data sets

Lagrangian particle dataset (2 years) for Agulhas region surface flow David Wichmann

Model code and software

OceanParcels/coherent_vortices_OPTICS: Release for publication of corresponding paper (Version v1.0) David Wichmann

OceanParcels/near_surface_microplastic: Release of code for near-surface microplastic simulations David Wichmann

Video supplement

Animation of finite-time coherent sets in the Agulhas region David Wichmann

Short summary
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.