Experimental comparison of coherent structures methods applied to oceanic flows

Based on velocity outputs from numerical model forecasts and their subsequent processing with Lagrangian Coherent Structures (LCS) methods, a series of field experiments was conducted offshore Martha’s Vineyard to specifically target the predicted LCS, with the goal of testing the reliability and utility of the approach. The resulting surface drifter trajectories were compared to the analyses of several Lagrangian processing methods, which were used on both the forecast model data for experimental design and the hindcast model data to explain the observed behaviors of drifters. The different LCS methods used include the Finite-Time Lyapunov Exponent method, the encounter volume method and clustering methods, such as fuzzy c-means and spectral clustering. The Objective Eulerian Coherent Structure (OECS) method was also tested in the field.