Dynamically consistent Lagrangian coherent structures

In this paper, we compute coherent structures based on radar data collected in Monterey Bay during August 2001 and August 2003. The Lagrangian structures are extracted from a finite-time Lyapunov exponent field. In contrast with earlier approaches, the integration time used in computing the Lyapunov exponents is not constant but adapts to the timescales of the different flow regimes present in the radar data. Nowcasts of the radar data are performed using open-boundary modal analysis (OMA) and the projection coefficients of this filtering method are used to identify periods corresponding to different dynamical regimes in the bay. Lyapunov exponents are computed within a single dynamical regime, hence they determine dynamically consistent coherent structures.