Forecasting long-lived Lagrangian vortices from their objective Eulerian footprints. (19th January 2017)

• Record Type: Journal Article
• Authors: Serra, Mattia; Haller, George
• Is Part Of: Journal of fluid mechanics. Volume 813(2017)
• Page Start: 436
• Page End: 457
• Publication Date: 2017-01-19
• Subjects: geophysical and geological flows, -- nonlinear dynamical systems, -- vortex flows; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2016.865
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : We derive a non-dimensional metric to quantify the expected Lagrangian persistence of objectively defined Eulerian vortices in two-dimensional unsteady flows. This persistence metric is the averaged deviation of the vorticity from its spatial mean over the Eulerian vortex, normalized by the instantaneous material leakage from the Eulerian vortex. The metric offers a model- and frame-independent tool for uncovering the instantaneous Eulerian signature of long-lived Lagrangian vortices. Using satellite-derived ocean velocity data, we show that Lagrangian vortex-persistence predictions by our metric significantly outperform those inferred from other customary Eulerian diagnostics, such as the potential vorticity gradient and the Okubo–Weiss criterion.