Forecasting Long-Lived Lagrangian Vortices from their Objective Eulerian Footprints

TL;DR

This paper introduces a new, model-independent metric to predict the long-term persistence of oceanic vortices by analyzing their Eulerian signatures, outperforming traditional diagnostics in satellite data.

Contribution

The paper develops a novel Eulerian persistence metric that accurately forecasts Lagrangian vortex longevity in unsteady flows, validated with satellite ocean velocity data.

Findings

The metric effectively predicts vortex persistence better than traditional diagnostics.

Satellite data confirms the metric's superior predictive performance.

The approach is model-independent and frame-independent.

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-independent 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.