On the concentration of near-inertial waves in anticyclones

TL;DR

This paper reveals a conservation law explaining why near-inertial waves concentrate in anticyclones, showing that this is due to wave scale reduction in steady background flows, supported by scaling and numerical analysis.

Contribution

It introduces a new conservation law for near-inertial waves in steady flows, linking wave concentration in anticyclones to spatial scale decrease, supported by simulations.

Findings

Near-inertial waves concentrate in anticyclones due to scale reduction.

The conservation law explains wave concentration phenomena.

Numerical simulations confirm the theoretical interpretation.

Abstract

An overlooked conservation law for near-inertial waves propagating in a steady background flow provides a new perspective on the concentration of these waves in regions of anticyclonic vorticity. The conservation law implies that this concentration is a direct consequence of the decrease in spatial scales experienced by an initially homogeneous wave field. Scaling arguments and numerical simulations of a reduced-gravity model of mixed-layer near-inertial waves confirm this interpretation and elucidate the influence of the strength of the background flow relative to the dispersion.