Wave-kinetic dynamics of forced-dissipated turbulent internal gravity waves

TL;DR

This paper investigates the dynamics of internal gravity waves in stratified media through simulations of the kinetic equation, revealing the roles of various interactions and the emergence of a condensate.

Contribution

It introduces a detailed simulation study of the forced-dissipated kinetic equation for internal gravity waves, highlighting the transition from nonlocal to local interactions and condensate formation.

Findings

Nonlocal interactions dominate early evolution.

Local interactions drive long-term energy cascade.

A condensate forms at small horizontal wavevectors.

Abstract

Internal gravity waves are an essential feature of stratified media, such as oceans and atmospheres. To investigate their dynamics, we perform simulations of the forced-dissipated kinetic equation describing the evolution of the energy spectrum of weakly nonlinear internal gravity waves. During the early evolution, three well-known nonlocal interactions, the Elastic Scattering, the Induced-Diffusion, and the Parametric Subharmonic Instability, together with a Superharmonic Resonance play a prominent role. In contrast, local interactions are responsible for anisotropic energy cascade on longer time scales. We reveal emergence of a condensate at small horizontal wavevectors that can be interpreted as a pure wave-wave interaction-mediated layering process.