Emergence of large scale structure in planetary turbulence

TL;DR

This paper introduces the SSST, a non-equilibrium statistical theory that predicts the formation and characteristics of large-scale structures like jets and vortices in planetary turbulence, validated by simulations.

Contribution

The paper presents the SSST framework that predicts the emergence and properties of large-scale structures in turbulent flows, a novel approach in planetary turbulence research.

Findings

SSST accurately predicts the threshold for structure formation.

Non-zonal structures emerge at lower energy input rates.

Emergence of structures influences jet formation dynamics.

Abstract

Planetary and magnetohydrodynamic drift-wave turbulence is observed to self-organize into large scale structures such as zonal jets and coherent vortices. In this Letter we present a non-equilibrium statistical theory, the Stochastic Structural Stability theory (SSST), that can make predictions for the formation and finite amplitude equilibration of non-zonal and zonal structures (lattice and stripe patterns) in homogeneous turbulence. This theory reveals that the emergence of large scale structure is the result of an instability of the interaction between the coherent flow and the associated turbulent field. Comparison of the theory with nonlinear simulations of a barotropic flow in a beta-plane channel with turbulence sustained by isotropic random stirring, demonstrates that SSST predicts the threshold parameters at which the coherent structures emerge as well as the characteristics of the emerging structures (scale, amplitude, phase speed). It is shown that non-zonal structures (lattice states or zonons) emerge at lower energy input rates of the stirring compared to zonal flows (stripe states) and their emergence affects the dynamics of jet formation.