Large-scale self-organisation in dry turbulent atmospheres

TL;DR

This paper demonstrates through high-resolution simulations that dry planetary atmospheres can spontaneously organize into large-scale structures via an inverse energy cascade, challenging previous assumptions about turbulence in three-dimensional flows.

Contribution

It provides the first direct numerical evidence that rotating and stratified three-dimensional flows in dry atmospheres support an inverse cascade, explaining large-scale structure formation.

Findings

Dry atmospheres can support inverse energy cascades.

Simulations show bidirectional energy transfer in rotating stratified flows.

Large-scale structures emerge spontaneously in the modeled atmospheres.

Abstract

How turbulent convective fluctuations organise to form large-scale structures in planetary atmospheres remains a question that eludes quantitative answers. The assumption that this process is the result of an inverse cascade was suggested half a century ago in two-dimensional fluids, but its applicability to atmospheric and oceanic flows remains heavily debated, hampering our understanding of the energy balance in planetary systems. We show with direct numerical simulations of spatial resolutions of 122882 $\times$ 384 points that rotating and stratified flows can support a bidirectional cascade of energy, in three dimensions, with a ratio of Rossby to Froude numbers comparable to that of the Earth's atmosphere. Our results establish that in dry atmospheres spontaneous order can arise via an inverse cascade to the largest spatial scales.