Self-organization of atmospheric macroturbulence into critical states of weak nonlinearity

It is generally held that atmospheric macroturbulence can be strongly nonlinear. Yet weakly nonlinear models successfully account for scales and structures of baroclinic eddies in the Earth atmosphere. Here we present a theory and simulations that suggest that weakly nonlinear models are so successful because atmospheric macroturbulence organizes itself into critical states of weak nonlinearity. By modifying the extratropical thermal stratification, atmospheric macroturbulence inhibits nonlinear eddy--eddy interactions and the concomitant inverse energy cascade from the length scales of baroclinic instability to larger scales. The theory and simulations point to fundamental constraints on the global circulations of Earth and other planets. For example, they constrain the thermal structure of planetary atmospheres, account for eddy scales and energies, and for the number of jets of a planet.