The emergence of multiple robust zonal jets from freely evolving, three-dimensional stratified geostrophic turbulence with applications to jupiter

Three-dimensional numerical simulations of freely evolving stratified geostrophic turbulence on the β plane are presented as a simplified model of zonal jet formation on Jupiter. This study samples the parameter space that covers the low, middle, and high latitudes of Jupiter by varying the central latitude of the β plane. The results show that robust zonal jets can emerge from initial small-scale random turbulence through the upscale redistribution of the kinetic energy in the spectral space. The resulting flow's sensitivities to the flow's deformation radius L_D and the two-dimensional Rhines length L_β = √U/β (U is the characteristic turbulence velocity and β is the meridional gradient of the planetary vorticity) are tested, revealing that whether the outcome of the upscale energy transfer becomes dominated by jets or vortices depends on the relative values of L_D and L_β. The values of L_β and L_D are varied by tuning the β-plane parameters, and it is found that the flow transitions from a jet-dominated regime in L_β ≤ L_D to a vortical flow in L_β ≥ L_D. A height-to-width ratio equal to f/N, the Coriolis parameter divided by the Brunt-Väisälä frequency, has previously been established for stable vortices, and this paper shows that this aspect ratio also applies to the zonal jets that emerge in these simulations.