Inverse cascade in zonal flows.

Zonal winds on Jovian planets play an important role in governing the cloud dynamics, transport of momentum, scalars, and weather patterns. Therefore, it is crucial to understand the evolution of the zonal flows and their sustainability. Based on the studies in two-dimensional (2D) β plane setup, zonal flow is believed to be forced at intermediate scales via baroclinic instabilities and the inverse cascade leads to the transfer of energy to large scales. However, whether such a process exists in three-dimensional(3D) deep convection system remains an open and challenging question. To explore a plausible answer, we perform Large Eddy Simulations in horizontally rotating Rayleigh-Bénard Convection for Rayleigh and Ekman number in the span 10⁸-10¹² and 10^-3 and 10^-8 respectively. We find the emergence of mean flow at the expense of small-scale turbulence. The negative production in the turbulent kinetic energy budgets analysis implies energy transfer from the fluctuating velocities to the mean flow. We intricately quantify the upscale transfer via inverse cascade by the means of the kinetic energy spectra and the energy flux. We conclude that energy deposited via buoyancy at small scales is transferred to large scales via inverse cascade.