Superrotation of the Venus’ atmosphere computed with a thermodynamic model

Abstract

A thermodynamic model is developed in which the dynamics of Venusian atmospheric superrotation is subordinated to thermal forcing. The key mechanism is a diurnal thermal tide, generated by simplified heating based on radiative balance between solar insolation and long-wave emission. This heating produces horizontal temperature gradients (day-night and equator-pole), which, through hydrostatic equilibrium, translate into geopotential gradients. These gradients act as the primary force in the equations of motion, increasing specific angular momentum with altitude and generating a superrotating zonal wind in the direction of planetary rotation, but opposed to the slow propagation of the thermal tide. Numerical integration across 24 tropospheric layers, coupled with a regolith thermal conductivity model (down to 19.1 m depth) to compute surface heat flux, demonstrates that thermally induced vertical circulation transports angular momentum from the surface to the cloud level. It is concluded that the diurnal thermal tide, driven by insolation gradients, is the fundamental mechanism generating and maintaining superrotation in Venus’ atmosphere. This novel thermodynamic approach provides a unified framework for understanding this phenomenon on slowly rotating planets.