Fully Developed Superrotation Driven by the Mean Meridional Circulation in a Venus GCM

Fully developed superrotation is reproduced for the first time in very long term simulations with a dynamical Venus general circulation model (GCM) driven by a zonally averaged component of the realistic solar heating only. Starting from a motionless state with temperature distribution including a low static stability layer in the lower cloud layer, the fast superrotating zonal flow of ~100 m/s is established after 500 Earth years. In this experiment, the mean meridional circulation is responsible for generating the superrotation, because effects of thermal tides, topography, radiation process, and cloud physics are excluded in the present simulations. Sensitivity experiments indicate that the vertical eddy viscosity smaller than 0.02 m ² /s is necessary for the fast superrotation to appear. The low static stability layer also strongly affects the superrotation with high-latitude jets through angular momentum transport by baroclinic/barotropic instability in the cloud layer.