Abstract: The super-rotation that is observed in the atmosphere of Venus and Titan is a specific feature that is not yet fully understood. The bulk of these atmospheres rotates much faster than the solid body of the planet, and the total angular momentum contained in the atmosphere is much larger than what would be contained if the atmosphere was rotating in average as the solid surface (which is the case for the Earth and Mars). Using Global Circulation Models of both Venus and Titan, we have obtained simulations that compare quite well with available observations for both atmospheres. Based on these simulations, we investigate some aspects of the super-rotation question, among which the respective role of rotation rate, thermal tides and other types of waves, the impact of seasonal variations on Titan, the role of the opacity layer located in altitude. Angular momentum exchanges with the surface and transport in the atmosphere are studied, as well as the influence of parameters such as the boundary layer scheme or the initial conditions. The similarities and differences between Venus and Titan illustrate the complexity of this circulation feature.

Additional materials: PDF of slides

ExoClimes 2010, Exeter, Tuesday 7^th Sep 2010