Simulations of superrotation using a GCM for Venus' middle atmosphere

A superrotation is simulated in a T10L100 general circulation model for Venus' middle atmosphere (VMAGCM), in which the radiative effects of aerosols are calculated. The simulation in a domain of 30-100 km is conducted under the condition of a bottom zonal flow with a velocity of 50 m s(-1) at the equator. Thermal tides contribute to the maintenance of the cloud-top superrotation together with meridional circulation and vertically propagating gravity waves. The meridional circulation and wave activity are sensitive to the vertical eddy diffusion. Although the equatorial zonal flow has a velocity of about 70 m s-1 when the vertical eddy diffusion coefficient (K-V) is set at 5.0 m s(-2), it has a velocity of > 100 m s(-1) when K-v = 2.5 m s(-2). The fully developed equatorial jet for the small Kt, case is enhanced at 65 km by small-scale gravity waves emitted from the cloud top.