Thermal structure of the atmosphere of Venus

The available data sets determining the thermal structure are critically discussed and combined into a mean model. The implications of the oberved contrasts for atmospheric motions, on small and large scales, are discussed. Greenhouse models which allow a convective atmosphere below 35 to 50 km give a reasonable explanation of the high surface temperature. Surprisingly, however, the deep atmosphere is generally stable. The radiative imbalance thus drives the general circulation rather than local convection. A distinct tropopause occurs at the cloud tops. Above this, the atmosphere is very stably stratified and not far from radiative equilibrium. Gravity waves are present. The upper atmosphere, with its very large day-night temperature contrast, must be in motion away from the sun, but velocities are strongly limited to a sizable viscous dissipation.