A General Circulation Model of a Venus-Like Atmosphere

Abstract

A three-dimensional general circulation model of a slowly rotating, massive atmosphere is forced with an axisymmetric radiative heating/cooling distribution to explore the heat and momentum budgets established in this type of atmosphere. In the model lower atmosphere, the mean meridional circulation, as suggested by Stone (1974), balances the differential radiative heating and maintains a statically stable, quasi-barotropic thermal state. However, the nature of this balance depends crucially on the momentum budget established. Although small-scale convection and eddies also play a role in maintaining the static stability of the lower atmosphere, eddy horizontal heat transport is completely negligible. The meridional circulation takes the form of multiple equator-to-pole cells, one above the other. The correlation of this vertical structure with the vertical distribution of radiative and convective/eddy heating suggests that the net heating vertical distribution produces this multicellular structure. The model results confirm the proposals of Gierasch (1975) and Rossow and Williams (1979) in a fully three-dimensional circulation. The mean meridional circulation, despite its multicellular form, interacts with quasi-barotropic eddies produced by zonal flow shell instability to produce a weak superrotation of the entire model atmosphere. This process is general enough to conclude that it will occur in all slowly rotating atmospheres; but, whether it can accelerate wind speeds as large as those observed on Venus, cannot be determined yet.