Axisymmetric Circulations Forced by Heat and Momentum Sources: A Simple Model Applicable to the Venus Atmosphere

Abstract

The parametric behavior of an axially symmetric circulation induced by heat and momentum sources is analyzed in the context of a simple Boussinesq model. Implications for the Venus atmosphere are examined in the light of recent data. For nearly inviscid flows in a stably stratified atmosphere, this work extends the analysis of Held and Hou to large thermal Rossby numbers (slowly rotating atmospheres). For parametric values appropriate to the Venus atmosphere, heat flux by the Hadley circulation leads to a temperature distribution nearly uniform with latitude, close to the asymptotic limit for a nonrotating atmosphere, while the zonal wind shows a strong polar jet but does not superrotate at the equator, contrary to what is observed on Venus. For the Venus atmosphere to superrotate above the cloud base, where most of the solar radiation is deposited, momentum sources and sinks must be provided by asymmetric motions to offset transports by the mean meridional circulation. Diagnostically, the eddy momentum source/sink pattern required by a given meridional cell depends upon both the sign of the vertical zonal wind shear and the direction of the meridional flow. For a realistic vertical zonal wind profile, the implication is that the observed superrotation on Venus can be supported by alternating layers of sources and sinks.