A Three–Dimensional Model of Dynamical Processes in the Venus Atmosphere

Abstract

Three–dimensional calculations of the circulation of the Venus atmosphere have resulted in mean zonal winds in the same direction and of the same magnitude as those observed, i.e., retrograde with speeds ∼100 m s⁻¹. The solutions exhibit other observed properties of the circulation: small horizontal temperature contrasts with the larger variations being between equator and pole, meridional velocities at mid and low latitudes less than 10 m s⁻¹, and the existence of planetary waves which at certain times show vertical flow field contours in a horizontal Y configuration. The mechanism maintaining the large zonal winds is a nonlinear instability involving both the mean meridional circulation and planetary–scale eddies. The meridional circulation is the principal means by which zonal momentum is transported vertically. Planetary–scale eddies are the principal means by which potential energy is released, and they are also significant in transporting angular momentum horizontally. Planetary rotation plays an important role in initially generating the mean zonal winds starting from rest. Initial conditions affect the characteristics of the solutions, including the magnitude of the mean zonal velocity and whether or not planetary waves are generated.