Dissipative Tides: Application to Venus' Lower Atmosphere

Abstract

A linearized planetary scale wave model is used to investigate the effects of thermal and mechanical damping on atmospheric tides. When the damping rate ? is comparable to the frequency of solar diurnal forcing &Omega (δ?0.1?), the circulation consists of three parts: a classical vertically propagating ?atmospheric tide ? in the upper atmosphere, a simple thermally direct subsolar-to-antisolar circulation or ?Halley cell? in most of the lower atmosphere, and finally, a reversed ?anti-Halley cell? near the surface. The near-surface circulation produces horizontal divergence near the subsolar point. While tides are a frequently encountered phenomenon (Venus, Earth and Mars), there is so far no observational evidence of a Halley circulation in any planetary atmosphere. A subsolar-antisolar circulation might be possible in Venus'slowly rotating lower atmosphere if the mechanical dissipation time scale is of the order of or less than a Venusian day. Such a circulation could be a factor in maintaining the superrotation of Venus' upper atmosphere.