General circulation in Venus’ atmosphere

This sketch shows the general atmospheric circulation at Venus. The main feature is a convection-driven ‘Hadley cell’, which extends from the equatorial region up to about 60° latitude in each hemisphere.

The trend is polewards at all levels, which can be observed by tracking winds (at about 50–65 km altitude above the surface), so the return branch of the cell must be in the atmosphere below the clouds.

A cold ‘polar collar’ is found around each pole at about 70° latitude; the Hadley circulation evidently feeds a mid-latitude jet at its poleward extreme, inside which there is a circumpolar belt characterized by remarkably low temperatures and dense, high clouds. Inside the collar, a thinning of the
upper cloud layer forms a complex and highly variable feature, called the ‘polar dipole’, or the south polar vortex. Since generally, thinner-thanaverage or lower-than-average clouds are often associated with descending air mass, and vice versa, the vortex may represent a second, high-latitude circulation cell, resembling winter hemisphere behaviour on Earth.