Effect of meridional circulation on the venusian cloud layer: A model study

Abstract

The meridional circulation can have a large influence on the cloud formation on Venus. In our model, the observed depression of near-infrared optical thickness at mid-latitude is reproduced as a result of the enhancement of cloud thickness at low and high latitudes. At high latitudes, the poleward transport of H 2SO 4-H 2O droplets in the upper atmosphere makes a thick cloud, since most of the H 2SO 4-H 2O droplets photochemically produced are transported poleward by the meridional circulation. At low latitudes, the large-scale ascent of the concentrated H 2SO 4 vapor forms a dense lower cloud in accord with observations by entry probes. The equatorward transport of H 2SO 4 vapor below the cloud by the meridional circulation and the sedimentation of droplets in the lower cloud leads to the accumulation of H 2SO 4 vapor around the cloud base at low latitudes. The H 2SO 4 vapor distribution agrees with the radio occultation observations. The middle cloud can be caused by the condensation of H 2SO 4 vapor carried aloft by convective mixing.