The Venus atmosphere

Venus possesses a very thick and hot atmosphere which mainly consists of carbon dioxide. Other atmospheric constituents are Nitrogen (3.5%), Argon and sulfur dioxide. Surface temperatures reach values of about 750 Kelvin (~475° C) at a surface pressure of 90 bar.

Venus is one of the brightest objects at the night sky, due to its highly reflective, dense cloud layer. This cloud layer, mainly composed of sulfuric acid droplets and located at an altitude of ~50-70 km,  covers the whole planet so that barely any sun light can reach the surface.

Venus rotates very slow (a Venus day is 234 Earth days long), but the atmosphere rotates much faster than the planet itself. Wind velocities of about 100 m/s are reached at the upper boundary of the cloud layer so that the atmosphere rotates with a period of only ~4-5 days. The processes leading to this so called superrotation are still not fully understood. It is assumed that the solar insolation in combination with different atmospheric waves plays an important role in this context.

Atmospheric waves in almost all dimensions are existent on Venus. Local wave phenomena like gravity waves are observed next to global wave phenomena like thermal tides. The gravity wave activity is strongly enhanced in the high latitude range of Venus. The processes leading to this latitudinal dependency  are still not completely understood. On the one hand, the highest topographical elevations are located in this area but on the other hand, the convective middle cloud layer is also extremely pronounced in the high latitudes of Venus. Gravity waves might therefore be induced by wind flow over topographical obstacles or by convection in the nearly adiabatic middle cloud layer might play an important role in this context [Tellmann et al., 2012]. Other possible source mechanisms are, for example, Kelvin-Helmholtz instabilities.

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