Vertical temperature profiles of the Venus atmosphere up to 80 km height
were calculated in a time dependent model. A steady state of the
atmospheric profiles was reached by numerical intergration from an
arbitrary initial distribution of temperature by assuming some
atmospheric parameters as surface pressure, planetary albedo etc. The
time-rate-of-change of temperature was determined by the vertical
divergence of the following fluxes: solar insolation, net infrared
radiation of the atmosphere and the ground surface, and sensible heat.
The radiation calculation was based on the absorption bands of carbon
dioxide and water vapor from the near to the far infrared region of the
spectrum. Absorption by clouds was taken into account in parameterized
form. Atmospheric profiles were calculated as a function of water vapor
content, height and absorptivity of the cloud layer, surface pressure,
eddy diffusion coefficient, planetaryalbedo, latitude, and time of day.
It appeared, that the lower layers of a pure carbon dioxide atmosphere
are convective with an adiabatic lapse rate of temperature. The lapse
rate of a carbon dioxide atmosphere with some additional water va- por
and thus strong absorption of solar energy is practically adiabatic due
to the downward transport of sensible heat. Comparison with direct
measurements indicates that the atmosphere below the c10ud level 4 is
likely to contain water vapor. A mixing ratio of 10- is sufficient to
explain the observed temperature profile.