Interpretations of the Infrared Limb-Darkening of Venus.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interpretations of the Infrared Limb-Darkening of Venus. Pollack, James B. ; Sagan, Carl Abstract The limb-darkening laws predicted for several models of the atmosphere and clouds of Venus are compared with limb-darkening observations in the 8-13 p interval. Model A attributes the limb darkening to pure molecular absorption by the atmosphere above the Cytherean cloud layer, Model B to multiple scattering by cloud particles of arbitrary albedo and alitude distribution. In each model, the temperature regime is considered specified, alternatively by convective and by radiative equilibrium. In Model A, limb darkening arises from the increase of temperature with atmospheric depth. In Model B, both the T- T relation and the dependence of emissivity on the angle of emergence contribute to the limb darkening. Each model can be made to agree with observation, with an appropriate specification of atmospheric and cloud parameters. If, in Model B, a cloud layer with a relatively sharp upper boundary is assumed, then the observational data imply a very high albedo for single scattering. In this case, the cloud temperature will be substantially higher than the measured blackbody temperature, due to the reflectivity of the clouds, and the clouds make a major addition to the atmospheric greenhouse effect in maintaining the high surface temperatures. However, Model B is also consistent with less extreme albedos for single scattering, provided the cloud layer has a diffuse vertical distribution. Publication: The Astronomical Journal Pub Date: October 1964 DOI: 10.1086/109497 Bibcode: 1964AJ.....69S.555P full text sources ADS |