Near Infrared Reflectivity of Venus and Ice Clouds

Abstract

The near infrared reflectivity of ice clouds is computed and compared to observations of Venus. The difficulty in making an exact correction for CO2 absorption precludes the possibility of either establishing or absolutely ruling out ice particles as the primary cloud constituent; however, it is possible to conclude that the clouds are not optically thick and composed of large ice crystals. There is still disagreement as to the quantitative significance of the infrared spectra, but, if it is assumed that a 20% depression may exist in the continuum near 2.0 ? then optically thin clouds (τ?5?10) of ice particles with radii ?4 ? are compatible with the observations. It is shown that there is a small amount of positive evidence for such clouds.