HIGH SURFACE TEMPERATURE ON VENUS . EVALUATION OF GREENHOUSE EXPLANATION

Calculations of the mean surface temperature of Venus are performed with a simple nongray radiation balance model. The model is based upon a balance of net incoming solar radiation and emerging thermal radiation at the top of the atmosphere. To calculate the emerging thermal radiation, it is assumed that the shape of the vertical temperature profile is similar to that observed by Mariner 5 and Venera 4-that is, a constant lapse rate of 9°C/km from the surface to a pressure level of a few tenths of an atmosphere, above which the temperature remains constant. Given the atmospheric composition and surface pressure, the surface temperature can be determined from the balance requirement at the top of the atmosphere. Calculations are performed for a low surface pressure (20 atm) and high surface pressure (65 atm) model. For a pure carbon dioxide atmosphere, the results indicate that mean surface temperatures of 500° to 550°K can be maintained in the 20-atm model, and 600° to 650°K in the 65-atm model, if water vapor mixing ratios are of the order of 10-3. © 1969.