The structure of the atmosphere of Uranus

Models of the interior of Uranus ( Podolak, 1976) suggest that the abundances of such substances as CH 4 are greatly enhanced with respect to solar abundances of heavy elements. Such enhancement leads to a new type of model atmosphere for Uranus, which agrees with observation if the internal energy flux is small (⩽10%) compared with the absorbed solar energy. An important feature of the models is the presence of a cloud of CH 4 droplets whose top is at a temperature of ≃90°K and a pressure of ≃4atm. Above the cloud, the atmosphere is stable because of the rapid decrease of the thermal flux with depth. Being saturated, most of the observable gaseous CH 4 is near the cloud; the CH 4 abundance above the cloud, of the order of 5 km-am, is a very sensitive function of the cloud-top temperature.