| Abstract: | A series of time-dependent radiative/convective models are presented for the atmosphere of Uranus. The effects of atmospheric dynamics have been omitted from the models. The inclination of the pole of rotation to the pole of the orbit, approximately 90°, produces large seasonal changes in the insolation. Because of the relatively small flow of heat from the interior, these seasonal changes cause the effective temperature, which is about 60°K, to vary through the 84-year orbital period by ～5°K at the poles, ～4°K at ±60° latitude, ～2°K at ±30° latitude, and ～0.5°K at the equator. For a particular latitude, the minimum effective temperature and the maximum convective flow of heat from the interior occur near the end of the period when the sun remains below the horizon during the Uranian day. If the methane mixing ratio is not limited by its saturated vapor pressure (SVP) in the convective region, the maximum convective flow would be a few times the orbital average convective flow and persist for an interval of several years. On the other hand, if the methane mixing ratio is limited by its SVP in the convective regions, the maximum convective flow could be orders of magnitude greater than the orbital average and could persist for less than an hour. If the orbital mean internal heat flow is negligible, the difference in effective temperatures between 30 and 60° latitude would be in the range 2 to 4°K. If the internal heat is taken to be about the maximum allowable and is assumed to be redistributed in the interior in a manner to compensate for the minimum in insolation at low latitudes, the corresponding temperature difference would be in the range to 2°K. In either case, the existing theory of atmospheric dynamics for the outer planets indicates that such large temperature differences will drive large-scale motions which would in turn reduce these temperature differences. |
