| A number of radiative-convective equilibrium states have been produced for the Giant Planets, with particular emphasis on Uranus and Neptune, in a broad-based examination of atmospheric thermal structures. The analysis includes non-uniform stratospheric aerosol heating, a "convective penetration" model for Neptune, and a treatment of CH(,4) non-LTE effects.;A wider range of models was considered for Uranus and Neptune, reflecting the comparatively sparse observational constraints on stratospheric temperatures in Uranus, and the relatively large heating required in the stratosphere of Neptune. For example, it was found that seasonal stratospheric variations may be very important in Uranus. Also, localized aerosol heating may be an important heat source in the upper atmospheres of both planets. For Neptune, however, the results presented here show that it is insufficient, regardless of the vertical distribution. One possible alternative is a "convective penetration" model, in which a relatively large ((TURN) 2%) stratospheric CH(,4) concentration is permitted, and in which the assumption of saturation equilibrium is applied at all levels. The resulting infrared spectrum for this model agrees quite favorably with the data.;A model was developed for the thermalization of solar energy absorbed under non-LTE conditions in the CH(,4) band groups centered at (lamda) (TURNEQ) 1.7 (mu)m, 2.3 (mu)m, and 3.3 (mu)m. Employing the non-LTE radiative transfer method devised by Hogan (1968; Ph.D. dissertation), a range of model atmospheres was produced, reflecting the uncertainties in collisional relaxation rates and their temperature dependences. The results show large departures from LTE in all models at pressures below about 0.01 mb, and significant effects on the upper stratospheric temperatures. Also, it was found that, while they are somewhat lessened, the relatively large discrepancies which exist between "occultation" profiles for the Giant Planets and LTE models cannot be attributed to CH(,4) non-LTE effects alone. On the other hand, it is equally certain that non-LTE effects cannot be neglected in modelling the upper stratospheres of these planets.;Given the diverse and complex natures of the atmospheres of the Giant Planets, most aspects of the computational procedure are described in detail. The overall method, which stems from earlier work by Professor Hogan (e.g., 1968, Ph.D. dissertation; Hogan et al., 1969, J. Atmos, Sci., V26, p. 898), is based on a straightforward flux divergence formulation, incorporating a number of numerical techniques and a convenient, but standard treatment of opacities.;The results for Jupiter show that the temperature profiles presented recently by Lindal et al. (1980, J. Geophys. Res., in press), based on their analysis of the Voyager radio occulation data, can be plausibly interpreted as arising, at least in part, from solar heating by non-uniformly distributed "aerosols." It was found that the overall energetics of the Voyager profiles, apparently, are not inconsistent with the nominal global heat deposition due to a "UV absorber" (as inferred from the planet's UV reflectivity). A similar conclusion holds for Saturn models, when compared with Kliore et al.'s (1980; J. Geophys. Res., in press) temperature profile, as derived from their recent Pioneer radio occultation measurements. |
