Global Climate Models of Titan, Uranus, and Neptune

We present the formulation of and some results from global climate models for Titan, Uranus, and Neptune. The model for Titan is a fully three-dimensional, modified version of NCAR's terrestrial global climate model, CAM-3. It includes forcing by Saturn's gravitational tides, a treatment of the planetary boundary layer and surface interactions, scattering and absorption of short-wave radiation, and absorption and emission of long-wave radiation. The physical properties and distribution of aerosols are constrained by Cassini observations. The climate models for Uranus and Neptune are two-dimensional, radiative-diffusive models which calculate sensible heat fluxes and latent-heat fluxes due to ortho-para hydrogen conversion in terms of a mixing-length formulation. The vertical pressure range in these models extends from 100 bars up to 0.1 mbar. Our main goal for the 2-d models is to establish the relative roles of sensible and ortho-para latent-heat fluxes in transporting heat laterally and vertically. We are also currently developing three-dimensional models of Uranus and Neptune based on modification of CAM-3. We will discuss how the parameterization of heat fluxes in the 2-d models can be adapted to model small-scale convection in the presence of ortho-para conversion in the 3-d models. This research is supported by the NASA Outer Planet Research Program.