Radiative Equilibrium - Photochemical Model of Titan's Atmosphere

Titan's thermal structure has been characterized and studied by radiative/convective models [1,2,3,4] that are based on an assumed height distribution of species. Likewise, photochemical models [5,6,7,8,9] also employ a temperature profile as basis for the calculations. In this presentation, we discuss preliminary results of a coupled self-consistent radiative equilibrium/photochemical model for the middle and lower atmosphere of Titan. The radiative equilibrium model includes CH₄ as the principal absorbent of thermal radiation, minor constituents, and the effect of pressure - induced absorption. The vertical distribution of species is calculated by a comprehensive photochemical model [9]. Our coupled radiative equilibrium/photochemical model is self-consistent, so that the temperature calculated in the radiative equilibrium model is used in the photochemical model to calculate the species vertical distribution, and this produced vertical distribution - in the radiation code, reiterating until both reach equilibrium. We are in the process of adding haze contribution to the radiative model for it serves as a main source of heating in the stratosphere. 1. Samuelson et al., Icarus, 53, 1983; 2. McKay et al., Icarus, 80, 1989; 3. Samuelson and Mayo, Icarus, 91, 1991; 4. McKay et al., Science, 253, 1991; 5.Yung et al., Astrophys. J. Suppl.,55,1984; 6. Toublanc, Icarus, 113, 1995; 7. Lara et al., JGR, 101, E10, 1996; 8. Lebonnois et al., Icarus,152, 2001; 9. Wilson and Atreya, JGR, E06002, 2004.