A coupled dynamics-microphysics model of Titan's atmosphere

Pascal Rannou (1) , Frédéric Hourdin (2) , Christopher P. Mckay (3) , David Luz (4, 5)

1 SA - Service d'aéronomie
2 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
3 National Aeronautics and Space Administration, Ames Research Center
4 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
5 Pôle Planétologie du LESIA

We have developed a coupled general circulation model of Titan's atmosphere in which the aerosol haze is treated with a microphysical model and is advected by the winds. The radiative transfer accounts for the non uniform haze distribution and, in turn, drives the dynamics. We analyze the GCM results, especially focusing on the difference between a uniform haze layer and a haze layer coupled to the dynamics. In the coupled simulation the aerosols tend to accumulate at the poles, at latitudes higher than ±60°. During winter, aerosols strongly radiate at thermal infrared wavelengths enhancing the cooling rate near the pole. Since this tends to increase the latitudinal gradients of temperature the direct effect of this cooling excess, in contrast to the uncoupled haze case, is to increase the strength of the meridional cells as well as the strength of the zonal winds and profile. This is a positive feedback of the haze on dynamics. The coupled model reproduces observations about the state of the atmosphere better than the uniform haze model, and in addition, the northern polar hood and the detached haze are qualitatively reproduced.

Domaines: Astrophysique [astro-ph]

Pascal Rannou, Frédéric Hourdin, Christopher P. Mckay, David Luz. A coupled dynamics-microphysics model of Titan's atmosphere. Icarus, 2004, 170, pp.443-462. ⟨10.1016/j.icarus.2004.03.007⟩. ⟨hal-03733019⟩