A NEW REPRESENTATION OF THE ABSORPTION BY THE CO2 15-MU-M BAND FOR A MARTIAN GENERAL-CIRCULATION MODEL

A model for absorption by the CO2 15-mum band has been adapted from the Morcrette et al. (1986) terrestrial wide-band model for use in a general circulation model of the Martian atmosphere. The absorption model is validated by comparison with exact line-by-line integrations for a set of atmospheric profiles characteristic of Martian conditions. The Doppler effect is included in a simple way with no significant increase of the computational cost. The model gives accurate results up to 80 km. The Doppler effect, in fact, is shown to be significant only above 50 km for mean Martian conditions. The transmissivities of the wide-band model are fitted to the results of a more accurate statistical narrow-band model. Various formulations of the statistical band model, including accurate representation of the Doppler effect (Fels, 1979; Zhu,1989) are validated by comparison with line-by-line results.