The radiative effects of Martian water ice clouds on the local atmospherictemperature profile

Mars Pathfinder made numerous discoveries, one of which was a deep temperat ure inversion that extended from about 15 km down to 8 km above the surface . It has been suggested by Haberle ct al. (1999. J. Geophys. Res. 104, 8957 -8974,) that radiative cooling by a water ice cloud may generate such an in version. Clouds can strongly affect the local air temperature due to their ability to radiate efficiently in the infrared and due to the low air mass of the martian atmosphere, which allows the temperature to change during th e relatively short lifetime of a cloud. We utilize a time-dependent microph ysical aerosol model coupled to a radiative-convective model to explore the effects water ice clouds have on the local martian temperature profile. We constrain the dust and water vapor abundance using data from the Viking Mi ssions and Mars Pathfinder. Water ice clouds with visible optical depths of tau greater than or equal to 0.1 form readily in these simulations, These clouds alter the local air temperature directly, through infrared cooling, and indirectly, by redistributing atmospheric dust. With this model we are able to reproduce the temperature inversions observed by Mars Pathfinder an d Mars Global Surveyor. (C) 2000 Academic Press.