CO2 Condensation in Baroclinic Eddies on Early Mars

Abstract

The efficacy of a cloud-radiative feedback on early Mars is reexamined in the context of the theory of baroclinic waves in midlatitudes. The feedback has been proposed to explain fluvial features on the surface of Mars. The radiative?convective models used to calculate the magnitude of the feedback require knowledge of the cloud depth, thickness, and areal coverage. Using a quasigeostrophic model and primitive equation simulations, it seems that less than 50% areal cloud cover is likely for early Mars, at least in midlatitudes. In accordance with previous studies for Earth, when condensational heating is included, the updraft region is narrower than in dry eddies. This results in reduced cloud cover and the feedback being weaker than previously thought. The simulations also show that condensation in eddies may have been important on a thick but cold early Mars but that its effects are much weaker for warmer climates.