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R. T. Clancy (SSI), A.V. Rodin (IKI, Moscow), R.J. Wilson (NOAA/GFDL)
The water ice clouds that appear in the martian troposphere provide a prominent positive feedback with the planetary heat balance, mainly due to the enhanced sedimentation and changing scattering properties of the nucleated dust particles. It has been recently shown that the incorporation of such a nonlinear feedback in a steady-state model may result in atmospheric temperature profiles with multiple steady states for typical aphelion season conditions. The question of the stability of these stationary states and their transitional dynamics is a significant issue in view of the seasonal evolution of martian atmospheric temperatures. The microphysics of the martian water ice clouds can be approximately represented by a nonlinear model of Brownian motion as a one-dimensional nonlinear stochastic oscillator in a self-consistent potential field. The criteria for stability of the climate states are derived from this approximate model and compared with the observed global temperature trend covering several Martian years. We present a time-dependent 1D model of the lower-to-mid atmosphere of Mars that interactively incorporates water ice cloud microphysics, a realistic radiation balance, and turbulent transport of the aerosols. It is shown that the atmosphere equilibrates to different stationary states depending on the initial conditions. The typical timescale of reconfiguration appears to be about 105 sec which is significantly separated from the eddy mixing and sedimentation timescales. The employed formalism and its applicability to comprehensive GCM simulations will be discussed.
The author(s) of this abstract have provided an email address for comments about the abstract: rodin@irn.iki.rssi.ru