due to adiabatic cooling, and the sink due to condensation. Uncertainties in updraft speeds and the populations of condensation nuclei (and hence cloud droplets) both contribute to the uncertainty in supersaturations realized in extraterrestrial clouds. Furthermore, the time constants Carlson et al. (1988) use for gravitational coalescence assume that the collection efficiency is unity, and those for sedimentation effectively assume a fixed width of the size distribution. Rather than attempting to constrain the many degrees of freedom using such a detailed approach, we choose instead to reduce the number of assumptions by simplifying the description of cloud microphysics.

Lunine et al. (1989)
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Lunine et al. (1989) consider a range of possible iron and silicate clouds in brown dwarfs; the possibilities differ in the nature of the balance between sedimentation and turbulent mixing. The framework is based on a theoretical investigation into iron clouds deep in the Jovian atmosphere by Prinn & Olaguer (1981), which in turn draws on an analysis of sulfuric acid clouds on Venus (Prinn 1974). These models represent a fleshing out of the discussion of vertical transport of condensates by Weidenschilling & Lewis (1973).

Two fundamental cloud types are treated by Lunine et al. (1989). The 