cloud of Jupiter as a framework for describing the model physics and evaluating the model performance. Finally we illustrate model applications by considering water, silicate, and iron clouds in the atmospheres of brown dwarfs and a cool extrasolar giant planet.

Previous Models {#previous}
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A great range of models have been used to represent clouds in the terrestrial atmosphere, which vary in the complexity by which atmospheric dynamics and cloud microphysics are treated. The most detailed models simulate three-dimensional cloud-scale motions and resolve the size distributions of cloud droplets (and the aerosols on which they form) and treat the interactions between dynamics, microphysics, and radiative transfer. The computational demands of such complex models limit their domain sizes to a few kilometers in each dimension. Present global-scale (general circulation) models greatly simplify the representation of clouds by parameterizing cloud-scale motions as well as cloud microphysical processes, and such simplifications lead to profound uncertainties in climate predictions from their simulations. Both types of models, as well as a range of intermediate models, can be considered appropriate for modeling the terrestrial atmosphere by virtue of the wealth of observational data available to constrain them; whether or not the unknowns in such models are 