while maintaining a constant mixing ratio (equivalently, mole fraction) below the cloud. Temperature and hence the saturation mixing ratio in the air column decrease with altitude, and the cloud base again appears where the saturation mixing ratio matches the sub-cloud mixing ratio. Above the cloud base, turbulent diffusion works toward maintaining a constant total mixing ratio ($q_{\rm t} = q_{\rm v} + q_{\rm c}$), which is the sum of the vapor ($q_{\rm v}$ = moles of vapor per mole of atmosphere) and condensate ($q_{\rm c}$ = moles of condensate per mole of atmosphere) mixing ratios, while sedimentation reduces $q_{\rm t}$ by transporting condensate downward. Note that by ignoring horizontal variability, any differences between (cloudy) updrafts and (potentially cloud-free) downdrafts are neglected.

A number of models for tropospheric condensation clouds have appeared in the planetary and astrophysical literature. Here we summarize a selection of them that contribute to the present work.

Lewis (1969)
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Lewis (1969) represents a foundation in the study of tropospheric clouds in the giant planets. In that work the term “precipitation” is used in the narrow sense used by chemists, in which condensates appear where the local saturation vapor pressure is exceeded by the actual vapor pressure, 