Drop growth due to high supersaturation caused by isobaric mixing

A new conceptual model is proposed for enhanced cloud droplet growth during condensation. Rapid droplet growth may occur in zones of high supersaturat ion resulting from isobaric mixing of saturated volumes with different temp eratures. Cloud volumes having a temperature different from the general clo ud environment map form due to turbulent vertical motions in a temperature lapse rate that is not pseudoadiabatic. This mechanism is most effective in the vicinity of cloud-top inversions. It is also shown that the isobaric m ixing of saturated and dry volumes with different temperatures may also lea d to high super-saturations. The high supersaturations are associated with zones of molecular mixing, and they have a characteristic size of the order of millimeters with a characteristic lifetime near tenths of a second. Som e small proportion of cloud droplets, over many supersaturation events, may Slow large enough to grow: effectively through collision-coalescence. This hypothesis of isobaric mixing may help explain freezing and warm drizzle f ormation.