  The formation of ice in mixed phase clouds greatly impacts Earths hydrologic
cycle. The intensity, distribution and frequency of precipitation as well as
radiative properties of clouds in the mid latitudes are strongly influenced by
the number concentration of ice particles. A long standing riddle in mixed
phase clouds is the frequent observation of measured ice particle
concentrations several orders of magnitude higher than measured ice nucleating
particle concentrations. Here, we report laboratory observations of copious
cloud droplets and ice crystals formed in the wake of a warm, falling water
drop. Aerosols were activated in the transient regions of very high
supersaturation due to evaporative mixing in the wake. We extend these results
to typical mixed phase atmospheric conditions, and our calculations show that
the induced evaporative supersaturation may significantly enhance the activated
ice nuclei concentration in the particles wake.
