<P> The Wegener -- Bergeron -- Findeisen process ( after Alfred Wegener , Tor Bergeron and Walter Findeisen ) , ( or `` cold - rain process '' ) is a process of ice crystal growth that occurs in mixed phase clouds ( containing a mixture of supercooled water and ice ) in regions where the ambient vapor pressure falls between the saturation vapor pressure over water and the lower saturation vapor pressure over ice . This is a subsaturated environment for liquid water but a supersaturated environment for ice resulting in rapid evaporation of liquid water and rapid ice crystal growth through vapor deposition . If the number density of ice is small compared to liquid water , the ice crystals can grow large enough to fall out of the cloud , melting into rain drops if lower level temperatures are warm enough . </P>
<P> The Wegener -- Bergeron -- Findeisen process ( after Alfred Wegener , Tor Bergeron and Walter Findeisen ) , ( or `` cold - rain process '' ) is a process of ice crystal growth that occurs in mixed phase clouds ( containing a mixture of supercooled water and ice ) in regions where the ambient vapor pressure falls between the saturation vapor pressure over water and the lower saturation vapor pressure over ice . This is a subsaturated environment for liquid water but a supersaturated environment for ice resulting in rapid evaporation of liquid water and rapid ice crystal growth through vapor deposition . If the number density of ice is small compared to liquid water , the ice crystals can grow large enough to fall out of the cloud , melting into rain drops if lower level temperatures are warm enough . </P>
in the burgeron process water droplets transform from
in the burgeron process water droplets transform from
vapor deposition
vapor deposition