The Bergeron-Findeisen process: an example

E. Linacre


Air saturated against water at -10ºC has a moisture content 121% that of air saturated against ice at the same temperature. So, if the space between a cloud droplet and a nearby ice crystal has an intermediate vapour pressure, it is about 10% less than that of the droplet’s surface and 10% more than that of the ice. These differences lead to transfer from the droplet to the space, and also from the space to the crystal. In other words, there is a net transfer from droplet to crystal; the latter grows at the expense of the droplet. This is the basis of the Bergeron-Findeisen process (Note 9.C)