Tor Bergeron

Tor Bergeron was a Swedish meteorologist who proposed a mechanism for the formation of precipitation in clouds. In the 1930s he and Walter Findeisen developed the concept that clouds contain both supercooled water and ice crystals, and that most precipitation forms as water evaporates from supercooled droplets and accretes onto ice crystals, which then fall as snow or melt into cold rain depending on the ambient air temperature, a process now known as the Bergeron process. He was one of the principal scientists of the Bergen School of Meteorology, which established the concept of weather fronts and a new model of the life cycle of extratropical cyclones, and he is credited with discovering the occlusion process that marks the final stage of that cycle.