Tor Bergeron (15 August 1891 – 13 June 1977) was a Swedish

meteorologist A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists in research, while th ...

who proposed a mechanism for the formation of

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hai ...

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...

s. In the 1930s, Bergeron and W. Findeisen developed the concept that clouds contain both supercooled water and ice crystals. According to Bergeron, most precipitation is formed as a consequence of water evaporating from small supercooled droplets and accreting onto ice crystals, which then fall as

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet ...

, or melt and fall as cold

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...

depending on the ambient air temperature. This process is known as the

Bergeron Process Bergeron is a surname of French origin. The name Bergeron may be derived from the Old German word ''berg'', meaning hill or mountain. It may also be derived from the old French ''berger'', meaning shepherd. Spelling variations include: Bergetr ...

, and is believed to be the primary process by which precipitation is formed. Bergeron was one of the principal scientists in the

Bergen School of Meteorology __NOTOC__ The "Bergen School of Meteorology" is a school of thought which is the basis for much of modern weather forecasting. Founded by the meteorologist Prof. Vilhelm Bjerknes and his younger colleagues in 1917, the Bergen School attempts to de ...

, which transformed this science by introducing a new conceptual foundation for understanding and predicting weather. While developing innovative methods of forecasting, the Bergen scientists established the notion of weather fronts and elaborated a new model of extratropical cyclones that accounted for their birth, growth, and decay. Bergeron is credited with discovering the occlusion process, which marks the final stage in the life cycle of an extratropical cyclone. In 1949 he was awarded the

Symons Gold Medal The Symons Gold Medal is awarded biennially by the Royal Meteorological Society for distinguished work in the field of meteorological science. It was established in 1901 in memory of George James Symons, a notable British meteorologist. Recipient ...

of the

Royal Meteorological Society The Royal Meteorological Society is a long-established institution that promotes academic and public engagement in weather and climate science. Fellows of the Society must possess relevant qualifications, but Associate Fellows can be lay enthus ...

. In 1966 he was awarded the prestigious

International Meteorological Organization Prize The International Meteorological Organization Prize is awarded annually by the World Meteorological Organization (WMO) for outstanding contributions in the field of meteorology and, since 1971, the field of operational hydrology. The prize, estab ...

from the

World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the Intern ...

References

*A complete bibliography for Bergeron can be found in Liljequist (1981): ** Liljequist, Gösta H. “Tor Bergeron: A Biography.” Pure and Applied Geophysics 119 (1981): 409–442. {{DEFAULTSORT:Bergeron, Tor 1891 births 1977 deaths Swedish meteorologists British emigrants to Sweden