Jacob Aall Bonnevie Bjerknes (2 November 1897 – 7 July 1975) was a meteorologist.
Jacob Aall Bonnevie Bjerknes was born in Stockholm, Sweden. His father was the Norwegian meteorologist Vilhelm Bjerknes, one of the pioneers of modern weather forecasting. His paternal grandfather was noted Norwegian mathematician and physicist, Carl Anton Bjerknes. His maternal grandfather was Norwegian politician, Jacob Aall Bonnevie after whom he was named.
Bjerknes was part of a group of meteorologists led by his father, Vilhelm Bjerknes, at the University of Leipzig. Together they developed the model that explains the generation, intensification and ultimate decay (the life cycle) of mid-latitude cyclones, introducing the idea of fronts, that is, sharply defined boundaries between air masses. This concept is known as the Norwegian cyclone model.
Bjerknes returned to Norway in 1917, where his father founded the Geophysical Institute, University of Bergen in Bergen. They organized an analysis and forecasting branch which would evolve into a weather bureau by 1919. The scientific team at Bergen also included the Swedish meteorologists Carl-Gustaf Rossby and Tor Bergeron. As pointed out in a key paper by Jacob Bjerknes and Halvor Solberg (1895-1974) in 1922, the dynamics of the polar front, integrated with the cyclone model, provided the major mechanism for north-south heat transport in the atmosphere. For this and other research, Jacob Bjerknes was awarded the Ph.D. from the University of Oslo in 1924.
In 1926, Jacob Bjerknes was a support meteorologist when Roald Amundsen made the first crossing of the Arctic in the airship Norge. In 1931, he left his position as head of the National weather service at Bergen to become professor of meteorology at the Geophysical Institute at the University of Bergen. Jacob Bjerknes lectured at the Massachusetts Institute of Technology during the 1933-1934 school year and emigrated to the United States in 1940 where he headed a government-sponsored meteorology annex for weather forecasting, at the department of physics of the University of California, Los Angeles. During the second world war Bjerknes served the US armed forces and serving as a colonel in the US Air Force he helped find the best dates for the Atomic bombings of Hiroshima and Nagasaki.
Bjerknes founded the UCLA Department of Meteorology (now the Department of Atmospheric and Oceanic Sciences). As a professor at the University of California, he was the first to see a connection between unusually warm sea-surface temperatures and the weak easterlies and heavy rainfall that accompany low-index conditions. At UCLA, Bjerknes and fellow Norwegian-American meteorologist, Jorgen Holmboe, further developed the pressure tendency and the extratropical cyclone theories.
In 1969, Jacob Bjerknes helped toward an understanding of El Niño Southern Oscillation, by suggesting that an anomalously warm spot in the eastern Pacific can weaken the east-west temperature difference, disrupting trade winds, which push warm water to the west. The result is increasingly warm water toward the east.
In 1928, he married Hedvig Borthen (1904-1998). They were the parents of two children. He died on 7 July 1975 in Los Angeles, California.
Honors and awards
He was made an Honorary Member of the Royal Meteorological Society in 1932 and a member of both the Norwegian Academy of Science and Letters and the Royal Swedish Academy of Science in 1933.
Royal Meteorological Society – Symons Gold Medal (1940)
American Geophysical Union – William Bowie Medal (1945)
Knight 1st Class of the Royal Norwegian Order of St. Olav (1947).
Swedish Society for Anthropology and Geography – Vega medal (1958)
World Meteorological Organization – International Meteorological Organization Prize (1959).
American Meteorological Society – Carl-Gustaf Rossby Research Medal (1960)
National Medal of Science (1966)
Tor Bergeron (15 August 1891 – 13 June 1977) was a Swedish meteorologist who proposed a mechanism for the formation of precipitation in clouds. 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, or melt and fall as cold rain depending on the ambient air temperature. This process is known as the Bergeron Process, 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, 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 of the Royal Meteorological Society. In 1966 he was awarded the prestigious International Meteorological Organization Prize from the World Meteorological Organization.
“…In May 1922 Bergeron was back in Bergen, for ever as he then thought. His intention was, to begin with, to find practical methods for the air mass and front analysis.
Jack Bjerknes, the chief of the Bergen weather service, had one year’s leave, and Bergeron acted as his substitute.
Among the meteorologists who worked in the weather service at that time and should be mentioned is the German G. Schinze. He was very careful in his analyses of the synoptic maps and created a good order in the map work. In 1926 Bergeron married Schinze’s sister Elfriede Schinze…”
Source: Tor Bergeron, A Biography by G. H. Liljequist, PAGEOPH, Vol. 119 (1980/81), Birkhäuser Verlag, Basel, p. 419