# Vilhelm Frimann Koren Bjerknes

# Vilhelm Frimann Koren Bjerknes

**1862-1951**

**Norwegian Geophysicist, Meteorologist, and Physicist**

Vilhelm Bjerknes made seminal contributions to the foundation of dynamic meteorology as a mathematically exact modern science with his theory of "physical hydrodynamics," while expanding practical meteorology with the development of synoptic meteorology and formula-based weather forecasting techniques. He also made important contributions to electrodynamic theory.

Bjerknes showed early signs of true genius as a youth already assisting his father, Carl Bjerknes (1825-1903), a physics teacher, with his theories on hydrodynamic forces and their similarities to electrodynamic forces. Vilhelm's formal training started with studies in mathematics and physics at the University of Kristiania (later Oslo) in 1880. Completing his masters degree (1887), he studied at Paris under physicist Jules-Henri Poincaré (1854-1912) on a state fellowship and went on to Bonn in 1890, becoming an assistant to and collaborator with Heinrich Hertz (1857-1894) in electrodynamic research. Bjerknes contributed resonance experimental verification of Hertz's electromagnetic wave theory along with adding to oscillatory circuit theory. Returning to Oslo he completed his Ph.D. with a focus on electrodynamics in 1892. Bjerknes settled into a professorship of applied mechanics and mathematical physics at the University of Stockholm in 1895, during which time he decided to return to hydrodynamics and his father's research but with limited success in the latter regard.

Bjerknes was much more open-minded in his research aspirations than his father's unformalized and eccentric goals. The study of circular or vortex motion and its stable characteristics in hydrodynamics had been advanced late in the century, and Bjerknes became interested in its applications to understanding the motion of the atmosphere and oceans. He realized that these—the two largest fluid systems on Earth—were energized to motion by the radiation of the Sun, requiring that both hydrodynamic as well as thermodynamic considerations be integrated. This he did in his theory of "physical hydrodynamics." Bjerknes particularly focused on application to the atmosphere by theorizing a rigorous mathematical interpretation of its dynamics with a systematic approach to analysis of atmospheric conditions, making possible more accurate weather forecasting.

While lecturing at MIT in 1905 and hoping to obtain American funding for his research, Bjerknes received a generous stipend (which continued until 1941) from the Carnegie Institute in Washington, D.C. By 1909 he began soliciting the meteorological community at large on his analysis techniques, stressing upper air wind data and other innovative observing methods conducive to better weather forecasting. Continuing his physics professorship at the University of Kristiania, Bjerknes began to draw bright post-graduate students to his call for meteorological research. These students included Harald Sverdrup (1888-1957), his son Jacob (1897-1975), Halvor Solberg (1895-1974), Carl-Gustav Rossby (1898-1957), and Tor Bergeron (1891-1977). Bjerknes was offered the chair of a new geophysical institute at the University of Leipzig in 1912, and several of his young collaborators followed him there to do research on storm movement forecasting, which was the most practical application in contemporary meteorology. By 1917, the war and the offer to found a geophysical institute at Bergen by his friend zoologist/explorer Fridtjof Nansen (1861-1930) brought him home to Norway.

Bjerknes intensified his ambitious program of systematic weather data gathering, analysis by mathematical and graphical techniques, and perfecting formulas for weather forecasting. The importance of timely weather forecasts brought support from the Norwegian government, which enabled him to start the West Norwegian Weather Service as part of the Bergen Geophysical Institute in mid 1918, which was expanded to a countrywide level. Bjerknes's dynamic meteorology theory was enhanced by his collaborators' theories and verification of the extratropical cyclone model, the polar front, and the airmass conception of analysis.

By 1926 the Bergen group of researchers had assumed the tasks of the weather service and the dissemination of Bjerknes's dynamic meteorology. Bjerknes left to resume his teaching of mechanics and mathematical physics at the University of Oslo. He began a series of textbooks on theoretical physics, and temporarily renewed research into his father's theories of hydrodynamic forces centering on "hydromagnetics" during this period. He retired from teaching in 1932 but continued to advocate the Bergen meteorology with great enthusiasm. Bjerknes published important seminal works supporting his dynamic meteorology theory and received many awards for his contributions to theoretical physics and modern meteorology.

**WILLIAM J. MCPEAK**

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