Vilhelm Bjerknes | |
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 Bjerknes, 1920s | |
| Born | Vilhelm Friman Koren Bjerknes (1862-03-14)14 March 1862 Christiania, Norway |
| Died | 9 April 1951(1951-04-09) (aged 89) Oslo, Norway |
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| Children | 2, includingJacob |
| Father | Carl Anton Bjerknes |
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| Doctoral advisor | Heinrich Hertz |
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Vilhelm Friman Koren Bjerknes (/ˈbjɜːrknɪs/BYURK-niss,Norwegian:[ˈʋɪlˌhɛlmˈbjæɾknɛs]; 14 March 1862 – 9 April 1951)[1][3][4][5][6] was a Norwegiangeophysicist andmeteorologist who did much to lay the foundation of the modern practice ofweather forecasting. He formulated theprimitive equations that are still in use innumerical weather prediction andclimate modeling. He founded the so-calledBergen School of Meteorology, which was successful in advancing weather prediction and meteorology in the early 20th century.
Born inChristiania (later renamed Oslo), Bjerknes enjoyed an early exposure tofluid dynamics, as assistant to his father,Carl Anton Bjerknes, who had discovered by mathematical analysis the apparent actions at a distance between pulsating and oscillating bodies in a fluid, and their analogy with the electric and magnetic actions at a distance.[7] Apparently no attempt had been made to demonstrate experimentally the theories arrived at by the older professor until Vilhelm Bjerknes, then about 17 or 18 years of age, turned his mathematical knowledge and mechanical abilities to the devising of a series of instruments by which all the well-known phenomena of electricity and magnetism were illustrated and reproduced by spheres and discs and membranes set into rhythmic vibration in a bath containing a viscous fluid such as syrup. These demonstrations formed the most important exhibit in the department of physics at the Exposition Internationale d'Électricité held in Paris in 1881, and aroused greatest interest in the scientific world.[8]
Vilhelm Bjerknes became assistant toHeinrich Hertz in Bonn 1890–1891 and made substantial contributions to Hertz' work onelectromagneticresonance. He succeeded in giving the explanation of the phenomenon called "multiple resonance," discovered by Sarasin and De la Rive. Continuing his experiments at the University of Christiania (1891–1892), he proved experimentally the influence which the conductivity and the magnetic properties of the metallic conductors exert upon the electric oscillations, and measured the depth to which the electric oscillations penetrate in metals of different conductivity and magnetic permeability (the "skin effect"). Finally, in 1895 he furnished a complete theory of the phenomenon of electric resonance, involving a method of utilizing resonance experiments for the determination of the wavelengths, and especially of the damping (the logarithmic decrement) of the oscillations in the transmitter and the receiver of the electric oscillations. These methods contributed much to the development of wireless telegraphy. His papers on electric oscillations were published inAnnalen der Physik (1891–1895).[8]
In 1895, he became professor of applied mechanics and mathematical physics at theStockholm University where he had been lecturer since 1893. There he elucidated the fundamental interaction between fluid dynamics andthermodynamics. His major contribution was theprimitive equations which are used inclimate models.[9]It was this work that inspired bothV. Walfrid Ekman andCarl-Gustav Arvid Rossby to apply it to large-scale motions in the oceans andatmosphere and to make modern weather forecasting feasible. Bjerknes himself had foreseen the possible applications as early as 1904. This attack upon the meteorological problems from a hydrodynamical point of view was after 1906 supported by theCarnegie Institution of Washington, D.C., of which he became a research associate. Two introductory volumes,Statics and Kinematics, of a greater work,Dynamic Meteorology and Hydrography, were published in 1913 under the auspices of the Institution.[8]
In his 1906 workFields of force, Bjerknes was the first to describe and mathematically derive translational forces onbubbles in an acoustic field, now known asBjerknes forces.[10]
In hisVorlesungen über Hydrodynamische Fernkräfte nach C. A. Bjerknes Theorie (1900–1902) he gave the first complete mathematical and experimental exposition of the discoveries of his father, whose age and excessive self-criticism had prevented him from finishing his work himself. In a later book,Die Kraftfelder (1909), he stated the same theory in a very much generalized form according to methods of his own.[8]
In 1907, Bjerknes returned to theRoyal Frederick University in Oslo before becoming professor ofgeophysics at theUniversity of Leipzig in 1912. In 1916, he started the publicationSynoptische Darstellung atmosphärischer Zustände über Europa. In 1917, he founded theGeophysical Institute, University of Bergen where he wrote his bookOn the Dynamics of the Circular Vortex with Applications to the Atmosphere and to Atmospheric Vortex and Wave Motion (1921), and laid the foundation for theBergen School of Meteorology, which was not a literal school but a school of thought on how the practice of weather forecasting and meteorology should be undertaken. He was the originator of an improved and more scientific weather service, afterwards controlled by his son and collaborator, the meteorologistJacob Bjerknes (1897–1975).[8]
From 1926 to his retirement in 1932, he held a position at theUniversity of Oslo. He was elected a member of theRoyal Swedish Academy of Sciences in 1905 and of thePontifical Academy of Sciences in 1936[11] and aFellow of the Royal Society.[1] He was awarded the 1932Symons Gold Medal of theRoyal Meteorological Society.[12]
He died of heart problems in Oslo. In 1893, Bjerknes had married Honoria Bonnevie, who in earlier years assisted him much in his scientific work.[8] Their sonJacob Aall Bonnevie Bjerknes also became a meteorologist.
The cratersBjerknes on the Moon andBjerknes[13] on Mars are named in his honor.
Every profession has its savants - geniuses who appear on the scene once in a generation to turn the accepted wisdom on its head. Psycho analysts had Sigmund Freud; economists had John Maynard Keynes; architects had Le Corbusier and Frank Lloyd Wright; and meteorologists remember Vilhelm Bjerknes who died 50 years ago today, on April 9th, 1951.
