Vilhelm Frimann Koren Bjerknes, For.Mem.R.S., Hon.F.R.S.E.

by A H R Goldie

Vilhelm Frimann Koren Bjerknes was born on March 14, 1862, the son of C A Bjerknes, Professor of Mathematics at Oslo, who was also an eminent research worker on Hydrodynamics. J Bjerknes, son of V Bjerknes, is a well-known meteorologist, so that three generations of the family have become distinguished in the dynamics of fluids and gases.

Vilhelm Bjerknes was educated at Oslo, and published his first paper, "New Investigations in Hydrodynamics", at the age of twenty. From1890 to 1891 he studied under Hertz. In 1893, the year of his marriage, he became Professor of Mathematics and Mathematical Physics at Stockholm, where in 1898 he enunciated his circulation principle. This states that if in a fluid the surfaces of equal pressure are parallel to the surfaces of equal density or specific volume, the existing circulation continues unchanged. If, on the other hand, the isobaric surfaces are inclined to the isosteric surfaces (the baroclinic as opposed to the parallel or barotropic arrangement of the fluid), then the rate of change of the circulation (C) in a closed circuit is equal to the number (M of solenoids formed by the intersection of successive isobaric surfaces with successive isosteric surfaces, i.e. dC/dt = N. Bjerknes made numerous physical applications of the theorem in meteorology and oceanography. In 1900-2 his Hydrodynamische Fernkräfte was published.

In 1907 Bjerknes left Stockholm for Oslo University, where he worked on his Dynamical Meteorology and Hydrography, published in 1910-I2 with financial assistance from the Carnegie Institution of Washington. In this work for the first time he showed the advantage of using the topography of the isobaric surfaces in the upper air.

In 1912 Bjerknes became Director of the new Geophysical Institute at Leipzig; there he started work on wave motion in the atmosphere on the rotating globe. He continued at Leipzig until 1917, when he returned to Norway to be Director of the B Division of the Geophysical Institute, Bergen, where, with the help of an enthusiastic group of young research workers, he developed the ideas which were soon to become known to the world as the Bergen theory of the depressions of temperate latitudes and their relation to the Polar Front.

Bjerknes returned again to Oslo in 1926 as Professor of Mathematics. There, in collaboration with J Bjerknes, H Solberg, and T Bergeron, he completed in 1933-34 the three-volume treatise Physical Hydrodynamics with Applications to Dynamical Meteorology.

V Bjerknes made numerous visits to this country from 1910 onwards. In 1919 he lectured to the Royal Meteorological Society on "The Structure of the Atmosphere when Rain is Falling", in 1924 to the Royal Institution on "The Forces which Lift Aeroplanes", and to the Royal Meteorological Society on "Polar Front Meteorology". In 1927 he visited Edinburgh and St Andrews in company with Nansen, Helland Hansen, and Sverdrup, and in 1936 he presided over the Edinburgh meetings of the International Association of Meteorology. In 1946, on the occasion of the deferred Newton Tercentenary Celebrations, he was a delegate with Störmer to the Royal Society, London.

Outside of his meteorological papers may be mentioned one on "Solar Hydrodynamics", which is a "hydrodynamical discussion of internal solar motions, especially vortex motions for explaining sunspots". It has much of interest for the meteorologist as well as the astronomer.

V Bjerknes, was a Foreign Member of the Royal Society (1933) and an Honorary Fellow of the Royal Society of Edinburgh (1930), Honorary Member (1913) and Symons Medallist (1932) of the Royal Meteorological Society, and LL.D. of the University of St Andrews (1926). He had a singularly attractive, frank, and modest personality, and his writing of English was concise, expressive, and a pleasure to read.

He died on April 9, 1951.

Vilhelm Frimann Koren Bjerknes's RSE obituary by A H R Goldie appeared in Royal Society of Edinburgh Year Book 1952, 5-6.

See also Obituary Notices of Fellows of the Royal Society, vii, 1950-51, pp. 303-317.