Vilhelm Bjerknes

In 1917, Bjerknes accepted a position with the museum in Bergen (Norway; now part of the University of Bergen), where he founded the Bergen Geophysical Institute. Bjerknes was 55 years old at the time and most historians agree this is where Bjerknes did his best work, continuing his research into the mathematical approach to weather forecasting. Working with his son Jacob and Jacob's fellow student Halvor Solberg, they were later joined by the Swedish meteorologist Tor Bergeron. Together, this extraordinary group of meteorologists put forward the theory that weather activity is concentrated in relatively narrow zones, which form the boundaries between warm and cold air masses. They called these zones "fronts," an analogy with the First World War battlefronts. The theory was widely acclaimed and became known as the "polar front theory of a developing wave cyclone" or, simply, the "polar front theory." What these scientists gave to the world was a working model of how a mid-latitude cyclone progresses through the stages of birth, growth, and decay. Their model marked a turning point in atmospheric science.

Atmospheric Fronts
Bjerknes, in collaboration with his son Jacob and other scientists at the Bergen School in Norway, developed the polar front theory. This theory is the basis for much of current weather forecasting, and described the interaction of warm and cold air masses. In the above map warm fronts are marked by red half circles, and cold fronts by blue triangles. (Map courtesy National Weather Service)

While at the Institute, in 1921, Bjerknes published "On the Dynamics of the Circular Vortex with Applications to the Atmosphere and to Atmospheric Vortex and Wave Motion." Now considered a classic, this work offered one of the first modern and extensive accounts of the structure and evolution of cyclones. This work remarkably remains unaltered to this day. Bjerknes made his final move in 1926 when he accepted the chair of the Department of Applied Mechanics and Mathematical Physics at the University of Oslo (Kristiania was renamed Oslo in 1925). There, in addition to his meteorological studies, he continued to study the hydrodynamical work started by his father. In 1926, he also produced the theory that sunspots are the erupting ends of magnetic vortices broken by the different rotation rates of the sun's poles (slower rotation) and equator (faster rotation).

During his years at the University of Oslo, Bjerknes attracted and inspired gifted students, by putting forth considerable effort into his teaching practices. He also published a book on vector analysis (mathematical treatments of physics concepts such as velocity, acceleration, and force) in 1929 that was produced as the first volume of a larger textbook on theoretical physics.

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On the Shoulders of Giants
Vilhelm Bjerknes
Mathematics and Meteorology
Continuing the Saga
Links and References

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