ROSSBY, CARL-GUSTAF ARVID

(b. Stockholm, Sweden, 28 December 1898; d. Stockholm, 19 August 1957)

meteorology, oceanography.

Rossby was the son of Arvid Rossby, a construction engineer, and Alma Charlotta Marelius. He entered the University of Stockholm in 1917, and studied mathematics, mechanics, and astronomy. His career in meteorology began in 1919, when he joined the scientific staff at the Geophysical Institute at Bergen, Norway. Here the polar-front theory of cyclones was being developed under the leadership of V. F. Bjerknes. In 1921 Rossby studied hydrodynamics at the Geophysical Institute of the University of Leipzig and worked at the Prussian Aerological Observatory at Lindenberg. In the same year he returned to Stockholm and entered the Swedish Meteorological and Hydrological Service. He took part in several meteorological and oceanographic expeditions. He also continued his studies of mathematical physics at the University and received his licentiate in 1925. In 1926 he won a one-year fellowship to the U.S. Weather Bureau in Washington. He remained in the United States for more than twenty years, marrying Harriot Alexander in 1929 and obtaining American citizenship in 1939.

Rossby was instrumental in bringing American meteorology to a position of world leadership. At first, however, his attempt to introduce the polar-front theory and other innovations was met with hostility at the U.S. Weather Bureau, which was largely bureaucratic rather than a center of scientific research. In 1927 Rossby accepted the chairmanship of the Committee on Aeronautical Meteorology of the Daniel Guggenheim Fund for Promotion of Aeronautics, in which capacity he established a model weather service for civil aviation in California. He became associate professor of meteorology at the Massachusetts Institute of Technology in 1928 and rapidly established a strong department.

Rossby was appointed assistant chief of the Weather Bureau, in charge of research and education, in 1939. During the next two years he worked at reorganizing the Bureau and strengthening its scientific mission. In 1941 Rossby became chairman of the newly founded department of meteorology at the University of Chicago, where he brought together an outstanding group of scientists from many different countries. During the early 1940’s, when the needs of warfare made meteorology a key science, Rossby organized a very effective military educational program in meteorology and worked for the establishment of an adequate global observing and forecasting service. Recognizing the importance of tropical meteorology, he was instrumental in founding the Institute of Tropical Meteorology at the University of Puerto Rico. He also reorganized the American Meteorological Society and established the Journal of Meteorology and later, in Sweden, the geophysical journal Tellus.

Rossby became increasingly active in promoting international collaboration in the late 1940’s. At the request of the Swedish government, he returned to Sweden in 1950 and organized the International Meteorological Institute. He continued to make extended visits to the United States during the 1950’s, mainly in connection with his work at the Woods Hole Oceanographic Institute.

Despite his strenuous work as organizer, director, and promoter, Rossby still found time and energy for high-quality research. His original contributions to meteorology reveal a deep insight into the fundamental processes taking place in the atmosphere and oceans. He produced many new ideas that he submitted for discussior to the group of scientists working around him, often approaching a complex problem by introducing bold simplifications to be accounted for later.

During the 1920’s Rossby worked on atmospheric turbulence and the theory of atmospheric pressure variations. While at MIT he continued his research on atmospheric and oceanic turbulence and introduced the concepts of mixing length, the roughness parameter, and the logarithmic wind profile. During his early years at MIT, Rossby applied thermodynamics to air mass analysis, a subject first systematically studied by T. Bergeron in 1928. Rossby designed a graphical method, the Rossby diagram, for the identification of air masses and the processes that give rise to their formation and modification (1932).

Pursuing a method advocated by W. N. Shaw during the 1920’s, Rossby and his collaborators developed the technique of isentropic analysis. Using this technique, which allowed the tracing of large-scale air currents, Rossby started his studies of the dynamics of the general circulation of the atmosphere. In connection with a project on long-range forecasting started in 1935, he began to investigate the circumpolar system of long waves, now called Rossby waves, in the westerly winds of the middle and upper troposphere. These waves exert a controlling influence on weather conditions in the lower troposphere. Rossby developed a dynamic theory of these long waves on the basis of the theorem of conservation of absolute vorticity (propounded by Helmholtz in 1858) and derived a simple formula, now called the Rossby equation, for their propagation speed (1939, 1940). This formula became perhaps the most celebrated analytic solution of a dynamic equation in meteorological literature.

Rossby’s theoretical analysis profoundly influenced both applied and theoretical meteorology and oceanography during subsequent decades. The applicability of his theoretical results convinced Rossby that the principal changes in the atmospheric circulation could be predicted by considering readjustments of the horizontal velocity field without taking into account changes in the vertical structure of the atmosphere. In 1940 he and his collaborators carried out the first numerical predictions for a “one-layer” barotropic atmosphere in which vorticity was conserved. These calculations and the introduction of high-speed electronic computers during the 1940’s set the stage for the simultaneous development of forecasting techniques and theory through comparisons of calculated and observed atmospheric states, as Bjerknes had envisioned in 1904.

Under Rossby’s leadership the research group at Chicago became engaged in synoptic, theoretical and experimental studies of the general circulation and developed most of the basic concepts of the jet stream, the core of high-speed winds embedded in the upper long waves; it was first revealed in the late nineteenth century by observation of the drift of cirrus clouds, but was systematically encountered and investigated only as a result of the establishment of a worldwide network of upper-air sounding stations during World War II. In analogy to his work on ocean currents (1936), Rossby found a partial explanation for the existence and maintenance of the observed latitudinal wind distribution that was based on the concepts of large-scale lateral mixing and conservation of absolute vorticity (1947).

Back in Stockholm, Rossby continued to work on problems of atmospheric and oceanic circulation and their interactions. In addition he began to study geochemistry in general and atmospheric chemistry in particular, seeing it as an opportunity to broaden the scope of meteorology. He organized an international network for the investigation of the distribution of trace elements in the atmosphere.

BIBLIOGRAPHY

I. Original Works. Bibliographies of Rossby’s works are in B. Bolin, ed., The Atmosphere and Sea in Motion, the Rossby memorial volume (New York, 1959), 60–64; and in the biography by H. R. Byers (see below). His writings include “Thermodynamics Applied to Air Mass Analysis,” Massachusetts Institute of Technology, Papers in Physical Oceanography and Meteorology, 1 (1932), no. 3; “A Generalization of the Theory of the Mixing Length With Application to Atmospheric and Oceanic Turbulence,” ibid., no. 4; “The Layer of Frictional Influence in Wind and Ocean Currents,” in Papers in Physical Oceanography and Meteorology, 3 (1935), no. 3, written with R. B. Montgomery; “Dynamics of Steady Ocean Currents in the Light of Experimental Fluid Mechanics,” ibid., 5 (1936), no. 1; and “Relation Between Variations in the Intensity of the Zonal Circulation of the Atmosphere and the Displacements of the Semi-Permanent Centers of Action,” in Journal of Marine Research, 2 (1939), 38–55, written with collaborators.

Later works are “Planetary Flow Patterns in the Atmosphere,” in Quarterly Journal of the Royal Meteorological Society (Toronto proceedings supp.), 66 (1940), 68–87; “The Scientific Basis of Modern Meteorology,” in U. S. Department of Agriculture, Yearbook of Agriculture (1941), 599–655; “Kinematic and Hydrostatic Properties of Certain Long Waves in the Westerlies,” in University of Chicago, Department of Meteorology, Miscellaneous Reports, no.5 (1942); “On the Propagation of Frequencies and Energy in Certain Types of Oceanic and Atmospheric Waves,” in Journal of Meteorology, 2 (1945), 187–204; “On the Distribution of Angular Velocity in Gaseous Envelopes Under the Influence of Large-Scale Horizontal Mixing Processes,” in Bulletin. American Meteorological Society, 28 (1947), 53–68; “On the Dispersion of Planetary Waves in a Barotropic Atmosphere,” in Tellus, 1 (1949), 54–58; and “On the Vertical and Horizontal Concentration of Momentum in Air and Ocean Currents,” ibid., 3 (1951), 15–27.

II. Secondary Literature. See T. Bergeron, “The Young Carl-Gustaf Rossby,” in B. Bolin, ed., The Atmosphere and Sea in Motion (New York, 1959), 51–55; B. Bolin, in Tellus, 9 (1957), 257–258; H. R. Byers, “Carl-Gustaf Rossby, the Organizer,” in B. Bolin, ed., op. cit., 56–59; and “Carl-Gustaf Arvid Rossby,” in Biographical Memoirs. National Academy of Sciences, 34 , no. 11 (1960), 249–270; and G. W. Platzman, “The Rossby Wave,” in Quarterly Journal of the Royal Meteorological Society, 94 (1968), 225–248.

Gisela Kutzbach