Carl-Gustaf Arvid Rossby (Swedish pronunciation: [kɑːɭˈgʉsˌtav ˈarvɪd ˈrɔsːby] 28 December 1898 – 19 August 1957) was a Swedish-born American meteorologist who first explained the large-scale motions of the atmosphere in terms of fluid mechanics. He identified and characterized both the jet stream and the long waves in the westerlies that were later named Rossby waves.
Carl-Gustaf Rossby was born in Stockholm, Sweden. He was the first of five children born to Arvid and Alma Charlotta (Marelius) Rossby. He attended where he developed his first interest in mathematical physics. Rossby came into meteorology and oceanography while studying geophysics under Vilhelm Bjerknes at the Geophysical Institute, University of Bergen in Bergen, Norway during 1919, where Bjerknes' group was developing the groundbreaking concepts that became known as the Bergen School of Meteorology, including theory of the polar front.
He also studied at the University of Leipzig and at the Lindenberg Observatory (Meteorologischen Observatorium Lindenberg) in Brandenburg where upper air measurements by kite and balloon were researched. In 1921 he returned to Stockholm to join the Meteorological and Hydrographic Office (which later became the Swedish Meteorological and Hydrological Institute) where he served as a meteorologist on a variety of oceanographic expeditions. While ashore between expeditions, he studied mathematical physics at the .