Carl-Gustaf Arvid Rossby (Swedish pronunciation: [kɑːɭ ˈɡɵ̂sːtav ˈǎrːvɪd ˈrɔ̌sːbʏ] 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.

While ashore between expeditions, he studied mathematical physics at the University of Stockholm (Filosofie Licentiat, 1925).

[3] In 1925 Rossby was granted a fellowship from the Sweden-America Foundation "to study the application of the polar front theory to American weather".

His appointment as chair of the department of meteorology at the University of Chicago in 1940 began the period in which he turned his attention to large-scale atmospheric motions.

[6] During World War II, Rossby organized the training of military meteorologists, recruiting many of them to his Chicago department in the post-war years where he began adapting his mathematical description of atmospheric dynamics to weather forecasting by electronic computer, having started this activity in Sweden using BESK.