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William Ferrel analysed atmospheric circulation on a rotating Earth. The Ferrel cell carries his name and describes the middle-latitude branch of the idealized meridional circulation.^[ref]

Its modern interpretation requires care: this mean circulation is thermally indirect and strongly affected by eddy transport. It is not simply a second thermally direct Hadley cell. The distinction links the historical three-cell picture to the conservation and transport arguments used in geophysical fluid dynamics.