three-cell model An approximate representation of the general circulation of the atmosphere. Air rises over the Equator and subsides over the sub-tropics; these are Hadley cells. Air subsides over polar regions and spreads into lower latitudes; these are polar cells. The Hadley and polar cells drive a third set of Ferrel cells in middle latitudes. See also Rossby waves.

three-cell model An attempt to represent the atmospheric circulation systems over a hemisphere by three adjoining vertical cells of meridional surface motion, transferring energy from equatorial to polar regions. This concept of heat transfer by meridional circulation has generally been superseded by more modern ideas of travelling waves. See also HADLEY CELL; and ROSSBY WAVES.