A very large-scale convection circulation in the atmosphere or ocean that takes place in a meridional plane, with northward and southward currents in opposite branches of the cell, and upward and downward motion in the equatorward and poleward ends of the cell. There are three annual mean meridional cells in each hemisphere, the strongest of which is the Hadley cell. A much weaker indirect cell is the Ferrel cell located between 30° and 60° latitude. There is a very weak direct cell in the polar latitudes. These are integral parts of the general circulation. Compare Hadley cell, polar cell.