A simple, vertical, thermally direct, tropical, atmospheric cell. Air rises at the inter-tropical convergence zone (ITCZ) and drifts polewards, cooling a little through a net loss of radiation, and thereby transferring heat. As the circumference of the Earth decreases with distance from the equator, the moving air has to converge. This combination of cooling and convergence, together with deflection by the Coriolis force, causes the air to sink around latitude 32°. The air then returns to the equator as surface winds. The basic components of this cell are: weak upper-air easterlies above the ITCZ, subtropical anticyclones at the descending limb, and easterly trade winds associated with the return of air to the equator, together with synoptic scale disturbances, such as easterly waves or tropical cyclones. The westerly subtropical jet is located at the poleward limit of the Hadley cell.

In the tropics, the rotationally confined, thermally direct Hadley circulations are important for maintaining the observed small meridional temperature gradients in low latitudes (Held and Hou (1980) J. Atmos. Sci. 37). The intensification and poleward expansion of the cross-equatorial Hadley cell can lead to westerly acceleration in the winter subtropics, and enhanced vertical shear of the zonal wind in the subtropics and mid-latitudes (Hou (1998) J. Atmos. Sci. 55, 14). See general circulation of the atmosphere.