Convection cell that forms in the tropical atmosphere North and South of the equator. Named after George Hadley who, in the 18th century, developed the classic model of the general circulation of the atmosphere based on convection. High temperatures cause the surface air in equatorial regions to warm and become buoyant. Rising away from the source of heat and under the effects of adiabatic cooling, the temperature of the air falls and it becomes less buoyant. Unable to sink back to the surface because of the warm air rising behind it, it is diverted North and South at the altitude of the tropopause and reaches between 20 and 30ºN and S before beginning to descend. The world's great hot desserts are located at these latitudes beneath the descending arms of the Hadley Cells where the subsiding air creates large, warm, subtropical anticyclones.