Hadley Cell

The Hadley cell is the tropical overturning circulation of the atmosphere, the equatorward, thermally direct limb of the three-cell general circulation. Warm, moist air rises in the Intertropical Convergence Zone, flows poleward aloft, sinks near 30 degrees latitude in the subtropical highs, and returns to the equator at the surface as the trade winds. Conservation of angular momentum in the upper poleward flow generates the subtropical jet stream. Sinking dry air at its poleward edge maintains the world’s major subtropical deserts and the horse-latitude calms. The cells are strongest in the winter hemisphere and shift seasonally with the thermal equator.