The movement of air from the equator towards the poles in a planet's atmosphere. Warm air near the equator rises and travels towards the poles, cooling as it does so until it becomes denser than the air below. It then sinks to the surface and returns to the equator, completing a cycle known as a Hadley cell. The tropical Hadley cells in the Earth's atmosphere extend to about 30° north and south of the equator, but there are two further sets of Hadley cells, one between 30° and 60° latitude, and another between 60° latitude and the poles, which are less prominent and less permanent than the tropical ones. On Venus, there is a single Hadley cell extending from the equator to the poles. The effect is named after the English meteorologist George Hadley (1685–1768).
Subjects: Astronomy and Astrophysics.