ハドレー循環
Heating of the earth at the thermal equator leads to large amounts of convection along the intertropical convergence zone. This air mass rises and then diverges, moving away from the equator in both northerly and southerly directions. As the air moves towards the mid-latitudes on both sides of the equator, it cools and sinks. This creates a ridge of high pressure near the 30th parallel in both hemispheres. At the surface level, the sinking air diverges again with some returning to the equator, creating the Hadley cell. Many of the world's deserts are caused by these climatological high-pressure areas.