trade winds, movement of air toward the equator, from the NE in the Northern Hemisphere and from the SE in the Southern Hemisphere. The trade winds originate on the equatorial sides of the horse latitudes, which are two belts of high air pressure, one lying between 25° and 30° north of the equator and the other lying between 25° and 30° south of it. The high air pressure in these belts forces air to move toward a belt of low air pressure along the equator called the doldrums. The air converging at the doldrums rises high over the earth, recirculates poleward, and sinks back toward the earth's surface in the region of the horse latitudes, thus completing a cycle. The air does not move directly north or south because it is deflected by the rotation of the earth. See wind; Coriolis effect.