Trade Winds

The trade winds are the persistent surface easterlies of the tropics, blowing from the subtropical highs near 30 degrees toward the equatorial low, the northeast trades in the Northern Hemisphere and the southeast trades in the Southern. They are the surface return branch of the Hadley cells, turned westward by the Coriolis force, and they converge at the Intertropical Convergence Zone. Steady at 10 to 20 knots, they were the highway of sailing-ship commerce, the origin of the name. They drive the equatorial ocean currents and the upwelling that cools the eastern tropical Pacific, the system that ENSO disrupts.