Trade Winds, the prevailing N. E. and S. E. winds, in the northern and southern hemispheres respectively, that blow from the parallels 30° N. and S. toward the equator. They are atmospheric currents moving toward the equator to fill the spaces left by the airs that have become heated and passed up to the more elevated portions of the atmosphere in the belt of the equatorial calms. These currents, moving continually toward larger parallels of latitude, do not at once acquire the increasing eastwardly movement of the portions of the earth's surface revolving beneath, and the lagging occasioned by the earth slipping away under them produces a deviation from a direct meridional movement as respects the surface of the earth, and an apparent progress of the currents toward the west. Beyond the limits stated above these currents merge into the regions of variable winds and calms. (See Meteorology, and Rain.) The trade winds have been known to Europeans since the end of the 14th century; to them Columbus owed his prosperous voyages to America, and they constitute a most important factor in the navigation of the ocean. The limits within which the trades prevail vary from month to month with the varying position of the sun, the range being about ten degrees.
In general the trade wind is not accompanied by clouds, and the air is comparatively dry. - See Maury's, Fitzroy's, and Andrau's trade-wind charts, the admiralty wind charts, and Coffin's "Winds of the Globe," to be published in 1876 by the Smithsonian institution; also Ferrels "Motions of Fluids and Solids" (New York, 1860).