Trade winds are the permanent east-to-west prevailing winds that flow in the Earths equatorial region. They blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. The trade winds have been used by sailors for centuries to cross the worlds oceans, enabling colonial expansion into the Americas and trade routes to become established across the Atlantic Ocean and the Pacific Ocean.
The formation of trade winds involves three factors: maximum heating of the air along the equator, the cycling of air between the equator and the Earth’s poles, and a phenomenon called the Coriolis force. The air around the equator heats up, and the warm, moist air rises in the atmosphere while cooler air closer to the poles sinks. As the warm air rises, it eventually cools and then sinks back to the Earth’s surface at more northern and southern latitudes. The cooler air then moves back toward the equator, where it’s once again heated up by the Sun and made to rise. This never-ending cycle of air is called the Hadley Cell. The rotation of the Earth causes the cycle of air to be deflected, and rather than blow north-to-south, the air instead blows east-to-west, creating trade winds.
Trade winds can be found about 30 degrees north and south of the equator. Right at the equator, there is almost no wind at all, an area sometimes called the doldrums. The Coriolis Effect, in combination with an area of high pressure, causes the prevailing winds, the trade winds, to move from east to west on both sides of the equator across this 60-degree "belt". As the wind blows to about five degrees north and south of the equator, both air and ocean currents come to a halt in a band of hot, dry air. This 10-degree belt around Earths midsection is called the Inter-Tropical Convergence Zone, more commonly known as the doldrums.
In conclusion, trade winds are winds that reliably blow east to west just north and south of the equator. They are caused by the strong warming and evaporation within the atmosphere around the equator. Trade winds have been used by sailors for centuries to travel across the worlds oceans, and they have a big influence on the climate to the north and south of the equator.
