Trade winds

The trade winds, or easterlies, are steady winds that blow from east to west near Earth's equator. They blow mostly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. These winds get stronger in winter and when a pattern in the far north called the Arctic oscillation is warm.

For many centuries, sailors have used trade winds to help their sailing ships travel across the oceans. These winds made it possible for European colonization of the Americas and helped create important trade routes over the Atlantic Ocean and the Pacific Ocean.

Trade winds also influence weather. They guide storms that form over the Atlantic, Pacific, and southern Indian oceans. These storms can bring rain to places like East Africa, Madagascar, North America, and Southeast Asia. When trade winds are weak, more rain may fall on nearby land.

The winds carry dust from the Sahara across the ocean to Latin America, the Caribbean Sea, and parts of North America. This dust can change the color of sunsets and affect air quality by adding small particles to the air.

History

See also: Age of Discovery, Volta do Mar, and Age of sail

The word "trade winds" comes from old times when "trade" meant a path or track. Long ago, sailors, especially from Portugal, learned how helpful these winds were for traveling across oceans. They used the winds to move from Africa toward Europe and to reach places like South Africa by sailing far out into the ocean and then turning east. It wasn’t until the 1500s that European sailors fully understood how the winds worked in the Pacific Ocean.

During the time when ships sailed using only wind power, knowing where the steady winds blew made it easier or harder to travel to different parts of the world. This affected how countries grew and shaped the world we live in today. By the 1800s, a man named Matthew Fontaine Maury gathered information to make maps showing wind and ocean currents for sailors all over the world.

Cause

See also: Air mass, Hadley cell, Humidity, Intertropical Convergence Zone, Monsoon, Monsoon trough, Near-equatorial trough, and Prevailing winds

The trade winds are steady winds that blow across the world's tropical areas. They are part of a large pattern of air movement called the Hadley cell. Near the equator, air rises and moves towards areas farther from the equator. This rising air creates a calm area known as the doldrums.

As the air moves away from the equator, it gets pushed to the west by the Earth's rotation, called the Coriolis effect. In the Northern Hemisphere, these winds blow mostly from the northeast, and in the Southern Hemisphere, they blow mostly from the southeast. Because of this, they are called the northeasterly trade winds in the north and the southeasterly trade winds in the south. These winds meet again at the doldrums near the equator.

Weather and biodiversity effects

Clouds that form in areas where trade winds blow are usually made of cumulus clouds and don’t grow taller than about 4 kilometres. Trade winds come more from the poles during colder months and are stronger in winter than in summer. For example, the windy season in the Guianas, located in South America, happens between January and April.

When a certain climate pattern in the Arctic is warm, trade winds become stronger in the tropics. But when this pattern is cold, the trade winds are weaker, leading to more rain in places like Central America.

In the middle of summer in the Northern Hemisphere, trade winds moving westward from the Caribbean Sea can reach parts of southeastern North America, such as Florida. Dust from the Sahara can travel over land, making the sky look white and leading to beautiful red sunsets, but it also harms air quality by adding tiny particles to the air. This dust can also hurt the health of coral reefs in the Caribbean and Florida.

Each year, millions of tons of dust from the Sahara cross the Atlantic Ocean, carrying important nutrients like phosphorus to help the soils of the Amazon.