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.

For many centuries, sailors have used trade winds to help their sailing ships travel across the oceans. These winds 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.

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.

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. Long ago, sailors, especially from Portugal, found these winds helpful 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 travel easier or harder to different parts of the world. This affected how countries grew and shaped our world today. By the 1800s, a man named Matthew Fontaine Maury made maps showing wind and ocean currents for sailors everywhere.

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 toward 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 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 where trade winds blow are usually cumulus clouds and stay below 4 kilometres tall. Trade winds blow more from the poles in colder months and are stronger in winter than in summer. For example, the windy season in the Guianas in South America happens between January and April.

When a 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 can also hurt air quality by adding tiny particles to the air. This dust can also harm 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.