Trade winds used by early explorers
Between about 30 degrees north and 30 degrees south of the equator, in a region called the horse latitudes , the Earth's rotation causes air to slant toward the equator in a southwesterly direction in the northern hemisphere and in a northwesterly direction in the southern hemisphere.
This is called the Coriolis Effect. 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 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 degree belt around Earth's midsection is called the Inter-Tropical Convergence Zone , more commonly known as the doldrums. Intense solar heat in the doldrums warms and moistens the trade winds, thrusting air upwards into the atmosphere like a hot air balloon.
As the air rises, it cools, causing persistent bands of showers and storms in the tropics and rainforests. The rising air masses move toward the poles, then sink back toward Earth's surface near the horse latitudes. The sinking air triggers the calm trade winds and little precipitation, completing the cycle. More Information What are the horse latitudes? What are the doldrums? What is a current? 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 degree belt around Earth's midsection is called the Inter-Tropical Convergence Zone , more commonly known as the doldrums. Intense solar heat in the doldrums warms and moistens the trade winds, thrusting air upwards into the atmosphere like a hot air balloon. As the air rises, it cools, causing persistent bands of showers and storms in the tropics and rainforests.
The rising air masses move toward the poles, then sink back toward Earth's surface near the horse latitudes. The sinking air triggers the calm trade winds and little precipitation, completing the cycle. More Information What are the horse latitudes? What are the doldrums? What is a current? The rotation of the Earth deflects the atmosphere, resulting in curved wind paths. This deflection, called the Coriolis Effect , sets up the complex global wind patterns that drive surface ocean currents.
It is named after the French mathematician Gaspard Gustave de Coriolis , who studied waterwheels to understand the transfer of energy in rotating systems.