types of winds in the world
types of winds in the world
Wind Sock
Wind is the movement of air, caused by the uneven heating of the Earth by the sun and the Earth's own rotation. Winds range from light breezes to natural hazards such as hurricanes and tornadoes. Wind socks, like this one near Crissy Field, San Francisco, California, indicate the relative speed and direction of the wind in a specific place.
Wind is the movement of air caused by the uneven heating of the Earth by the sun. It does not have much substance—you cannot see it or hold it—but you can feel its force. It can dry your clothes in summer and chill you to the bone in winter. It is strong enough to carry sailing ships across the ocean and rip huge trees from the ground. It is the great equalizer of the atmosphere, transporting heat, moisture, pollutants, and dust great distances around the globe. Landforms, processes, and impacts of wind are called Aeolian landforms, processes, and impacts.
Differences in atmospheric pressure generate winds. At the Equator, the sun warms the water and land more than it does the rest of the globe. Warm equatorial air rises higher into the atmosphere and migrates toward the poles. This is a low-pressure system. At the same time, cooler, denser air moves over Earth’s surface toward the Equator to replace the heated air. This is a high-pressure system. Winds generally blow from high-pressure areas to low-pressure areas.
The boundary between these two areas is called a front. The complex relationships between fronts cause different types of wind and weather patterns.
Prevailing winds are winds that blow from a single direction over a specific area of the Earth. Areas where prevailing winds meet are called convergence zones. Generally, prevailing winds blow east-west rather than north-south. This happens because Earth’s rotation generates what is known as the Coriolis effect. The Coriolis effect makes wind systems twist counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
The Coriolis effect causes some winds to travel along the edges of the high-pressure and low-pressure systems. These are called geostrophic winds. In 1857, Dutch meteorologist Christoph Buys Ballot formulated a law about geostrophic winds: When you stand with your back to the wind in the Northern Hemisphere, low pressure is always to your left. (In the Southern Hemisphere, low-pressure systems will be on your right.)
Wind Zones
The Earth contains five major wind zones: polar easterlies, westerlies, horse latitudes, trade winds, and the doldrums.
Polar Easterlies
Polar easterlies are dry, cold prevailing winds that blow from the east. They emanate from the polar highs, areas of high pressure around the North and South Poles. Polar easterlies flow to low-pressure areas in sub-polar regions.
Westerlies
Westerlies are prevailing winds that blow from the west at midlatitudes. They are fed by polar easterlies and winds from the high-pressure horse latitudes, which sandwich them on either side. Westerlies are strongest in the winter, when pressure over the pole is low, and weakest in summer, when the polar high creates stronger polar easterlies.
The strongest westerlies blow through the “Roaring Forties,” a wind zone between 40 and 50 degrees latitude in the Southern Hemisphere. Throughout the Roaring Forties, there are few landmasses to slow winds. The tip of South America and Australia, as well as the islands of New Zealand, are the only large landmasses to penetrate the Roaring Forties. The westerlies of the Roaring Forties were very important to sailors during the Age of Exploration, when explorers and traders from Europe and western Asia used the strong winds to reach the spice markets of Southeast Asia and Australia.
Westerlies have an enormous impact on ocean currents, especially in the Southern Hemisphere. Driven by westerlies, the powerful Antarctic Circumpolar Current (ACC) rushes around the continent (from west to east) at about 4 kilometers per hour (2.5 miles per hour). In fact, another name for the Antarctic Circumpolar Current is the West Wind Drift. The ACC is the largest ocean current in the world, and is responsible for transporting enormous volumes of cold, nutrient-rich water to the ocean, creating healthy marine ecosystems and food webs.
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