Winds

Local and Global Winds

~ General Information on Winds ~

What is Wind?

Wind is the sideways movement of cool air from an area of high pressure to an area of low pressure. The name of a wind tells the direction it blows from; for example, a west wind blows from west to east.
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How Does Wind Occur?

The difference in pressure, stated above, that moves air, creating wind, is caused by the differences in the heating of the Earth's surface. Since the warmer the air gets, the less pressure it exerts, uneven heating results in differences in air pressure.

~ Local Winds ~

Local winds are one of the two variants of wind, still convection currents, but on a smaller scale, hence the name. They are created in the same way that all winds are created, with the unequal heating of Earth's surface. Unlike global winds, local winds change speed and direction often.

Things to remember:


  1. Air that is warmer has a lower pressure and density, while air that is cooler has a higher pressure and density
  2. As a result of their densities, warmer air will rise while cooler air sinks
  3. Air moves from areas of high pressure to areas of low pressure

Land Breezes

Occurring only at night, this type of local wind blows when the land is colder, making it at a higher pressure and density, in contrast to a warmer body of water, at a lower density and pressure. The cold air above the land will go from that area of higher pressure to the body of water with lower pressure, underneath the current of warmer air going in the opposite direction, rising and traveling from the body of water to eventually get colder above the land, and sink to continue this convection current.
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Sea Breezes

This local wind, almost the opposite of a land breeze, occurs only at night and blows when the body of water is colder, making it at a higher pressure and density, in contrast to warmer land, at a lower density and pressure. The cold air above the body of water will go from that area of higher pressure to the land with lower pressure, underneath the current of warmer air going in the opposite direction, rising and traveling from the land to eventually get colder above the sea, and sink to continue this convection current.
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~ Global Winds ~

Global winds are one of the two variants of wind, still convection currents, but on a much larger scale, hence the name. They are created in the same way that all winds are created, with the unequal heating of Earth's surface. Unlike local winds, global winds blow steadily over long distances, and always in the same direction. These winds form massive convection currents from the Poles to 30 degrees N and S, and then from there to the Equator.

The Coriolis Effect:

The Earth rotates from west to east, and the global winds are affected, blowing to the east instead of blowing strait.

Horse Latitudes

These calm areas of falling air are located at about 30 degrees N and S, between the great convection currents that form global winds where the cool air is falling back down to continue the cycle. They are named for when sailors would get trapped moving to other places because there was no wind to push the sails and have to drop horses into the water to make the ship lose weight and to conserve food.
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Trade Winds

These global wind patterns between 0 and 30 degrees N and S are strong winds blowing from the horse latitudes to the Equator. They are used by sailors to move their cargo and trade goods with countries across the ocean.
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Polar Easterlies

These global winds, located just beneath the poles for which they are named, blow cold air away from the poles and towards the equator to be carried bey the other winds in the convection current.
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Jet Streams

These global winds blowing 200-400 kilometers per hour blow in bands, hundreds of kilometers wide from west to east at the top of the troposphere are used by airplane pilots to move faster and save fuel.
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