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The Global Wind Belts
Question: What are global wind belts?
The global wind belts are formed by two main factors: the unequal heating of the earth by sunlight and the earth's spin.
Here is a simple explanation of the process.
The unequal heating makes the tropical regions warmer than the polar regions. As a result, there is generally higher pressure at the poles and lower at the equator. As I hope you know, wind flows from high to low pressure.
So the atmosphere tries to send the cold air toward the equator at the surface and send warm air northward toward the pole at higher levels.
Unfortunately, the spin of the earth prevents this from being a direct route, and the flow in the atmosphere breaks into three zones between the equator and each pole.
These form the six global wind belts: 3 in the Northern Hemisphere (NH) and 3 in the Southern (SH). They are generally known as:
1) The Tradewinds, which blow from the northeast (NH) and southeast SH), are found in the subtropic regions from about 30 degrees latitude to the equator.
2) The Prevailing Westerlies (SW in NH and NW in SH) which blow in the middle latitudes. Most of North America fits into this belt and that is why our weather usually comes from west.
3) The Polar Easterlies which blow from the east in the polar regions.
This is a basic explanation, but of course in the everyday situation there are major variations.
Since a picture is worth a thousand words, here is a good diagram of the global wind belts.
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The Weather Doctor's Weather Almanac The Global Wind Belts
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