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Air pressure & wind - Coggle Diagram
Air pressure & wind
Air pressure
Air pressure is the weight per unit of area of a column of air that reaches to the top of the atmosphere.
It decreases with increasing altitude because as you move higher there is less and less air above you.
Air pressure is, on average, highest at sea level and drops to about half its sea-level value at an average altitude of about 18,000 feet.
Cause of Changes
Humidity
Humidity, the amount of water vapor in the air, affects air pressure too.
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Thus, if the atmosphere has high humidity it creates higher air pressure.
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Temperature
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Cold air is relatively dense. It has more air molecules per unit volume so it exerts relatively high pressure.
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Wind
Air moves from area where the air pressure is relatively high toward areas where the air pressure is relatively low. This movement of air is what we call wind.
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Explanation
Because the Earth's surface is curved rather than flat, not all areas receive the same amount of radiation
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Air over the heated surface expands and becomes less dense. As the air becomes less dense, its air pressure decreases.
If a nearby are is not heated as much, the air above the less-heated area will be cooler and denser. The cool, dense air with a higher pressure flows underneath the warm, less dense air.
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Coriolis effect
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Winds do not travel directly north or south, because the Earth is rotating.
The apparent curving of the path of winds due to the Earth's rotation is called the Coriolis Effect.
Because of the Coriolis Effect in the Northern Hemisphere, winds traveling north curve to the east, and winds traveling south curve to the west