Earth and Space Science / Unit 7: The Atmosphere and Weather
7.3 Air Pressure and Wind
Notes
Air pressure is the weight of air above a point. It decreases with altitude.
- Measured with a barometer (a falling reading often means stormy weather coming; rising means fair weather).
- Warm air is less dense: low pressure (rising air, clouds). Cool air is denser: high pressure (sinking air, clear skies).
- Wind is air moving from high to low pressure; larger pressure differences make stronger winds.
- The Coriolis effect turns winds right in the Northern Hemisphere, left in the Southern.
- Global belts: trade winds, westerlies, polar easterlies. Jet streams are fast winds near the tropopause.
Practice
Wind blows from:
Air moves to even out pressure differences.
A falling barometer reading usually means:
Falling pressure signals rising air and clouds.
Sinking air is associated with:
Sinking air warms and dries.
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