Air Pressure
Don’t let it get you down!
What is Air Pressure?
Air Pressure is the result of the weight of a column of air pushing down on an area What causes Air Pressure? It is caused by gravity pulling the molecules of air towards the center of the Earth How does Air Pressure relate to Density? As air pressure increases, so does the density of the air. As the air molecules are pulled towards the center of the Earth, they become more closely packed close to the surface of the Earth. At the surface of the Earth the air pressure is high and so is the density. |
How can affect air pressure and density?
- Elevation - air pressure and density decreases as you go up
- On Earth - if you are at sea level the air pressure/density is higher than if you are on top of a mountain!
- In the Layers of the Atmosphere: The troposphere has the highest air pressure/density and the exosphere has the lowest air pressure/density
- Temperature - higher temperature = lower density and lower pressure
- Watch Out! The idea that temperature affects air pressure will be VERY important when we start to study weather!
Air Pressure and Weather
You will learn more about this over the next few weeks - but air pressure is important for predicting and understanding weather.
- Uneven heating of the Earth (by the Sun) creates masses of air with different properties (temperature, density, pressure).
- Wind is created when air molecules move from areas of low pressure (low density) to areas of high pressure (high density)
- Areas of low pressure can create strong storms as air rushes into them, leaving areas of high pressure (high density)
- A drop in air pressure can be a warning that a strong storm is coming!
Measuring Air PressureBarometer: instrument that measures air pressure.
Air pressure is measured in millibars (mbs) or inches of mercury (inHG) |
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There are two types of barometers:
1000 mbs (or 29.923 inHG) is “normal” at sea level
822 mbs (26.05 inHG) is the record low and was associated with a hurricane.
Drops in pressure are associated with oncoming storms
- Mercury Barometer – consists of a glass tube that’s open on the bottom end and partially filled with Mercury
- Aneroid Barometer – an instrument that has an airtight metal chamber that is sensitive to changes in the air pressure. Aneroid means “without liquid"
1000 mbs (or 29.923 inHG) is “normal” at sea level
822 mbs (26.05 inHG) is the record low and was associated with a hurricane.
Drops in pressure are associated with oncoming storms