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Air Pressure

Air Pressure. Air Pressure. Air Pressure is a measure of the force of the air pressing down on the earth’s surface. Air Pressure can vary at any particular point on the Earth depending on the density of the air. Density = mass / volume. Factors that affect Air Pressure.

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Air Pressure

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  1. Air Pressure

  2. Air Pressure • Air Pressure is a measure of the force of the air pressing down on the earth’s surface

  3. Air Pressurecan vary at any particular point on the Earth depending on the density of the air • Density = mass / volume

  4. Factors that affect Air Pressure • Temperature • Water Vapor • Elevation

  5. Definitions • Density = Mass / Volume. - Warm air is less dense than cool air. - Moist air is less dense than dry air. - Air at high altitudes is less dense than air at lower altitudes.

  6. TEMPERATURE AND AIR PRESSURE Molecules move faster HEAT Move apart (less dense) LESS AIR PRESSURE

  7. HIGH TEMPERATURE, LOW AIR PRESSURE LOW TEMPERATURE, HIGH AIR PRESSURE

  8. AMOUNT OF WATER VAPOR consists of air and water molecules

  9. More water vapor means less air molecules Less dense LOW AIR PRESSURE DRY AIR = HIGH AIR PRESSURE (more dense)

  10. Where is air pressure higher, up in the mountains or down in the valley? http://www.youtube.com/watch?v=GWEyFbyvElc&feature=related

  11. This bottle was photographed at 3600m (left) then again at sea level (right) At sea level, because air is compressible, the weight of all that air above us compresses the air around us, making it denser. We all live underneath a huge ocean of air that is several miles deep: the atmosphere. The pressure on our bodies is about the same as ten meters of sea water pressing down on us all the time.

  12. Density = Mass / Volume  Warm air is less dense than cool air. Warm air rises. Cool air sinks.  Air at high altitudes is less dense than air at lower altitudes.

  13. Factors Affecting Air Pressure

  14. Measuring Air Pressure Types of Barometer Air Pressure is measured by an instrument calledBarometer • Mercury Barometer VIDEO: Why use mercury? • Aneroid

  15. Air pressure increases, column of mercury rises • Air pressure decreases, column of mercury drops Video (minute 2): http://www.youtube.com/watch?v=-gGBMCqBoSE&feature=related

  16. Air Pressure & Weather

  17. Weather map High Pressure System: Indicates clear, calm conditions with reduced chance of precipitation. Drier air usually results in a greater range of high and low temperatures. Low pressure system: Increased cloudiness, winds, temperatures, and chance of precipitation.

  18. High pressure generally means fair weather Air mass in upper atmosphere No clouds Warm, moist air cannot rise Layer of Air

  19. Low pressure generally means cloudy, rainy weather Warm air rises, clouds form Air masses move apart

  20. QUESTIONS – use your knowledge of air pressure to explain the following situations • A falling barometer is followed by several days of rainy weather. • Some people find it hard to breathe at high altitudes. • A rising barometer indicates a spell of cool dry weather.

  21. More Questions • A series of hot, humid days is preceded by a falling barometer. • A southern, coastal areas tend to have lower air pressure than an inland area farther north. • Rapidly dropping temperatures are accompanied by a rising barometer.

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