Air pressure


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Air pressure

  1. 1. Air Pressure The pressure exerted on an object by the air. – Occurs in all directions  up, down, sideways
  2. 2. Air Pressure A barometer is used to measure the amount of pressure in the air. – Units = mmHg (millimeters of Mercury) or atm (atmospheres)
  3. 3. Barometers Rapidly falling pressure almost always means an approaching storm system. Rapidly rising pressure almost always means clearing and cooler weather is ahead.
  4. 4. Winds Winds are created by horizontal air pressure differences – pressure gradients Uneven heating of the Earth creates pressure differences
  5. 5. What affects wind? Pressure differences- Cause air to move The Coriolis Effect- causes global winds to be deflected Friction- slows down air, which changes wind direction
  6. 6. Measuring Pressure Isobars- lines of equal pressure – Much like contour lines, but instead of elevation, they are lines of equal pressure – Are used to predict where weather is moving
  7. 7. Jet Stream  Fast flowing, relatively narrow air currents found just under the tropopause  Form at the boundaries of adjacent global wind belts
  8. 8. Global Winds Global winds are created by the unequal heating of Earth. The equator is much hotter than the rest of Earth, causing an extremely low pressure.
  9. 9. Global Winds This causes air from adjacent areas to move towards the equator. This movement begins a chain reaction of air movement throughout Earth, creating 6 wind belts.
  10. 10. High Pressure Zone/Cyclone  Occurs when temperatures are cold  Little or no moisture (humidity) – The air is heavy and sinks towards Earth’s surface  Winds move outward and clockwise around the center of a cyclone
  11. 11. Low Pressure Zone/Anticyclone Occurs when temperatures are warm Can have large amounts of moisture (humidity) – The air is light and rises upward into the atmosphere Winds move outward and counterclockwise around the center of the anticyclone
  12. 12. The Coriolis Effect The Coriolis effect is a result of the spinning of Earth. As Earth spins, anything moving in a straight line from North to South will be deflected sideways. – In the Northern Hemisphere, winds, water, and other fluids will be deflected to the right at a 90o angle. – In the Southern Hemisphere, everything will be deflected to the left at a 90o angle.
  13. 13. Assignment Complete procedure questions for “Air Pressure Demonstration” Identify Types of Energy Transfers Worksheet