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  • 1. Air and Weather
  • 2. Air and the Sun
    • weather begins w/ the sun
      • provides energy for making weather
      • amount of energy reaching Earth different in different places
        • more at equator less at poles
      • uneven heating causes air to move - makes weather
  • 3.
    • most of the sun’s energy never reaches Earth
      • lost in space
    • the energy that does reach Earth
      • 3/10 reflected back into space
      • 3/10 warms the air
      • 4/10 warms land and ocean
    • atmosphere traps the heat
      • greenhouse effect
        • w/o greenhouse effect most of the sun’s energy would be reflected back into space and the surface would be too cold to support life
  • 4. Air Masses
    • air masses: huge bodies of air, covering thousands of km
      • has same general properties as the land or water over which it forms
        • moisture content and temperature
    • moist air masses form over water
    • dry air masses form over land
    • air masses that form over the poles are cold
    • air masses that form over the equator/tropics are warm
  • 5.  
  • 6. Air Masses Meet
    • when 2 air masses meet they usually don’t mix
      • form a border called a front
      • most weather happens along fronts
    • cold front forms when cold air mass catches up to a warm air mass
      • colder air mass forces the warmer air up into the atmosphere
      • as warmer air is pushed upwards it cools and makes clouds
      • rain develops - thunderstorms occur along cold fronts
  • 7.
    • warm front forms when warm air mass catches up to cold air mass
      • warm air slides over the colder, thicker air
      • clouds form
      • steady snow or rain may fall as the front approaches and passes
      • then the sky becomes clear and temps rise
    • if a front stops moving it is a stationary front
      • can stay in one spot for several days
      • constant fall of rain or snow
  • 9. Air Masses Move
    • wind speed often increases as a front approaches
      • direction also changes
    • air pressure changes as air masses move over an area
      • front moves closer - air pressure drops
      • Front moves over the area - air pressure rises
  • 10.
    • temp changes as a front moves over an area
      • warmer air comes from a warm front
      • cooler air comes from a cold front
  • 11. Summary
    • sun provides energy to make weather
    • atmosphere traps heat near Earth’s surface - greenhouse
    • air masses form over continents and oceans
      • when 2 air masses meet they form a front
      • fronts: areas where most weather happens