ChapD1.2

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Air Masses Weather

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ChapD1.2

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

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