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  1. 1. The Earth’s Atmosphere <ul><li>Composition  </li></ul><ul><li>Structure   </li></ul>
  2. 2. <ul><li>thin layer of gases enveloping Earth </li></ul><ul><li>no well-defined upper boundary – just fewer and fewer atoms </li></ul><ul><li>density decreases with altitude because number of atoms decrease </li></ul>What is the Atmosphere? View of the atmosphere from the space shuttle
  3. 3. Air Pressure <ul><li>atmosphere – exerts pressure </li></ul><ul><li>the pressure is from the mass of the atoms </li></ul><ul><li>gravity – compresses air near surface (increase density) </li></ul><ul><li>felt by any surface in contact with air </li></ul><ul><li>sea level pressure = 15 lb/in 2 </li></ul>
  4. 4. Composition of Atmosphere <ul><li>atmosphere is a mixture of </li></ul><ul><li>gases, solid particles, water droplets </li></ul><ul><li>Small changes are always happening </li></ul><ul><ul><li>physical processes (volcanoes), </li></ul></ul><ul><ul><li>biological (plants and animals – transpiration and respiration), </li></ul></ul>
  5. 5. <ul><li>major gases: N 2 and O 2 </li></ul><ul><li>lesser amounts of noble gases </li></ul><ul><li>(Ar, Ne, Kr, Xe) </li></ul><ul><li>plus Hydrogen (H) and Helium (He) </li></ul><ul><li>N 2 : </li></ul><ul><ul><li>78% volume </li></ul></ul><ul><li>O 2 : </li></ul><ul><ul><li>21% volume </li></ul></ul>Permanent Gases
  6. 6. <ul><li>Water vapor (H 2 0) </li></ul><ul><li>Carbon Dioxide (CO 2 ) </li></ul><ul><li>Ozone (O 3 ) </li></ul>Variable Gases
  7. 7. <ul><li>source of this gas: evaporation from Earth’s surface </li></ul><ul><li>water cycle – moves water between oceans, land and atmosphere </li></ul><ul><li>75% Earth’s surface covered by some form of water ground water </li></ul><ul><li>extremely important: clouds, absorb energy </li></ul>Water Vapor This satellite image shows the relative amounts of water vapor: Dark – low water, white – high water vapor
  8. 8. <ul><li>sources: respiration, organic decay, volcanoes, natural and man-made caused fires </li></ul><ul><li>important Greenhouse gas </li></ul><ul><li>More Carbon dioxide means more heating of the Earth </li></ul>Carbon Dioxide (CO 2 ) Very emotional issue for Americans - Are we having a bad effect on the atmosphere of the Earth???
  9. 9. Ozone (O 3 ) <ul><li>consists of 3 O atoms (O 2 + O = O 3 ) </li></ul><ul><li>highest concentration in stratosphere </li></ul><ul><ul><li>shields surface from UV radiation </li></ul></ul><ul><ul><li>UV radiation splits O 3 molecule </li></ul></ul><ul><li>also contributor to smog  effects people and vegetation </li></ul>
  10. 10. Solids and liquids in the atmosphere <ul><li>small solid particles and liquid droplets </li></ul><ul><li>associated with human and natural processes </li></ul><ul><li>larger particulate matter – dust, volcanoes, sea spray and combustion </li></ul><ul><li>major component of urban smog </li></ul>
  11. 11. Vertical Structure of the Atmosphere <ul><li>no clearly defined upper boundary </li></ul><ul><li>density decreases with elevation </li></ul><ul><li>We divide the atmosphere into layers based on: </li></ul><ul><ul><li>Changes in temperature </li></ul></ul>
  12. 12. Density <ul><li>Gravity pulls the atmosphere downward </li></ul><ul><li>atmosphere made up of gases which can be compressed </li></ul><ul><li>lower atmosphere greater density </li></ul>
  13. 13. Temperature Layers from Earth’s surface <ul><ul><li>Troposphere </li></ul></ul><ul><ul><li>Stratosphere </li></ul></ul><ul><ul><li>Mesosphere </li></ul></ul><ul><ul><li>Thermosphere </li></ul></ul>Not shown here – The Exosphere! Let’s learn a little about each layer!
  14. 14. <ul><ul><li>lowest layer; temperature decreases with altitude </li></ul></ul><ul><ul><li>thinnest layer (8-16 km, avg. 11 km) </li></ul></ul><ul><ul><li>where weather occurs </li></ul></ul><ul><ul><li>primarily heated by Earth’s surface </li></ul></ul>Troposphere
  15. 15. Troposphere – when a cloud reaches the top of this layer, they cannot go higher so they flatten out.
  16. 16. Stratosphere <ul><ul><li>found above the troposphere </li></ul></ul><ul><ul><li>temperature rises with elevation </li></ul></ul><ul><ul><li>Ozone Layer located here </li></ul></ul><ul><ul><li>upper stratosphere temperature increases with </li></ul></ul><ul><ul><li>altitude due to absorption of UV (ultraviolet) radiation in the ozone layer </li></ul></ul>Without the ozone layer protecting us, we could not live on the surface of the Earth!
  17. 17. Mesosphere <ul><ul><li>above the stratosphere </li></ul></ul><ul><ul><li>temperature decreases with altitude </li></ul></ul><ul><ul><li>Meteorites and space dust burns up in this layer </li></ul></ul>
  18. 18. Thermosphere <ul><ul><li>above the mesosphere </li></ul></ul><ul><ul><li>temperature increases with altitude </li></ul></ul><ul><ul><li>contains a special part called the ionosphere </li></ul></ul>
  19. 19. Ionosphere Quartz Lake State Park, Alaska (Curtis, 1996) <ul><ul><li>defined based on electrical characteristics within the thermosphere </li></ul></ul><ul><ul><li>absorbs cosmic rays, gamma rays, X-rays, </li></ul></ul><ul><ul><li>some UV rays </li></ul></ul><ul><ul><li>contains ions: charged electrical particles </li></ul></ul><ul><ul><li>visible light is emitted when ions are bombarded by </li></ul></ul><ul><ul><li>cosmic radiation  produce aurora borealis, aurora australis </li></ul></ul>