Notes
Slide Show
Outline
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Atmospheric Structure and Composition
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Definitions
  • Atmosphere: The thin envelope of gases surrounding the earth
  • Highly compressible


  • Density decreases rapidly with height


  • Air: A mechanical mixture of gases and aerosols
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Vertical Structure of Atmosphere
  • Troposphere (surface to 8-20 km)
  • Upper boundary varies from about 8 km (poles in winter) to about 20 km (tropics)
  • Weather and climate layer
  • Most of atmosphere’s mass; all of its water
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Vertical Structure of Atmosphere
  • Troposphere (surface to about 8-20 km)
  • Upper boundary varies from about 8 km (poles in winter) to about 20 km (tropics)
  • Weather and climate layer
  • Most of atmosphere’s mass; all of its water


  • Stratosphere (8-20 km up to about 50 km)
  • Ozone (O3) Layer
  • Temperature inversion
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Vertical Structure (ctd.)
  • Mesosphere (50-80 km)
    • Temperature decreases with height.  Why?


  • Thermosphere (80-? km)
    • Temperature inversion.  Why?
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Vertical Structure (ctd.)
  • Homosphere vs. Heterosphere
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Vertical Structure (ctd.)
  • Homosphere vs. Heterosphere
  • Transition zones between layers
    • Tropopause
    • Stratopause
    • Mesopause
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Defining Layers by Function – the Ozonosphere
  • Roughly corresponds to the stratosphere


  • How does the ozone layer work?


  • Why is there a “hole” in the ozone layer?


    • Why no “hole” where the pollution is produced?
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Defining Layers by Function – the Ionosphere
  • Upper mesosphere + thermosphere
  • Produces the aurora borealis and aurora australis
  • D Layer – absorbs AM radio waves; disappears at night
  • E Layer – weakens at night
  • F Layer – reflects AM radio waves
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Composition of the Air
  • Uniform gases
  • Nitrogen (N2) 78%, (O2) 21%,
  • Argon (Ar) 1%, trace gases (Neon, Helium, Methane (CH4), etc.)


  • Variable gases
  • Water Vapor (H2Ov), O3, CO2
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Composition (ctd.)
  • Aerosols
  • Solid: Ice/salt crystals, soil particles, volcanic dust
  • Condensation nuclei


  • Liquid:  Water droplets (cloud, fog)
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Origin of the Atmosphere
  • Volcanoes release H2, CO2, H2Ov, N2, NH3, CH4
  • No O2 or O3, so no land organisms!
  • One-celled aquatic organisms release CO2 to atmosphere when breaking down food through fermentation
  • Simple aquatic plants took in CO2 and released O2 to atmosphere via photosynthesis
  • O3 formed from the O2
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Origin of Atmosphere (ctd)

  • CO2 gets stored in shells and decaying plants
  • N2 builds up in atmosphere