Atmosphere
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Transcript

  • 1. The Atmosphere Structure and Change
  • 2. Overview
    • Structure
      • Compositional structure
      • Temperature structure
      • Functional structure
    • Change
      • Natural sources of change
      • Natural influences on pollution
      • Anthropogenic pollution
  • 3. General
    • Thermopause is considered the outermost boundary of the atmosphere.
      • 480km, 300 mi above surface
    • The Exosphere extends beyond the thermopause
      • Rarefied (near vacuum)
      • Sparse Hydrogen and Helium atoms
      • Extends to 20,000 miles (32,000 km) from Earth’s surface
    • Density of Atmosphere increases near the surface
      • 90% of atmospheric mass occurs within 16,000 meters of surface
      • Air pressure (sea level): 1013.2 mb; 101.32 kPa; 29.92 in
        • Air pressure decreases with decreasing density (i.e., altitude)
  • 4.  
  • 5.  
  • 6.
    • Atmospheric gases held by Earth’s gravity
      • Earth’s gravity weakens with altitude
      • Changes density profile
      • Sorts atmosphere into different layers
    • Three different ways of looking at atmospheric layering
      • Composition
        • Homosphere
        • Heterosphere
      • Temperature
        • Troposphere (Tropopause)
        • Stratosphere (Stratopause)
        • Mesosphere (Mesopause)
        • Thermosphere (Thermopause)
      • Function
        • Ozonosphere
        • Ionosphere
  • 7. Composition
    • Homosphere
      • Gases evenly mixed
      • Exceptions
        • Water vapor (clouds)
        • Ozone layer
        • Point sources at surfaces
      • Over 99% of Atmosphere
    • Heterosphere
      • Uneven mixture of gases, sorted by atomic and molecular weight
  • 8.  
  • 9. Temperature
    • Troposphere
      • 90% of Atmosphere
        • Nearly all of the water vapor and weather
      • Supports life
      • Upper boundary: Tropopause
        • 18 km (11mi) at equator, 12 km (8 mi) mid-latitudes, 8 km (5 mi) at poles
        • Varies with temperature (solar heating)
      • Temperatures decrease with altitude
        • Normal Lapse Rate: 6.4 o C/km (3.5 o F/ft)
        • Environmental Lapse Rate
        • Inversions
        • Crucial for understanding weather
        • Heated by the Earth’s surface
    • Stratosphere
    • Mesosphere
    • Thermosphere
  • 10.
    • Stratosphere
      • 18 – 50 km (11 –31 mi) above surface
      • Ozone layer
      • Temperature increases with altitude
        • Heating from absorption of ultraviolet light by ozone
        • At lower levels, heated by surface emanations as well
      • Upper boundary: Stratopause
    • Mesosphere
      • 50 – 80km (30 – 50 mi) above surface
      • Temperature decreases with altitude
      • Upper boundary: Mesopause
        • Coldest region in atmosphere
        • Emanations from the stratosphere provide heat source
  • 11.
    • Thermosphere
      • 80 – 480 km (50-300 mi) on average
      • Upper Boundary: Thermopause
        • Actual altitude varies between 250 – 550 km (155 – 340 mi)
          • Increases with increased solar activity
      • Extremely high temperatures but little sensible heat
        • Heated by direct exposure to incoming solar radiation
        • Air particles have extremely high kinetic energy (temperature)
        • Low density of particles means fewer collisions of particles, lower overall capacity to store heat
  • 12.  
  • 13. Function
    • Classifies atmospheric layers according to how they shield the surface from harmful radiation
    • Ozonosphere
      • O 3
      • Absorbs short-wave radiation and reradiates it as long-wave radiation
      • Shields surface from harmful ultraviolet radiation
      • Various pollutants deplete ozone
    • Ionosphere
  • 14.  
  • 15.
    • Ozonosphere
    • Ionosphere
      • Absorbs short-wave radiation
        • Cosmic rays, Gamma rays, X-rays, shorter UV
      • High energy radiation tends to knock electrons off of the atmospheric gas atoms, producing positively charged ions
  • 16.