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Atmosphere
 

Atmosphere

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    Atmosphere Atmosphere Presentation Transcript

    • The Atmosphere Structure and Change
    • Overview
      • Structure
        • Compositional structure
        • Temperature structure
        • Functional structure
      • Change
        • Natural sources of change
        • Natural influences on pollution
        • Anthropogenic pollution
    • 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)
    •  
    •  
      • 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
    • 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
    •  
    • 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
      • 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
      • 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
    •  
    • 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
    •  
      • 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
    •