Composition of the atmosphere

• Patching up the ozone hole

  • Early research of ozone layer done by Halley VI Research Station

    • Used a spectrophotometer (makes measurements of O₃ from ground

    • Dr. Shanklin notices a decline in the ozone (c. 1981)

    • Every one percent of loss to the ozone can cause up to 100,000 cases of skin cancer in the US alone

    • Chlorine was getting into the low level of the stratosphere and reacting with the ozone

    • Stabilized in the 90s and are coming back up

  • Ozone is measured by a Dobson unit

    • 1 Dobson unit = number of molecules of ozone required to create a layer of pure ozone 0.01 mm think at a temperature of 0C and pressure of 1 atmosphere

  • Compressed to sea-level pressure, ozone would form a layer about the height of two pennies stacked together. Levels in the ozone hole are much less - only the height of a single dime

    • 3 cents separates us from the UV of the sun

  • Ozone in the stratosphere

    • Ozone (O₃)

      • O2 absorbs ultraviolet radiation (180nm240nm) -> O3

      • O3 absorbs ultraviolet (290nm-300nm)

        • Protects harmful UVB rays from the sun

    • Ozone depleted by CFC (chlorofluorocarbon)

      • CFCs- chemicals used in refrigeration systems

      • Migrate from the surface into upper atmosphere

      • Cl breaks down O3 molecules

  • 1987 Montreal Protocol: global agreement to protect the Ozone layer, cut global CFC consumption by 50% by 1999

• Atmospheric gases (inactive and active)

Temperature structure of the Atmosphere

• Vertical structure of the atmosphere

  • Homosphere

    • Where atmosphere is evenly mixed

      • Exception is Oxone

    • Radiatively and chemical inactive gases:

      • Nitrogen

      • Argon

  • Composition of the atmosphere

    • Radiatively and chemically active gases

      • O2

        • Easily combines with other substances (chemically active)

        • As O3 absorbs ultraviolet radiation in the upper atmosphere (radiatively active)

      • Water Vapor

        • Important to greenhouse effect

      • CO2

        • Greenhouse effect

        • Consumed by green plants for photosynthesis

        • Carbon cycle

      • Methane

        • Efficient greenhouse gas compared to CO2 or water vapor

        • Naturally produced by wetlands, organics broken down in absence of oxygen

        • Also on the rise like CO2 but in small values

          • Also because of natural gas industry and livestock

    • Ozone in the Troposphere

      • O3 is a pollutant near earth's surface

        • Natural O3 from organic chemicals

        • Human made O3 from burning of gasoline and other fossil fuels and sunlight

          • Most prevalent cities during summer

          • Upper lever (stratosphere) O3 -. Protective shield

          • Lower layer (troposphere) 03 -. Pollutant

• Troposphere

  • All human activity; most weather and climate phenomena happen

  • Lowest atmospheric layer (0-16km)

    • 8-16km thick - thinker at equator, thinner near poles

    • Temperature

• Lapse rate: rate of temp change with altitude

  • Environmental lapse rate: lapse rate at a particular location

• Stratosphere

  • 16km-50km

  • Strong absorption of uv

    • Contains ozone layer

      • Warming w/ altitude

    • Little mixing with air

    • Thinner at the poles

  • Stratosphere is cooling

    • Group of scientist looked at how temp is changing in the higher levels of the atmosphere

    • Why would it be cooling

      • Atmosphere is heating up so much that heat can't escape higher

• Mesosphere and Thermosphere

  • Mesosphere (50kn-80km)

    • Cools with altitude

  • Thermosphere

    • Warms with altitude

    • Gases are layered by molecular mass and charge

• Ionosphere (60-40)

  • Electrically charged particles : ions and free electrons

  • Aurora borealis and australis

  • GPS, TV, satellite EM signals disrupted by activity in ionosphere and solar particles

• Atmospheric pressure and density

  • Air pressure and density change with altitude

    • Atmospheric pressure - weight of air column above a unit area (due to gravity)

    • Standard unit of atmospheric pressure -> standard atmospheric pressure at sea level = 1013.2 hPa

  • Coors Field in Denver is the "hittingest" ballpark

    • More homeruns, more fly balls

    • More doubles, triples

    • Why

      • Atmospheric pressure at Denver is low

  • Air pressure decreases with altitude

  • Decreasing total weight of the overlaying atmospheric molecules

  • Air density decreases with altitude