Earth’s Atmosphere
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Earth’s Atmosphere & Weather. Characteristics of the Atmosphere. 1 st Atmosphere. Composition - H 2 , He Lost to space early in Earth's history because: Earth's gravity is not strong enough to hold lighter gases

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Characteristics of the atmosphere

Characteristics of theAtmosphere

1 st atmosphere
1st Atmosphere

  • Composition - H2, He

  • Lost to space early in Earth's history because:

    • Earth's gravity is not strong enough to hold lighter gases

    • Earth still did not have a differentiated core (solid inner/liquid outer core) which creates Earth's magnetic field (magnetosphere = Van Allen Belt) which deflects solar winds.

  • Once the core differentiated the heavier gases could be retained

2 nd atmosphere
2nd Atmosphere

  • Produced by volcanic out-gassing.

  • H2O, CO2, SO2, CO, S2, Cl2, N2, H2 and NH3 (ammonia) and CH4 (methane)

  • No free O2 at this time

  • Ocean Formation - As the Earth cooled, H2O produced by out-gassing could exist as liquid in the early Archean, allowing oceans to form.

Addition of o 2
Addition of O2

  • Photochemicaldissociation - breakup of water molecules by UV radiation

    • Produced O2 levels approx. 1-2% current levels

    • At these levels O3 (Ozone) can form to shield Earth surface from UV

  • Photosynthesis –

    • CO2 + H2O + sunlight  glucose + O2

    • O2 produced by cyanobacteria, and eventually higher plants

  • Present composition
    Present Composition

    • 78% Nitrogen

    • 21% Oxygen

    • 1% Other trace gases

    Layers of the atmosphere
    Layers of the Atmosphere

    • Caused by temp. differences

    • These differences result from how solar energy is absorbed as it moves through the atmosphere

    Earth s atmosphere weather

    4 main layers of the atmosphere
    4 Layers of the Atmosphere

    Earth s atmosphere weather


    • Closest to Earth

    • Nearly all weather occurs here

    • Almost all H2O vapor and CO2

    • Temp. decreases with altitude because air in this layer is heated from below by thermal energy that is re-radiated from Earth’s surface


    • Upper boundary of the troposphere

    • Jet stream

      • Varies with latitude & seasons

      • 250 mph

      • East wind


    • 16 – 50 km

    • Ozone layer is here

    • Temp. increases because air is heated from above by absorption of solar radiation by ozone

    • Jets fly here to avoid turbulence

    • Stratopause - upper boundary

    Ozone layer
    Ozone Layer

    • Ozone is made of 3 atoms of oxygen (O3)

    • ≈ 2-3 mm thick if it were at sea level

    • Purpose - absorbs harmful UV radiation from the Sun


    • 50 – 85 km

    • Temp. decreases as altitude increases

    • Mesopause - Upper boundary

    • AvgTemp. = - 90oC

    • COLDEST layer in the atmosphere

    • Meteors begin to disintegrate here

    Red sprite
    Red Sprite



    Blue jets
    Blue Jets

    E l ves emission of light and very low frequency perturbations
    E.L.Ves of Light and Very low frequency perturbations


    • 90 km ~ 1000 km

    • Space begins here (~100 km)

    • Temp. increases as altitude increases

    • Can’t read temp. with a thermometer because air particles are too far apart

    • Space Shuttle & ISS orbit here

    • Ionosphereis the lower region

    • Aurora occur here


    • End of the atmosphere

    • Almost a vacuum

    • Where light elements escape Earth’s gravity

    Earth s atmosphere weather


    The water cycle

    The Water Cycle

    Temperature humidity

    Temperature & Humidity


    • A measure of the kinetic energy of the molecules of a substance

    Methods of heat transfer
    Methods of Heat Transfer

    • Conduction – direct transfer

    • Convection – bulk movement of particles

    • Radiation – electromagnetic waves

    Where does radiation go
    Where does radiation go?

    • 25% penetrates Earth’s atmosphere

    • 20% absorbed by the atmosphere

    • 30% scattered back into space (albedo)


    • Varies due to

      • Cloud cover

      • Particulate matter (dust, pollen, ash, etc.)

      • Sun’s angle

      • Surface (water vs. land)

    Differential heating
    Differential Heating

    • Earth’s surface is heated unevenly due to:

      • Geographic position (latitude)

      • Land vs. Water

      • Altitude

      • Ocean currents

      • Cloud cover

      • Albedo


    • The amount of water vapor in the air

    • 90% of water vapor comes from oceans (evaporation)

    • The warmer air is, the more water vapor it can hold

    Dew point
    Dew Point

    • The temp. at which water vapor begins to condense

    • If the dew point and air temp. are the same, the following will form:

      • At ground level = dew or frost

      • Just above ground = fog

      • Higher levels = clouds

    Relative humidity
    Relative Humidity

    • The amount of water vapor in the air expressed as a percentage of the amount required to saturate the air at the current temp.

      % R.H. = Actual absolute humidity x 100

      Maximum absolute humidity


    • Used to measure humidity

    • Made with 2 thermometers

      • Dry bulb

        • Measures air temp.

      • Wet bulb

        • Cooler than dry bulb

        • Uses evaporation to measure temp.

      • Wet bulb depression – difference between dry & wet bulb temps.

    Pollution its effects on the atmosphere

    Pollution Effects On the Atmosphere


    • Tiny, solid particles

      • Volcanic dust

      • Ash f/ fires

      • Microscopic organisms

      • Mineral particles f/ the soil

      • Pollen f/ plants

      • Particles f/ meteors

      • Salt f/ the ocean

  • Can be suspended for mo’s or yrs

  • Fly ash from burning wastes
    Fly ash from burning wastes,TSHA:2006-08,TSHA:en

    Air pollutants
    Air Pollutants

    • Any substance that is in the atmosphere & is harmful to people, animals, plants or property

    • Main source is burning of fossil fuels

      • These release harmful substances SO2, hydrocarbons, N oxides, CO & Pb into the air


    Earth s atmosphere weather

    Earth s atmosphere weather

    Breaking down the ozone layer
    Breaking Down the Ozone Layer

    • CFC’s (chlorofluorocarbons) break down the ozone layer

      • They used to be used in refrigerators, air conditioners & exhaust compounds

    Earth s atmosphere weather


    Temperature inversions
    Temperature Inversions

    • When a layer of warm air is on top of cool air

      • This can trap polluted air beneath

      • Topography can make it worse

      • Smog occurs b/c of the pollutants & lack of circulation

    Temperature inversion
    Temperature Inversion

    Earth s atmosphere weather

    Earth s atmosphere weather

    How to control smog
    How to Control Smog

    • Prevent the release of pollutants

    • Passage of laws

    • Community awareness

    • Personal responsibility

    Earth s atmosphere weather

    Earth s atmosphere weather

    Atlanta, GA