The Atmosphere

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The Atmosphere

• Evolution
• Structure
• Composition

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Evolution of the Atmosphere

• 1. ASTRONOMICAL ATMOSPHERE
• Formation of the solar system 4.6 x 109 yrs. ago.
• Heavier elements produced in supernovas.
• Early cold Earth had an atmosphere of H2, He,
  CH4, NH3 and water vapor (from bombardment by
  comets). This early atmosphere is thought to be
  much like those of the Jovian planets.
• Sun retained H and He and became a fusion
  reactor.
• When Sun ignited, Earth was too close to retain H
  and He which were lost to space.

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Evolution of the Atmosphere

• 2. GEOLOGICAL ATMOSPHERE
• Outgassing by volcanoes and other fissures
  enriched the Earths atmosphere in H2O and CO2.
• Hawaiian volcanoes emit about 80 water vapor and
  about 12 carbon dioxide.
• Thus, after the Earth solidified, the atmosphere
  was largely composed of these compounds.
• Comets continued to bombard the early Earth
  providing water and other atmospheric gases.

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Evolution of the Atmosphere

• 3. BIOLOGICAL ATMOSPHERE
• Very little oxygen until plant life evolved.
• If all plant life was extinguished, we would run
  out of oxygen in as little as 40 years!
• 1 of the O2 may have come from lightning strikes
  or UV solar radiation
• 2 H2O energy -- 2 H2 O2
• 99 came from the growth of plants
• 6 CO2 6 H2O energy -- C6H12O6 6 O2
• Note without O2 there would be no O3 layer

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Harts Model of Evolution of Atmosphere

• M.H. Hart, Icarus 33 (1978) 23-39.

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Evolution of the Atmosphere

• 4. SOCIO-ECONOMIC ATMOSPHERE
• Since the Industrial Revolution, the atmosphere
  has changed drastically from its earlier forms.
  Humans have changed its composition through
  pollution of all kinds (smoke, smog, acids).
• Our use of fossil fuels has led to the following
  one way and unsustainable equation
• C6H12O6 6 O2 -- 6 CO2 6 H2O energy
• Fossil Fuels Biological Oxygen -- Excess
  greenhouse gases energy

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Anthropogenic Paradox

• Will Homo sapiens, through overpopulation,
  resource depletion, and misuse of technology
  upset the natural rhythms of organic life on our
  planet?
• The Anthropogenic Paradox implies the unintended
  possible self-destruction of Homo sapiens
  sapiens, the first species to be fully aware of
  its own extinction.
• The Anthropocene is the term used for the current
  and recent era in which humans are influencing
  global processes. When did this begin? 1990?
  1790? early agriculture?

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GAIA

• The Gaia hypothesis (Lovelock, 1979), named after
  the ancient Greek goddess of the Earth, proposes
  that living and nonliving components of the earth
  can be viewed as a complex interacting system
  having a regulatory effect on the Earth's
  environment.
• Example CO2 increases warm the Earth,
• Warmth stimulates more plankton growth,
• Plankton emits Dimethyl Sulfate (DMS) which makes
  clouds brighter,
• Brighter clouds cool the Earth.
• "People sometimes have the attitude that Gaia
  will look after us. But thats wrong. If the
  concept means anything at all, Gaia will look
  after herself. And the best way for her to do
  that might well be to get rid of us.
• James Lovelock, (1987).

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• Structure and Composition

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Structure

• LAYER A (km) P (atm) T (oC) COMMENTS
• Exosphere 500 0 103 Edge of space, light gases
  escape
• Thermosphere 90 10-7 -90 to103 Stable, Solar
  absorption by O O2
• Mesosphere 60-90 10-5 0 to -90 Mixed layer,
  coldest region
• Stratosphere 20-50 10-2 -40 to 0 Stable, Solar UV
  absorbed by O3
• Troposphere 0-10 1 to 0.1 40 to-40 Layer of
  weather, water vapor rules

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• Structure

Source Anthes 1.4
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Composition

• Nitrogen 78.08
• Oxygen 20.95
• Water Vapor 0 to 4
• Argon 0.93
• CO2 0.0385 385 ppm

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The Minor Constituents
Note Every known chemical compound has been
found in the atmosphere in some concentration
(e.g. paint fumes, lead compounds, CCl4, etc.)
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Weather Elements

• Air Temperature Thermometer
• Air Pressure Barometer
• Humidity Psychrometer
• Clouds Cloud types and amounts
• Precipitation Liquid or Frozen
• Visibility For Aviation
• Wind Speed and Direction
• Air Quality Pollution Load

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Definitions

• Weather The state of the atmosphere at a given
  place and time.
• Weather elements T, P, humidity, clouds,
  precipitation, visibility, wind, air quality.
• Meteorology Scientific study of the weather.
• Ancient meaning (Aristotle) was much broader.
• Climate Aggregate of regional weather conditions
  over time.
• Usually a 30-year average over a region plus
• A statement about frequency of extreme
  conditions,
• such as lightning strikes, tornadoes, or
  drought.
• Climatology Scientific study of climate.
• Includes fields such as applied climatology,
  climate
• modeling, and climate dynamics.

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Definitions (cont.)

• Physical Oceanography -- Chemistry and dynamics
  of oceans, including currents, waves, air-sea
  interaction, and topics such as El Niño and La
  Niña.
• Atmospheric Science -- Umbrella term covering
  explosion of research specialties since about
  1960. Meteorology, Climatology, Cloud Physics,
  Atmospheric Chemistry, Numerical Weather
  Prediction, Satellite and Radar Meteorology, etc.
• Global Change -- Umbrella term for study of the
  complex interactions of the atmosphere,
  lithosphere, hydrosphere, and biosphere on all
  temporal and spatial scales plus the human or
  social dimensions of environmental change.