2.7 - Atmosphere

Comprehensive notes on Unit 2, Chapter 7, the atmosphere. Learn about composition, layers, climactic effects; as well as human caused processes such as ozone depletion, and global warming - and thereabouts, the effort to limit them!

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  • Created on: 22-01-12 20:36
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2.7. The Atmosphere.
COMPOSITION
Is a dynamic equilibrium, for processes that change
levels (respiration/Photosynth.), only varied over large time-scales.
o CHANGES WITH TIME
DIURNAL:- CO2 rises at night (no photosynth.); and falls during day.
: Water vapour varies due to transpiration, evaporation, and precipitation ­ which vary with temperature.
LONG TERM: Changes with solar and geological processes (and human activity)
o CHANGES WITH ALTITUDE
Temperatue ­ decreases with altitude in the troposphere (Infa-red heating)
Increases with altitude in the stratosphere (solar rays)
Pressure ­ decreases with altitude (less gravity)
o SOLAR RADIATION & THE ATMOSPHERE
Sun produces energy from nuclear fusion (H+H>H) as electromagnetic
radiation
Nitrogen 78% Used in proteins (amino acid n-terminal)
Oxygen 21% Aerobic Respiration
Carbon Dioxide 0.038% Greenhouse Gas & Photosynthesis
Methane 0.00017% Greenhouse Gas & source of carbon for
chemoautotrophs
Ozone 0.000007% Absorbs UV light in stratosphere
Water Vapour VARIABLE ­ up to 4% Physiological Solvent, Photosynthesis etc.
Earth receives: visible light, UV, IR. << absorbed by atmosphere: ozone (stratos.) / reflected by clouds / absorbed by
gases.
HUMAN IMPACTS
o GLOBAL CLIMATE CHANGE
THE GREENHOUSE EFFECT ­ Controls the energy and heat balance (above) of the Earth.
Light > absorbed by Earth > Infa-red radiation > partly absorbed by atmos. gases > warming
THE ENHANCED GREENHOUSE EFFECT
-Human activities = more "greenhouse" gases (natural or not) = more warming
-CO2 from fossil fuels, methane from paddy fields/landfill/livestock, nitrogen oxides, CFCs
-Tropospheric Ozone = photochemical breakdown of nitrogen oxides

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CONSEQUENCES OF GLOBAL CLIMATE CHANGE: +4oc in next 100 years
SEA LEVEL RISE
Thermal Expansion: Slight expansion seas with heat = rise. Slow process: deep water must be brought to surface to heat.
Melting Land Ice: Only land ice will contribute to sea level rise when melting, or glacial displacement of sea water.
CHANGES IN CLIMATE
Wind Patterns: Change in direction, frequency and strength = more storm damage & change in rain patterns.…read more

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Effects of the positive feedback mechanism / WARMING...
Increased rate of decomposition = more CO2
Reduced ice mass = less albedo / methane release = more heating
Forest fires more common = more CO2
Effects of the negative feedback mechanism / Maintaining Equilibrium...
Increased temp. = increased photosynthesis = more carbon removal / sequestration in lignin = less C02 = less heating
Increased temp.…read more

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ClO2 > more chlorine. REPEAT: ClO2 > Cl + O2
The reaction begins & ends with a chlorine radical!
Removes starting materials for reactions which maintain ozone = more ozone depletion.
POLLUTION FROM CFCs
Chlorofluorocarbons = Only Chlorine, Fluorine, and Carbon. Used to be used in aerosols.
Low solubility & chemical stability = remain in atmosphere (stratosphere) > Broken down by UV, release Chlorine.…read more

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