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Planetary Atmospheres, the Environment
and Life (ExCos2Y)
Revision
Chris Parkes [email protected]
Rm 455 Kelvin Building
Lecture Content
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1. Composition of the Atmospheres of Earth, Mars and Venus
2. Evolution of Earth’s Atmosphere
3. Structure of Planetary Atmospheres
4. Solar Radiation
5. Atmospheric Convection
6. Wind
7. Water
8. Storm Systems
9. Climate Change
10. Revision
Reading:
The Cosmic Perspective, chapter on planetary atmospheres
by Bennett, Donahue, Schneider, Voit. Publisher: Addison Wesley
Atmosphere, Weather and Climate
by Barry, Chorley. Publisher: Routledge
1. Composition of the Atmospheres
of Earth, Mars and Venus
• Physical characteristics of planets
• Atmospheric composition of Planets
– Earth: Nitrogen, Oxygen Mars/Venus: CO2
– Mars: low pressure, Venus: high pressure
• Gain & Loss mechanisms
• Thermal Escape:
– Temperature
– Gravity, Mass & Radius of planet – Escape Velocity
2. Evolution of Earth’s Atmosphere
• Habitable zone – liquid water
• The Oxygen cycle
– photosynthesis & Oxygen
absorbtion in balance
• Oxygen in atmosphere over
time
– 3 reservoir model: oxygen
produced by life,
anaerobic/aerobic life
• Water Cycle
• Carbon dioxide Cycle
• Self-regulation and the “Gaia”
hypothesis
Reducing
Oxygenating
Atmosphere
volcanic
gases
photochemistry
Shallow Ocean
weathering
photosynthesis
volcanic
gases
Deep Ocean
3. Structure of Planetary Atmospheres
• 4 distinctive layers with
boundaries
– Troposphere, Stratosphere,
Mesosphere, Thermosphere
• Temperature profile
– Greenhouse gases
– Ozone in stratsophere
• Comparison of
atmosphere’s of Earth,
Venus & Mars
• Absorption spectrum of atmosphere
– Spectrum of incoming & outgoing
radiation
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Insolation – daily & annual variation
Albedo
Energy budget
Greenhouse effect
Wm-2μm-1
4. Solar Radiation
Radiation
Sun:
Incoming
Earth:
Outgoing
μm
5. Atmospheric Convection
Hot air rises, expands circulation cell
– Heating at equator, cooling at polesHadley cell
– Coriolis Effect east/west winds disrupts Hadley cell
• Three cell model of
Earth’s atmosphere
– Convection in Sea Breezes
5. Atmospheric Convection
Hot air rises, expands circulation cell
– Heating at equator, cooling at polesHadley cell
– Coriolis Effect east/west winds disrupts Hadley cell
• Three cell model of
Earth’s atmosphere
– Convection in Sea Breezes
6. Wind
easterlies
Wind
jet streams
Forces:
Pressure gradient
Coriolis
Centripetal
Friction
Global wind belts
Air masses & Fronts
Jet Streams
westerlies
trade winds
ITCZ, Doldrums
Polar Front
7. Water
The effects of Waters
Heat Capacity of water
Wind – water interaction
Ocean Circulation
El Nino
8. Storm systems
• Storm Systems
– Hurricanes
• Formation
• Structure
– Tornados
• Formation
– Dust Devils, Water Spouts
9. Climate Change
• Key evidence
– Ice Core data
– Atmospheric CO2
• Clear Effects
– Glacier Melting
– Sea Rises
• Model Predictions
– Need to act
2009
385 ppm