Planetary Atmospheres, the Environment and Life (ExCos2Y) Revision Chris Parkes Rm 455 Kelvin Building

Lecture Content 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

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 1. Composition of the Atmospheres of Earth, Mars and Venus

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 Atmosphere Shallow Ocean Deep Ocean Reducing Oxygenating volcanic gases weathering volcanic gases photochemistry photosynthesis

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

4. Solar Radiation Absorption spectrum of atmosphere –Spectrum of incoming & outgoing radiation Insolation – daily & annual variation Albedo Energy budget Greenhouse effect Wm -2 μm -1 μmμm Sun: Incoming Earth: Outgoing Radiation

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 Wind Forces: Pressure gradient Coriolis Centripetal Friction Global wind belts Air masses & Fronts Jet Streams trade winds westerlies easterlies jet streams 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 CO 2 Clear Effects –Glacier Melting –Sea Rises Model Predictions –Need to act ppm