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The Earth’s Atmosphere

The Earth’s Atmosphere. What holds the Earth’s atmosphere to the planet?. GRAVITY . Development of the Earth’s Atmosphere. Primordial atmosphere (4.6 to 4.0 bya) Evolutionary atmosphere (4.0 to 3.3 bya) The living atmosphere (3.3 bya to 500 mya) The modern atmosphere (500 mya to present).

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The Earth’s Atmosphere

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  1. The Earth’s Atmosphere

  2. What holds the Earth’s atmosphere to the planet? GRAVITY 

  3. Development of the Earth’s Atmosphere • Primordial atmosphere (4.6 to 4.0 bya) • Evolutionary atmosphere (4.0 to 3.3 bya) • The living atmosphere (3.3 bya to 500 mya) • The modern atmosphere (500 mya to present)

  4. Primordial Atmosphere (4.6 to 4.0 bya) • Materials from original solar nebula • hydrogen (H) • ammonia • methane (CH4) • water vapor (H2O) • NO OXYGEN

  5. Evolutionary Atmosphere (4.0 to 3.3 bya) • Volcanic eruptions cause outgassing ofH2O vapor • Clouds and rain form • surface water accumulates • (short periods of water vapor, carbon dioxide and other gases -- no oxygen)

  6. The Living Atmosphere (3.3 bya to 500 mya) • Photosynthetic Cyanobacteria develop in shallow waters • Photosynthesis --> release oxygen • @ 2 bya, ozone (03) forms --> protects Earth from UV

  7. The Modern Atmosphere (500 mya to the present) • Nitrogen, N2 (78%) • Oxygen, O2 (21%) 99.9% • Argon, Ar (0.9%) Trace gases • water vapor (0-4%) • carbon dioxide (.036%), methane (greenhouse gases) • nitrogen oxides, sulfur oxides (acid rain and more) • many other trace gases • particulate (dust)

  8. Atmospheric Pressure Atmospheric Pressure

  9. Mercury Barometer - Invented by Toricelli, 1643 Atmospheric Pressure Pressure can be thought of as the weight of all overlying air (though, in reality, pressure exerts force in all directions). Average Sea Level Atmospheric Pressure: 29.92” of Mercury76 cm of Mercury1013 millibars (mb)

  10. Aneroid Barometer- also altimeter Average Sea Level Atmospheric Pressure: 29.92” of Mercury76 cm of Mercury1013 millibars (mb)

  11. Atmospheric Pressure Is Related to Weather Conditions More-Dense, High Pressure Air Sinks: Fair Weather Less-Dense, Low Pressure Rises: Clouds and Stormy Weather

  12. The Vertical Thermal Structure of the Atmosphere IONOSPHERE OZONOSPHERE

  13. Temperature, Precipitation, and Elevation Temperature decreases with increasing elevation. Precipitation increases with increasing elevation.

  14. Temperature Inversions When warmer air overlies cooler air, pollutants and fog are trapped beneath the inversion. Common Winter Radiation Inversion in Valleys

  15. Temperature Inversions Common Summer Inversion in Los Angeles

  16. Troposphere [tropopause at 8-18 km, or 5-11 miles] • Troposphere • contains 90% of the mass of the atmosphere • decrease of mass with altitude • mostly mixed gases (not layered) • clouds / weather layer • temperatures decrease with altitude - WHY?

  17. mesosphere Stratosphere [stratopause at 50 km, about 30 miles] • decrease in amount of gases with altitude • mixed gases (not stratified) except for ozone layer • temperatures increase with altitude [tropopause at 8-18 km, or 5-11 miles]

  18. Aurora borealis / australis • The northern / southern lights • Thermosphere and uppermost Mesosphere • solar wind (clouds of electrically charged particles) • Earth’s magnetic field directs them towards poles • excite oxygen (O) and nitrogen (N2) ions in ionosphere  emit light

  19. The Importance of Stratospheric Ozone • Ozone forms naturally in stratosphere • UV radiation (sun) --> mutations • plankton reduced (food chain base), crops decline • weaker immune systems, skin cancer • Stratospheric ozone (O3) absorbs UV rays light  O2 2 O then O + O2  O3 UV rays  O3 O2 + O

  20. The Importance of Stratospheric Ozone • CFC’s • link to ozone hole established in 1970s • Chloroflourocarbons (refrigerants, aerosols) • one Cl can decompose more than 100,000 O3 • Montreal Protocol, 1987: U.N. agreement on ban • up to 10 years for rising CFC gases to reach stratosphere; once in the stratosphere, CFC’s can last up to 50-100 years Cl2 + light ---> 2 Cl Cl + O3 ---> ClO + O2 CLO + O = Cl + O2

  21. Ozone Hole Splits, Spring 2002(total area smaller than 2001)

  22. September 25, 2003

  23. Key Points • Development of Earth’s atmosphere • Vertical structure of the atmosphere • 4 temperature layers • changes in pressure • Aurora borealis / australis • the ozone layer

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