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The Atmosphere

The Atmosphere. An ocean of air. Outline. The biosphere – an environment for life. The atmosphere – recycling bin or garbage can? Atmospheric physics – pressure, temperature and density. The nature of pressure. The Biosphere.

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The Atmosphere

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  1. The Atmosphere An ocean of air

  2. Outline • The biosphere – an environment for life. • The atmosphere – recycling bin or garbage can? • Atmospheric physics – pressure, temperature and density. • The nature of pressure.

  3. The Biosphere • The sum total of everything that makes up the environment for life. • A concept that emphasizes the interconnectedness of life, how living beings interact with each other and with their surrounding environment. • Encourages us to take a broader view of what is a “resource”. • Atmosphere, Lithosphere, Hydrosphere. • Encourages us to recognize the finite extent of all resources.

  4. The Atmosphere • The air is not “living”, but it is essential for life. • Historically, the atmosphere was thought of as a dumping ground. • Science has shown that the atmosphere is really a “recycling bin” and a vital link connecting nearly all life processes on earth.

  5. What is the Atmosphere? • The atmosphere is made of gases and vapors which are trapped by the earth’s gravitational field, extending out about 600 miles from the earth’s surface. • The primary components are, by volume: • 78%, N2; 21%, O2; 1% Ar • Trace components include: • CO2, H2O, CH4, CFC’s, O3, He, Ne, H2, … • This composition has varied only slightly over time.

  6. Sources and Sinks • DYNAMICAL STABILITY. • The atmosphere is stable but not stagnant. • Most of the atmospheric constituents are entering and leaving the atmosphere continuously. • “Sources” add constituents to the atmosphere. • “Sinks” remove them. • Picture a bathtub with the faucet on and the drain open. • Vital chemicals “cycle” through the biosphere by means of these sources and sinks.

  7. Chemical Cycles • Carbon • Oxygen • Nitrogen • CO2 • O3 • H2O

  8. The Carbon Cycle:

  9. The Nitrogen Cycle:

  10. Energy use and the Biosphere • Energy in the form of fossil fuels represents a traditional resource – something that we can extract from the environment for our benefit. • Its extraction, production and use represents a number of new sources of chemicals to the biosphere, disrupting some cycles, whacking others out of balance. • e.g. Carbon dioxide and global warming. • Nitrogen Fertilizers and Eutrophication. • CFC’s and the Ozone layer. • Acid rain

  11. Atmospheric Physics • Atmospheric properties: It’s a fluid. • A fluid is a phase of matter that flows to take the shape of its container. • Liquids have a well-defined surface, Gases don’t. • Just like solid objects, Fluids can be acted on by forces, have energy, etc. (Physics is physics) • However, since they don’t have a recognizable shape or extent, we’ll need to make some new definitions.

  12. Fluid density and pressure • Fluids (gases and liquids) have mass and are acted on by gravity. • Density = Mass / Volume • e.g. Dwater = 1 gram /cm3 = 1000 kg/m3 • Density of air at ground level = 1.3 kg/m3 • Fluids move and flow due to the action of forces • Pressure = Force / Area. • The bed of nails. • 1 atmosphere = 1 x 105 N / m2 = 1 x 105 Pascal.

  13. Eureka! • Greek scientist and engineer, Archimedes. • Lived in Syracuse. Helped fight against the Romans. • Developed the concept of density for the sake of determining whether his king’s crown was real gold or not. He thought to compare mass to volume. • The key breakthrough was to measure Volume by seeing how much water was displaced when the object was submerged. • Got the idea from taking a bath!

  14. Pressure in a fluid in gravity. • Pressure is the cumulative weight of all the fluid above some surface and increases with depth. • Pressure in a fluid at rest at the same height is the same – Pascal’s principle. P Weight = D*V*g P P P + W/Area

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