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Earth's Atmosphere

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Earth's Atmosphere

  1. 1. Earth’s Protective Blanket Atmosphere
  2. 2. Earth's Atmosphere What's an atmosphere?  Air surrounding a planet  Earth's atmosphere has 5 layers  Different planets have different layers and different gases in their atmospheres What does it do?  Protects from Sun's heat (and space's cold)  day/night temps would be extreme without blanket of gases  Protects from Sun's harmful rays  solar (ultraviolet) radiation would destroy all life if not filtered out Thermosphere Mesosphere Exosphere Troposphere Stratosphere
  3. 3. Layers Identified by Temperature Temperature changes determine layers Top region and transition to next layer called: Tropopause Stratopause Mesopause Mesopause Tropopause Stratopause
  4. 4. Earth's atmosphere, a mixture of gases: • N2, O2, Ar, CO2, and others gases plus water vapor, dust, etc. •Earth's gravity holds more air molecules near it's surface than in the upper atmosphere where gravitational forces are weaker
  5. 5. Atmospheric Pressure Higher altitudes=  Fewer molecules pushing on each other and their surroundings  Lower pressure  Less concentrated oxygen levels
  6. 6. Density Amount of matter within a specific volume  # of atoms occupying a particular space  how close together the atoms are packed SI base units = g/cm3 or g/ml
  7. 7. Altitude & Density As air pressure decreases, density of air also decreases  Air particles are not squashed together as tightly the higher one goes (because of gravity) Air at sea level and 8km both have 21% oxygen But 21% of 100 = 21, while 21% of 10 is only 2! At 8km there are fewer molecules per cubic cm, so you take in less oxygen with each
  8. 8. Layers of Earth’s Atmosphere Troposphere  Where we live Stratosphere  Ozone layer Mesosphere  Meteors burn up Thermosphere  Space shuttle  Aurora Borealis Exosphere  Thin, outer layer Exosphere
  9. 9. Troposphere  Thinnest layer (4 to 12 miles thick)  Thickness depends on terrain, season, time of day & latitude  Holds ~80% of Earth's atmospheric mass  Highest pressure at lowest levels  Most weather occurs here  Water vapor (& clouds), wind, lightning  Jet stream (river of 250 mph winds) is just below the Tropopause (upper boundary) or in the lowest parts of the stratosphere  Temperature cools as you go up  Sun heats ground, which radiates warmth to air above it  Air is warmest near the ground 14o C (57o F)  Air cools ~6.4o C every 1 km you go up  Top of Troposphere is -50o C (-58o F)
  10. 10. Greenhouse Effect  Solar radiation that reaches earth is absorbed by:  Earth's surface (50%)  land heats quicker and radiates sooner  bodies of water heat slower and hold onto heat longer  Earth's atmosphere (15%)  35% of Solar radiation is reflected from  Earth's atmosphere  Clouds  Earth's surface (i.e. snow, sand)  Some of the heat absorbed by Earth's surface is released into the atmosphere
  11. 11. Air Pollution  Nitrogen Oxides  Damage lung tissue  Sources:  car, plane, mower engines  lightening burning N2 in air  Sulfur Oxides  Damage lung tissue  Sources:  burning coal  volcanic eruptions  Carbon Monoxide  Causes asphyxiation  Sources:  gasoline engines (automobiles, chainsaws, trains, etc.)  forest fires, woodstoves, cigarettes  Airborne Lead  Destroys brain tissue  Source: leaded gasoline  Particulates
  12. 12. Levels are Falling Except CO2
  13. 13. Stratosphere  Thickness from 33 to 40 km (20-25 miles)  Depends on Troposphere's thickness  Top boundary (Stratopause) at 50km above sea level Contains the Ozone Layer  Earth's "sunscreen" Temperatures rise as you go up  Heat trapped by ozone warms layer  -50o C to -3o C to (-58o to 27o Fahrenheit) Very stable/stagnant layer  Little to no wind (not much mixing)  Jet aircraft fly lower stratosphere  No water vapor/clouds (very dry)
  14. 14. Ozone Layer O3 Molecules Absorbs UV light which cause skin cancer & cataract Absorbs heat Toxic to breathe
  15. 15. "Hole" in the Ozone Layer Chlorine & Bromine bind to oxygen & deplete ozone Mostly at the south pole where Artic winds carry Cl & Br up into the Stratosphere Localized & seasonal "thinning" - not a complete "hole" CFCs in refrigerants Montreal Protocol Some studies show reversal
  16. 16. Mesosphere  About 35 km (22 miles) thick  From 50 to 85 kilometers above sea level (31 - 53 mi.)  Upper boundary called Mesopause  Temperatures decrease with altitude  Meteors burn up in this layer  Seen as "shooting stars"  Tiny particles (sand or pebble-size)  Rock, dust or metal particles  High speed (tens of thousands of miles/hr)  Hard to study, not much known  Sounding rockets take measurements
  17. 17. Thermosphere  Thickest layer (250-560 miles)  From 90 km (56 miles) to 1,000 km (621 mi) above sea level  Upper boundary: Thermopause  Predominant gases is Helium  Temperatures rise with altitude  Sun's activity (solar flares, day/night) affect the temperature  Upper part ranges from 500°C - 2,000°C (3,632°F or higher)!  "Ionosphere" - sublayer that contains plasmas (free p's & e's)  ions aligned with Earth's magnetic fields collide with solar flare ions, causing auroras  Different gasses cause different colors  Radio waves bounce off ionosphere to extend range  Space shuttle, satellites & ISS orbit in this layer  Considered "outer space" by most people  Gas molecules very far apart & very excited
  18. 18. Exosphere Region where atoms and molecules start to escape Earth's gravitation Very thin, outer layer No clear upper boundary with space Mostly Hydrogen
  19. 19. Homemade weather balloon experiment
  20. 20. Global Warming Average global temperatures have increased by about 1o C over the past 150 years. How do we know this?
  21. 21. Global Temperature Monitoring Land, air or sea? Urban “island” effect Weather balloon & satellite  Satellite orbit adjustment US vs. UK boat measurements Historical estimates Little Ice Age “Frost Fairs” Medieval Warm Period Ice core & Tree ring sampling Statistics & adjustments
  22. 22. The Big Picture
  23. 23. Causes of Global Climate Change Solar activity Earth's elliptical orbit Volcanic Eruptions Greenhouse gases Carbon Dioxide Methane Nitrous Oxide Water Vapor
  24. 24. Carbon Dioxide Correlation doesn't = cause How much CO2 will cause significant change? Humans contribute 3% Increase of 65 parts per million over past 50 years 380 out of every million air molecules are CO2
  25. 25. Which Came First?

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