22.1 Introduction to the Atmosphere

1. 22.1 Introduction to the Atmosphere (Layers & composition) By Unknown Author & Bill Holmes, U. of Michigan Modified by Laura Smith

2. Thin Blue Line Click on picture or title

3. The Atmosphere • The layers of gas surrounding the Earth • Mixture of chemicals (elements and compounds) called AIR • Protects Earth from solar radiation • Helps regulate temperature on the planet • Divided into layers based on temperature changes with increasing altitude

4. Composition of the Atmosphere

5. Composition of the Atmosphere Argon,

7. Which Gas Makes Up More of Our Atmosphere: NitrogenorOxygen? This question will try to trick you in the future!

8. NITROGEN • Nitrogen makes up about 78% of Earth’s atmosphere and is maintained through the nitrogen cycle.

9. NITROGEN • Nitrogen is removed from the air mainly by the action of nitrogen-fixing bacteria. • Decay releases nitrogen back into the atmosphere.

10. OXYGEN • Oxygen makes up about 21% of Earth’s atmosphere. • Land and ocean plants produce large quantities of oxygen in a process called photosynthesis. Stromatolites Cyanobacteria

11. OXYGEN • Bacteria and plants add oxygen from the air as part of their life processes. • Animals removeoxygen from the air.

12. WATER VAPOR • As water evaporates from oceans, lakes, streams, and soil, it enters air as the invisible gas water vapor. • Plants give off water vapor during transpiration; animals during respiration.

13. WATER VAPOR As water vapor enters the atmosphere, it is removed by the processes of condensation and precipitation in the hydrologic, or water cycle.

14. WATER VAPOR • The humidity is a measure of the water vapor in the air. • The percentage of water vapor in the atmosphere varies depends on factors such as time of day, location, and season.

15. WATER VAPOR • Relative humidity changes with temperature.

16. OZONE Ozone is a gas molecule that is made up of three oxygen atoms • Ozone in the upper stratosphere forms the ozone layer, which absorbs harmful ultraviolet radiation from the sun.

17. OZONE • Ozone in the upper stratosphere forms the ozone layer, which absorbs much of the harmful ultraviolet radiation from the sun.

18. OZONE • Without the ozone layer, living organisms would be severely damaged by the sun’s ultraviolet rays.

19. OZONE • Unfortunately, a number of human activities damage the ozone layer. • ChloroFluoroCarbons (CFCs) (originally used in aerosols & refrigerants & styrofoam manufacturing) break apart ozone molecules creating a “hole”in the ozone layer

20. Good Ozone, Bad Ozone Too little there... CFC’s and halons from air conditioners and refrigerators break down the protective ozone layer. Too much here... Vehicles, power plants and factories emit air pollution that forms ground-level ozone.

21. Sources of Ground-Level Ozone NOx, VOC + sunlight Ozone Hot sunny days

22. OZONE HOLE • NASA Exploring Ozone Click title for 2:20 min video

23. OZONE HOLE • OZONE HOLE 1979-2007 MOVIE

24. OZONE HOLE • Ozone Movie

25. PARTICULATES • Many natural and manmade particulates are in the atmosphere • Dust, pollen, volcanic eruptions and sea spray all add natural, tiny solid particles to the atmosphere.

26. Primary Pollutants • Man-made particulates = pollution

27. Atmospheric Pressure Atmospheric Pressure the force per unit area that is exerted on a surface by the weight of the atmosphere

28. Atmospheric Pressure • Gravity holds the gases of the atmosphere near Earth’s surface. • As a result, the air molecules are compressed together and exert force on Earth’s surface.

29. Atmospheric Pressure Atmospheric Pressure is measured with a barometer.

30. Atmospheric Pressure

31. Atmospheric Pressure • Atmospheric pressure is exerted equally in all directions—up, down, and sideways-- and results from collision of gas particles.

32. Atmospheric Pressure At higher altitudes, or elevations, air molecules are farther apart and exert less pressure on each other (and you).

33. Layers of the Atmosphere Troposphere: (“change”) • Lowest layer (0-18 km = 0-10 miles) • Warmestlayer; decreases going up (20° at bottom to -60° at top) • Weather occurs here; clouds form at top • Water vapor & CO2 • All Life • Hot Air Balloons, airplanes, birds • Densest & smallest layer

34. Layers of the Atmosphere Stratosphere: (“Layer”) • Second layer (18-50 km = 28-31 miles) • Ozone layer (@20-30km) blocks UV rays • Temp. goes up as you go up (-60° bottom to 0° at top) • Windy & Dry • Weather balloons • Some jet planes and clouds at bottom

35. Layers of the Atmosphere Mesosphere: (“middle”) • Third layer (50 - 80 km= 53-62 miles) • Meteors burn up • Coldest layer (0° at bottom to -80°C at top)

36. Layers of the Atmosphere Outer Space (‘Exosphere’) Ionosphere: • At Mesopause & in both Meso- & Thermo- spheres • 96-112+ km • Solar energy removes electrons • Four layers of ions and electrons • Causes Aurora Borealis&Australis • Bounces radio waves (esp. AM) IONOSPHERE

37. Layers of the Atmosphere Outer Space (‘Exosphere’) Thermosphere: (“Heat”) • Highest layer (80 ~ 500 km = 82-~373 mi) • K.E. of particles equal to 2000°C! • Aurorae • Satellites and Space Stations

38. Layers of the Atmosphere “PAUSES” • Breaks between layers • Delineated by changes in temperature direction (starts rising or falling here) • All layers and pause heights vary based on latitude and season THERMOPAUSE MESOPAUSE STRATOPAUSE TROPOPAUSE

39. Layers of the Atmosphere Outer Space (‘Exosphere’) Exosphere: (“EXIT”) • Highest layer (Above ~ 500 km) • Some consider this outside the atmosphere • Blends with the complete vacuum of space (No limit) • Temperature drops again

40. How the Temperature Changes in the Layers • Temperature trends alternate from layer to layer • These shifts are the boundaries between layers • Memorize these!

41. Silly way to remember the order of the layers • E xtra • T errestrials • M ay • S wim • Tonight

42. Temperature Inversions • Warm air rises • Cold air sinks • Cool air during the winter, or from ocean influences, gets trapped beneath warmer air passing over mountains = temperature inversions

43. Temperature Inversions Denver, CO Salt Lake City, UT Los Angeles, CA

44. What Was the Early Atmosphere Like? • 4.4 billion years ago: • Formed by volcanic eruptions and meteorite impacts • Mostly carbon dioxide, water vapor, and some nitrogen • No known life A bright Geminid meteor pierces the night sky over California's Mojave Desert in 2009. http://news.nationalgeographic.com/news/2011/09/110907-gold-metals-earth-meteors-oldest-rocks-nature-science/

45. Plants Changed the Atmosphere • Tiny marine plants (cyanobacteria, phytoplankton, and algae) appear: • Photosynthesize carbon dioxide to oxygen • Over millions of years: carbon dioxide falls and oxygen rises

46. Evidence? • Fossils - Plants need carbon dioxide and animals need oxygen - Earliest fossils = plants only (so there was carbon dioxide)

47. Animal fossils later appear in rocks (so oxygen was in the air at that time)

48. More evidence • Glacial Ice Cores - Some glaciers (frozen rivers of ice) have existed for millions of years. - When the glacier freezes, it traps bubbles of the current atmosphere.

49. We can sample the glaciers (ice cores) and measure the abundance of gases trapped inside.

50. Ice cores show us that: Oldest ice contains no oxygen, but plenty of carbon dioxide and nitrogen As ice gets younger, the carbon dioxide falls and oxygen rises