Atmosphere

1. Atmosphere

2. What is it? • The gaseous portion of the planet; its envelope of air • Weather is the state of the atmosphere at any given time and place • Climate is weather over many years in a specific location

3. What composes the Atmosphere? • Nitrogen and oxygen make up most of the dry atmosphere • Nitrogen makes up about 78% • Oxygen is about 21% • Argon is about 0.93% • Carbon dioxide is 0.397% • Other gases including neon, helium and methane make up the rest • Water vapor is present at about 0.25% by mass (varies from ~0% to 4%)

5. What composes the atmosphere • Carbon dioxide is important because it is an active absorber of heat (greenhouse gas) • Water vapor is also important because it is the source of clouds and precipitation • Water vapor also absorbs heat given off by the Earth and solar energy from the sun

6. Ozone • Ozone (O3) is very crucial to life on Earth • Single oxygen molecules combine with O2 to create O3 in the presence of a catalyst • Filters most of the UV radiation from the sun • Ozone is most common in the stratosphere (layer of the atmosphere) • Low level ozone (troposphere) is a pollutant • Component of smog • Interferes with photosynthesis and stunts growth in plants • Also acts as a greenhouse gas

7. Layers of the Atmosphere • Troposphere: 0-15km • Stratosphere: 15-50 km • Mesosphere: 50-85 km • Thermosphere: 85-1000 km • Atmosphere properties video:

8. Layers of the Atmosphere

9. Layers of the Atmosphere • Troposphere is the location of weather and greenhouse effect • Temperature decreases as you increase altitude (17ºC to -52ºC) • Contains 75% of the atmosphere by mass and 90% of the water vapor

10. Layers of the Atmosphere • Stratosphere is where the ozone layer resides, protecting the planet from UV radiation • Temperature increases and you increase altitude (top stratosphere ~3ºC) • Planes cruise at the bottom of the stratosphere • Contains 20% of the atmosphere by mass

11. Layers of the Atmosphere • Mesosphere is where meteors burn up • Temperature decreases as you increase altitude (low as -90ºC); coldest layer • Contains very few molecules of atmosphere

12. Layers of the Atmosphere • Thermosphere contains the ionosphere which causes the northern lights and the reflection of radio waves • Temperature increases as you increase altitude (up to 2000ºC) • Contains very few molecules of atmosphere • Standard Deviants

13. Why is the sky blue? • Weather Channel video

14. How do we affect the Atmosphere?

15. Carbon Cycle • Generally, anything made of carbon is organic • Carbon is also found in diamonds, graphite, and most recently carbon nanotubes

16. Carbon cycle • Carbon gets stored in pools (or sinks) including plants and animals, soil and rocks, fossil fuels, oceans, and the atmosphere • Atmosphere: carbon dioxide • Plants/animals: energy sources • Ocean and soil can absorb some carbon dioxide from the air • Fossil fuels can store carbon long term (released when they are burned)

17. Carbon cycle

18. Plants/animals • Respiration (plants or animals) release carbon into atmosphere • Living plants are mostly carbon sinks, locking up carbon into sugar • When organisms die they release their carbon • Burning a tree releases carbon into the atmosphere

19. Rocks/soil • Rocks and soil absorbs carbon from the atmosphere • Sedimentary rocks (limestone, chalk, etc) can store lots of carbon for long periods • Typically held until released by a volcano • Fossil fuels store large amounts of carbon and are released into the atmosphere when burned

20. Oceans • Oceans store large amounts of carbon (much in the form of carbonates, often on the sea floor) • Gradually transformed into sedimentary rocks • Increase in water temperature may reduce carrying capacity of oceans • Increase in carbon in the oceans/water leads to increasing the acidity

21. Nitrogen Cycle • Nitrogen is also necessary for life • DNA and proteins wouldn’t exist without nitrogen • Fortunately there is a lot of nitrogen in the atmosphere • N2 must be split into individual nitrogen atoms to be usable: nitrogen fixation • Nitrogen has several pools (sinks): atmosphere, plants/animals, soil/rocks, and oceans • APEX Videos

22. Nitrogen Cycle • Most nitrogen fixation is done by bacteria, small amount occurs due to lightning • Plants obtain nitrogen from soil • Animals obtain nitrogen by eating • Animal wastes and decaying organisms return nitrogen to the soil- must be reprocessed by bacteria • Some nitrogen can be transferred from soil/rocks to atmosphere by volcanic eruptions • Nitrogen reaches rivers/ocean by runoff (some is good, but there can be too much

23. Human Effect on Nitrogen Cycle • Humans have added nitrogen to the atmosphere, oceans, ground/soil • Atmosphere: industrial pollutants • Ground/soil: crop fertilizers • Rivers/oceans: fertilizer runoff • Nitrogen runoff leads to fast growth of algae: eutrophication (use up too much oxygen) • Nitrogen oxide pollutants lead to nitric acid (acid rain)

25. The Sun and Heat • If the sun turned off the Earth would drop to below -200ºC within 2 weeks • Sun’s heat keeps the Earth’s cycles in balance • Heat is actually energy in transit • When something hot touches something cold, heat is transferred from the hot to the cold object • What happens when you leave a hot drink on the counter

26. Heat transfer • Three ways heat moves between objects: radiation, convection, and conduction • Radiation is transfer of heat by light waves (sun heating Earth with UV, visible, and infrared light) • Conduction is transfer of heat by direct contact (heating hamburger) • Convection is the transfer of heat by movement of gases or liquids (steam from hot chocolate, hot air rises and cold air sinks) • APEX Videos

27. Radiation • Three things happen when radiation hits something: transmission, reflection, absorption • Transmitted light goes through object without affecting it very much (window) • Some light can be reflected (see yourself in a window/mirror) • Some light is absorbed, heating the material (black car hood most is absorbed)

28. Radiation

29. Radiation • Black items absorb more radiation than white things (becomes warmer) • What you actually see is the reflected light from the object, not what is absorbed

30. Heat capacity • Heat capacity is the ability of an object to hold heat • Water has a large heat capacity, this means that it takes a lot of heat to raise the temperature • Takes a lot more energy to raise the temperature of the oceans than the atmosphere • Oceans stabilize the Earth’s temperature

31. Heat capacity • Different surfaces on Earth heat up differently • Differences in temperature cause convection • Convection drives ocean and wind currents • In particular, it is the primary driver of weather

32. Heating the Earth

33. Heating the Earth • 70% reaches the Earth • Some absorbed by atmosphere • Most absorbed by Earth, which is then radiated out as infrared light, use for photosynthesis, or moved by conduction or convection

34. Heating the Earth

35. Greenhouse effect • A car left in the sun on a hot day is a great example of the greenhouse effect • Most of the light is transmitted though the windows • Absorbed by inside of the car (upholstery) • Re-emits it as infrared radiation • Glass reflects more infrared than visible, trapping in the heat • APEX Videos

36. Greenhouse Gases • Water vapor • Carbon dioxide • Methane • Nitrous oxide • Other manmade chemicals

37. Why the Wind Blows? • Different parts of Earth heat up different amounts • The heating differences make air move around as it tries to reach equilibrium of temperature and pressure • Conditions change, so balance is never reached • Different places receive different amounts of solar radiation (equator vs. poles)

38. Why the Wind Blows • Different environments reflect different amounts of light (albedo: snow vs. ocean, 95% vs. 10%) • Antarctica is colder because it has more ice compared to Artic circle with more water • Rotation of Earth causes how much radiation a location receives to change throughout day • (Daily heating and cooling is called diurnal cycle) • Tilt of the Earth’s axis creates seasons as we revolve around the sun (APEX videos)

39. Why the Wind Blows • Clouds can retain heat at night (trap long wavelength infrared radiation) • They also block sunlight during the day, keeping the Earth cooler • In general clouds cool the planet by 11ºC (~20ºF)

40. Why the Wind Blows • When cold and warm air mix, the more dense cold air ends up on the bottom • Leads to a difference in air pressure • Warm air expands and rises, cold air shrinks and compresses • The higher air pressure tries to reach equilibrium with lower pressure: generally moves toward the low pressure side

41. Air moving do to pressure • APEX Diagrams

42. Why the Wind Blows • During the day water remains cooler than the land (heat capacity) • Results in a sea breeze: wind blowing from the ocean to land during the day • At night land cools quickly while the water remains warm • Results in a land breeze: wind blowing from land to sea during night

43. Why the wind blows • Elevation differences also create localized wind patterns • Sun heats up sides and bottom of valley • Warmed air moves up sides of valley: valley breeze • Middle of the valley’s air is not heated as much causing the rising air to expand into a cooler area, eventually falling back to the bottom • At night the reverse occurs: mountain breeze • APEX videos

44. Which way the wind blows • Different temperatures caused by uneven heating is the driving force of weather events • The biggest difference in temperature is between the poles and the equator • Hot areas (equator) become low pressure zones (L) as warm air leaves • High-pressure area is created high above the surface • Cold areas (poles) become high pressure zones (H) • Low-pressure area created high above surface

45. Which way the wind blows • High pressure above equator, low pressure above poles in the troposphere • Creates circulating wind as air flows from high to low pressure

46. Which way the wind blows • Winds do not appear to go in straight line on the surface due to the Coriolis effect • Curves the wind due to rotation of the Earth • Causes a massive amount of variation in the pattern of global air flow • Three major convection cells: a circular movement created by the transfer of heat energy • APEX videos

47. Which way the wind blows

48. Which way the wind blows • Terminology note: eastern wind means it is coming from the east • Three major wind systems: trade winds, westerlies, and easterlies • Trade winds blow from horse latitudes to equator • Westerlies blow from horse latitude to subpolar lows • Easterlies blow from polar regions to subpolar regions • APEX Videos

49. When winds collide • A polar front is the area between polar easterlies and westerlies • Cold air from pole meets warm air from westerlies • Along the front is the polar jet stream (fast moving “river” of air about 10km up) which travels around 250mph • Jet stream follows roughly the subpolar low-pressure zone • Subtropical jet stream occurs between trade winds and westerlies (around horse latitudes)

50. When winds collide • In the U.S. unusually cold weather is the result of the jet stream dipping south and bring cold air from the north • Keep in mind that the location of the jet stream and polar front changes over time