Ch.17 Notes Mc Neely 2009


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Ch.17 Notes Mc Neely 2009

  1. 1. The Atmosphere Ch. 17 Earth-Space Science Bremen High School Teacher : Aaron McNeely
  2. 2. Weather and Climate (Sec 17.1) <ul><li>Earth’s Atmosphere: </li></ul><ul><ul><li>The gases that surround the earth </li></ul></ul><ul><ul><li>Where weather occurs </li></ul></ul><ul><li>Weather : The state of the atmosphere at a given place or time </li></ul><ul><li>Climate is based upon observations of weather over many years </li></ul><ul><li>Climate helps describe a place or region </li></ul>
  3. 3. Composition <ul><li>Air is a mixture of different gases and particles </li></ul><ul><li>Contents: </li></ul><ul><ul><li>Nitrogen (78%) </li></ul></ul><ul><ul><li>Oxygen (21%) </li></ul></ul><ul><ul><li>Argon and others (1%) </li></ul></ul>
  4. 4. Slice of Atmosphere? 1% CO 2 , Argon, Others 21% Oxygen 78% Nitrogen
  5. 5. Other Components <ul><li>Water vapor, source of all clouds and precipitation </li></ul><ul><li>Ozone, form of oxygen (O 3 ) that protects surface from sun’s ultraviolet light </li></ul>
  6. 6. Pollution <ul><li>Artificial gases and particles placed into the atmosphere </li></ul><ul><li>About half consists of automobile exhaust </li></ul>
  7. 7. Height of the Atmosphere <ul><li>Thins rapidly with height, also pressure </li></ul><ul><li>Atmospheric pressure is the actual weight of the atmosphere resting over your head </li></ul><ul><li>Rapid change in elevation can create uncomfortable pressure changes (ear popping) </li></ul>
  8. 8. Pressure vs. Altitude (height) <ul><li>Pressure lies along the bottom axis, altitude along the vertical </li></ul><ul><li>Below how many miles is roughly half of the atmosphere? </li></ul>
  9. 9. Atmospheric Layers <ul><li>The atmosphere is divided into four vertical layers based upon temperature changes </li></ul><ul><li>4 Layers : </li></ul><ul><ul><li>Troposphere </li></ul></ul><ul><ul><li>Stratosphere </li></ul></ul><ul><ul><li>Mesosphere </li></ul></ul><ul><ul><li>Thermosphere </li></ul></ul>
  10. 10. Troposphere <ul><li>Bottom layer </li></ul><ul><li>Temperature decreases with height </li></ul><ul><li>Height : 0-7 miles </li></ul><ul><li>Tropopause : Boundary between troposphere and stratosphere </li></ul><ul><li>Where most of our weather occurs </li></ul>
  11. 11. Stratosphere <ul><li>Second layer </li></ul><ul><li>Temperature remains constant, then increases with height </li></ul><ul><li>Height : 7-30 miles </li></ul><ul><li>Stratopause : Boundary between the stratosphere and mesosphere </li></ul><ul><li>The “ozone layer” lies at a height of 15 miles within the stratosphere </li></ul>
  12. 12. Mesosphere <ul><li>Third layer of the atmosphere </li></ul><ul><li>Temperature decreases with height </li></ul><ul><li>Height : 30-50 miles </li></ul><ul><li>Mesopause : Boundary between the mesosphere and Thermosphere </li></ul>
  13. 13. Thermosphere <ul><li>Lat layer, gradually merges into outer space </li></ul><ul><li>Temperature increases with height </li></ul><ul><li>Height : 50-90 miles </li></ul><ul><li>The aurora or northern lights occur in the thermosphere </li></ul>
  14. 14. Atmospheric Temperature Change <ul><li>Temperature lies along the bottom axis, height along the vertical </li></ul><ul><li>The behavior of temperature defines each of the atmospheric layers </li></ul>
  15. 15. Layers Summary <ul><li>Select the appropriate letter in the figure to the right that identifies each of the following layers of the atmosphere: </li></ul><ul><li>_____ mesosphere </li></ul><ul><li>_____ troposphere </li></ul><ul><li>_____ thermosphere </li></ul><ul><li>_____ stratosphere </li></ul>
  16. 16. Earth-Sun Relationships <ul><li>Earth’s Motions : Earth has two principal motions: </li></ul><ul><ul><li>Rotation : Earth’s 24 hour spin on its axis, results in the day </li></ul></ul><ul><ul><li>Revolution : Earth’s 365 day journey around the sun, results in the year </li></ul></ul>
  17. 17. Rotation & Revolution
  18. 18. Earth’s Seasons Northern hemisphere directed towards the sun Northern hemisphere directed away from the sun
  19. 19. Seasons <ul><li>The seasons begin with events named solstices and equinoxes </li></ul><ul><li>Winter and Summer, the most extreme of the seasons, are solstices </li></ul><ul><li>Spring and Autumn, the “middle” seasons, are equinoxes </li></ul>
  20. 20. Season Summary Tropic of Capricorn (-23.5) Winter (N) Summer (S) Dec 21 Solstice Equator (0) Autumn (N) Spring (S) Sept 21 Equinox Tropic of Cancer (+23.5) Summer (N) Winter (S) June 21 Solstice Equator (0) Spring (N) Autumn (S) Mar 21 Equinox Sun Overhead (latitude) Season (North & south) Event
  21. 21. Seasons Summary <ul><li>Select the appropriate letter in the figure below that identifies each of the following months: </li></ul><ul><li>_____ March </li></ul><ul><li>_____ June </li></ul><ul><li>_____ December </li></ul><ul><li>_____ September </li></ul>
  22. 22. Earth’s Orientation & Seasons <ul><li>Earth tilted 23.5° compared to the sun </li></ul><ul><li>Earth’s axis tilted compared to its orbit </li></ul><ul><li>Tilt results in the northern and southern hemispheres of earth each being directed toward the sun at different times during the year </li></ul><ul><li>Tilt is cause of earth’s seasons </li></ul><ul><li>Axis will always point to the star Polaris (North Star) in our lifetimes </li></ul>
  23. 23. Earth’s Tilted Axis
  24. 24. <ul><li>Geography: Seasons </li></ul>
  25. 25. Length of Day & Night <ul><li>Changes due to earth’s tilt and revolution </li></ul><ul><li>Equinoxes, both day and night are 12 hours </li></ul><ul><li>Summer solstice, more hours of day, less of night </li></ul><ul><li>Winter solstice, less hours of day, more of night </li></ul>
  26. 26. Day & Night Hours Midnight Noon Days
  27. 27. Earth’s Tropics <ul><li>The two Tropics lie 23.5 ° north and south of the equator </li></ul><ul><li>Latitudes where the noon sun is directly overhead during summer and winter </li></ul><ul><li>At the equinoxes, the noon sun lies directly overhead at the equator </li></ul>
  28. 28. Arctic & Antarctic <ul><li>Arctic and Antarctic circles both lie 90°-23.5° = 66.5° north and south </li></ul><ul><li>Areas greater in latitude of the circles can experience 24 hours of day and night depending on the seasons </li></ul>
  29. 29. Tropics and Circles
  30. 30. Equinoxes
  31. 31. Planetary Positions <ul><li>In elliptical orbits </li></ul><ul><li>Perihelion : Position closest to sun </li></ul><ul><li>Aphelion : Position farthest from sun </li></ul><ul><li>Earth </li></ul><ul><ul><li>Perihelion: Jan 02 </li></ul></ul><ul><ul><li>Aphelion: July 04 </li></ul></ul>
  32. 32. Elliptical Orbit (Keplerian) Sun Earth Oval in diagram is very exaggerated, earth’s orbit is close to circular
  33. 33. Earth’s Revolution <ul><li>At perihelion, earth revolves faster in its orbit, slower at aphelion </li></ul><ul><li>Sun’s apparent size changes slightly as a result </li></ul>
  34. 35. Close and Far
  35. 36. Climate Factors (Sec 17.3) <ul><li>The main determinant of climate is latitude </li></ul><ul><li>Closer to equator, warmer climate </li></ul><ul><li>Other: </li></ul><ul><ul><li>Large bodies of water </li></ul></ul><ul><ul><li>Altitude </li></ul></ul><ul><ul><li>Cloud cover </li></ul></ul><ul><ul><li>Ocean currents </li></ul></ul>
  36. 37. Land and Water <ul><li>Land heats rapidly and to higher temperatures compared to water </li></ul><ul><li>Land also cools rapidly and to lower temperatures than water </li></ul><ul><li>Marine locations have a nicer climate </li></ul><ul><li>Southern Hemisphere : More ocean than land creates moderate climates </li></ul>
  37. 38. Ocean vs. Land
  38. 39. Hemispheres N S E W
  39. 40. Altitude <ul><li>Higher elevations experience a cooler climate compared to locations near sea level </li></ul>
  40. 41. High and Low Altitude
  41. 42. Cloud Cover <ul><li>Albedo : The fraction of total radiation that is reflected by a surface </li></ul><ul><li>Clouds have high albedos </li></ul><ul><li>Cloud cover creates a cooler day, a warmer night </li></ul><ul><li>In day, clouds provide shade </li></ul><ul><li>At night, clouds prevent the heat from escaping into space </li></ul>
  42. 43. Cool Days, Warm Nights Cloudy skies create cooler days and warmer nights
  43. 44. Urban Heat Islands <ul><li>Cities are often 6-8 º warmer than surrounding countryside </li></ul><ul><li>Reasons: </li></ul><ul><ul><li>Less green plants </li></ul></ul><ul><ul><li>Concrete structures and roads absorb heat, release slowly at night </li></ul></ul>
  44. 45. Wash DC Urban Heat Island
  45. 46. Urban Heat Island Profile
  46. 47. World Temperatures <ul><li>Isotherms are lines on a weather map connecting points of equal temperature </li></ul><ul><li>Temperatures generally range east to west, parallel to latitude </li></ul><ul><li>Temps decrease from equator to poles </li></ul>
  47. 48. Isotherms <ul><li>The lines generally trend west to east, and cooler from south to north </li></ul>
  48. 49. Ocean Isotherms