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Earth’s Motions, Solar Radiation, and the Seasons

Earth’s Motions, Solar Radiation, and the Seasons. Rotation - The spinning of the Earth on its Axis. It takes the Earth 23 hours, 56min, and 4 seconds to rotate. Earths Rotation Causes sunrise / sunset star trails daily events. The Earth Rotates in a Counterclockwise Direction (CCW).

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Earth’s Motions, Solar Radiation, and the Seasons

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  1. Earth’s Motions, Solar Radiation, and the Seasons

  2. Rotation- The spinning of the Earth on its Axis

  3. It takes the Earth 23 hours, 56min, and 4 seconds to rotate.

  4. Earths Rotation Causessunrise / sunset star trails daily events

  5. The Earth Rotates in a Counterclockwise Direction (CCW)

  6. Revolution- The Earth Revolves around the Sun

  7. It take the Earth 365 days to Revolve around the Sun

  8. Earths Revolution CausesSeasonsAnnual Events

  9. The Earth Revolves in its orbit in a Counterclockwise Direction (CCW)

  10. A. Earth's Revolution and Rotation

  11. 1. The earth's orbital path is an ellipse: (a flattened out circle)

  12. 2. Perihelion= point of closest approach to the sun (January) = 9.1x107 miles

  13. 3. Aphelion= point of farthest approach = 9.4x107 miles (July)

  14. 4. Earth's rotation= spin about it's axis. Axis points to Polaris (the North Star)

  15. B. Solstices and EquinoxesTilt of the earth's axis = 23.50 always pointed to Polaris

  16. Tilt

  17. 1. Summer Solstice = June 21 Northern hemisphere receives the sun's light most directly (insolation) First day of summer. On the summer solstice, the direct sun rays are at =23.50 N latitude = the tropic of Cancer

  18. Summer Solstice • Sunlight is most direct at the Tropic of Cancer (23.5 N) on ~ June 21.

  19. Tropic of Cancer Equator Prime Meridian Tropic of Capricorn SOLSTICE Summer (June 21st-ish) Sun Located at the Tropic of Cancer Winter (December 21st-ish) Sun Located at the Tropic of Capricorn

  20. Local Noon Shadow

  21. June Solar Insolation

  22. 2. Winter Solstice = December 21 Northern hemisphere receives the sun's light least directly. First day of winter. On the winter solstice, the direct sun rays are at 23.50 S latitude = the tropic of Capricorn

  23. Winter Solstice • Sunlight is most direct at the Tropic of Capricorn (23.5 S) on ~ January 21.

  24. Local Noon Shadow

  25. Solar Insolation • Energy received by the earth at various latitudes for December 21 (solstice)

  26. December Solar Insolation

  27. 3. Equinoxes: days in which the direct sunlight is on the equator. Equal heating on both hemispheres. Days = nights.

  28. a. Mar 21. the vernal equinox. First day of spring Direct rays of the sun are directly above the Equator.

  29. b. Sept. 21: the autumnalequinox: first day of fall. Direct rays of the sun are directly above the Equator.

  30. Tropic of Cancer Equator Prime Meridian Tropic of Capricorn EQUINOX Equinoxes (Equal Day and Equal Night, 12 hours) Spring (Vernal Equinox) March 21st-ish Fall (Autumnal Equinox) September 21st-ish Sun Located on Celestial Equator (Earth’s Equator)

  31. Equinox Shadow Sun rises due East, Sun sets due West

  32. 4. Solar Declination: latitude where the noontime sun is directly overhead, on any given day.

  33. 5. Factors that affect the amount of insolation we get.

  34. a. Amount of daylight:longer day => more heatshorter day => less heatArtic Circle = +66.50 N lat. no day in winter, no night in summer.Antarctic Circle = 66.50S lat.

  35. Day Light Hours (Solstice)

  36. Day Light Hours (Equinox)

  37. Day Light Hours

  38. b. Solar angle:The smaller the solar angle, the more the beam is spread out => less intensity => less heat

  39. Changing Aspect Angle • Direct Sunlight is more intense and concentrated. • Solar Incidence Angle is Latitude and Time Dependent • Seasonal and Diurnal

  40. c. Beam Depletion:Some of the sun's light is reflected back into space, and some is absorbed. The rest goes through.

  41. Incident Angle

  42. Earth’s Circle of Illumination 50 % of the earth’s surface is illuminated by the sun, every hour of every day.

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