1. Lab # 9 pg 179 Earth – Sun Relations

2. Weather ► The state of the atmosphere at a particular place for a short period of time. ► Described by measuring the four basic elements: temperature, moisture, air pressure, and wind (direction and velocity).

3. Temperature ► Most important variable; it controls the other variables. ► Example cool air high pressure system, and warm air low pressure system. ► Earth is heated from the Sun.

4. Solar Heat ► Intensity - the angle at which the rays strike the surface of the Earth. ► Duration- number of hours of daylight in a 24 hour period. ► They both will determine the amount of solar radiation any place on Earth will receive.

5. Ray Diagram on Pg 180 ► The angle from the Sun to point A is 90 O. The sun beam projected will cover an area of 10mm. ► If the angle from the Sun to point B is 30 O. The sun beam projected will cover an area of 17mm. ► Thus the rays hitting point A are?? Stronger

6. Solar Radiation ► Why is it warmer at the equator? ► The greater the angle the stronger the intensity. ► Tropic of Cancer – 23.5 N Lat. ► Tropic of Capricorn – 23.5 S Lat.

7. Solar radiation would be constant if it were not for: ► The Earth’s rotates on its axis on a 23.5 0 and revolves around the Sun ► Throughout the year the Earth’s axis is pointed to the same place. ► The Earth rotates counter clockwise ► One whole revolution = 24 hours. ► If the Earth was not titled then we would not have seasons.

8. Days of the year ► Summer Solstice – (ours June 20-22) longest day of the year the day with the greatest number of hours of daylight. ► Winter Solstice – (ours Dec 21) shortest day of the year because it is the day with the least hours of daylight.

9. Circle of Illumination ► This is what gives us darkness at night and light during the day. ► Arctic circle – 66.5 O N Latitude ► Antarctic circle – 66.5 O S Latitude ► Both have 24 hours with and without sun.

10. Solstice # 1 ► June 20-22 ► For us this is the Summer Solstice. ► Rays of the Sun are directed toward the Tropic of Cancer. The rays hit this area at 90 O. ► If we lived below the equator then it would be the Winter Solstice. ► Because of the tilt, more solar intensity hits the tropic of Cancer and less at the tropic of Capricorn. ► Circle of illumination South pole 0 hrs of sun and North pole 24 hours of sun.

11. Equinox ► Rays of the Sun are migrating between the Tropic of Cancer and the Tropic of Capricorn. ► At this time rays of the Sun are vertical at the equator. ► This occurs Mar 21-22 and Sept 22-23

12. Solstice # 2 ► Dec. 20-22 ► For us this is the Winter Solstice. ► Rays of the are directed toward the Tropic of Capricorn. The rays hit this area at 90 O. ► At this time the rays hit the equator at less then 90 O. ► The rays hit the Tropic of Cancer at a smaller angle. ► Remember the greater the angle the stronger the intensity. ► Circle of illumination N pole 0 hrs of sun and South 24 hours of sun.

13. Equinox ► Suns rays hitting Equator at 90 O angle ► Less at both tropics ► First day of spring and fall. ► March 21 - 22 and Sept. 21 - 22 ► Circle of illumination cuts through the poles, thus 12 hours of light and dark at the poles.

14. The Sun is Directly Overhead Equator 0 O Lat. Overhead Mar 21 and Sept. 21 Tropic of Cancer 23.5 O N Lat. Overhead on June 21 Tropic of Capricorn 23.5 O S Lat. Overhead Dec. 21

15. Analemma Figure 12.5 pg 183 ► Tells us where the sun is overhead at noon time in the world. ► Used for navigation before GPS. ► Nov.4 the sun is overhead at noon time at 15 O S Latitude ► April 15 9 O N Latitude

16. Chapter Summary pg 187 ► Questions 1, 4, 5 & 6 ► # 1 Solar radiation 0 O - 30 O = 50% 30 O - 60 O = 36% 60 O - 90 O = 14% ► # 4 The greater the angle the stronger the intensity.  This is because of the angle that the rays hit the Earth.