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Earth-Sun Relations Lab# 10 Exercise #12 page 173. 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). Temperature.
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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).
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.
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.
Ray Diagram on Page 174 • The angle from the Sun to point A is 90O.The sun beam projected will cover an area of 10mm. • If the angle from the Sun to point B is 30O. Thesun beam projected will cover an area of 17mm. • Thus the rays hitting point A are?? Stronger
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.
Solar radiation would be constant if it were not for: • The Earth’s rotates on its axis on a 23.50 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.
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.
Circle of Illumination • This is what gives us darkness at night an light during the day. • Artic circle – 66.5 ON Latitude • Antarctic circle 66.5 OS Latitude • Both have 24 hours with and without sun.
Solstice # 1 • June 20-21 • For us this is the Summer Solstice. • Rays of the Sun are directed toward the Tropic of Cancer. The rays hit this area at 90O. • 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.
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 20-22 and Sept 20-22
Solstice # 2 • Dec. 20-21 • For us this is the Winter Solstice. • Rays of the are directed toward the Tropic of Capricorn. The rays hit this area at 90O. • At this time the rays hit the equator at less then 90O. • 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.
Equinox • Suns rays hitting Equator at 90O 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.
The Sun is Directly Overhead Tropic of Cancer 23.5O N Lat. Overhead on June 21 Equator 0O Lat. Overhead Mar 21 and Sept. 21 Tropic of Capricorn 23.5O S Lat. Overhead Dec. 21
Analemma Figure 12.6 page 177 • 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 15O S Latitude • April 15 9O N Latitude
Chapter Summary pg 181 • Questions 1,5,6 &10 • # 1 Solar radiation 0O-30O = 50% 30O-60O = 36% 60O-90O = 14% • The greater the angle the stronger the intensity. • This is because of the angle that the rays hit the Earth.