Review Question In your own words, define Geography. BAD Answer: The science that studies the relationships between natural and cultural systems and the interdependence of the two over space and time These are not YOUR words!

Review Question Sunspots A) Are produced by coronal mass ejections B) Are caused by solar wind C) Have activity cycles D) Are clouds of electrically charged particles

Review Question According to Wein’s Law A) The electromagnetic spectrum divides radiant energy B) Longer wavelengths have higher energy C) Shorter wavelengths have high energy D) The Earth is an open system in terms of energy

Review Question Solar rays pass through more atmosphere before reaching the poles, so more energy is lost to ____________, ______________, and _______________. Absorption, scattering, and reflection

Chapter 2 Solar Energy to Earth and the Seasons Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen

Perihelion and Aphelion

The Seasons Seasonality: the variation of the sun’s position over the horizon; the changing daylength during the year Seasons result from: variations in the sun’s altitude – angle between the horizon and the sun the suns’s declination – latitude of the subsolar point and daylength - duration of exposure to insolation

Reasons for Seasons Revolution Rotation Tilt of Earth’s axis Axial parallelism Sphericity

Reasons for Seasons Revolution Earth revolves around the Sun Voyage takes one year Earth’s speed is 107,280 kmph (66,660 mph) Rotation Earth rotates on its axis once every 24 hours Rotational velocity at equator is 1674 kmph (1041 mph)

Revolution and Rotation Figure 2.13

Reasons for Seasons Tilt of Earth’s axis Axis is tilted 23.5° from plane of ecliptic Axial parallelism Axis maintains alignment during orbit around the Sun North pole points toward the North Star (Polaris) Sphericity

Axial Tilt and Parallelism Figure 2.14

Seasonal Observations Figure 2.17

Seasonal Observations SUMMER HEMISPHERE Carrollton = 33°N What is Sun’s angle (at noon) on June 21? 90 – |(latitude – subsolar point)| 90 – | (33 – 23.5) | = 80.5 ° WINTER HEMISPHERE 90 – (latitude + subsolar point) What is the Suns’ angle (at noon) on Dec 21? 90 – ( ) = 33.5 °

Seasonal Observations What is the noon altitude of the sun at Carrollton at the equinoxes? Use either summer or winter hemisphere equation 90 – |(latitude – subsolar point)| 90 – |(33 – 0)| = 57°

Annual March of the Seasons Winter solstice – December 21 or 22 Subsolar point Tropic of Capricorn Spring equinox – March 20 or 21 Subsolar point Equator Summer solstice – June 20 or 21 Subsolar point Tropic of Cancer Fall equinox – September 22 or 23 Subsolar point Equator

Annual March of the Seasons Figure 2.15

End of Chapter 2 Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen