Review QuestionIn 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 QuestionSunspots

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 QuestionAccording 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 QuestionSolar rays pass through more atmosphere before reaching the poles, so more energy is lost to ____________, ______________, and _______________.

Absorption, scattering, and reflection

Chapter 2Solar Energy to Earth and

the Seasons

Geosystems 6eAn Introduction to Physical Geography

Robert W. ChristophersonCharles 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 sunthe suns’s declination – latitude of the subsolar pointand 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)

RotationEarth 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 parallelismAxis 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 + 23.5) = 33.5 °

Seasonal ObservationsWhat 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 SeasonsWinter solstice – December 21 or 22

Subsolar point Tropic of Capricorn

Spring equinox – March 20 or 21Subsolar point Equator

Summer solstice – June 20 or 21Subsolar point Tropic of Cancer

Fall equinox – September 22 or 23Subsolar point Equator

Annual March of the Seasons

Figure 2.15

End of Chapter 2

Geosystems 6eAn Introduction to Physical Geography

Robert W. ChristophersonCharles E. Thomsen