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The Atmosphere: Composition, Structure & Temperature
Earth-Sun Relationships
Honors E&S 1
Earth-Sun Relationships
Nearly all of the energy that drives Earth’s variable weather & climate comes from

the sun
o Earth intercepts only a minute percentage of the energy given off by the Sun less than one two-billionth
Solar energy is not distributed evenly over Earth’s surface

o Varies with latitude, time of day, and season

Unequal heating of Earth creates winds and drives the ocean’s currents

Variations in solar heating are caused by the motions of Earth relative to the Sun by
variations in Earth’s land-sea surface
Earth’s Motion

Rotation is the spinning of Earth about its axis
o Once every 24 hours

Circle of illumination- line separating the dark half of Earth from the
lighted half

Revolution refers to the movement of Earth in its orbit around the Sun
o Earth travels at 113,000 km/min (70,000 mph) in an elliptical orbit
Seasons

Long summer days expose us to more solar radiation
 Annual shifting of the solar angle or altitude of the Sun
o Affects the amount of energy received at Earth’s surface

When Sun is high in the sky the solar rays are most concentrated

The lower the angle, the more spread out and less intense the solar
radiation reaching the surface
o Angle of the sun determines the amount of atmosphere the rays must
penetrate
Shultz revision of Schott ‘04
D:\769871556.doc
1
The Atmosphere: Composition, Structure & Temperature
Earth-Sun Relationships

Honors E&S 1
The longer the path, the greater the chances for absorption, etc.
o The nearer a place is to the latitude receiving vertical rays of the Sun, the higher
will be its noon Sun and the more intense will be the radiation it receives
Earth’s Orientation

Causes fluctuations in the Sun angle & length of daylight

Earth’s axis is tilted at 23.5, called the inclination of the axis
o No inclination would mean no seasons

Always pointed the same direction (North Star)
Solstices and Equinoxes

On June 21 or 22, Earth is in a position where the axis of the northern hemisphere is
tilted 23.5 toward the sun
o Vertical rays strikes 23.5 N latitude

Tropic of Cancer
o In Northern Hemisphere = Summer Solstice
 On December 21 or 22, Earth is in an opposite position
o Vertical rays strike 23.5 S

Tropic of Capricorn
o In Northern Hemisphere = Winter Solstice
 Equinoxes occur halfway between solstices (equal night)
o September 22 or 23 = autumnal equinox
o March 21 or 22 = spring equinox (vernal)
o Sun’s rays are located at 0
Shultz revision of Schott ‘04
D:\769871556.doc
2