GEOG 1300 Chapter 2 and 3a
The solar system, Sun, and Earth.
Earth’s orbit is elliptical. At perihelion (closest) on January 3. At aphelion (furthest) on July 4.
Solar Winds are responsible for the auroras.
Seasonality refers both to the seasonal variation of the sun’s position above the horizon and
changing day lengths during the year.
Seasonal variation is response to the sun’s altitude (angle between the horizon and the sun).
The sun’s declination is the latitude of the sub solar point.
Reasons for the seasons
Revolution: Speed with Earth’s distance from the sun determines the time required for one
complete Orbit around the sun.
Rotation: Turning of the Earth on its axis, reasons for day and night. Circle of illumination is the
dividing line between day and night, intersects the equator.
1. Coriolis Effect- Deflection of air and water
2. Tides- water reacts to gravitational pull of sun and moon
3. Day and Night- variations of exposure to sunlight.
Tilt of the Earth’s axis: The tilt is 23.5; this is relative to the plane of the ecliptic. A plane that
touches all points of Earth’s orbit. This leads to the North Star.
Axial Parallelism: remains in fixed alignment with Polaris throughout the year.
Sphericity- Uneven distribution of sunlight to the Earth’s Surface
Annual March of the Seasons
Solstices- Sun’s perpendicular (vertical rays) hit 23.5 N or S
1. June Solstice- Summer in North, longest day of the year. June 20-21
2. December Solstice- Winter in N shortest day of the year. December 21-22