Geog 210 Assignment 1 Fall 2002
Earth-Sun Relationship
Geog 210 Assignment 1 Fall 2002
Due Date: Tuesday October 15, 2002
NAME ______
1. Introduction
The purpose of this assignment is to introduce you to some of the important aspects of earth-sun relationship. In class I showed the seasonal path of the earth using the globe and slide projector (sun). Make sure that you need to understand these fundamental relationships by drawing the relative positions of the following features: Earth’s axis, North and South Poles, Equator, circulation of illumination, subsolar point, Tropic of Cancer and Capricorn, Arctic and Antarctic Circles. Use the circles provided in the next section to draw these. (each 1 point, 10 points total for each diagram)
2. Sun angle
As you recall, the earth’s axis remains a constant tilt with respect to the solar system as the Earth revolves (axial parallelism). Thus, the latitude of the subsolar point, known as the Sun’s declination, changes with seasons, and the angle of the sun’s rays striking any given place on Earth changes throughout the year.
As I told you in class, the noon sun angle can be estimated by the simple formula
90 º - latitude (± declination of the Sun)
In other words, for equinox conditions, when the subsolar point is at the Equator (declination = 0º), the noon angle for any place on earth is simply 90 º - latitude
For solstice conditions,
If the sub-solar point is “in” the hemisphere of the place in question, add 23.5º
If the sub-solar point is “out” the hemisphere of the place in question, subtract 23.5º
*** Angles should NOT exceed 90º !!!.
EQUINOXES – March 21 or September 23
At what latitude is the noon sun directly overhead on this date? ______
What is the noon sun angle (altitude) for
90 ºN ______23.5 ºS ______
66.5 ºN ______40 ºS ______
40 ºN ______66.5 ºS ______
23.5 ºN ______90 ºS ______
0 ºN ______
Sun’s Rays
OUR SUMMER SOLSTICE – June 21
At what latitude is the noon sun directly overhead on this date? ______
What is the noon sun angle (altitude) for
90 ºN ______23.5 ºS ______
66.5 ºN ______40 ºS ______
40 ºN ______66.5 ºS ______
23.5 ºN ______90 ºS ______
0 ºN ______
Sun’s Rays
OUR WINTER SOLSTICE – December 22
At what latitude is the noon sun directly overhead on this date? ______
What is the noon sun angle (altitude) for
90 ºN ______23.5 ºS ______
66.5 ºN ______40 ºS ______
40 ºN ______66.5 ºS ______
23.5 ºN ______90 ºS ______
0 ºN ______
Sun’s Rays
3. Day length
The duration of solar energy received at a location is a function of the length of time in the Sun above the horizon.
3.1 On what dates are the lengths of day and night exactly equal for all locations on the globe?
______& ______
At the June 21 solstice (our summer solstice)
3.2 What portion of the Earth’s surface is exposed to the Sun’s rays for 24 hours?
______
3.3 What portion receives no radiation in a 24 hour period?
______
3.4 Day length at the Equator will be _____hrs