Geog 210 Assignment 1 Summer 2004

Earth-Sun Relationship

Due Date: Thursday June 24, 2004 *** Angles should NOT exceed 90º nor negative!!!.

NAME ______EQUINOXES – March 21 or September 23

At what latitude is the noon sun directly 1. Introduction overhead on this date? ______

The purpose of this assignment is to introduce What is the noon sun angle (altitude) for you to some of the important aspects of earth- sun relationship. In class I showed the 90 ºN ______23.5 ºS ______seasonal path of the earth using the globe and 66.5 ºN ______40 ºS ______slide projector (sun). Make sure that you need 40 ºN ______66.5 ºS ______to understand these fundamental relationships 23.5 ºN ______90 ºS ______by drawing and labeling the relative 0 ºN ______positions of the following features: Earth’s axis, North and South Poles, Equator, circle of illumination, subsolar point, Tropic of Cancer and Capricorn, Arctic and Antarctic Sun’s Rays Circles. Use the circles provided in the next section to draw these for all three cases. (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 OUR SUMMER SOLSTICE – June 21 the Earth revolves (axial parallelism). Thus, the latitude of the subsolar point, known as the At what latitude is the noon sun directly Sun’s declination, changes with seasons, and overhead on this date? ______the angle of the sun’s rays striking any given place on Earth changes throughout the year. What is the noon sun angle (altitude) for

As I told you in class, the noon sun angle can 90 ºN ______23.5 ºS ______be estimated by the simple formula 66.5 ºN ______40 ºS ______40 ºN ______66.5 ºS ______90 º - latitude (± declination of the Sun) 23.5 ºN ______90 ºS ______0 ºN ______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 Sun’s Rays

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 Geog 210 Assignment 1 Summer 2004

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