Please use the analemma to answer the questions below. The Analemma You can calculate the angle of the sun’s rays relative to the Earth’s surface (noon sun angle) by using a graph called an Analemma. An Analemma shows the latitudinal position of the noon sun relative to the Earth’s surface throughout the year. The Latitude where the sun is directly over (Vertical) the Earth’s surface on any given day is known as Sub Solar Point (SSP). The first two pieces of information needed to calculate the ANS is a Latitude and SSP. The distance between Latitude and a SSP is called Zenith Angle (Z). Zenith Angle (Z) is the difference between your latitude and the Sub Solar Point (SSP). Zenith is an Absolute value and cannot be negative and is measured in degrees! Finding the Zenith Angle:
Please use the analemma to answer the questions below.
The Analemma
You can calculate the angle of the sun’s rays relative to the Earth’s surface (noon sun angle) by using a graph called an Analemma. An Analemma shows the latitudinal position of the noon sun relative to the Earth’s surface throughout the year. The Latitude where the sun is directly over (Vertical) the Earth’s surface on any given day is known as Sub Solar Point (SSP).
The first two pieces of information needed to calculate the ANS is a Latitude and SSP. The distance between Latitude and a SSP is called Zenith Angle (Z).
Zenith Angle (Z) is the difference between your latitude and the Sub Solar Point (SSP).
Zenith is an Absolute value and cannot be negative and is measured in degrees!
Finding the Zenith Angle:
If the Sub Solar Point (SSP) and your Latitude are in the same hemisphere, you need to take the difference between your latitude and Sub Solar Point (SSP) (expressed in absolute form).
If the Sub Solar Point (SSP) and your Latitude are in different hemispheres, you need to add your Latitude and the Sub Solar Point (SSP).
Finding the Noon Sun Angle:
By knowing Zenith Angle (Z), you can calculate the angle of the noon sun (ANS) for any Latitude on any date using the following formula:
Noon Sun Angle (ANS) =90 – Zenith Angle
***Noon Sun Angle is also expressed using the terms ANS or Solar Elevation (SE). You will see it both ways in this class.
Example 1: You want to find the noon sun angle for 100N Latitude on May 21st.
The Sub Solar Point (SSP) for May 21st is 20oN
The equation would be: ANS=90o– (20 – 10) or 80o
Example 2. You want to find the noon sun angle for 250S Latitude on May 21st.
The Sub Solar Point (SSP) for May 21st is 200N
The equation would be: ANS = 90o- (25 +20) or 45o
ANS is ALWAYS (900 - Zenith).
A negative answer means the sun never rose above the horizon.
Answer the following questions using the Analemma at to the back of this lab.
1. Using the Analemma, determine the Sub Solar Point (SSP) for the following dates. (N or S)
April 6th __________ January 21st __________
November 22nd _________ May 10th _____________
2. What is the noon sun angle (ANS) for the following dates, for a location of 38oN?
May 5th _____________ January 6th________________
March 21st _____________ Your Birthday ____________
3. What is the noon sun angle (ANS) for the following Latitudes on June 1st?
75oN _________________ 80oS ________________
25oN _________________ 52oS ________________
4. Today, what is the Latitude of the sub solar point?
5. What is the angle of the noon sun as seen from JJC today?
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