Seasons. Reasons for the Seasons: Tilt of Earth ’ s axis Axial parallelism Sphericity.
-
Upload
abner-paul -
Category
Documents
-
view
222 -
download
0
Transcript of Seasons. Reasons for the Seasons: Tilt of Earth ’ s axis Axial parallelism Sphericity.
Seasons
Reasons for the Seasons:
• Tilt of Earth’s axis
• Axial parallelism
• Sphericity
Landmark dates ...
December Solstice • December 21/22
March Equinox • March 20/21
June Solstice • June 20/21
September Equinox, • September 22/23
Landmark latitudes ...
Equator = 0o
Tropic of Cancer = 23.5oN
Arctic Circle = 66.5oN
Tropic of Capricorn = 23.5oS
Antarctic Circle = 66.5oS
On each day,…..1. What is subsolar point (SSP)?
SSP is latitude where sun is directly
overhead; where sun’s rays are vertical.
2. At what latitude will sun’s rays be oblique/tangent?
3. Where is Circle of Illumination?
separates light and dark halves
December Solstice
1.SSP?
23.5oS
2. tangent rays ?
66.5oN, 66.5oS
3. C.I. is tangent?
at 66.5oN, 66.5oS
March Equinox
1.SSP?
0°
2. tangent rays?
90oN, 90oS
3. C.I. is tangent?
at 90°N, 90°S
June Solstice
1. SSP?
23.5oN
2. tangent rays?
66.5oN, 66.5oS
3. C.I. is tangent?
66.5oN, 66.5oS
September Equinox
1.SSP?
0°
2. tangent rays ?
90oN, 90oS
3. C.I. is tangent?
at 90°N, 90°S
Animated tour of the seasons
Annual March of the Seasons
Angle of noon sun in a location=
90 - difference in degrees between latitude
of location and SSP
Latitude?
Solution:Angle of noon sun (March 22) = 50SSP (March 22) = 0
50 = 90 – (? – 0)? = 40
for June 21:73 = 90 – (?-23.5)?-23.5 = 27? = 40.5
What is the angle of the noon sun in Duluth on September Equinox?
= 90 – ( 47N – 0)
= 43 degrees
What is the angle of the noon sun in Duluth on December Solstice?
= 90 – ( 47N – 23.5 S)
= 90 – 70.5
= 19.5 degrees
What is the angle of the noon sun in Duluth on June Solstice?
= 90 – (47N – 23.5 N)
= 90 – 23.5
= 66.5 degrees
What is the angle of the noon sun in Duluth today (January 27)?
SSP today is approx. 20˚S.
= 90 – (47N – 20 S)= 90 – 67= 23 degrees