1. Variation of Insolation

2. When insolation strikes the Earth… ADD HERE
Variation in Intensity and Angle of Insolation
When insolation strikes the Earth… ADD HERE
Intensity of Insolation = The rate at which solar energy is received by a given area per unit of time.
Insolation is measured in joules/m/s.
There are several factors that can affect the intensity of insolation receives by a certain area on Earth’s surface.
90°

3. Earth’s Shape Factors that Affect the Intensity of Insolation
Sun’s Rays
90°
Earth is a sphere. Due to its shape… ADD HERE
All other areas of Earth’s surface would receive less direct insolation.

4. Factors that Affect the Intensity of Insolation
Earth’s Atmosphere
When the Sun is directly overhead, … ADD HERE
The Sun’s radiation passes through a smaller area of the atmosphere.
The Sun’s radiation passes through a greater area of the atmosphere. The radiation has a stronger chance of being reflected, absorbed or scattered in the atmosphere.

5. Latitude Factors that Affect the Intensity of Insolation
During the Summer Solstice
(June 21st), the maximum intensity of insolation (90°) strikes the Tropic of Cancer
– 23 ½ ° N
90°

6. Factors that Affect the Intensity of Insolation
Latitude
During the Winter Solstice (December 21st), the maximum intensity of insolation (90°) strikes the Tropic of Capricorn
– 23 ½ ° S
90°

7. Factors that Affect the Intensity of Insolation
Latitude
During the Fall and Spring Equinox (Sept. 23rd and March 21st ), the maximum intensity of insolation (90°) strikes the Equator 0°
90°

8. Factors that Affect the Intensity of Insolation
Seasonal Change
Due to the Earth’s tilted axis (23 ½ °) and the its revolution around the Sun, … ADD HERE

9. Time of Day Factors that Affect the Intensity of Insolation
Solar Noon
Maximum insolation will… ADD HERE

10. Duration of Insolation = … ADD HERE
Factors that Affect the Duration of Insolation
Duration of Insolation = … ADD HERE
Latitude and Seasonal Change

11. Factors that Affect the Duration of Insolation
Latitude and Seasonal Change
During the summer solstice, NY state receives more direct insolation because the Sun is higher in the sky. Likewise, the apparent path the Sun takes from sunrise to sunset is greater.
Sun rises North of East and sets North of West
Summer Solstice = 15 hrs. of daylight
Apparent Pathways of of the Sun from NY State
During the winter solstice, NY state receives less direct insolation because the Sun is lower in the sky. Likewise, the apparent path the Sun takes from sunrise to sunset is small.
Sun rises South of East and sets South of West
Winter Solstice = 9 hrs. of daylight
During the equinoxes, NY state receives more insolation when compared to the winter solstice, but less when compared to the summer solstice. Likewise, the apparent path the Sun takes from sunrise to sunset is greater when compared to the winter solstice, but less when compared to the summer solstice.
Sun rises dueEast and sets dueWest
Equinoxes = 12 hrs. of daylight

12. Relationship of Surface Temperature to Insolation
The temperature of the Earth’s surface at a given location will change throughout the day ….as well as throughout the year.

13. Yearly Maximum and Minimum Temperatures
In Westhampton Beach, the maximum intensity and duration of insolation is on June 21st – the Summer Solstice. Yet, the maximum temperature here is not felt until late July or early August.
Why???
Westhampton Beach, NY
June 21
81°F
Westhampton Beach, NY
August 3
93°F
It takes time for the change in balance between energy received from the sun (insolation) and energy lost from the Earth (surface radiation) to occur.
After the summer solstice, the Earth continues to heat up due to a general increase in insolation. It isn’t until a month later when the balance between incoming insolation and terrestrial radiation is the same.
The result? An increase in surface temperature!

14. Yearly Maximum and Minimum Temperatures
The same process occurs for when Westhampton Beach receives its minimum temperatures.
Westhampton Beach, NY
Dec. 21
37°F
Westhampton Beach, NY
February 3
20°F
It takes time for the change in balance between energy received from the sun (insolation) and energy lost from the Earth (surface radiation) to occur.
After the winter solstice, the Earth continues to lose heat due to a general decrese in insolation. It isn’t until a month later when the balance between incoming insolation and terrestrial radiation is the same.
The result? An decrease in surface temperature!

15. Times of Daily Maximum and Minimum Temperatures
In Westhampton Beach, the maximum intensity of insolation would be at solar noon – when the Sun is highest in the sky. Yet the maximum temperature of the day would not be at solar noon, but later in the afternoon.
Again, there is a need for a balance to be reached between insolation and terrestrial radiation. It takes time for the Earth’s surface to “heat up” after solar noon and for the surface temperature to reflect this.