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Variation of Insolation. Insolation can vary by changes in its intensity and duration . Variation in Intensity and Angle of Insolation. When insolation strikes the Earth at 90° (perpendicular to the Earth surface), it has maximum intensity .
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Variation of Insolation Insolation can vary by changes in its intensityand duration.
Variation in Intensity and Angle of Insolation When insolation strikes the Earth at 90° (perpendicular to the Earth surface), it has maximum intensity. 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°
Factors that Affect the Intensity of Insolation Earth’s Shape Sun’s Rays 90° Earth is a sphere. Due to its shape, only one area of the planet can receive maximum intensity of insolation (Sun’s rays = 90°). All other areas of Earth’s surface would receive less direct insolation.
Factors that Affect the Intensity of Insolation Earth’s Atmosphere When the Sun is directly overhead, the intensity of insolation is greatest. The Sun’s radiation passes through a smaller area of the atmosphere. When the Sun is on the horizon (dusk/dawn), the intensity of insolation is smallest. 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.
Factors that Affect the Intensity of Insolation Latitude During the Summer Solstice (June 21st), the maximum intensity of insolation (90°) strikes the Tropic of Cancer – 23 ½ ° N 90°
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°
Factors that Affect the Intensity of Insolation Latitude During the Fall and SpringEquinox(Sept. 23rd and March 21st), the maximum intensity of insolation (90°) strikes the Equator 0° 90°
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, the maximum intensity of insolation will vary between 23 ½ ° N to 23 ½ °S throughout the year.
Factors that Affect the Intensity of Insolation Time of Day Solar Noon Maximum insolation will occur for an area when solar noon is reached.
Factors that Affect the Duration of Insolation Durationof Insolation= The length of time insolation is received within a day. Latitude and Seasonal Change
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
Relationship of Surface Temperature toInsolation The temperature of the Earth’s surface at a given location will change throughout the day ….as well as throughout the year. A rise in temperature will occur when the intensity and/or duration of insolation received is greater than the energy lost by the earth’s surface radiation.
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!
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 decrease 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!
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.
