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Insolation
• INcoming SOLar radiATION
• Strength is dependent on1. Angle of insolation
2. Duration of insolation
3. Type of surface receiving the insolation
EM Energy Interactions in Environment
• Refracted – bent as pass through
• Reflected – bounced off
• Scattered – refracted or reflected in various directions
• Transmitted – passed through
• Absorbed – taken into
Electromagnetic Spectrum
• Organisms vary in their ability to sense different parts of the spectrum.
Angle of Insolation
• A measure of how high the Sun is in the sky
• The higher the Sun, the more direct the Sun’s rays.
• The more direct the rays, the greater the amount of insolation.
• What time of day is insolation the greatest?
• Angle changes throughout the year
• In Northern Hemisphere – Rays are most direct in summer.
• Direct rays strike the Tropic of Cancer on the Summer Solstice.
• What time of the year is insolation the greatest in the S. Hemisphere?
• As you travel poleward, the angle of insolation decreases.
• How does this affect global heating?
• How do temperatures compare between the tropics and the poles?
• This difference in heating drives the Earth’s weather systems.
Effect of Angle of Insolation
Same amount of incomingenergy.
The more direct the anglethe more ‘concentrated’ the energy
Equator30 °
45°
Poles
_____ ______ __________ _____________________________
Relative amount of incoming energy
Greater the angle, the less ‘concentrated’ the energy
Intensity of insolation depends upon:
• Latitude
–Farther you are from the equator the less energy reaches you
Same area coveredDifferent amounts of energy
Less energy: colder
More energy: warmer
Less energy: colder
• Season
–More energy reaches you in summer than in winter
Monthly Insolation Values
Annually, energy transfers from the Equator to the Poles on a global scale.
Watch how this happens over a year!....
JANUARY
-10.0 0.8 11.6 22.4 33.2 (oC )
FEBRUARY
MARCH
APRIL
MAY
JUNE
JULY
AUGUST
SEPTEMBER
OCTOBER
NOVEMBER
DECEMBER
JANUARY
Duration of Insolation
• This is the length of daylight in a day.
• The longer the amount of daylight, the greater the amount of insolation.
• What time of year has the longest hours of daylight?
Length of Daylight
Absorption of Insolation• Absorption depends on texture and
color.• The rougher the texture, the more
absorption takes place.• Darker colors absorb insolation at a
greater rate the lighter colors.• Which absorbs more? A blacktop
parking lot or a snowy field?
• Since dark colors absorb heat radiation then light colors reflect radiation.
• Light energy reflected from a surface is called albedo.albedo.
• Surfaces with high albedo reflect a lot of light
• For instance, snow has a high albedo. The surface of the moon has a high albedo. A mirror has a high albedo.
• Name a type of surface with a low albedo.
Albedo of selected surfacesSURFACE % reflected
Dense, dry, clean snow 86-95
Clean sand 37
Ice sheet 26
Grass 25
Decidudous forest 17
Pine forest 14
Ploughed field---moist 14
Swamp 10-14
Presence of cloud cover
Clouds absorb and reflect some incoming energy. In the day, less heat will reach the ground
At night, clouds act as blankets to prevent heat from returning to space
Effect of Angle of Insolation
• More energy reaches the equator than the poles
• There is a gain of energy at the equator
• There is a loss of energy at the poles
• Unequal heating of earth causes giant convection cells to form
• Result = global winds
Winds and Ocean Currents
The energy of the earth is not static
It can be transferred either by winds or ocean currents.
Most of the insolation reaches the earth and heats up the oceans and the seas
Temperatures of areas near the coast are modified. Example Vancouver and Ottawa
Formation of convection cells
• Warm air rises
• Cool air sinks
• Convection cells form
• Earth is spinning: adds another factor in formation of global winds– Coriolis effect
Coriolis Effect
• objects moving in the northern hemisphere are deflected toward the right of their direction of motion
• Objects moving in the southern hemisphere are deflected toward the left of their direction of motion
Resulting wind pattern is called3-celled model of global air
circualtion
Review• What is insolation?• What are 3 things that affect insolation?• What time of day is insolation the
greatest?• What time if year is insolation the
greatest?• How does latitude affect insolation?
Review
• How does color affect absorption of radiation?
• What is albedo?
• Name a surface that has high albedo.
Lag Time of Maximum Heat
• The maximum heat produced by the Sun does not occur at the same time as maximum insolation
• This is due to the time it takes for the object or surface to heat up.
June 21 Dec 21
• So, even though maximum insolation is in June, the warmest month is July/August due to the time it takes for the atmosphere to warm to the max.
• The same is true for daily heating. Even though the maximum insolation is at noon, the hottest time of day is late afternoon
The Greenhouse Effect• The greenhouse effect is the rise in
temperature of Earth’s atmosphere.
• This rise is caused by certain gases.(Water vapor, carbon dioxide, nitrous oxide, and methane, for example)
• These gases trap energy from the sun.
• Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder.
• Because of how they warm our world, these gases are referred to as greenhouse gases.
Greenhouse Effect cont.
Global Warming
• This is NOT the same as the Greenhouse Effect
• This is due, in part, to a build up of greenhouse gases.
• The increase in theses gases are due, in part, to human influences.
Review
• Why is the hottest part of the day not the same as the time of maximum insolation?
• What is the Greenhouse Effect?
• What are some greenhouse gases?
• Is the Greenhouse Effect the same as Global Warming?
• What is Global Warming?