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.

http://www.epa.gov/

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?