Insolation

Objective TSWBAT: Explain the factors affecting insolation Explain the relationship between temperature and insolation Describe evidence for Earth’s radiative balance Define insolation, radiative balance Describe the four ways the atmosphere is heated.

What could cause us to have different amounts of sunlight/insolation?

1. Angle 90o (direct rays) most intense insolation < 90o (less direct rays) least intense insolation

Angle and Temperature 90o = higher temperature low angles = lower temperatures

2. Earth’s Shape If the Earth was flat, the angles would all be 90o (high temperatures) The Earth is curved, so we get angles from 0o to 90o (range of temperatures)

3. Latitude Fall/Spring – Equinox (March 21st and Sept 23rd) Perpendicular (90°) at the Equator (0°) Angle of incidence decreases as latitude increases (lowest at the North Pole (90°N) and South Pole (90°S)) 12 hours of daylight everywhere Altitude of noon sun: 47° Not tilted toward/away from sun Sunrise/set - E W

Fall/spring

Summer Solstice (June 21st) Perpendicular (90°) at the tropic of cancer (23 ½ °N) 12 hours of daylight at equator (0°) 15 hours of daylight 43°N (Cambridge) 24 hours of daylight 90°N 9 hours of daylight at 40°S 0 hours of daylight at 90°S Altitude of noon sun: 70.5° Tilted toward the sun Sunrise/set - NE NW

Summer Solstice

Winter Solstice Dec 21st Perpendicular (90°) at the tropic of Capricorn (23 ½ °S) 12 hours of daylight at equator (0°) 9 hours of daylight 43°N (Cambridge) 0hours of daylight 90°N 15 hours of daylight at 40°S 24 hours of daylight at 90°S Altitude of noon sun: 23 ½ ° Tilted away from the sun Sunrise/set - SE SW

Winter Solstice

4. Seasons Changes angles for latitudes NY: Summer 70o, Fall/Spring 47o, Winter 23 ½ o

5. Time of Day Sunrise and sunset have low angles (lower temperatures) Noon has the highest angle We (NY) never get a 90o angle at noon

So, if you have a greater angle of insolation, what happens to intensity and temperature? Intensity will increase and temperature will increase

6. Tilt of Axis If there was no tilt, there would be no change in the seasons. The angles would stay the same, similar to Fall/Spring.

7. Parallelism of Axis Helps to change the angles for the latitudes It makes the axis tilt toward the sun or away from the sun as it revolves around the sun

8. Revolution Same as Parallelism of Axis and Seasons Changes the angles for the latitudes

9. Rotation Causes the angles to change during the day Refer to Time of Day

Duration of Insolation Means number of daylight hours If the angle of insolation is low, there is a small duration of insolation (low temperatures) Creates unequal distribution of heat Why does this happen? Tilted axis of rotation – greater amounts of insolation in the summer (northern hemisphere), less during the winter

Duration of insolation NY: Winter: 23 ½ o, 8 hours of daylight, low temperatures, Dec 21st Summer: 70o, 15 hours of daylight, high temperatures, high angle, high intensity Fall/Spring - 47o 12 hours of daylight.

Radiative balance A condition in which a body gives off as much heat as it receives. Insolation from Sun = infrared energy from Earth http://www.ieagreen.org.uk/tecres/tecim2.jpg

Evidence for radiative balance: daily http://apollo.lsc.vsc.edu/classes/met130/notes/chapter3/graphics/t_diurnal3.free.gif

Evidence of Radiative balance 1. Hottest and coolest times of day (4pm (maximum radiative energy) and 6am(minimum radiative energy)) 2. Hottest and coolest times of year (July/Aug (maximum radiative energy) and Jan/Feb (minimum radiative energy))

Is Earth really in radiative balance? Radiative balance means insolation = re-radiation. Over long periods of time, Earth is in radiative balance. Temperatures taken year to year vary though (short periods).

Heating the atmosphere Direct absorption of radiation from the sun Re-radiation of long-wave radiation from earth’s surface Conduction Latent heat of condensation

1. Direct absorption of radiation from the sun Gases absorb long-wave and short-wave radiation Transferred into heat energy

2. Re-radiation of long-wave radiation from earth’s surface Short wave radiation is absorbed by earth Reradiates long wave infrared radiation also called terrestrial radiation Gases in the atmosphere absorb this infrared reradiation and are heated

3. Conduction Transfer of heat by direct molecular contact Not all heat energy in rocks reradiate back Some is through direct contact of the hot rocks with the atmosphere

4. Latent heat of condensation Water vapor condenses to liquid water - Release (condensation) of latent heat gain (evaporation) of latent heat – cooling effect

Ex) body sweat evaporates and draws heat away from your body Ex) body sweat evaporates and draws heat away from your body. The heat is stored in water vapor and rises in the atmosphere. When it condenses, heat is releases as latent heat. Clouds form and massive storm systems Body sweat may help form a cloud!!