1. Earth-Sun Relationships
Nearly all of the energy that drives Earth’s variable weather and climate comes from the SUN.

2. SOLAR ENERGY The amount of solar energy received varies with: Latitude
Time of day
Season of the year

3.  Reasons for the Seasons
Seasonal changes occur because of the tilt of Earth’s axis!!!
Notice the angles at which the sun’s rays strike the surface
**Earth’s axis always points toward the North Star as it revolves around the sun
***Tilt of axis = seasonal changes

4. *The difference is the angle at which the radiation hits the surface!!
MORE CONCENTRATED!
MORE SPREAD OUT!

5. Solstices
• The summer solstice = June 21 or 22 in the Northern Hemisphere and is the “official” first day of summer
-Sun Directly above 23.5˚N
The winter solstice = December 21 or 22 in the Northern Hemisphere and is the “official” first day of winter.
-Sun Directly above 23.5˚S
Summer Solstice
Winter Solstice

6. Equinoxes
-During an Equinox the sun’s rays are exactly vertical over the equator.
-All latitudes receive 12 hours of daylight!
The spring equinox = March 21 or 22 in the Northern Hemisphere.
The autumnal equinox =September 21, or 22 or 23 in the Northern Hemisphere.

7. Energy Transfer as Heat
 Three mechanisms of energy transfer as heat are: conduction, convection, radiation

8. What Happens to Solar Radiation?
 When radiation strikes an object, there usually are 3 different results:
1. Absorbed: (Converted to heat = temp. increase).
2. Transmitted: Energy passes through. During this, energy can be scattered, producing a large number of weaker rays
3. Reflected: Some radiation may bounce off the object without being absorbed or transmitted. Reflected radiation has the same intensity as incoming radiation

9. Solar Radiation
• 50 % of the solar energy reaches Earth’s surface and is absorbed.
20 % absorbed by the atmosphere
20 % reflected from clouds
5% reflected by atmosphere
5 % reflected by surface of Earth
** water vapor and carbon dioxide are the major absorbing gases

10. Greenhouse effect is the natural heating of Earth’s Surface due to the concentration of specific greenhouse gases in the atmosphere.
Short video
mainly by water vapor and carbon dioxide.
Other greenhouse gases include Methane, Nitrous Oxide, Ozone, and a few others in small concentrations

11. Review Question
Describe what 3 things can happen to solar radiation when it strikes an object
The object can absorb, transmit (scatter), or reflect the radiation