1. 23.2 Solar Radiation & the Atmosphere Electromagnetic Radiation The EM spectrum Radiation is energy that does no require matter to travel. It travels as waves through space. Radiation travels fastest through a vacuum... 300,000 km/s Wavelengths in meters The Electromagnetic Spectrum http://www.youtube.com/watch?v=cfXzwh3KadE 5:19

2. Absorption The molecules of N 2 and O 2 in the upper atmosphere absorb the short wavelengths (Gamma, X-rays, & UV) Absorption occurs in the thermosphere and mesosphere. In the stratosphere, UV rays are absorbed and act upon oxygen to form ozone.

3. Absorption The molecules of N 2 and O 2 in the upper atmosphere absorb the short wavelengths (Gamma, X-rays, & UV) Absorption occurs in the thermosphere and mesosphere. Why is the thermosphere hot? Why is the mesosphere cold? How is ozone formed? Does any UV get to Earth? Why is the thermosphere hot? Why is the mesosphere cold? How is ozone formed? Does any UV get to Earth? The small amount of UV that reaches the Earth’s surface causes sunburn.

4. Scattering Clouds, dust, and gas molecules bend rays in many directions. Short waves like blue, are more easily scattered, so our sky looks blue... More scattering, and the sunset looks red

5. Reflection Of the total EM radiation to reach earth: ~ 30% is scattered back into space ~ 20% is absorbed by the atmosphere (stratosphere & troposphere) ~ 50% is absorbed by the surface See Table on p. 465 The Earth’s surface affects the % solar radiation reflected or absorbed.

6. Earth’s Surface How much solar radiation, that reaches the earth, is reflected back into space? 6% from the atmosphere 4% from the surface 20% off of clouds

7. Absorption and Infrared Energy When you feel warm from the sun, you are feeling IR radiation. Rocks, soil, oceans, and water in our atmosphere absorb this energy and re-emit that energy. Most of the energy is absorbed by water vapor and CO 2 in the atmosphere.

8. The Greenhouse Effect Normally the amount of solar energy trapped is ~ equal to that which is lost to space. But, human activities has changed that balance. CO 2 absorbs IR very effectively

9. Variations on Temperature Radiation from the sun does not heat the earth equally at all places, at all times. Factors affecting temperature: Latitude – primary factor Elevation – colder at higher latitudes Water – moderates temperatures A delay in heating of the atmosphere occurs both seasonally and daily. When is the summer solstice? When is the sun at its highest in the sky?

10. Conduction & Convection Conduction – molecules in a solid move faster as they are heated; energy is transferred. Convection – energy moving through a fluid (liquid & gas)