1. Warm Up 3/6/08
More solar energy reaches the equatorial regions than the polar regions because the equatorial regions
a. are covered by a greater area of land.
b. have more vegetation to absorb sunlight.
c. receive sun rays closest to vertical.
d. have days with more hours of sunlight.
Most important weather phenomena occur in the ____.
a. stratosphere c. mesosphere
b. thermosphere d. troposphere
The form of oxygen that combines three oxygen atoms into each molecule is called ____.
a. ozone c. thermopause
b. argon d. chlorofluorocarbon
Answers: 1) c. 2) d. 3) a.

2. Heating the Atmosphere
Chapter 17, Section 2

3. Energy Transfer as Heat
Heat – the energy transferred from one object to another because of a difference in their temperatures
Temperature – measure of the kinetic energy (energy of motion) of the individual atoms or molecules in a substance
Three mechanisms of energy transfer as heat are conduction, convection, and radiation

4. Heat Transfer

5. Conduction
Conduction – the transfer of heat through matter by molecular activity
The energy of molecules is transferred by collisions from one molecule to another
Heat flows from the higher temperature matter to the lower temperature matter
Different materials conduct heat better than others
Metals are good conductors, while air is a poor conductor of heat
Conduction is only important between Earth’s surface and the air directly in contact with the surface

6. Conduction

7. Convection
Much of the heat transfer that occurs in the atmosphere is carried on by convection
Convection – the transfer of heat by mass movement or circulation within a substance
Convection takes place in fluids, like the ocean and air, where the atoms and molecules are free to move about
Convection also takes place in solids, such as Earth’s mantle, which behave as fluids over long periods of time
Most of the heat acquired by radiation and conduction in the lowest layer of the atmosphere is transferred by convective flow

8. Convection

9. Concept Check What is convection?
Convection is the transfer of heat by mass movement or circulation within a substance.

10. Electromagnetic Waves
The sun is the ultimate source of energy that creates our weather
All radiation from the sun (electromagnetic waves), whether X-rays, radio waves, or heat waves, travel through the vacuum of space at 300,000 km/s (only slightly slower through our atmosphere)
Electromagnetic waves move outward from their source and come in a variety of sizes
The most important difference between types is their wavelength (Radio waves have the longest, and Gamma waves have the shortest)
Visible light is a small part of this electromagnetic spectrum (each color corresponds to a specific wavelength of visible light), the combination of which is white light

11. Electromagnetic Spectrum

12. Concept Check Which electromagnetic wave has the longest wavelength?
Radio Waves

13. Radiation
Radiation – the transfer of energy (heat) through space by electromagnetic waves
Unlike conduction and convection, radiant energy can travel through the vacuum of space
The four laws governing radiation
All objects, at any temperature, emit radiant energy
Hotter objects radiate more total energy per unit area than colder objects do
The hottest radiating bodies produce the shortest wavelengths of maximum radiation
Objects that are good absorbers of radiation are good emitters as well

14. Three Mechanisms of Heat Transfer

15. What Happens to Solar Radiation?
When radiation strikes an object, there usually are three different results
Some energy is absorbed by the object
Substances such as water and air are transparent to certain wavelengths of radiation
Some radiation may bounce off the object without being absorbed or transmitted

16. Reflection and Scattering
Reflection – occurs when light bounces off an object
The reflected radiation has the same intensity as the incident (coming in) radiation
Scattering – produces a larger number of weaker rays that travel in different directions
About 30 % of solar energy is reflected back into space, this energy is lost and doesn’t go into heating the atmosphere
Small particles in the atmosphere also help scatter solar radiation
About half of the solar radiation that is absorbed at Earth’s surface arrives as scattered light

17. Reflection and Scattering

18. Concept Check
How much solar energy is reflected back to space?
30%

19. Absorption
About 50 % of the solar energy that strikes the top of the atmosphere reaches Earth’s surface and is absorbed, then is redirected skyward
The atmosphere absorbs the longer wavelengths emitted by Earth, with water vapor and carbon dioxide
Gases in the atmosphere will eventually radiate away some of this energy
Earth’s surface is continually supplied with heat from the atmosphere as well as from the sun
Greenhouse Effect – the heating of Earth’s surface and atmosphere from solar radiation being absorbed and emitted by the atmosphere, mainly by water vapor and carbon dioxide
Some incoming solar radiation is not absorbed and reradiated, but instead is used by plants for photosynthesis
Solar energy is the main energy source for virtually all life on Earth

20. Heating of the Atmosphere

21. Distribution of Incoming Solar Radiation

22. Assignment Read Chapter 17 (pg. 476-493)
Do Chapter 17 Assessment #1-30 (pg )

23. Cool Down
List and describe the three major mechanisms of heat transfer in the atmosphere.
Dark objects tend to absorb more radiation than light-colored objects. Explain whether dark objects or light objects on Earth’s surface would be better radiators of heat.
What is one thing new that you learned today? Explain.