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Chapter 17

Chapter 17. The Atmosphere: Structure and Temperature. Section 17.2. Heating the Atmosphere. Heating the Atmosphere. Energy Transfer as Heat Heat is the energy transferred from one object to another because of a difference in their temperatures.

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Chapter 17

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  1. Chapter 17 The Atmosphere: Structure and Temperature

  2. Section 17.2 Heating the Atmosphere

  3. Heating the Atmosphere Energy Transfer as Heat • Heat is the energy transferred from one object to another because of a difference in their temperatures. • Temperature is a measure of the average kinetic energy of the individual atoms or molecules in a substance. • Kinetic energy is the energy of motion. • When energy is transferred to the gases in the air, those particles move faster and the air temperature increases. • Energy is always transferred from high energy to low energy.

  4. Heating the Atmosphere Energy Transfer as Heat • There are three mechanisms of energy transfer as heat: • Conduction • Convection • Radiation • All three of these processes happen simultaneously in the atmosphere. • Conduction is the transfer of heat through matter by molecular activity (collisions of molecules). • Air is a poor conductor, and thus, conduction is only important between Earth’s surface and the air directly in contact with the surface. • Conduction is the least important mechanism of heat transfer

  5. Heating the Atmosphere Energy Transfer as Heat • Convection is the transfer of heat by mass movement or circulation within a substance. • Convection takes place in fluids (liquids and gases) as well as in solids (i.e. the mantle). • Most of the heat acquired by radiation and conduction in the lowest layer of the atmosphere is transferred by convective flow.

  6. Question: Which of the following is NOT true about radiation? • Radiation cannot travel through a vacuum. • The hottest radiating bodies produce the shortest wavelengths. • All objects emit radiant energy. • Objects that absorb radiation well emit radiation equally as well.

  7. Heating the Atmosphere

  8. Heating the Atmosphere Energy Transfer as Heat • Electromagnetic Waves • The sun emits light and heat as well as the ultraviolet rays that cause a suntan. These forms of energy are only part of a large array of energy emitted by the sun, called the electromagnetic spectrum.

  9. Electromagnetic Spectrum

  10. Visible Light consists of an Array of Colors

  11. Question: The average kinetic energy of the atoms or molecules in a particular substance in known as • Temperature. • Heat. • Conduction. • Convection.

  12. Question: Because of convection, the warmest air in a room • Spreads out in all directions. • Rises toward the ceiling. • Transfers heat to the walls. • Sinks toward the floor.

  13. Heating the Atmosphere Energy Transfer as Heat • Radiation is the transfer of energy (heat) through space by electromagnetic waves. • Radiation travels out in all directions and unlike conduction and convection, it can travel through the vacuum of space. • Solar energy reaches Earth by radiation. • There are 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. Heating the Atmosphere What Happens to Solar Radiation? • When radiation strikes an object, there are usually three different results: • Some energy is absorbed by the object. • Substances such as water and air are transparent to certain wavelengths of radiation. • These substances transmit radiant energy. • Some radiation may bounce off the object without being absorbed or transmitted.

  15. Heating the Atmosphere

  16. Question: Which of the following is an example of radiation? • A metal spoon becomes warm after being set in a pot of boiling water. • Warm water rises because it is less dense than cool water. • Pancake batter cooks quickly after being spooned onto a hot griddle. • Our atmosphere is constantly being heated by the sun.

  17. Heating the Atmosphere What Happens to Solar Radiation? • When radiation bounces off an object, it can be either reflected or scattered. • Reflection: Occurs when light bounces off an object. • Reflected light has the same intensity as the incident ray. • Scattering: Produces a larger number of weaker rays that travel in different directions. • Light disperses both forward and backward, but most of the energy is dispersed forward. • Accounts for the brightness and blue color of the sky. • About 30% of the solar energy reaching the outer atmosphere is reflected back to space.

  18. Heating the Atmosphere

  19. Heating the Atmosphere Absorption • About half of the solar radiation that is absorbed at Earth’s surface arrives as scattered light. • About 50% of the solar energy that strikes the top of the atmosphere reaches Earth’s surface and is absorbed. • Most of this energy is reradiated skyward. • The atmosphere effectively absorbs the longer wavelengths emitted by Earth (water vapor and carbon dioxide are the major absorbers).

  20. Heating the Atmosphere Absorption • Without the absorbing gases, Earth would not be suitable for humans and other life forms. • This important phenomenon is called the greenhouse effect.

  21. Question: The blue color of the sky is the result of • Conduction. • Scattering. • Reflection. • Absorption.

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