1. The Atmosphere Preview Understanding Concepts Reading Skills
Interpreting Graphics

2. Understanding Concepts
1. As you move through the layers of the atmosphere and get farther and farther from the surface of Earth, what happens to the air temperature?
A. The air temperature steadily increases.
B. The air temperature steadily decreases.
C. The average air temperature remains constant.
D. The air temperature falls, rises, falls, rises, and falls again.

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1. As you move through the layers of the atmosphere and get farther and farther from the surface of Earth, what happens to the air temperature?
A. The air temperature steadily increases.
B. The air temperature steadily decreases.
C. The average air temperature remains constant.
D. The air temperature falls, rises, falls, rises, and falls again.

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2. Without the evolution of photosynthesis, which element would still be missing from Earth’s atmosphere?
F. oxygen
G. nitrogen
H. hydrogen
I. chlorophyll

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2. Without the evolution of photosynthesis, which element would still be missing from Earth’s atmosphere?
F. oxygen
G. nitrogen
H. hydrogen
I. chlorophyll

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3. Which type of cloud formation is a good indication that a thunderstorm might be approaching?
A. cirrostratus
B. cirrocumulus
C. stratocumulus
D. cumulonimbus

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3. Which type of cloud formation is a good indication that a thunderstorm might be approaching?
A. cirrostratus
B. cirrocumulus
C. stratocumulus
D. cumulonimbus

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4. In which level of the atmosphere could the temperature reach 980 °C (1,796 °F)?

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4. In which level of the atmosphere could the temperature reach 980 °C (1,796 °F)?
Answer: thermosphere

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5. What happens to the dew point as humidity increases? Will water condense more or less easily as the humidity increases?

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5. What happens to the dew point as humidity increases? Will water condense more or less easily as the humidity increases?
Answer: The dew point increases as humidity increases, which makes it easier for water to condense.

12. Reading Skills LIGHTNING
The first stage in the process of lightning formation happens when an electric field builds up in a tall cloud. This electric field is the result of ions separating within the cloud and forming layers with different polarities. Positive ions tend to come together near the top of the cloud, and negative ions come together near the bottom.
As a result of the electric field, free electrons in the cloud begin to move very quickly. They begin to collide with particles and knock loose more electrons, which then begin accelerating as well. The result is a chain reaction, known as an electron avalanche. This chain reaction creates a path of positively charged ions, called a step leader, which extends down toward Earth.

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LIGHTNING, continued
When the positive charge is great enough, a lightning strike occurs. Charges nearest the ground cause a return stroke of negative charge to spread upward toward the cloud. The return stroke sends out photons and shows us the brilliant displays of lightning that we see in a stormy sky. The return stroke also causes the shock wave that we hear as thunder.

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6. Which part of the lightning bolt connects first with particles from the ground?
F. the step leader
G. the return stroke
H. the electron avalanche
I. the negative cloud layer

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6. Which part of the lightning bolt connects first with particles from the ground?
F. the step leader
G. the return stroke
H. the electron avalanche
I. the negative cloud layer

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7. How does the electric field form that causes lightning?
Answer: Charges separate into layers in a cloud.

17. Interpreting Graphics
The graphic below shows the amount of ozone, O3, that is found at different levels of the atmosphere. Use this graphic to answer questions 8–11.

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8. Which layer of the atmosphere does B represent?
A. the mesosphere C. the thermosphere
B. the stratosphere D. the troposphere

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8. Which layer of the atmosphere does B represent?
A. the mesosphere C. the thermosphere
B. the stratosphere D. the troposphere

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9. The point in the atmosphere with the highest concentration of ozone is the ozone layer. Within which atmospheric layer is the ozone layer located?
F. the ionosphere H. the thermosphere
G. the stratosphere I. the troposphere

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9. The point in the atmosphere with the highest concentration of ozone is the ozone layer. Within which atmospheric layer is the ozone layer located?
F. the ionosphere H. the thermosphere
G. the stratosphere I. the troposphere

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10. Which area of the graph indicates the part of the atmosphere that contains the air that you breathe?
A. area A C. area C
B. area B D. area D

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10. Which area of the graph indicates the part of the atmosphere that contains the air that you breathe?
A. area A C. area C
B. area B D. area D

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11. As you move upward from the surface of Earth, what happens to the concentration of ozone in the atmosphere as you pass the tropopause?

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11. As you move upward from the surface of Earth, what happens to the concentration of ozone in the atmosphere as you pass the tropopause?
Answer: The concentration of ozone increases as you go up the stratosphere, then begins to diminish.