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Study Guide

Section 13.1

Section 13.2

Section 13.3

Section 13.4

Chapter Assessment

Image Bank

Section 13.1 Main Ideas• For a thunderstorm to occur, there must be abundant

moisture in the lower levels of the atmosphere and a mechanism to lift the moisture so it can condense. In addition, the air must be unstable so that the growing cloud will continue to rise.

• Thunderstorms are classified according to the mechanism that caused the air to rise. In an air-mass thunderstorm, the cloud rose because of unequal heating of Earth’s surface within one air mass. In a frontal thunderstorm, the air rose because it was pushed up by an advancing air mass.

Section 13.1 Study Guide

Section 13.2 Main Ideas• Lightning is produced when an advancing stepped leader

unites with an upward-moving return stroke. Thunder is the sound made by the rapid expansion of air around the lightning bolt as a result of extreme heating of the lightning channel.

• Thunderstorms can damage property and cause loss of life. The hazards of thunderstorms include lightning, violent winds, hail, floods, and tornadoes.

• The Fujita tornado intensity scale classifies tornadoes according to wind speed, path of destruction, and duration.

Section 13.2 Study Guide

Section 13.3 Main Ideas• Tropical cyclones derive their energy from the evaporation

of warm ocean water and the release of heat.

• The Saffir-Simpson hurricane scale classifies hurricanes according to intensity.

• Hurricane hazards include violent winds, floods, and storm surges. The National Hurricane Center tracks hurricanes and issues advance warnings to help reduce loss of life.

Section 13.3 Study Guide

Section 13.4 Main Ideas• Examples of persistent weather events include floods,

droughts, cold waves, and heat waves.

• The heat index assesses the impact of humidity combined with excessive heat on the human body. The wind-chill index estimates the heat loss from human skin caused by a combination of cold air and wind.

Section 13.4 Study Guide

1. Which of the following states experiences the highest number of thunderstorm days annually?

a. Oklahoma c. Florida

b. Tennessee d. Iowa

Multiple Choice

Chapter Assessment

Almost the entire state of Florida experiences more than 70 thunderstorm days annually.

2. The ____ causes the illumination that you see as lightning.

a. stepped leader c. channel

b. return stroke d. thunder

The stepped leader is the invisible channel of negatively charged air that moves from the cloud toward the ground. The return stroke rushes upward from the ground to meet it, illuminating the channel with about 100 million V of electricity.

Multiple Choice

Chapter Assessment

Multiple Choice

3. Which classification on the Fujita tornado intensity scale represents a strong tornado?

a. F0 c. F3

b. F1 d. F5

Chapter Assessment

F0 and F1 are classified as weak tornadoes. F2 and F3 are classified as strong tornadoes. F4 and F5 are classified as violent tornadoes.

Multiple Choice

4. Which of the following areas is least likely to be hit by a hurricane or typhoon?

a. western Africa

b. eastern United States

c. southern Japan

d. eastern India

Chapter Assessment

As a general rule, the most likely areas to be hit by a hurricane are on the eastern side of continents. Australia is the exception; both its east and west coasts are vulnerable.

Multiple Choice

5. Cold waves are caused by ____.

a. high-pressure systems

b. low-pressure systems

c. mT air masses

d. cT air masses

Chapter Assessment

Cold waves are brought on by large high-pressure systems that originate in the polar regions.

Short Answer

6. Explain why cold-front thunderstorms can last through the night?

Chapter Assessment

Cold-front thunderstorms get their initial lift from the push of cold air. They are not dependent on daytime heating. The thunderstorm can persist as long as the flow of moist, warm air into it is not disrupted.

Short Answer

7. What is wind shear and why is it important in the formation of tornadoes?

Chapter Assessment

Wind shear is when wind speed and direction change suddenly with height. This can produce a horizontal rotation near Earth’s surface. If this occurs close to the thunderstorm’s updrafts the twisting column of wind can be tilted from a horizontal to vertical position.

True or False

8. Identify whether the following statements are true or false.

______ Tornadoes can occur virtually anywhere on Earth.

______ Typical thunderstorms last about two hours.

______ High instability in the atmosphere limits thunderstorms.

______ Air-mass thunderstorms generally occur during

mid-afternoon.

______ Tropical disturbances have a cyclonic circulation.

Chapter Assessment

true

false

true

true

false

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Chapter 13 Images

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