## StartUp Activities

LAUNCH L

How does a cold air mass form?

An air mass is a large volume of air that has the characteristics of the area over which it formed.

Procedure t^

1. Read and complete the lab safety form.

2. Place a full tray of ice cubes on a table. Place a pencil under each end of the tray to raise it off the table.

3. Slide a liquid-crystal temperature strip under the ice-cube tray.

4. Place two pencils across the top of the tray, and another temperature strip across them.

5. Record the temperature of each strip at 1-min intervals for about 5 min.

6. Make a graph of the temperature changes over time for each temperature strip.

Analysis

1. Describe what happened to the temperatures above and below the tray.

2. Explain how this models a mass of cold air.

Visit glencoe.com to

^ study entire chapters online;

• Interactive Time Lines

• Interactive Figures

• Interactive Tables

► review content with the Interactive Tutor and take Self-Check Quizzes.

Visit glencoe.com to

^ study entire chapters online;

• Interactive Time Lines

• Interactive Figures

• Interactive Tables

► review content with the Interactive Tutor and take Self-Check Quizzes.

Types of Fronts Make the following Foldable to help identify the four types of fronts.

STEP 1 Layer three sheets of paper so that the top margin or about 3 cm of each sheet can be seen.

STEP 2 Make a 3-cm horizontal cut through all three sheets on about the sixth line of the top sheet.

STEP 3 Make a vertical cut up from the bottom to meet the horizontal cut.

STEP 3 Make a vertical cut up from the bottom to meet the horizontal cut.

STEP 4 Place the three sheets on top of a fourth sheet and align the tops and sides of all sheets. Label the four tabs Cold Fronts, Warm Fronts, Stationary Fronts, and Occluded Fronts. The Foldable can be placed in a notebook or stapled along the left edge.

IFMIiMli* Use this Foldable with Section 12.2.

As you read this section, summarize what you learn about the different fronts. Include sketches of air movement and the weather map symbol for each type.

STEP 1 Layer three sheets of paper so that the top margin or about 3 cm of each sheet can be seen.

STEP 2 Make a 3-cm horizontal cut through all three sheets on about the sixth line of the top sheet.

Section 12.1

Objectives

I Compare and contrast weather and climate.

I Analyze how imbalances in the heating of Earth's surface create weather.

I Describe how air masses form.

I Identify five types of air masses.

Review Vocabulary heat: transfer of thermal energy from a warmer material to a cooler material

New Vocabulary weather climate air mass source region

Figure 12.1 A desert climate is dry with extreme variations in day and night temperatures. Only organisms adapted to these conditions, such as this ocotillo, can survive there.

314 Chapter 12 • Meteorology

Les David Manevitz/SuperStock