Worldwide Wind 1-2 KEY CONCEPTS AND PROCESS SKILLS KEY VOCABULARY ACTIVITY OVERVIEW E-191

Transcription

1 Worldwide Wind 40- to minute sessions ACTIVITY OVERVIEW COMPUTER 68 SIMUL ATION Students use a computer simulation to identify the most common wind direction in a particular location. They share their data with the class and construct a map of global wind patterns. KEY CONCEPTS AND PROCESS SKILLS (with correlation to NSE 5 8 Content Standards) 1. Scientists sometimes work together to gather evidence and make conclusions. (History and Nature of Science: 1) 2. Wind is the movement of air that results from differences in air pressure and/or air temperature. (EarthSci: 3) 3. Global patterns of atmospheric movement influence local weather. (EarthSci: 1) KEY VOCABULARY latitude prevailing wind E-191

2 Activity 68 Worldwide Wind MATERIALS AND ADVANCE PREPARATION For the teacher 1 Transparency 68.1, Key to Wind Currents on Earth * 1 overhead projector For each pair of students * 1 computer with Internet access For each student 1 Student Sheet 68.1, My Wind Data 1 Student Sheet 68.2, Wind Currents on Earth *Not supplied in kit Reserve a computer lab, if necessary, so that there is a computer available for each pair of students. Note that although the activity itself may take 1 2 class periods, the amount of computer time students need for recording their data takes significantly less than one period. Before class, set up the computers to link to the Issues and Earth Science student page of the SEPUP website. Scroll down the web page to Activity 68 of Unit E, Weather and Atmosphere, to find the link to the simulation. TEACHING SUMMARY Getting Started 1. Review how to collect data from the computer simulation. Doing the Activity 2. Students collect data on wind directions in a particular city. Follow-Up 3. Students share their results and analyze global wind patterns.if this works) E-192

3 Worldwide Wind Activity 68 BACKGROUND INFORMATION Wind Formation and Global Wind Patterns Wind is the horizontal movement of air. This movement is the result of temperature gradients caused by the uneven heating of earth surfaces. As radiant energy strikes the earth, the regions near the equator warm more than the polar regions do. Warm tropical waters radiate heat energy to the atmosphere above. The result is air that warms and rises because it is less dense. As the warm air rises over the equatorial regions, a low-pressure area forms. The air continues to rise and travels north and south away from the equator. The farther it gets from the equator, the cooler the air becomes, causing it to sink. This cooler, denser air creates areas of high pressure, and the resulting difference in pressure creates wind. Globally, this process occurs as warm air rises in warm equatorial regions and cooler air sinks near the poles. Were it not for the earth s rotation, only two major convection cells would span the globe (see Figure 1). But due to the Coriolis effect caused by the rotation of the planet, six different global wind belts occur within specific latitudes and circulate heat energy in the earth s atmosphere (see Figure 2). The global direction of the prevailing wind within a cell is generally the same, but variations occur, such as the jet stream and winds at different altitudes. The names of these global bands are based on the direction from which the winds originate. For example, between 30 to 60 north latitude the prevailing winds blow from west to east, and are referred to as the Westerlies. Figure 1: Predicted Wind Patterns without Earth s Rotation North Pole Figure 2: Global Prevailing Winds North Pole Easterlies 60 N 30 N 60 N 30 N Westerlies Northeast trade winds Equator 0 30 S 60 S South Pole Equator 0 30 S 60 S South Pole Easterlies Westerlies Southeast trade winds 2562 LabAids SEPUP Issues Earth Sci SB Figure: EaSB E LegacySansMedium 10/11.5 inner core E-193

4 Activity 68 Worldwide Wind TEACHING SUGGESTIONS GETTING STARTED 1. Review how to collect data from the computer simulation. Distribute a copy of Student Sheet 68.1, My Wind Data, to each student. Explain to students that they will record several days of wind data on this single sheet. Days that had no wind are recorded at the bottom of the page. Have students refer to Procedure Step 6 of the Student Book to see how to correctly record the data. DOING THE ACTIVIT Y 2. Students collect data on wind directions in a particular city. Assign each pair of students a city number from 1 to 16, which they record at the center of Student Sheet Students begin the simulation by clicking on the number that corresponds to their city number. They then place the cursor over a date to find out about the wind on a particular day, recording the data for each date on Student Sheet Each arrow represents the wind, so that the arrow indicates the direction from which the wind is blowing into the city. You may want to review this point, since it is the reverse of the use of arrows in a wind vane (in which the head of the arrow faces into the wind). In procedure step 8, after students have recorded all of their data, they work with their partners to identify the most common wind direction (such as northeast or southwest) in their city. They are to describe the prevailing wind for their city. Remind students that prevailing wind is described as the direction the wind is blowing from. Point out that they have determined the mode for their data set and emphasize that, especially with data like this, the mode is an important form of analysis. FOLLOW-UP 3. Students share their results and analyze global wind patterns. Have students report their results to the class, and record this data on a transparency of Student Sheet Be sure that students also record the data from the other 15 cities on their copies of Student Sheet 68.2, Wind Currents on Earth. Explain that latitudinal boundaries where winds blow into each other are low-pressure areas where air rises. This may seem counterintuitive to some students because they might think that the winds would push against each other and create higher pressure. Similarly explain that boundaries where winds blow away from each other are high-pressure areas in which air descends. Analysis Questions 1 and 2 ask students to describe any global patterns that they see. Discuss students responses with the class. SUGGESTED ANSWERS TO QUESTIONS 1. Look carefully at Student Sheet Describe any overall pattern that you see. The prevailing winds move in the same direction within horizontal bands defined by latitude. 2. Summarize global wind patterns by constructing a table to record the prevailing wind direction at different latitudes. (Remind student that the Prevailing Wind Direction is the direction from which the wind is blowing.) A sample table is shown below. 3. Look at the direction of the prevailing winds over North America. Based on the direction of the prevailing wind, would you expect weather systems over the United States to travel from east to west or west to east? Latitude N N 30 0 N 0 30 S S S From west to east since the prevailing wind direction is from the southwest. Prevailing Wind Direction northeast southwest northeast southeast northwest southeast E-194

5 Key to Wind Currents on Earth 2006 The Regents of the University of California N 90 S N 60 S 30 N 0 30 S Issues and Earth Science Transparency 68.1 E-195

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7 Name Date My Wind Data N W City E S 2006 The Regents of the University of California Issues and Earth Science Student Sheet 68.1 E-197

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9 Name Date Wind Currents on Earth 2006 The Regents of the University of California 90 N 90 S 60 N 60 S 30 N 0 30 S Issues and Earth Science Student Sheet 68.2 E-199

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