heat transfer and the movement of air - ms. maglothin

42 STC/MS™ CATA S T R O P H I C EV E N T S

INTRODUCTIONHow can a hang glider stay up in the air forhours without a motor? How can a bird soarover an open field without flapping its wings?They can do these things largely because of heattransfer and the motion of air. As the wings of aglider or a bird lift it up in the air, gravity pullsit down. This means that glider pilots and soar-ing birds need to find constant upward forces tostay in the air. Do you know where these forcescome from? They come from huge masses ofwarm, rising air. Flat fields, dark pavement, andlow-lying towns absorb a great deal of heat earlyin the day. These materials also give off largeamounts of heat. Where there is a warm surface,you are sure to find warm, rising air.

In this lesson, you will investigate what hap-pens to air when it is heated or cooled by thesurface beneath it. How does heat move betweenthe earth’s surface and the air above it? How dosurface temperatures on the earth affect thetemperature of air above it and the way air

4Heat Transfer and theMovement of Air

LESSON

OBJECTIVES FOR THIS LESSON

Investigate the effect of surfacetemperature on the temperature of theair above the surface.

Hypothesize how heat is transferredbetween the earth’s surface and the airabove it.

Observe and describe the effect ofsurface temperature on the movement ofair above the surface.

Determine the basic conditions underwhich water moves through the air.

Develop working definitions for theterms “stable air mass” and “unstableair mass.”

Hang gliders stay aloft by taking

advantage of rising currents of air.

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STC/MS™ CATA S T R O P H I C EV E N T S 43

moves? You will investigate these ideas in Lesson4. Then, in Lesson 5, you will look at what hap-pens when air masses of different temperaturesmeet.

MATERIALS FORINQUIRY 4.1

For you1 completed copy of

Student Sheet3.1b: Interpreting aData Table

1 copy of StudentSheet 4.1:Investigating theTemperature of Air

For your group1 tote tray2 Convection Tubes™1 120-mL plastic

container of hotwater (with screw-top lid)

1 120-mL plasticcontainer ofcrushed ice (withscrew-top lid)

1 stopwatch1 digital thermometer 1 ruler1 paper towel2 rubber bands2 pieces of plastic

wrap

MATERIALS FORINQUIRY 4.2

For your group 1 tote tray2 Convection Tubes1 120-mL plastic

container of hotwater (with screw-top lid)

1 120-mL plasticcontainer ofcrushed ice (withscrew-top lid)

1 piece of plastictubing

1 small funnel1 punk stick1 flashlight1 small aluminum

pan1 ruler2 paper towels2 rubber bands2 pieces of plastic

wrapScissors

Getting Started

1. Go over your homework from Lesson 3,Student Sheet 3.1b: Interpreting a DataTable, with your teacher. As you do, thinkabout the following:

A. What was the temperature of PortlandParklands at 2:00 P.M.?

B. How do you think this temperaturemight compare with the temperature ofthe Atlantic Ocean near Portland, Maine,at 2:00 P.M.?

C. How do you think the temperature ofthe earth’s surface affects the temperatureof air above it?

D. How do you think the temperature ofthe air affects how air moves?

Discuss your ideas with the class.

2. In this lesson, you will investigate how thetemperature of a surface affects air tem-perature, air movement, and the formationof clouds. Your teacher will show you aConvection Tube™. Brainstorm with yourclass ways in which you might use thetube to explore this interaction.


LESSON 4 HE AT TR A N S F E R A N D T H E MO V E M E N T O F AI R

Inquiry 4.1Investigating theTemperature of Air

PROCEDURE

1. Look over Student Sheet 4.1:Investigating the Temperature of Air asyour teacher discusses it. Read the ques-tion at the top of the student sheet. Youwill complete the student sheet as youconduct Inquiry 4.1.

2. Observe as your teacher demonstratesthe setup and Steps 5 through 12 ofthe Procedure. Review Figures 4.1and 4.2 with your teacher at thistime.

3. How would you make this investiga-tion a fair test? List your ideas underQuestion 1 on Student Sheet 4.1.

4. Make a prediction, then record itunder Question 2 on the studentsheet. Discuss your prediction withyour class.

5. Collect your materials. With yourgroup, practice reading the ther-mometers inside the cylinders. Thenumber on the thermometer high-lighted with green is the correcttemperature. If two numbers thatare not green are highlighted, youcan average them.

6. If it has not been done for you, fillone plastic container with hotwater and one with ice water(crushed ice).

7. Use the digital metal thermometer tomeasure the temperature of the hotwater. Also measure the temperature

Figure 4.1 Place a container of water under each

Convection Tube.

Hot water Crushed ice

of the crushed ice. Write the temperaturesfor cold and hot water in Table 1 on thestudent sheet.

8. Before you place each container of water(without its lid) under a Convection Tube,record the starting temperatures of boththermometers in both cylinders on Table1 of the student sheet. Write them acrossfrom Time 0:00. (Thermometer A is thetop thermometer.)

9. Set your stopwatch at zero. Place thecontainer of hot water under oneConvection Tube. Place the container ofcold water under the other ConvectionTube, as shown in Figure 4.1. Then startthe stopwatch.



10. Record the changes in temperature ineach Convection Tube every minute for 3 minutes in Table 1. If the temperaturegoes higher than the thermometer’s high-est temperature, you can record 30+ °Con your data table. (Do not touch the out-side of the cylinder. Your hand may affectthe temperature readings.)

11. If it gets difficult to see inside theConvection Tube, use a paper towel toremove moisture from the base. Attach a

paper towel to a ruler with a rubber bandand use this device to clear the cylinderand base, as shown in Figure 4.2. Afterclearing the Convection Tube, you cancover your containers of water or icewith plastic wrap and secure the wrapwith a rubber band.

12. Clean up.

REFLECTING ON WHAT YOU’VE DONE

1. Answer these questions; then discuss yourresults with the class.

A. How did the temperature of each con-tainer of water affect the temperature ofthe air above it?

B. The movement of heat is called heattransfer. Describe the heat transferbetween the container of hot water and the air. Describe the heat transferbetween the container of cold waterand the air.

C. Under what conditions was it difficultto see through a cylinder? Why do youthink this happened?

D. Why do you think covering the con-tainer helped to keep the cylinder clear?

2. Read “What’s the Forecast?” on pages50–53 before Inquiry 4.2 begins.

Figure 4.2 Clearing the Convection Tube



Figure 4.3 Putting smoke into the Convection Tube

Inquiry 4.2Investigating How Warm Airand Cool Air Move

PROCEDURE

1. Record the purpose of this investigationin your notebook. Write it in the form ofa question. Then share it with your groupor class. Also share with the class yourideas on how to test this question.

2. Your teacher will demonstrate how to dothis investigation. Follow along usingProcedure Steps 4 through 9.

3. Make a prediction. How do you think airwill move above a hot surface? How doyou think air will move above a cold sur-face? Record your prediction in yournotebook. Discuss your ideas with yourgroup or class.

4. Pick up your materials. Set up theConvection Tubes with hot and coldwater, as you did in Inquiry 4.1. You willnot be recording temperature changes inthis investigation. Use the ruler and papertowel to clear the cylinder or cover thecontainers with plastic wrap.

5. Attach the funnel and tubing to theConvection Tube with cold water. (It isvery important that you begin with thecold water.)

6. When you are ready, ask your teacher tolight your group’s punk stick. Immediatelyblow it out and hold the smoking punkover the aluminum pan, as shown inFigure 4.3. Hold the funnel at an angleover the punk so the smoke goes inside.Do not touch the funnel with the burningpunk.

SAFETY TIP

Follow safety pre-cautions whenworking with aburning punk. Donot walk aroundthe room with thepunk while it isburning.



continue to hold the burning punk.) Clearthe cylinder with the ruler and papertowel if needed. Place the punk under thefunnel to add smoke to the ConvectionTube with hot water. Observe. Use theflashlight to view the smoke.

9. When you have finished observing theConvection Tube with hot water, clean up.Carefully dip just the tip of the punk intoa container of water. This will stop the tipfrom smoldering. Then cut off the wet tip.

7. Your teacher will turn off the classroomlights. Use your flashlight to see thesmoke particles moving. Hold the flash-light behind the Convection Tube andthen at the top of it. Do not cover theopening of the Convection Tube. (SeeFigure 4.4 [A] and [B].) Kneel down soyou can see the smoke at eye level as itenters the Convection Tube. Talk to yourpartners about how the smoke moves.

8. Move the tubing and funnel to theConvection Tube with hot water. (Onemember of your group should carefully

(A) (B)

Figure 4.4 (A) Shine the

flashlight from behind the

Convection Tube to view

the air as it enters the

cylinder. (B) Hold the

flashlight at the top of the

Convection Tube to see

the smoke throughout the

cylinder. Do not block the

opening of the cylinder.



REFLECTING ON WHAT YOU’VE DONE

1. Answer these questions in your sciencenotebook; then discuss them with theclass:

A. On the basis of your temperaturereadings in Inquiry 4.1, how does thetemperature of a surface affect the tem-perature of the air above it?

B. How did the air, which was visiblebecause of the smoke, move in theConvection Tube when the water underit was cold? Explain why you think thishappened.

C. What happened to the air inside theConvection Tube when the water was hot?Explain why you think this happened.

D. Why do you think moisture formed onthe inside of the Convection Tube withhot water? How do you think this relatesto cloud formation on the earth?

E. Apply what you observed in Lesson 4to the earth. If the earth’s surface is cold,what will happen to the air above it? Ifthe surface is hot, what will happen tothe air above it?

2. Read “Air Masses,” on page 49.

3. With your teacher’s help, develop workingdefinitions for the terms “stable air mass”and “unstable air mass.” Record your defi-nitions in your science notebook. Applywhat you observed in this lesson to cloudformation. When do you think clouds aremore likely to form: when stable airremains close to the earth’s surface orwhen unstable air rises and moves quicklyto high altitudes?

4. Look ahead to Lesson 5, in which you willconnect two Convection Tubes to investi-gate what happens when air masses meet.



AIR MASSESWhen air moves over different surfaces—forexample, cold mountains or a warm ocean—ittakes on the temperature and humidity (mois-ture) conditions of that area. Because of this,air separates into massive pockets, or airmasses. An air mass has the same temperatureand moisture content throughout. It can extendfor hundreds or thousands of kilometers.

Once formed, air masses can move and carrytheir weather conditions to another area. Forexample, air masses that come out of northernCanada are cold and dry. Air masses that formover cold oceans bring cold temperatures and

moisture in the form of ice or snow. Air massesfrom the Gulf of Mexico that are warm andmoist bring clouds and rain showers. Air massesfrom Texas, New Mexico, and Arizona that arewarm and dry bring hot temperatures in thesummer.

Where cold and warm air masses meet, adistinct boundary forms between them. Thecold air mass may slide under the warm oneand lift it up. The weather at the boundarybecomes unstable. When this happens, stormyweather may be ahead.

Where do you think different air masses often meet in the United States? Why?

Cool humid air

Cold dry air

Warm humid airHot dry air

Warm humid air



Why is radar so important to the study ofthunderstorms, high winds, and tornadoes?Radar is important primarily because thesestorms cannot be seen from satellites, and theycan develop very quickly.

Satellites are also important tools for Ryan.Satellites orbiting in space take pictures ofclouds covering the earth. A series of picturesover time can show meteorologists how a largestorm, such as a hurricane, moves and can helppredict the path it might take.

What will the weather be like today? Many ofus want to know, so we turn on the television tosee what the weather forecasters have to say. Inthe Washington, D.C., area, we may be tuningin to meteorologist Bob Ryan.

“An important part of my job,” says Ryan, “isto make the forecast as clear and understand-able as possible.” Whether he is forecasting ablizzard, severe thunderstorms, or a sunnyspring day, “it comes down to hand-holdingwith people because they are concerned. Theyask: ‘Can I go out? What should I wear?’” Hetries to give people as much information as pos-sible. That helps them make good decisions.

Researching the Weather Although many people watch Bob Ryan on tele-vision, he is more than a television reporter. Asa meteorologist, Ryan is a scientist who studiesweather data and model predictions from theNational Center for Environmental Prediction(NCEP). Through NCEP, Ryan has access todata from more than 3500 weather stations.Every hour, these stations provide informationon air temperature, air pressure, wind directionand speed, relative humidity, and precipitation.

Ryan also uses Doppler radar to detect howair is moving. How does Doppler radar work?Think of the sound a train makes as itapproaches. As it gets nearer to you, the pitchof the sound gets higher. As it moves away, thepitch gets lower. Doppler radar works some-thing like that. If the Doppler frequency isincreasing, a storm is moving toward the radar.If the frequency is decreasing, a storm is mov-ing away from the radar. Doppler radar hasenabled forecasters like Ryan to provide peoplewith early warnings of potential danger.

WHAT’S THEFORECAST?

Bob Ryan, meteorologist and TV weather

forecaster

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Doppler radar tower



reports the forecast for the first time on theradio at 3:30 P.M. Then, with weather imagesmoving across a computerized map, heexplains the forecast to television viewers at4:00, 5:00, 6:00, and 11:00 P.M.

Ryan gives his forecast in front of a greenboard called a “chroma-key.” The computerimage of each map is electronically projectedonto any lime green space on the board. Thepublic sees Ryan in front of the computerimages, even though they are not really behindhim. Can you guess why he doesn’t wear limegreen?

Inspiring the Next GenerationSome years ago, Ryan decided he wanted to getmore young people excited about the weather.He created a program called 4-WINDS to teachstudents about weather. With the help of areabusinesses, Ryan’s TV station donated weatherstations to local schools. Each weather stationcontains instruments for measuring weathervariables (including temperature, pressure,

In addition to radar and satellite informa-tion, Ryan also uses data from ground weatherinstruments (for example, thermometers,anemometers, and barometers). Even specialairplanes collect data that are mapped and fedinto computer models. The computer modelscalculate wind, precipitation, temperature,and weather movement at locations aroundthe globe. Ryan compares predictions calcu-lated by several different models to see howwell they agree.

Ryan says that the science of weather fore-casting is a lot like the science of medicine.Medical doctors use all the available tests, X-rays, and other methods to diagnose a patient’scondition. Meteorologists do the same thing toarrive at a forecast, he says. They ask: “What arethe weather data and the calculations showing?What does it mean to our local area?”

Presenting the WeatherWhen Ryan presents the weather, he decideswhat part of the local weather is most impor-tant to viewers. “Each situationis a little bit different,” he says.If thunderstorms are forming inthe mountains, he shows theradar pattern. “If I’m following atropical system, like a hurri-cane, I might use almost hourlysatellite images,” he explains.

Ryan often links his weatherreport to other news. Forinstance, he once showed atropical storm forming over thePacific Ocean. He explained howthe storm’s rainfall could helpput out fires that were raging inMexico.

Once Ryan has an idea forthe forecast, he works withanother meteorologist to set upweather images on a computersystem. At 3:20 P.M., Ryan putstogether the final forecast. He

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Bob Ryan working in the Channel 4 Storm Center



term forecasts, to studying global climate change,to managing water resources. Most of all,” hesays, “it should be something you consider funand look forward to doing.” �

humidity, and wind)and a computer tostore the data. In2000, students from200 schools partici-pated in the project,using their computersto exchange weatherdata on the Internet.

Ryan hopes thatyoung people whoare interested in theweather will have abetter understandingof science and maybeeven become meteo-rologists. They needto have a strongbackground in mathand science and dowell in those sub-jects, he says. Ryanlearned about weatherby studying science incollege and earning amaster’s degree in physics and atmosphericscience.

“I think there’s a lot of opportunity for peopleinterested in this field—from improving short-

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Bob Ryan gives his forecast in front of a green board called a “chroma-key.” The public

sees what is shown on the TV monitor in the upper left-hand corner.



everyday life. My students were gettingvery accurate weather forecasts for ourarea within 24 to 36 hours because theycould track patterns. It really made animpression when they could see some-one else calling our system over theInternet. And there we were on Channel 4[the station Bob Ryan works for]. Or theNational Weather Service would call [toget our data]. The students were doing‘adult’ work.” Because of the 4-WINDSProgram, May continued, several of herstudents developed a great interest inearth science and meteorology.

Carol is one such student. She wrote inher journal that “when the wind is fromthe southwest and the barometric pres-sure is falling, something is going to comeout of the sky. Then we just use the ther-mometer to figure out what that some-thing is, snow or rain. This weather stuffis a cinch!”

Shawn agreed. “I can predict whattomorrow’s weather will be because I canfind out what the weather is right now,”she said. “I’m good at it, but I don’t thinkI’m a threat to Bob Ryan . . . yet!”

Weather Forecasting Can Be Cool . . .or Hot!When Vicky participated in the 4-WINDSProgram with her classmates atMountain View School in Haymarket,Virginia, she found that “it was like find-ing out how a magician does his tricks.They use computers and technology tohelp them figure out the answers to thequestions,” she said. “I thought weatherforecasting was a ‘luck’ thing. Maybe yougot it right, or maybe you were way off.”She found out that she could make pre-dictions that were “pretty close” by look-ing at patterns of temperature, wind, andpressure.

“I used to think that computers werejust for games and for typing,” saidVicky’s classmate Shawn. “But there areother things you can do. I like using the4-WINDS station because it lets me knowwhat’s going to happen. I’m getting betterand better at figuring the weather out.”

According to Amanda May, Vicky andShawn’s teacher, participating in 4-WINDS“gave the students a tremendous know-ledge of how technology is used in

heat transfer and the movement of air - ms. maglothin

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