4
Heat Transfer and the
Movement of Air
INTRODUCTION
How can a hang glider stay up in the air for
hours without a motor? How can a bird soar
over an open field without flapping its wings?
They can do these things largely because of heat
transfer and the motion of air. As the wings of a
glider or a bird lift it up in the air, gravity pulls
it down. This means that glider pilots and soaring birds need to find constant upward forces to
stay in the air. Do you know where these forces
come from? They come from huge masses of
warm, rising air. Flat fields, dark pavement, and
low-lying towns absorb a great deal of heat early
in the day. These materials also give off large
amounts of heat. Where there is a warm surface,
you are sure to find warm, rising air.
In this lesson, you will investigate what happens to air when it is heated or cooled by the
surface beneath it. How does heat move between
the earth’s surface and the air above it? How do
surface temperatures on the earth affect the
temperature of air above it and the way air
© CHUCK FISHMAN/WOODFIN CAMP & ASSOCIATES
LESSON
Hang gliders stay aloft by taking
advantage of rising currents of air.
OBJECTIVES FOR THIS LESSON
Investigate the effect of surface
temperature on the temperature of the
air above the surface.
Hypothesize how heat is transferred
between the earth’s surface and the air
above it.
Observe and describe the effect of
surface temperature on the movement of
air above the surface.
Determine the basic conditions under
which water moves through the air.
42 STC/MS™ C ATA S T R O P H I C E V E N T S
Develop working definitions for the
terms “stable air mass” and “unstable
air mass.”
moves? You will investigate these ideas in Lesson
4. Then, in Lesson 5, you will look at what happens when air masses of different temperatures
meet.
Getting Started
over your homework from Lesson 3,
1. Go
Student Sheet 3.1b: Interpreting a Data
Table, with your teacher. As you do, think
about the following:
A. What was the temperature of Portland
Parklands at 2:00 P.M.?
B. How do you think this temperature
might compare with the temperature of
the Atlantic Ocean near Portland, Maine,
at 2:00 P.M.?
C. How do you think the temperature of
the earth’s surface affects the temperature
of air above it?
D. How do you think the temperature of
the air affects how air moves?
Discuss your ideas with the class.
this lesson, you will investigate how the
2. In
temperature of a surface affects air tem-
MATERIALS FOR
INQUIRY 4.1
MATERIALS FOR
INQUIRY 4.2
For you
1 completed copy of
Student Sheet
3.1b: Interpreting a
Data Table
1 copy of Student
Sheet 4.1:
Investigating the
Temperature of Air
For your group
1 tote tray
2 Convection Tubes
1 120-mL plastic
container of hot
water (with screwtop lid)
1 120-mL plastic
container of
crushed ice (with
screw-top lid)
1 piece of plastic
tubing
1 small funnel
1 punk stick
1 flashlight
1 small aluminum
pan
1 ruler
2 paper towels
2 rubber bands
2 pieces of plastic
wrap
Scissors
For your group
1 tote tray
2 Convection Tubes™
1 120-mL plastic
container of hot
water (with screwtop lid)
1 120-mL plastic
container of
crushed ice (with
screw-top lid)
1 stopwatch
1 digital thermometer
1 ruler
1 paper towel
2 rubber bands
2 pieces of plastic
wrap
perature, air movement, and the formation
of clouds. Your teacher will show you a
Convection Tube™. Brainstorm with your
class ways in which you might use the
tube to explore this interaction.
STC/MS™ C ATA S T R O P H I C E V E N T S
43
LESSON 4
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
Inquiry 4.1
Investigating the
Temperature of Air
PROCEDURE
over Student Sheet 4.1:
1. Look
Investigating the Temperature of Air as
your teacher discusses it. Read the question at the top of the student sheet. You
will complete the student sheet as you
conduct Inquiry 4.1.
as your teacher demonstrates
2. Observe
the setup and Steps 5 through 12 of
the Procedure. Review Figures 4.1
and 4.2 with your teacher at this
time.
AIR
of the crushed ice. Write the temperatures
for cold and hot water in Table 1 on the
student sheet.
you place each container of water
8. Before
(without its lid) under a Convection Tube,
record the starting temperatures of both
thermometers in both cylinders on Table
1 of the student sheet. Write them across
from Time 0:00. (Thermometer A is the
top thermometer.)
your stopwatch at zero. Place the
9. Set
container of hot water under one
Convection Tube. Place the container of
cold water under the other Convection
Tube, as shown in Figure 4.1. Then start
the stopwatch.
would you make this investiga3. How
tion a fair test? List your ideas under
Question 1 on Student Sheet 4.1.
a prediction, then record it
4. Make
under Question 2 on the student
sheet. Discuss your prediction with
your class.
your materials. With your
5. Collect
group, practice reading the thermometers inside the cylinders. The
number on the thermometer highlighted with green is the correct
temperature. If two numbers that
are not green are highlighted, you
can average them.
not been done for you, fill
6. Ifoneit has
plastic container with hot
water and one with ice water
(crushed ice).
the digital metal thermometer to
7. Use
measure the temperature of the hot
water. Also measure the temperature
44 STC/MS™ C ATA S T R O P H I C E V E N T S
Hot water
Figure 4.1
Crushed ice
Place a container of water under each
Convection Tube.
LESSON 4
the changes in temperature in
10. Record
each Convection Tube every minute for
3 minutes in Table 1. If the temperature
goes higher than the thermometer’s highest temperature, you can record 30+ °C
on your data table. (Do not touch the outside of the cylinder. Your hand may affect
the temperature readings.)
11.
If it gets difficult to see inside the
Convection Tube, use a paper towel to
remove moisture from the base. Attach a
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
paper towel to a ruler with a rubber band
and use this device to clear the cylinder
and base, as shown in Figure 4.2. After
clearing the Convection Tube, you can
cover your containers of water or ice
with plastic wrap and secure the wrap
with a rubber band.
12. Clean up.
REFLECTING ON WHAT YOU’VE DONE
these questions; then discuss your
1. Answer
results with the class.
A. How did the temperature of each container of water affect the temperature of
the air above it?
B. The movement of heat is called heat
transfer. Describe the heat transfer
between the container of hot water
and the air. Describe the heat transfer
between the container of cold water
and the air.
C. Under what conditions was it difficult
to see through a cylinder? Why do you
think this happened?
D. Why do you think covering the container helped to keep the cylinder clear?
“What’s the Forecast?” on pages
2. Read
50–53 before Inquiry 4.2 begins.
Figure 4.2
Clearing the Convection Tube
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LESSON 4
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
Inquiry 4.2
Investigating How Warm Air
and Cool Air Move
PROCEDURE
the purpose of this investigation
1. Record
in your notebook. Write it in the form of
a question. Then share it with your group
or class. Also share with the class your
ideas on how to test this question.
teacher will demonstrate how to do
2. Your
this investigation. Follow along using
Procedure Steps 4 through 9.
AIR
a prediction. How do you think air
3. Make
will move above a hot surface? How do
you think air will move above a cold surface? Record your prediction in your
notebook. Discuss your ideas with your
group or class.
up your materials. Set up the
4. Pick
Convection Tubes with hot and cold
water, as you did in Inquiry 4.1. You will
not be recording temperature changes in
this investigation. Use the ruler and paper
towel to clear the cylinder or cover the
containers with plastic wrap.
the funnel and tubing to the
5. Attach
Convection Tube with cold water. (It is
very important that you begin with the
cold water.)
you are ready, ask your teacher to
6. When
light your group’s punk stick. Immediately
blow it out and hold the smoking punk
over the aluminum pan, as shown in
Figure 4.3. Hold the funnel at an angle
over the punk so the smoke goes inside.
Do not touch the funnel with the burning
punk.
SAFETY TIP
Figure 4.3
Putting smoke into the Convection Tube
46 STC/MS™ C ATA S T R O P H I C E V E N T S
Follow safety precautions when
working with a
burning punk. Do
not walk around
the room with the
punk while it is
burning.
LESSON 4
teacher will turn off the classroom
7. Your
lights. Use your flashlight to see the
smoke particles moving. Hold the flashlight behind the Convection Tube and
then at the top of it. Do not cover the
opening of the Convection Tube. (See
Figure 4.4 [A] and [B].) Kneel down so
you can see the smoke at eye level as it
enters the Convection Tube. Talk to your
partners about how the smoke moves.
the tubing and funnel to the
8. Move
Convection Tube with hot water. (One
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
continue to hold the burning punk.) Clear
the cylinder with the ruler and paper
towel if needed. Place the punk under the
funnel to add smoke to the Convection
Tube with hot water. Observe. Use the
flashlight to view the smoke.
you have finished observing the
9. When
Convection Tube with hot water, clean up.
Carefully dip just the tip of the punk into
a container of water. This will stop the tip
from smoldering. Then cut off the wet tip.
member of your group should carefully
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
(A)
(B)
cylinder. Do not block the
opening of the cylinder.
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LESSON 4
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
REFLECTING ON WHAT YOU’VE DONE
these questions in your science
1. Answer
notebook; then discuss them with the
class:
A. On the basis of your temperature
readings in Inquiry 4.1, how does the
temperature of a surface affect the temperature of the air above it?
B. How did the air, which was visible
because of the smoke, move in the
Convection Tube when the water under
it was cold? Explain why you think this
happened.
C. What happened to the air inside the
Convection Tube when the water was hot?
Explain why you think this happened.
D. Why do you think moisture formed on
the inside of the Convection Tube with
hot water? How do you think this relates
to cloud formation on the earth?
48 STC/MS™ C ATA S T R O P H I C E V E N T S
AIR
E. Apply what you observed in Lesson 4
to the earth. If the earth’s surface is cold,
what will happen to the air above it? If
the surface is hot, what will happen to
the air above it?
2. Read “Air Masses,” on page 49.
your teacher’s help, develop working
3. With
definitions for the terms “stable air mass”
and “unstable air mass.” Record your definitions in your science notebook. Apply
what you observed in this lesson to cloud
formation. When do you think clouds are
more likely to form: when stable air
remains close to the earth’s surface or
when unstable air rises and moves quickly
to high altitudes?
ahead to Lesson 5, in which you will
4. Look
connect two Convection Tubes to investigate what happens when air masses meet.
LESSON 4
AIR MASSES
When air moves over different surfaces—for
example, cold mountains or a warm ocean—it
takes on the temperature and humidity (moisture) conditions of that area. Because of this,
air separates into massive pockets, or air
masses. An air mass has the same temperature
and moisture content throughout. It can extend
for hundreds or thousands of kilometers.
Once formed, air masses can move and carry
their weather conditions to another area. For
example, air masses that come out of northern
Canada are cold and dry. Air masses that form
over cold oceans bring cold temperatures and
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
moisture in the form of ice or snow. Air masses
from the Gulf of Mexico that are warm and
moist bring clouds and rain showers. Air masses
from Texas, New Mexico, and Arizona that are
warm and dry bring hot temperatures in the
summer.
Where cold and warm air masses meet, a
distinct boundary forms between them. The
cold air mass may slide under the warm one
and lift it up. The weather at the boundary
becomes unstable. When this happens, stormy
weather may be ahead.
Cold dry air
Cool humid air
Warm humid air
Hot dry air
Warm humid air
Where do you think different air masses often meet in the United States? Why?
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H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
MATTHEW BAILEY/NSRC
LESSON 4
WHAT’S THE
FORECAST?
Researching the Weather
Although many people watch Bob Ryan on television, he is more than a television reporter. As
a meteorologist, Ryan is a scientist who studies
weather data and model predictions from the
National Center for Environmental Prediction
(NCEP). Through NCEP, Ryan has access to
data from more than 3500 weather stations.
Every hour, these stations provide information
on air temperature, air pressure, wind direction
and speed, relative humidity, and precipitation.
Ryan also uses Doppler radar to detect how
air is moving. How does Doppler radar work?
Think of the sound a train makes as it
approaches. As it gets nearer to you, the pitch
of the sound gets higher. As it moves away, the
pitch gets lower. Doppler radar works something like that. If the Doppler frequency is
increasing, a storm is moving toward the radar.
If the frequency is decreasing, a storm is moving away from the radar. Doppler radar has
enabled forecasters like Ryan to provide people
with early warnings of potential danger.
50 STC/MS™ C ATA S T R O P H I C E V E N T S
Bob Ryan, meteorologist and TV weather
forecaster
Why is radar so important to the study of
thunderstorms, high winds, and tornadoes?
Radar is important primarily because these
storms cannot be seen from satellites, and they
can develop very quickly.
Satellites are also important tools for Ryan.
Satellites orbiting in space take pictures of
clouds covering the earth. A series of pictures
over time can show meteorologists how a large
storm, such as a hurricane, moves and can help
predict the path it might take.
NOAA/DEPARTMENT OF COMMERCE
What will the weather be like today? Many of
us want to know, so we turn on the television to
see what the weather forecasters have to say. In
the Washington, D.C., area, we may be tuning
in to meteorologist Bob Ryan.
“An important part of my job,” says Ryan, “is
to make the forecast as clear and understandable as possible.” Whether he is forecasting a
blizzard, severe thunderstorms, or a sunny
spring day, “it comes down to hand-holding
with people because they are concerned. They
ask: ‘Can I go out? What should I wear?’” He
tries to give people as much information as possible. That helps them make good decisions.
Doppler radar tower
LESSON 4
In addition to radar and satellite information, Ryan also uses data from ground weather
instruments (for example, thermometers,
anemometers, and barometers). Even special
airplanes collect data that are mapped and fed
into computer models. The computer models
calculate wind, precipitation, temperature,
and weather movement at locations around
the globe. Ryan compares predictions calculated by several different models to see how
well they agree.
Ryan says that the science of weather forecasting is a lot like the science of medicine.
Medical doctors use all the available tests, Xrays, and other methods to diagnose a patient’s
condition. Meteorologists do the same thing to
arrive at a forecast, he says. They ask: “What are
the weather data and the calculations showing?
What does it mean to our local area?”
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
reports the forecast for the first time on the
radio at 3:30 P.M. Then, with weather images
moving across a computerized map, he
explains the forecast to television viewers at
4:00, 5:00, 6:00, and 11:00 P.M.
Ryan gives his forecast in front of a green
board called a “chroma-key.” The computer
image of each map is electronically projected
onto any lime green space on the board. The
public sees Ryan in front of the computer
images, even though they are not really behind
him. Can you guess why he doesn’t wear lime
green?
Inspiring the Next Generation
Some years ago, Ryan decided he wanted to get
more young people excited about the weather.
He created a program called 4-WINDS to teach
students about weather. With the help of area
businesses, Ryan’s TV station donated weather
stations to local schools. Each weather station
contains instruments for measuring weather
variables (including temperature, pressure,
STC/MS™ C ATA S T R O P H I C E V E N T S
MATTHEW BAILEY/NSRC
Presenting the Weather
When Ryan presents the weather, he decides
what part of the local weather is most important to viewers. “Each situation
is a little bit different,” he says.
If thunderstorms are forming in
the mountains, he shows the
radar pattern. “If I’m following a
tropical system, like a hurricane, I might use almost hourly
satellite images,” he explains.
Ryan often links his weather
report to other news. For
instance, he once showed a
tropical storm forming over the
Pacific Ocean. He explained how
the storm’s rainfall could help
put out fires that were raging in
Mexico.
Once Ryan has an idea for
the forecast, he works with
another meteorologist to set up
weather images on a computer
system. At 3:20 P.M., Ryan puts
Bob Ryan working in the Channel 4 Storm Center
together the final forecast. He
51
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
humidity, and wind)
and a computer to
store the data. In
2000, students from
200 schools participated in the project,
using their computers
to exchange weather
data on the Internet.
Ryan hopes that
young people who
are interested in the
weather will have a
better understanding
of science and maybe
even become meteorologists. They need
to have a strong
background in math
and science and do
well in those subjects, he says. Ryan
Bob Ryan gives his forecast in front of a green board called a “chroma-key.” The public
learned about weather
sees what is shown on the TV monitor in the upper left-hand corner.
by studying science in
college and earning a
master’s degree in physics and atmospheric
term forecasts, to studying global climate change,
science.
to managing water resources. Most of all,” he
“I think there’s a lot of opportunity for people
says, “it should be something you consider fun
interested in this field—from improving shortand look forward to doing.” 52 STC/MS™ C ATA S T R O P H I C E V E N T S
MATTHEW BAILEY/NSRC
LESSON 4
LESSON 4
Weather Forecasting Can Be Cool . . .
or Hot!
When Vicky participated in the 4-WINDS
Program with her classmates at
Mountain View School in Haymarket,
Virginia, she found that “it was like finding out how a magician does his tricks.
They use computers and technology to
help them figure out the answers to the
questions,” she said. “I thought weather
forecasting was a ‘luck’ thing. Maybe you
got it right, or maybe you were way off.”
She found out that she could make predictions that were “pretty close” by looking at patterns of temperature, wind, and
pressure.
“I used to think that computers were
just for games and for typing,” said
Vicky’s classmate Shawn. “But there are
other things you can do. I like using the
4-WINDS station because it lets me know
what’s going to happen. I’m getting better
and better at figuring the weather out.”
According to Amanda May, Vicky and
Shawn’s teacher, participating in 4-WINDS
“gave the students a tremendous knowledge of how technology is used in
H E AT T R A N S F E R
AND THE
MOVEMENT
OF
AIR
everyday life. My students were getting
very accurate weather forecasts for our
area within 24 to 36 hours because they
could track patterns. It really made an
impression when they could see someone else calling our system over the
Internet. And there we were on Channel 4
[the station Bob Ryan works for]. Or the
National Weather Service would call [to
get our data]. The students were doing
‘adult’ work.” Because of the 4-WINDS
Program, May continued, several of her
students developed a great interest in
earth science and meteorology.
Carol is one such student. She wrote in
her journal that “when the wind is from
the southwest and the barometric pressure is falling, something is going to come
out of the sky. Then we just use the thermometer to figure out what that something is, snow or rain. This weather stuff
is a cinch!”
Shawn agreed. “I can predict what
tomorrow’s weather will be because I can
find out what the weather is right now,”
she said. “I’m good at it, but I don’t think
I’m a threat to Bob Ryan . . . yet!”
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