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WATER IN THE AIRWeather Balloons
Inv. 6 Part 5
WEATHER BALLOONS
Meteorologist use them to get information about the troposphere.
A large balloon filled with helium or hydrogen.
Signals from balloon are received and recorded at a ground station.
WEATHER BALLOON
A small computer called a radiosonde is attached to the balloon.
The radiosonde has instruments for measuring air pressure, air temperature, relative humidity, wind speed, and direction.
WEATHER BALLOON VIDEO
After you watch the video be prepared to share your thoughts.
VIDEO DISCUSSION
Why do you think meteorologists use helium or hydrogen in their balloons?
These gases are less dense than the surrounding air, so the balloon floats up.
What do you think happens to the volume of the balloon as it rises in the atmosphere?
Surrounding air pressure decreases, so the volume of the balloon increases. Eventually it pops.
WEATHER BALLOON MULTIMEDIA
Watch CD-ROM SimulationTurn to page 39 in lab book as you work with the CD-ROM.
PAGE 39(LB) DISCUSSION
What was the trend in air pressure as altitude increased in Chicago? In Phoenix?
Air pressure decreased in both locations. Air pressure readings were almost the same.
Describe the temperature trends in both Chicago and Phoenix.
Temperature in both locations decreases with altitude.
PAGE 39(LB) DISCUSSION CONT.
Was the trend the same in both cities? Phoenix’s temperature started higher than
Chicago at ground level, but it ended up lower at the highest altitude.
Which weather factors varied the most between Chicago and Phoenix?
Temperature and dew point varied the most. In Chicago the lines touched and in Phoenix they never touched.
PAGE 39(LB) DISCUSSION CONT.
Do you think it might be a cloudy day in Chicago? What evidence do you have?
The weather would be cloudy. The dew point and temperature were very close at a particular altitude.
At what altitude would you see clouds? 5000 to 6000 meters if condensation nuclei
were present.
PAGE 39(LB) DISCUSSION CONT.
Do you think it might be a cloudy day in Phoenix? What evidence do you have?
The sky was probably clear with no clouds. Dew point and temperature were never the same.
REA
DIN
G
•Starting on page 43 read
“Weather Balloons and Upper-Air Soundings”
•Complete the “Think Questions” at the end.
SOUNDING
This is the set of data from a weather balloon.
Open to page 81 in the Resource Book, where you will find sounding for 4 different cities.
What 4 cities are represented? Phoenix, Chicago, Boston, San Fransisco What information is recorded? Dew point, air temperature, and altitude
EX
AM
PLE O
F P
LO
TTIN
G D
ATA
•The data for Oakland has been done
•Let’s go over it.
AN
ALY
ZIN
G T
HE
DA
TA
•Open up to page 40 of your lab book.
•Each person in your lab group will plot the data for one of the cities.
•Graph the altitude vs. air temperature in red
•Graph the altitude vs. dew point in green
Air Temperature and Dew Point
Alt
itud
e (
Mete
rs)
COMPARE CITIES SOUNDING
How are the plots alike?-Both air temperature and dew point decrease as the balloon rises.
How are the plots different?-Some dew point and air temperature lines
cross; others do not cross or even come close.
THINKING ABOUT CONDENSATION
What is dew point”-The temperature at which condensation occurs.
Look at the graph for your city. Did condensation occur anywhere along the balloon’s upward journey? How do you know?-If the air temperature were the same as the
dew point, condensation could have occurred.
THINKING ABOUT CONDENSATION
What would you expect to see in the sky if condensation occurred?-Clouds
Which cities most likely had clouds on this day? Why do you think so?-Chicago and Boston because the dew point
and temperature lines are almost the same.
THINKING ABOUT CONDENSATION
At what altitude might you expect to see clouds in Boston on this day?-Between 800 and 1700 meters
Would you have expected to see clouds in Phoenix? Why or Why not?-Probably not. The temperature and dew point lines never crossed.
REVIEW OF ATMOSPHERIC MOISTURE
What is water vapor?-The gaseous form of water. It is invisible.
How do the processes of evaporation and condensation affect the amount of water vapor in the air?-When energy is added to a liquid water, it
can evaporate, adding water vapor to the air. When water vapor cools it condenses forming liquid water. Clouds and precipitation form.
REVIEW OF ATMOSPHERIC MOISTURE
What is relative humidity?-The amount of water vapor in air compared
to the amount of water vapor needed to saturate the air at a specific temperature. Recorded as a percentage.
How does temperature affect relative humidity?-If temperature increases, relative humidity
decreases and vice versa.
REVIEW OF ATMOSPHERIC MOISTURE
What ingredients are needed to make a cloud?-Moisture, energy transfer, and condensation
nuclei. Temperature needs to decrease to the dew point so water can condense on condensation nuclei.
