Water in the
Atmosphere
Chapter 16 Section 4
Pages 545-550
Humidity
• Humidity- A measure of the amount of
water vapor in the air.
• Relative Humidity- The percentage of
water vapor in the air compared to the
maximum amount that the air can hold at
that temperature.
Relative Humidity Problems:
• If 10°C Holds a maximum of 8 grams of
water vapor.
• What is the humidity if 8 grams of water
vapor are in the air?
Relative Humidity Problems:
• If 10°C Holds a maximum of 8 grams of
water vapor.
• What is the humidity if 8 grams of water
vapor are in the air?
• If the air is holding 4 grams of water vapor,
what is the relative humidity?.
R. Humidity Depends ON:
• The temperature.
• Warm air is less dense.
– Has more room to hold water vapor.
• Cold air is more dense
– Has less space to hold water vapor
Measuring Humidity
• Psychrometer- An
instrument used to measure
relative humidity, consisting
of a wet-bulb thermometer,
and a dry-bulb thermometer.
• Evaporation is a
____________ process.
Relative Humidity
• If the relative
humidity is high,
will there be
much of a
temperature
difference
between the
thermometers
and why?
Dew Point
• Dew Point- The temperature at which
condensation begins.
• If the temperature= dew point
– Relative humidity = 100%
Cloud Formation
• 1. Air is warmed and rises
– Infrared Radiation Heats Surface.
– Evaporates water.
Cloud Formation
• 2. Warm, Moist air rises.
• Air Expands as it rises.
• Air Cools at the Dry Adiabatic Lapse Rate
(Dry ALR= 10°C for every 1km)
Cloud Formation
• 3. Condensation Occurs.
• Must occur on condensation nuclei
– Dust
– Salt
– Smoke
Cloud Formation
• 4. Condensation Level
– The level at which condensation occurs.
– Relative humidity = 100%
• Temp and Dew Point are =
Cloud Formation
• 5. Cloud Forms:
– Air now cools at the Wet ALR= 5-9°C
– Cools slower because condensation releases
some heat.
Cloud
Identification
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Chapter 16 Section 4
Pages 548-550
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Directions
Notes
Quiz
Click on an Icon to navigate:
Directions
1. Use the arrows to navigate through this
PowerPoint
2. Click through the following slides on
clouds and copy the notes onto your
note sheet.
3. Be sure to sketch the shape of each
cloud in your notes as well.
4. Take the Cloud Quiz.
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Cumulus
• Means heap or mass.
• Fair weather clouds.
• Can grow to be very
tall.
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Altocumulus
• Alto- means that they
form at a medium
altitude.
• Look like cumulus
clouds.
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Cumulonimbus
• Thunderstorm Clouds
sometimes called
thunderheads.
• Tallest clouds, they
grow from cumulus
clouds. Produce
heavy rain.
• The suffix nimbus
means rain.
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Mammatus Clouds
• Round, downwardextending protrusions.
• Bag like sacs.
• Usually occurs along
with some
cumulonimbus
clouds.
• May indicate very
severe weather.
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Stratus
• Strato- means
“spread out”
• Flat layered clouds.
• Usually cover most of
the sky.
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Nimbostratus
• Prefix nimbus means
rain.
• Flat layered clouds.
• Accompany warm
fronts.
• Bring rain, snow, sleet
or freezing rain.
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Altostratus
• Look like stratus
clouds high in the
atmosphere.
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Cirrus Clouds
• Feathery “hooked”
ends
• Made up of ice
crystals
• First to arrive with a
warm front.
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Cirrocumulus
• Look like cumulus
clouds.
• High in the
atmosphere.
• Made of ice crystals.
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Fog
• A cloud that occurs at or
near the ground.
• Forms when the ground
cools after a warm humid
day.
• The air above the ground
cools to the dew point.
• The sun “burns” off the
fog. (evaporates)
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Question
• Explain how clouds are classified?
• Use the Sky Watcher Chart to help you.
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Quiz
Quiz
• Directions:
– Read each question.
– Click on the letter of your choice.
– If you get a question wrong, the button will
turn red. Try again.
– If you get the question right, move on to the
next question by clicking the arrow.
– Click the arrow to the right to begin.
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Quiz
1. These clouds cover the sky
and bring rain, snow or sleet.
A Stratus
B Cirrus
C Cumulus
D Nimbostratus
Quiz
2. What type of cloud is
feathery or wispy?
A Cirrus
B Stratus
C Cumulus
D Nimbus
Quiz
3. What type of cloud means
“heap” or “pile”?
A Stratus
B Cirrus
C Cumulus
D Mammatus
Quiz
4. Identify this cloud that
occurs on the ground.
A Cirrus
B Cumulus
C Stratus
D Fog
Quiz
5. Identify this Cloud:
A Cirrus
B Mammatus
C Cumulus
D Cumulonimbus
Great Job!
• Congratulations on being able to correctly
identify the types of clouds! You are on
your way to becoming a meteorologist.
Keep up the great work!
• Read pages 167-173
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