Clouds
What are clouds?
A cloud is a large collection of very tiny droplets of water or ice crystals. The
droplets are so small and light that they can float in the air.
How are clouds formed?
All air contains water, but near the ground it is usually in the form of an invisible
gas called water vapor. When warm air rises, it expands and cools. Cool air can't
hold as much water vapor as warm air, so some of the vapor condenses onto tiny
pieces of dust that are floating in the air and forms a tiny droplet around each dust
particle. When billions of these droplets come together they become a visible
cloud.
Why are clouds white?
Clouds are white because they reflect the light of the sun. Light is made up of
colors of the rainbow and when you add them all together you get white. The sun
appears a yellow color because it sends out more yellow light than any other color.
Clouds reflect all the colors the exact same amount so they look white.
Why do clouds turn gray?
Clouds are made up of tiny water droplets or ice crystals, usually a mixture of both.
The water and ice scatter all light, making clouds appear white. If the clouds get
thick enough or high enough all the light above does not make it through, hence
the gray or dark look. Also, if there are lots of other clouds around, their shadow
can add to the gray or multicolored gray appearance.
Why do clouds float?
A cloud is made up of liquid water droplets. A cloud forms when air is heated by
the sun. As it rises, it slowly cools it reaches the saturation point and water
condenses, forming a cloud. As long as the cloud and the air that its made of is
warmer than the outside air around it, it floats!
How do clouds move?
Clouds move with the wind. High cirrus clouds are pushed along by the jet stream,
sometimes traveling at more than 100 miles-per-hour. When clouds are part of a
thunderstorm they usually travel at 30 to 40 mph.
Why do clouds form at different heights in the atmosphere?
The characteristics of clouds are dictated by the elements available, including the
amount of water vapor, the temperatures at that height, the wind, and the interplay
of other air masses.
How is fog formed?
There are many different types of fog, but fog is mostly formed when southerly
winds bring warm, moist air into a region, possibly ending a cold outbreak. As the
warm, moist air flows over much colder soil or snow, dense fog often forms.
Warm, moist air is cooled from below as it flows over a colder surface. If the air is
near saturation, moisture will condense out of the cooled air and form fog. With
light winds, the fog near the ground can become thick and reduce visibilities to
zero.
(Graphic Credit: USA TODAY.)
Cirrus
Clouds
Cirrus clouds are the most common of the high clouds. They are composed of ice and are
thin, wispy clouds blown in high winds into long streamers. Cirrus clouds are usually white
and predict fair to pleasant weather. By watching the movement of cirrus clouds you can
tell from which direction weather is approaching. When you see cirrus clouds, it usually
indicates that a change in the weather will occur within 24 hours.
Cirrostratus clouds are thin, sheetlike high clouds that often cover the entire sky. They
are so thin that the sun and moon can be seen through them. Cirrostratus clouds usually
come
12-24
hours
before
a
rain
or
snow
storm.
Cirrocumulus clouds appear as small, rounded white puffs that appear in long rows. The
small ripples in the cirrocumulus clouds sometime resemble the scales of a fish.
Cirrocumulus clouds are usually seen in the winter and indicate fair, but cold weather. In
tropical
regions,
they
may
indicate
an
approaching
hurricane.
"Alto"
Clouds
Altostratus clouds are gray or blue-gray mid level clouds composed of ice crystals and
water droplets. The clouds usually cover the entire sky. In the thinner areas of the clouds,
the sun may be dimly visible as a round disk. Altostratus clouds often form ahead of
storms
with
continuous
rain
or
snow.
Altocumulus clouds are mid level clouds that are made of water droplets and appear as
gray puffy masses. They usually form in groups. If you see altocumulus clouds on a warm,
sticky morning, be prepared to see thunderstorms late in the afternoon.
Stratus
Clouds
Stratus clouds are uniform grayish clouds that often cover the entire sky. They resemble
fog that doesn't reach the ground. Light mist or drizzle sometimes falls out of these
clouds.
Stratocumulus clouds are low, puffy and gray. Most form in rows with blue sky visible in
between them. Rain rarely occurs with stratocumulus clouds, however, they can turn into
nimbostratus
clouds.
Nimbostratus clouds form a dark gray, wet looking cloudy layer associated with
continuously falling rain or snow. They often produce precipitation that is usually light to
moderate.
Cumulus
Clouds
Cumulus clouds are white, puffy clouds that look like pieces of floating cotton. Cumulus
clouds are often called "fair-weather clouds". The base of each cloud it flat and the top of
each cloud has rounded towers. When the top of the cumulus clouds resemble the head of
a cauliflower, it is called cumulus congestus or towering cumulus. These clouds grow upward
and they can develop into giant cumulonimbus clouds, which are thunderstorm clouds.
Cumulonimbus clouds are thunderstorm clouds. High winds can flatten the top of the cloud
into an anvil-like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail,
lightning and even tornadoes. The anvil usually points in the direction the storm is moving.
Special
Clouds
Mammatus clouds are low hanging bulges that droop from cumulonimbus clouds. Mammatus
clouds
are
usually
associated
with
severe
weather.
Lenticular clouds are caused by a wave wind pattern created by the mountains. They look
like
discs
or
flying
saucers
that
form
near
mountains.
Fog is a cloud on the ground. It is composed of billions of tiny water droplets floating in
the air. Fog exists if the atmospheric visibility near the Earth's surface is reduced to 1
kilometer
or
less.
Contrails are condensation trails left behind jet aircrafts. Contrails form when hot humid
air from jet exhaust mixes with environmental air of low vapor pressure and low
temperature. The mixing is a result of turbulence generated by the engine exhaust.
Green Clouds are often associated with severe weather. They form when the clouds are
illuminated by light reflected off green vegetation, such as large corn fields or a heavily
wooded forest. In the Great Plains region of the U.S. green clouds are associated with
storms
likely
to
produce
tornadoes.
Cloud Chart
Cloud Group
Cloud Height
Cloud Types
High Clouds = Cirrus
Above 18,000 feet
Cirrus
Cirrostratus
Cirrocumulus
Middle Clouds = Alto
6,500 feet to 18,000 feet
Altostratus
Altocumulus
Up to 6,500 feet
Stratus
Stratocumulus
Nimbostratus
Low Clouds = Stratus
Clouds with Vertical Growth
Cumulus
Cumulonimbus
Special Clouds
Mammatus
Lenticular
Fog
Contrails
Information from : http://www.weatherwizkids.com/cloud.htm
Reading Comprehension: Informational/Weather
Name: ________________________________ Date: ___________________________
©2004abcteach.com
CLOUDS
Clouds are an important part of the water cycle. The
water cycle is the movement of water from the Earth into the
sky and then back down to Earth again. Did you know that
over 70% of the Earth is covered in water? Water on Earth is in the form of salt
water (97%), the water that is found in the oceans and saltwater lakes, and fresh
water (3%), the water that is found in rivers, ponds, lakes, streams and
underground. The sun heats water on the surface of the Earth, and causes it to
evaporate. Evaporation is the process when water moves from being a liquid to
being vapor. Water vapor is made up of tiny water droplets in the air. Water can
also move into the air through transpiration. Transpiration is the movement of
water out of plants. During photosynthesis, plants make oxygen and water. Water
then moves out of tiny holes on the leaves and into the air. The water vapor rises
up into the atmosphere, and as it cools, it condenses. When the water vapor
condenses it forms clouds. Precipitation happens when so much water vapor
condenses that the air cannot hold it anymore. The clouds get so heavy that
some of the water must fall back down to Earth as rain, snow, sleet or hail.
There are many different types of clouds. The type of cloud depends on
how high up in the atmosphere the water condenses. The atmosphere is the
blanket of air that covers the Earth.
Stratus clouds
Stratus clouds occur below 6,000 feet. These clouds look like flat sheets of
clouds, and can mean an overcast or rainy day. These clouds are usually a
uniform color of gray, and cover most of the sky.
Cumulus clouds
Cumulus clouds are also below 6,000 feet, and look like big fluffy balls of
cotton! They usually mean that the weather will be nice; however, sometimes
they can get very tall and turn into thunderheads. These clouds are usually flat
on the bottom, but have very lumpy tops. Cumulus clouds usually form alone,
and there is a lot of blue sky between different clouds.
Cirrus clouds
These wispy clouds usually form above 18,000 feet. Cirrus clouds
generally move from west to east. They form when water vapor forms ice
crystals, and they are so thin because of the height at which they form. There is
very little water vapor above 18,000 feet, and so big thick clouds cannot form.
These are the three main types of clouds that can form; however, there are
also several combination clouds.
Reading Comprehension: Informational/Weather
Name: ________________________________ Date: ___________________________
©2004abcteach.com
Combination Clouds
Stratocumulus clouds usually form below 6,000 feet, and usually form in
rows or patches, with blue sky in between. The color of stratocumulus clouds can
be from white to dark gray, but precipitation hardly ever falls from these clouds.
Nimbostratus clouds also form below 6,000 feet, and usually produce a
steady form of precipitation. Steady precipitation isn’t like a hard thunder shower,
but can instead last for several hours or even more than a day. Nimbostratus
clouds are so thick that you can’t see the sun or the moon through them.
Altostratus clouds form higher than stratocumulus or nimbostratus clouds.
They form between 6,000 and 20,000 feet. Altostratus clouds cover the entire sky
over a large area, and usually produce steady precipitation ahead of a storm.
You can see a bit of the sun through the clouds, but the sun will be hazy or
‘watery’. Even though you can see the sun, altostratus clouds do not let enough
sunlight through to produce shadows.
Altocumulus clouds also form between 6,000 and 20,000 feet. These
clouds look like puffy gray balls or blobs, and sometimes appear in rows. Part of
these clouds is usually darker than the rest, and this helps to set them apart from
higher cirrocumulus clouds. If you see these clouds on a hot summer morning it
often means that there will be thunderstorms in the afternoon.
Cirrostratus clouds form even higher than most altostratus and
altocumulus clouds, at above 18,000 feet. These clouds are so thin that you can
see the moon and the sun clearly. Sometimes you only know that there are
cirrostratus clouds in the sky because you can see a fuzzy halo around the sun
or the moon. This halo is caused because the ice crystals in the cloud bend the
light from the sun and the moon. Cirrostratus clouds usually mean that there will
be rain or snow within 24 hours.
Other mixed clouds that form high in the sky are cirrocumulus clouds. They
also form above 18,000 feet. They can look like small rounded puffs or cotton
balls, either alone or in rows. When the puffs are in rows, the sky has a rippling
look, and this is how you can tell that they are cirrocumulus clouds, and not cirrus
or cirrostratus clouds.
Finally, there are the cumulonimbus clouds. These clouds are
thunderstorm clouds. The word nimbus or nimbo means precipitation producing
cloud. Nimbostratus clouds produce steady rain and cumulonimbus clouds
produce thunderstorms.
Clouds can be fluffy and white, or heavy and gray. They can bring rain and
snow, or day long drizzle. But whatever color or shape they come in, they still do
the same thing. They return water to the Earth, and they are an important part of
the water cycle.
Reading Comprehension: Informational/Weather
Name: ________________________________ Date: ___________________________
©2004abcteach.com
Questions on Clouds
1. How much of the Earth is covered in water?
__________________________________________________________________
2. How is the water on Earth split up?
__________________________________________________________________
3. What is evaporation?
__________________________________________________________________
4. What is the process called when water moves from plants into the air?
__________________________________________________________________
5. Describe the water cycle. Include how water moves into the air and back to Earth.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
6. What is the atmosphere?
__________________________________________________________________
7. Describe the three main cloud types.
a) ______________________________________________________________
________________________________________________________________
b) ______________________________________________________________
________________________________________________________________
c) ______________________________________________________________
________________________________________________________________
8. What cloud types occur above 18,000 feet? Include mixed types in your answer.
__________________________________________________________________
__________________________________________________________________
9. What happens with nimbostratus clouds?
__________________________________________________________________
__________________________________________________________________
10. If you see altocumulus clouds on a summer morning, what do you think might
happen in the afternoon?
__________________________________________________________________
11. You have been waiting all summer for the first snowfall. It’s almost here! What type
of cloud will tell you that snow may be coming, and from what type of cloud will
snow fall?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
12. What do the words nimbo and nimbus mean?
__________________________________________________________________
Reading Comprehension: Informational/Weather
Name: ________________________________ Date: ___________________________
©2004abcteach.com
Answers to Clouds
1. 70% of the Earth is covered in water.
2. 97% of water is saltwater and 3% is freshwater.
3. Evaporation is the process through which water moves from being a liquid to
being vapor.
4. The process by which water moves from plants into air is called transpiration.
5. The sun heats the water and causes the water to evaporate. Water also enters
the air through transpiration. Water vapor moves up through the air until it
condenses into clouds. When so much water has condensed that the air cannot
hold it any longer precipitation occurs. Water falls back to Earth as rain, snow,
sleet or hail.
6. The atmosphere is the blanket of air that covers the Earth.
7. a) Stratus clouds – occur below 6,000 feet and look like flat sheets of clouds.
They are usually gray and cover most of the sky.
b) Cumulus clouds – occur below 6,000 feet and look like fluffy balls of cotton.
Usually mean nice weather, but can turn into thunderheads. Flat on the bottom
and lumpy on top.
c) Cirrus clouds – occur above 18,000 feet. Form when water vapor forms ice
crystals. They are so thin because there isn’t much water vapor above 18,000
feet.
8. Cirrus clouds, altostratus clouds, altocumulus clouds, cirrostratus clouds and
cirrocumulus clouds can all form over 18,000 feet.
9. Nimbostratus clouds form below 6,000 feet and produce a steady form of
precipitation. They are so thick that you can’t see the sun or the moon.
10. Altocumulus clouds on a hot summer morning can mean that a thunderstorm will
form in the afternoon.
11. Cirrostratus clouds usually mean that there will be rain or snow in 24 hours, and
either nimbostratus or cumulonimbus clouds will bring snow.
12. The words nimbo and nimbus mean ‘precipitation producing cloud’.
CLOUD IN A BOTTLE
MATERIALS:



2-liter clear plastic pop bottle
matches (children will need adult assistance to light matches)
warm water
PROCESS:
Fill the clear plastic 2-liter bottle one-third full of warm water and place
the cap on. As warm water evaporates, it adds water vapor to the air
inside the bottle. This is the first ingredient to make a cloud.
Squeeze and release the bottle and observe what happens. You’ll notice
that nothing happens. Why? The squeeze represents the warming that
occurs in the atmosphere. The release represents the cooling that occurs
in the atmosphere. If the inside of the bottle becomes cover with
condensation or water droplets, just shake the bottle to get rid of them.
Take the cap off the bottle. Carefully light a match and hold the match
near the opening of the bottle.
Then drop the match in the bottle and quickly put on the cap, trapping the
smoke inside. Dust, smoke or other particles in the air is the second
ingredient to make a cloud.
Once again, slowly squeeze the bottle hard and release. What happens? A
cloud appears when you release and disappears when you squeeze. The
third ingredient in clouds is a drop in air pressure.
EXPLANATION:
Water vapor, water in its invisible gaseous state, can be made to
condense into the form of small cloud droplets. By adding particles such
as the smoke enhances the process of water condensation and by
squeezing the bottle causes the air pressure to drop. This creates a
cloud!