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.
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Why are clouds white?
Since light travels as waves of different lengths, each color
has its very own unique wavelength.
Clouds
are white because their water droplets or ice crystals
are large enough to scatter the light of the seven wavelengths
(red, orange, yellow, green, blue, indigo, and violet), which
combine to produce white light.
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.
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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.
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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.
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Fog
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.
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
Low Clouds =
Stratus
Up to 6,500 feet
Stratus
Stratocumulus
Nimbostratus
Clouds with Vertical Growth
Cumulus
Cumulonimbus
Special Clouds
Mammatus
Lenticular
Fog
Contrails
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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
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.
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Cirrocumulus clouds
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.
Altostratus 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.
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Altocumulus clouds
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.
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Stratocumulus 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
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.
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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
is 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
congest us
or towering cumulus. These clouds grow upward and
they can develop into giant cumulonimbus clouds,
which are thunderstorm clouds.
Cumulonimbus 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.