Transcript All_About_Clouds - Moore Middle School

All About Clouds
Clouds
• For a cloud to form, there must be water
vapor in the air.
• humidity- the measure of the amount of
water vapor in the air.
• relative humidity- the percentage of the
amount of water vapor in the air compared
to the maximum amount of water the air
can hold. Measured with a psychrometer.
precipitation
Forms of precipitation:
a) rain- drops of water that are at least .5
mm in diameter (mist or drizzle if smaller)
b) sleet- drops of water that freeze as they
fall from the sky; sleet-ice particles that are
less than 5mm in diameter
c) freezing rain- don’t freeze as they fall but
freeze as they touch something cold such
as tree branches or power lines.
more forms of precipitation
d) hail- round pellets of ice larger than 5 mm
in diameter that form in cumulonimbus
clouds; sent up and down in the cloud,
freezing a new layer of ice around the
hailstone.
e) snow- water vapor in a cloud is converted
directly into ice crystals
What is a cloud?
• 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.
Why do clouds look white?
• Clouds reflect sunlight, making them white.
• Clouds reflect all the colors of the rainbow the
same amount, making them appear a white
color.
Why do some clouds appear gray?
• When the clouds get really thick or really
high in the sky, all the light can’t travel
through the cloud. This makes the cloud
look gray instead of white.
• The shadows of other clouds can make
some clouds appear gray also.
How are clouds formed?
Clouds form when:
1. warm air rises, expands and cools.
2. some of the vapor condenses onto tiny
pieces of dust because cool air can’t hold
as much water as warm air.
3. A tiny droplet forms around each dust
particle.
4. They become a visible cloud when
billions of these droplets come together.
Various Cloud Types
• Stratus clouds- low level clouds that are
thick enough to block the sun
• Cumulus clouds- low to midlevel clouds
that are puffy and white
• Cirrus clouds- thin, whispy clouds that are
high in the troposphere
• Nimbus clouds- bring rain; dark colored
Click here to see a video about cloud formation
• Click to view animation of precipitation
over mountains:
• http://bcs.whfreeman.com/thelifewire/conte
nt/chp56/5602001.html
Click here to see a
video detailing the
various cloud types!