4.02 Analyze the formation of
clouds and their relation
to weather systems
Essential Question
Clouds are made up of millions of tiny
droplets of water and ice.
Each of these droplets of water is
smaller than a grain of flour, and they
are so light that they can float on air.
When pilots in airplanes fly through
clouds they can see nothing but
clouds. It's like being inside a thick
fog or a steamy room.
How do Clouds form?
Clouds form when the relative
humidity 100%.
Humidity is the amount of water
vapor in the air. So when the air
is very saturated with water vapor
(can’t hold anymore “invisible
water”) the relative humidity is
100%.
How are clouds made?
These 3 conditions are
necessary for clouds to form:
•evaporation
• cooling
•condensation
The air around us contains water
vapor (water vapor is a gas). Water is
constantly evaporating into the air.
When this air rises it gets cooler and
the water vapor condenses (it turns
into tiny drops of water) to form
clouds. FYI: condensation is the
reverse of evaporation.
What do clouds tell us?
• Clouds just don’t happen - there’s
always a reason
• A particular cloud’s shape and location
depend on (and can therefore tell us
about):
- the movement of the air
- amount of water vapor in air
- stability (flat clouds = stable air while
puffy clouds = unstable air)
How are clouds named?
Clouds are named according
to their altitude (how high up
something is in the sky) and
their general shape
These are low level clouds,
usually ground level to 5,000
feet. They appear as unbroken
sheets of low gray clouds.
They are bringing light rain,
light snow, or drizzle. (Fog is a
stratus cloud on the ground.)
These clouds are white, puffy
heaps that look like cotton
balls or cauliflower . They are
also low clouds from ground
level to 5, 000 feet. These
clouds indicate that the
weather will be good.
These clouds indicate an
immediate threat of bad weather.
It could be a sprinkle or heavy
precipitation. If they are at the
beginning of a cold front, gusty
winds or a thundershower may
follow.
Nimbus clouds are storm clouds.
They are dark and gray.
Cirrus Clouds are the highest
and whitest in the sky; 20,000
to 40,000 feet . They are thin
and made up of ice droplets.
They signal the weather will
be changing.
What makes rain?
Remember, clouds are made up of
millions of droplets of water and ice
that are very small and very light. They
are so small and light that they can
float on air. When these small droplets
collide with each other, they join
together. They get larger and heavier
until they get too heavy to float. Then
they fall to the ground as raindrops.
Credits
• Fuller Photo Gallery
http://www.fullerphotos.co.uk/storm2.htm
• Cloud and Weather Photo Gallery
http://www.jburroughs.org/science/astromet/clouds/gallery.html
• Enchanted Learning
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/clouds/