8.2 Precipitation

Precipitation

What is Precipitation

Precipitation is any form of
water that falls from clouds
and reaches Earth’s surface

●Examples:

○Rain

○Snow

○Sleet

○Freezing Rain

○Hail

Multiple Choice

Which of the following is NOT a type of Precipitation?

• Rain

• Sleet

• Rock

• Snow

Not all clouds produce precipitation!

●For precipitation to occur, cloud droplets or ice crystals must
grow heavy enough to fall through the air

How does it work?

●Cloud droplets grow by
colliding and combining
with other droplets

●As droplets grow larger,
they move faster and
collect more small
droplets

●The droplets become
heavy enough to fall out of
the cloud as raindrops

Multiple Choice

What happens when water droplets become heavy enough?

• They make snow inside the cloud

• They fall out of the cloud

• They freeze on their way out of the cloud

• They bring the cloud down to Earth

Rain
●The most common type of precipitation is RAIN!

●Drops of water are called rain if they are at least 0.5
millimeters in diameter

●Precipitations made of smaller drops of water is called
drizzle

○If they are even smaller, they are called mist

●Drizzle and mist usually fall from stratus clouds

Multiple Choice

What type of clouds does Drizzle and Mist usually fall from?

• Cirrus Clouds

• Cumulonimbus Clouds

• Stratus Clouds

• Altocumulus Clouds

Hail

●Hailstones are round pellets of
ice larger than 5 millimeters in
diameter

●Hail forms ONLY inside
cumulonimbus clouds during
thunderstorms

Multiple Choice

True or False: Hail is a pellet of ice larger than 5 millimeters in diameter

• True

• False

Hail Life Cycle

●A hailstone starts as an ice pellet inside a cold
region of a cloud.

●Strong updrafts carry the hailstone up through
the cold region many times

●Each time the hailstones goes through the cold
region, a new layer of ice forms around it

●Eventually the hailstone becomes heavy enough
to fall to the ground

Fun Fact!

●If you cut a hailstone in half, you will see shells
of ice, like layers of an onion

Snow

●Snowflakes are water vapor in a
cloud that is converted directly
into ice crystals

●Snowflakes have an endless
number of different shapes and
patterns, no two are the same!

●Powdery snow is produced
when snow falls through cold,
dry air

●When snow falls through humid
air that is close to freezing, the
snowflakes tend to join together
into larger clumps

Multiple Choice

Snow is water vapor in a cloud that is converted directly into ______

• ice crystals

• freezing rain

• spheres

• round pellets

Sleet

●Sleet is when raindrops
fall though a layer of air
that is below 0 degrees
celsius (the freezing point
of water)

●As they fall, the
raindrops freeze into
solid particles of ice

●Sleet is smaller than 5
millimeters in diameter

Freezing Rain

●Freezing Rain is when raindrops falling
through cold air do not freeze in the air,
but instead freeze when they touch a
cold surface

●In an ice storm, a smooth, thick layer of
ice builds up on every surface

○The weight of this can break tree
branches and cause them to fall onto
power lines

○This can also make sidewalks and roads
slippery and dangerous

Multiple Choice

The difference between sleet and freezing rain is _________

• sleet does not freeze in the air

• freezing rain freezes in the air

• sleet is freezes when it touches a cold surface

• freezing rain freezes when it touches a cold surface