Download Water in the Atmosphere

Water in the Atmosphere
Chapter 16.4
Humidity
• A measure of the amount of water vapor in
the air
• How much water vapor air holds depends
on temperature
• Warm air holds more water vapor than
cold air
Relative Humidity
• The amount of water vapor in the air
compared to the maximum amount of
water vapor air can hold at a particular
temperature
Blue = amount of water
in the air
Yellow = amount of water
air can actually hold
Measuring Relative Humidity
• R.H. can be
measured with a
psychrometer
To find relative humidity:
• Look across from
dry-bulb temp
• Look down from
difference
between dry-bulb
and wet-bulb
temp (dry-wet =
difference)
• Result is relative
humidity
Cloud Formation
• Clouds form when water vapor in the air
condenses to form liquid water or ice
crystals
• Dew point – the temperature at which
condensation begins
• Clouds need particles on which to condense
(salt, dust, or smoke)
• Dew or frost is when water vapor condenses
on a surface
Clouds
Cirrus - feathery
Stratus – flat layers
Cumulus – fluffy, rounded
Nimbus added to cloud type
indicates precipitation
Cloud Combinations
Altocumulus – high puffy
Cirrocumulus - fish scales
Predicts rain
Altostratus- high layered
Cumulonimbus – often
Produce thunderstorms
Let’s
Make
A
Cloud
Precipitation
• Any form of water that falls from clouds
and reaches the surface
Rain – water droplet at least 0.5 mm in
diameter
Sleet – rain that falls through a freezing
layer of air and falls to the ground
Freezing rain – rain that freezes after
hitting the surface
Precipitation
Snow – water vapor that freezes directly into
ice crystals
and stays solid all the way to surface
Hail – droplet of water that freezes high in a
cloud, falls and gathers more moisture in
the cloud and is forced upward in the
cloud by updrafts to freeze. Falls to
ground when it becomes too heavy.