1. Water in the Atmosphere
Chapter 16.4

3. 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

4. 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

5. Measuring Relative Humidity
R.H. can be measured with a psychrometer

6. 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

7. 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

8. Clouds Cumulus – fluffy, rounded Cirrus - feathery
Nimbus added to cloud type indicates precipitation
Stratus – flat layers

9. Cloud Combinations Altocumulus – high puffy Altostratus- high layered
Cirrocumulus - fish scales
Predicts rain
Cumulonimbus – often
Produce thunderstorms

10. Let’s
Make A
Cloud

11. 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

12. 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.