Clouds
C
What are clouds made of?
• Water vapor condensed to liquid or ice.
• Air that has reached dew point
• Condensation nuclei (dust, salt, smoke,
pollutants)
Environmental Lapse Rate
Temperature drops 5C every 1000 meters due to the
expansion of air.
McDonald Pass is 1924 meters, Helena elevation is 1324
meters.
• What is the temperature difference?
Expansion
Compression
Three ways air is lifted.
1. Orographic lifting
2. Frontal Wedging
3. Convective lifting.
Orographic lifting
• “RainShadow
Effect”
Oregon Rain shadow Effect. - Mt.
Hood is the snowcapped Peak.
Frontal Wedging
Convective Lifting
Different types of clouds indicate
different types of weather.
• Cirrus: High feathery clouds—usually clear
skies
• Stratus: Layered clouds from wind blowing
horizontally—usually associated with fronts of
moisture with stable air.’
• Cumulus: Puffy clouds from convection
moving clouds vertically
• Cumulonimbus: Large and tall clouds which
produce heavy precipitation.
Cirrus
Cumulus
Cumulonimbus
Stratus
Why don’t all
clouds produce
precipitation?
• For precipitation to occur on
earth, water droplets must
grow by 1,000,000 times.