C

Clouds

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.