Chapter 2

Weather Factors

Sections 4 and 5

Water in the Atmosphere and

Precipitation

Humidity

• Humidity is a measure of the amount of water vapor in the air.

• Relative humidity is the % of water vapor in the air compared to the maximum amount the air could hold.

Dew Point

• The temperature at which condensation begins.

Types of Clouds

• Meteorologists classify clouds into three main types:– Cumulus = looks like cotton balls, low to the ground (2km to

18km), usually mean fair weather except for cumulonimbus clouds which bring thunderstorms

– Stratus = flat gray layers, middle altitudes, cover all or most of the sky making it cloudy out and can lead to drizzling, rain, or snow

– Cirrus = wispy feathery clouds, form at high altitudes with cold temperatures, made of ice crystals

What Is Precipitation?

• Precipitation - Any form of water that falls from clouds and reaches Earth’s surface.

Rain

• Most common type •At least 0.5 mm in

diameter

Sleet

• Ice particles smaller than 5 mm• Rain which freezes through a layer of

cold AIR

Freezing Rain

• Raindrops which freeze when they touch a cold surface.

Hail

• Pellets of ice larger than 5 mm.

• Forms only inside cumulonimbus clouds during thunderstorms.

Snow

• Water vapor in a cloud that is changed directly into ice crystals.

Review Questions

• Pg. 66 = #1-3• Pg. 70 = #1-4

• Complete sentences and everyone turns in their own paper.