Clouds

Why is the sky blue?

• "White" sunlight enters the atmosphere

• molecules in the air are just the right size to scatter light from the blue end of the visible spectrum.

• The other colors pass through

And Clouds Are White Because...?

...the water droplets that make up clouds are much larger than the molecules that scatter blue light. The clouds scatter and reflect all the visible colors of light that strike them.

And Clouds Are Gray Because...?

• if the cloud is thick enough, light does not penetrate completely through the cloud, resulting in dark, heavy-looking cloud bottoms

Why do clouds form? • Clouds are nothing more than

water vapor that condenses into a visible form.

• The sun heating the earth’s surface evaporates water to the atmosphere where it cools and condenses.

Classification of Clouds

• Clouds are classified by Form Altitude

• Three forms Stratus Cirrus Cumulus

• Three altitudes Low, middle,

high

Cloud Types

Latin Root Translation Example

Cumulus heap cumulus

stratus layer altostratus

Cirrus curl of hair cirrus

Nimbus rain cumulonimbus

Alto high altostratus

Stratus• Sheetlike or

layered clouds.• Lowest in the

sky.• Light or dark

gray, covering most of the sky,

• Includes fog.

Stratus

• Uniform, thick to thin layered clouds

• Below 6,000 feet

Stratus

Stratus

Altostratus

• Thin, uniform, sometimes with "wide corduroy" appearance

• 6,000 - 20,000 feet

Nimbostratus

Stratocumulus

• Broad and flat on the bottom, puffy on top

• Below 6,000 feet

Cumulus

• Puffy clouds • Below 6,000

feet

Cumulus

Fair Weather Cumulus

• Appearance of floating cotton

• Lifetime of 5 – 40 minutes

Cumulus

Cumulonimbus

• Appear as Thunderheads

• Located near ground to above 50,000 feet

Cumulonimbus

Cumulonimbus

Upward developing cloud

Altocumulus

• Medium-sized puffy clouds

• 6,000 - 20,000 feet

Altocumulus

Altocumulus

Cirrus

• Appear thin, wispy, often with a “mare's tail”

• Above 18,000 feet

Cirrostratus

• Appear as thin, layer, above thunderheads

• Above 18,000 feet

Cirrocumulus

• Small puffy clouds

• Above 18,000 feet

Cloud Levels

Fog

Radiation Fog

• Results from the cooling of air that is in contact with the ground.

• Due to nightly cooling of the Earth.

Advection Fog

• condensation of water vapor that results from the cooling of warm moist air as it moves across a cold surface.

Upslope Fog

• results from the lifting and adiabatic cooling of air rising up a slope of land.

Steam Fog• Condensation of

water vapor.

• Results from cool air moving over a warm body of water, lake or stream.

Drizzle

• Precipitation consisting of small drops, smaller than .5mm in diameter

Precipitation

• Sleet – ice pellets that form when rain falls through a layer of freezing air.

• Glaze Ice – thick layer of sheet ice formed when rain freezes when it contacts a surface.

Hail• Precipitation in

the form of ice.• Grows as

frozen water travels up and down in a cloud.

• Combination of different sized cloud droplets to form larger droplets.

Coalescence 

• Supercooling.• process by which water droplets

are induced to remain liquid below 0°C .

• Freezing Nuclei.• condensation nuclei with a

crystalline structure like that of ice.

Cloud Seeding

• Addition of freezing nuclei to supercooled clouds in an attempt to induce or increase precipitation.

Special Clouds:Lenticular

Mammatus

Noctilucent