Clouds

Clouds  Tiny droplets of water and/or ice crystals piled together  Droplets are seven times smaller than the width of a hair  White because visible light from the sun is reflected off of them  Dark when they get thick, not allowing the sun to shine through.

Cloud Formation  The droplets come from evaporation, which is caused by the sun’s heat  Water vapor rises when it is heated  As it rises, it expands, then cools  As it cools, it condenses

Adiabatic Temperature Change  The concept of cooling from expansion and heating from contraction  Rather than adding or subtracting heat, a gas cools or becomes hot from simply expanding or contracting

Condensation Nuclei  When water vapor cools, it attaches to tiny particles in the air  Salt particles from the ocean, dust, or smoke  If the temperature is below freezing, ice crystals form, which can fall as snow.

Cloud Impact on Weather and Climate  Help trap heat emitted from the Earth’s surface.  Provide shade from the Sun  Warming nights and cooling days moderate temperature changes  Precipitation

Types of Clouds  By altitude –Cirrus—highest clouds; consist of only ice crystals –Alto—medium clouds; mid-level clouds that may contain ice crystals or liquid water droplets –Stratus—lowest clouds; usually contain water droplets, but if cold enough, can produce ice crystals

Types of Clouds  By Physical Appearance –Cirrus—wispy, like feathers; means “curl” in Latin –Cumulus—puffy, fluffy, mounded; means “heap” in Latin –Stratus—layered like thin sheets covering most of the sky; means “layer” in Latin

Precipitation  Rain  Snow  Sleet  Freezing rain  Hail