Clouds

Cloud Formation  Condensation - water vapor gathers and forms water droplets or ice crystals (deposition)  1) Warm air rises taking along vapor, cools and condenses  2) Molecules (dust, salt, ash – condensation nuclei) combine with water vapor and form droplets

Where clouds form  Word parts indicate where clouds form and describe appearance –Strato – layered clouds, usually form below 6,500 feet –Cumulo – fluffy clouds that grow upward –Alto - between 6,500 and 20,000 feet –Cirro – feathery clouds forming above 20,000 feet –Nimbo – refer to dark rain clouds

Where clouds form

High Level Clouds  Bases above 20,000 ft (7,000 m)  Composed of ice crystals  Types: Cirrus, cirrocumulus, cirrostratus

High level clouds: Cirrus Clouds  Thin, wispy, and fibrous, hair-like in appearance  Indicate fair weather

High level clouds  Cirrocumulus – extremely high –Occur before snowfall, made entirely of ice  Cirrostratus – indicate snow or rain, blanket sky –Produce halos around Sun and moon

Middle level clouds  Bases between 6,500 and 20,000 ft  Associated with light precipitation  Contain ice crystals and/or water droplets  Types: Altocumulus and Altostratus

Middle level clouds: Altocumulus  Puffy with noticeable height piling upward  Commonly followed by thunderstorms

Middle level clouds: Altostratus  More uniform coverage, still layered  Gray or bluish in color  Indicates an approaching thunderstorm or cyclone

Low Level Clouds  Bases lie below 6,500 ft (2,000 m)  Mostly water droplets  Some ice crystals in cold climates  Types: Nimbostratus, Cumulonimbus, Stratocumulus, Stratus, and fog

Low level clouds  Nimbostratus –Dark gray, layered clouds –Produce steady rain  Cumulonimbus –Also low level, but produce heavy rain, thunder, lightning, or hail

Low level clouds: Stratus Clouds  Substantial, flat or layered  Appear before thunderstorms, but produce little precipitation  Usually the lowest  Appear overcast

Low level clouds: Stratocumulus  Layers of puffy clouds, flat on top  Often cover sky in winter  Can produce precipitation

Low level clouds: Fog  “Cloud” that is touching the ground  Becomes stratus when it lifts