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How can clouds form?

How can clouds form?. Air needs to be cooled to saturation. I.e. air cooled to dew point. I.e air reaches 100% RH As air rises, it cools * How to force air to rise: Topography fronts convection Convergence ---> <---- 2) Surface cools off quickly by emitting radiation

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How can clouds form?

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  1. How can clouds form? • Air needs to be cooled to saturation. I.e. air cooled to dew point. I.e air reaches 100% RH • As air rises, it cools * How to force air to rise: • Topography • fronts • convection • Convergence ---> <---- 2) Surface cools off quickly by emitting radiation 3) Air moves over colder surface/ into cooler area

  2. Cloud characteristics • Clouds are identified by their height (low, medium and high) and by their visual characteristics (flat or puffy). • The four basic cloud groups are: • Cirrus: _________________________ • Cumulus: _______________________ • Stratus: ________________________ • Nimbus: ________________________

  3. Where do these terms come from? • The basic classification terminology has Latin roots: • Stratus (Latin for "layer") to describe sheet-like (stable) clouds. • Cumulus (Latin for "puffy") to denote a cloud with some puffy vertical (unstable) extent. • Cirrus (Latin for "curl of hair") denotes a wispy high level cloud. • Nimbus (Latin for "violent rain") means a rain cloud.

  4. Cloud Classification As a first distinction, we classify clouds by the height of the cloud base. LOW CLOUDS • Low clouds have a base below 5000ft. • Stratocumulus (Sc), Stratus (St) and are the primary low-level clouds

  5. Cloud Classification MIDDLE CLOUDS • Middle Clouds have a cloud base in the range of 2 - 7 km (6000-23,000ft). • Altostratus (As) and altocumulus (Ac) are the primary middle level clouds.

  6. Cloud Classification HIGH CLOUDS • High clouds typically refer to clouds with a base above 7 km (23,000ft) altitude. • Cirrus (Ci), Cirrostratus (Cs), and Cirrocumulus (Cc) are all high level clouds.

  7. Cloud Classification • High level clouds tend to be fuzzy in comparison to low level clouds. • This is primarily because high level clouds are made of ice crystals instead of droplets. • Ice crystals usually evaporate slowly and thus have more time to diffuse.

  8. Cloud Classification Three primary cloud classes overlap the height bands: • Cumulus (Cu) • Cumulonimbus (Cb) • Nimbostratus (Ns) “nimb-” defines that the cloud is precipitating. “cumul-” defines that the clouds are a result of convection. “strat-” defines that the clouds are layered clouds. Various terms are commonly intermixed and aren’t limited to any given altitude.

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