Ceiling
The lowest cloud layer that is reported as broken or overcast. If the sky is totally obscured, then it is the height of the vertical visibility.
Cloud
A visible collection of minute particle matter, such as water droplets and/or ice crystals, in the free air. A cloud forms in the atmosphere as a result of condensation of water vapor. Condensation nuclei, such as in smoke or dust particles, form a surface upon which water vapor can condense.
Broken
The amount of sky cover for a cloud layer between 5/8ths and 7/8ths, based on the summation layer amount for that layer.
Overcast
The amount of sky cover for a cloud layer that is 8/8ths, based on the summation layer amount for that layer.
Obscuration
Any phenomena in the atmosphere, excluding precipitation, that reduces horizontal visibility. According to the National Weather Service, some of the obstructions to visibility include blowing and widespread dust, fog (including freezing fog and patchy fog), haze, mist, sand and blowing sand, smoke, blowing spray, and volcanic ash.
Vertical Visibility
The distance an observer can see vertically into an undefined ceiling, or the height corresponding to the top of a ceiling light projector beam, or the height at which a ceiling balloon disappears during the presence of an indefinite ceiling.
Originally posted 2014-04-09 22:16:01.
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