“Overcast”的意思、由来-开放百科全书

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Overcast

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{{Otheruses}}Overcast or overcast weather, as defined by the World Meteorological Organization, is the meteorological condition of clouds obscuring at least 95% of the sky.^[1] However, the total cloud cover must not be entirely due to obscuring phenomena near the surface, such as fog.^[2]

Overcast, written as "OVC" in the METAR observation, is reported when the cloud cover is observed to equal eight oktas (eighths).^[1]^[3] An overcast sky may be explicitly identified as thin (mostly transparent), but otherwise is considered opaque, which always constitutes a ceiling in aviation meteorology.^[2]

Sometimes clouds can be different colors such as black or white, but overcast usually refers to darker skies.^[4] In some cases, it can be impossible to see distinct borders of clouds or the sky may be covered by a single type of cloud, such as stratus and the whole sky will be a dull white.

Periods of overcast weather can range from a few hours to several days. Overcast weather can also affect people suffering from seasonal affective disorder.

The same weather, when observed from above, might be referred to as (an) undercast.^[5]

References

1. ^¹{{cite web|url=http://www.dmi.dk/dmi/koder.pdf |format=pdf |title=Aerodrome Weather Report |publisher=World Meteorological Organization |accessdate=30 August 2016 |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20120224010553/http://www.dmi.dk/dmi/koder.pdf |archivedate=24 February 2012 |df= }}
2. ^¹{{cite web |url=http://glossary.ametsoc.org/wiki/Overcast |title=Overcast |publisher=American Meteorological Society |accessdate=30 August 2016}}
3. ^{{cite web |url=http://www.eumetcal.org/resources/ukmeteocal/rapid_cyclo/www/english/glossary/overcast.htm |title=Overcast |publisher=Eumetcal |author=World Meteorological Organization |accessdate=30 August 2016}}
4. ^Oxford English Dictionary, 3rd ed. (website), s.v. “overcast," 2a and 2b. http://www.oed.com/view/Entry/134377#eid32922408 (Accessed September 7, 2016).
5. ^{{cite web|url=http://glossary.ametsoc.org/wiki/Undercast |title=Undercast |publisher= American Meteorological Society|accessdate=30 August 2016}}

{{climate-stub}}État du ciel

1 : Clouds

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