nacreous cloud


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Related to nacreous cloud: Noctilucent cloud, Polar stratospheric cloud

nacreous cloud

n.
A stratospheric cloud resembling a cirrus, showing iridescent coloration when the sun is several degrees below the horizon.

[From nacre (from the iridescent coloring of mother-of-pearl).]
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.nacreous cloud - a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon
cloud - a visible mass of water or ice particles suspended at a considerable altitude
References in periodicals archive ?
Also known as nacreous clouds, they form at altitudes of 20-30 kilometers at very low temperatures (about -95[degrees]F), and because of their slimness are generally only visible before sunrise or after sunset.
The iridescent nacreous clouds - considered rare as they are usually found only in very cool air - come from ice crystals refracting the sun's rays.
Incredibly, gusts reached 144mph in the Cairngorm mountains and there were nacreous clouds, which the Met Office said are usually seen in polar regions.