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Credit & Copyright: Christa Harbig
Explanation:
What's happening to this cloud?
Ice crystals in a distant cirrus cloud are acting like little floating
prisms.
Known informally as a fire rainbow for its flame-like appearance, a
circumhorizon arc
appears parallel to the horizon.
For a circumhorizontal arc
to be visible,
the Sun must be at least 58 degrees high in a sky where
cirrus clouds present below
--
in this case
cirrus fibrates.
The numerous, flat,
hexagonal ice-crystals
that compose the
cirrus cloud must be
aligned horizontally
to properly
refract sunlight in a collectively
similar manner.
Therefore, circumhorizontal
arcs are
somewhat
unusual to see.
The featured fire rainbow was photographed earlier this month near
North Fork Mountain in
West Virginia,
USA.
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A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: clouds
Publications with words: clouds
See also: