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Credit & Copyright: P-M Hedén (Clear Skies,
TWAN)
Explanation:
Sunlight ripples through a dark sky on this Swedish summer midnight
as noctilucent or night shining clouds seem to imitate the
river below.
In fact, the seasonal clouds
often appear
at high latitudes in corresponding summer months.
Also known as
polar mesospheric
clouds, they form as water vapor is driven into the
cold upper atmosphere.
Fine dust supplied by
disintegrating
meteors or volcanic ash provides sites where water vapor can
condense, turning to ice at the cold temperatures
in the mesosphere.
Poised at the edge of space some 80 kilometers above,
these icy clouds really do reflect sunlight toward the ground.
They are visible here even though the Sun itself was below the horizon,
as seen on July 16 from Sweden's
Färnebofjärdens
National Park.
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: noctilucent clouds
Publications with words: noctilucent clouds
See also: