Nacreous Clouds over Sweden
Vivid and lustrous,
wafting iridescent waves of color filled this mountain
and skyscape near Tanndalen, Sweden on January 3.
Known as nacreous
clouds or mother-of-pearl clouds, they are rare.
This northern winter season they have been making
unforgettable appearances at high latitudes, though.
A type of
polar stratospheric cloud, they form
when unusually cold temperatures in the usually cloudless
form ice crystals.
Still sunlit at altitudes of around 15 to 25 kilometers the clouds can
diffract sunlight after sunset and before the dawn.
Authors & editors:
NASA Web Site Statements, Warnings,
NASA Official: Jay Norris.
A service of:
& Michigan Tech. U.
Publications with keywords: clouds
Publications with words: clouds