Interesting Images: Nacreous Clouds
Clouds in the stratosphere are very rare. Yet for the past week they have been seen every day. Yesterday, Feb 2nd, Sean Crane of Harrogate UK hopped out of his bath to photograph the display:
These fantasticaly-colored clouds are floating more than 80,000 feet above Earth's surface. Normally, the thin air up there is crystal clear. Not this week. Water molecules are crystalizing in the lower stratosphere and the resulting ice crystals are assembling into polar stratospheric clouds (PSCs).
Also known as "nacreous" clouds, PSCs form in the lower stratosphere when temperatures drop to a staggeringly-cold -85ºC. High-altitude sunlight shining through tiny ice particles ~10µm wide produce bright iridescent colors by diffraction and interference.
Because these clouds require extreme cold, they are most often seen around the Arctic Circle. In recent days, however, they have been spotted as far south as the UK.
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