Polar stratospheric clouds

• Weather watchers have captured images of rare iridescent clouds over Scotland, northern England and the West Midlands.

ABOUT THE PSC

• The Polar stratospheric clouds, also known as nacreous clouds, are among the rarest and most stunning atmospheric phenomena.
• These resemble mother of pearl, and usually develop in extremely cold air above the polar regions.
• Nacreous clouds are an indicator of especially cold air high in the atmosphere.
• They are best known for the beautiful pastel light they reflect after sunset and before sunrise.
• These clouds form over the polar regions and are made of smaller ice particles than those that form more common clouds.
• The effect, reminiscent of a thin layer of oil on top of water, is produced as the sunlight diffracts around the tiny ice crystals inside them.
• PSCs provide a surface for chemical reactions where benign forms of chlorine are converted into reactive, ozone-destroying forms.
  • They also remove nitrogen compounds that would otherwise moderate the destructive impact of chlorine on the ozone layer.