Nacreous clouds

Nacreous clouds 2 Feb 2

Over the last couple of days, towards sunrise and sunset, our skies have contained something that I never really hoped to see, because it was so rare:   a phenomenon known as nacreous clouds.

This morning, from our front windows, we were gazing at a kaleidoscope of colour, obviously very high in the atmosphere, dazzlingly brilliant.  These clouds have been sighted all over Scotland, and social media are buzzing with them.

What are they?

Nacreous clouds a 2 Feb 7Nacreous clouds form in the stratosphere, between nine and 16 miles above the Earth, at temperatures of around -85ºC.  They are composed of ice particles which are of a consistent size throughout, dispersing rays of sunlight into a spectrum of colour through diffraction and interference.  They are usually only seen over high latitudes, during the winter.  This is in contrast to noctilucent clouds, which occur around midsummer, and form much higher in the atmosphere – in the mesopause, between 50 and 53 miles above the Earth.

There’s a downside to their beauty, however.   The website Atoptics says that nacreous clouds are signs of the destruction of ozone over the Antarctic and Arctic:  “Their surfaces act as catalysts which convert more benign forms of man-made chlorine into active free radicals (e.g. CIO, chlorine monoxide).”   Through a series of chain reactions, these radicals destroy ozone molecules.

Cloud formation is doubly harmful because it also removes gaseous nitric acid from the stratosphere which would otherwise combine with CIO to form less reactive forms of chlorine.”   Atoptics

Nacreous clouds 2 Feb 16

You could tell how high the clouds were because of their relatively unchanging position against the much lower, dark rainclouds that were scudding across from the west.  Some had a beautiful rippled effect, while others were slowly expanding into the thinnest layers of pearlescent white.  The colours ranged from gold, through mauve and pink to brilliant turquoise and green.   For a time they were so bright that they dazzled your eyes.  Despite their obvious warning, I have never seen anything so beautiful in the sky.

More information:

Photos copyright © Colin Woolf

Comments

  1. jenny owen says:

    Wow. How lucky to see that!

  2. Gorgeous clouds. At the moment, all we’re seeing for days on end is dreary grey.

  3. Amazing phenomenon beautifully captured and explained. Wow!

    • Thank you, Jessica! I was interested to read that there are two types of nacreous clouds – Type I are not quite so brilliant, composed of liquid droplets, while Type II are the brilliant ones. Yesterday’s were certainly not as bright, so we may in fact have seen both.

  4. Absolutely stunning. My parents also saw these clouds over Lancashire last night and said they were spectacular.

  5. Lucky you…we haven’t caught them yet….keep getting calls from friends which only makes us more jealous!!!

  6. Amazing clouds! Though ignorance is bliss at times…hope they remain a lovely rarity…

  7. Shame that such beauty it a portent of something far more malevolent.

  8. What a spectacle! Sad to think that’s the ozone layer being destroyed. A beautiful death.

  9. They look amazing and thanks for the explanation too!

  10. We had a couple of incidences of these during Henry; they’re an amazing sight. The last time I encountered the word “nacreous” so many times in 48 hours was when I was reading the collected works of Lovecraft.🙂

  11. Yes, we had a lot on Monday, and one again this afternoon. I took some photos on the phone, but they didn’t come out too well, glad yours have….beautiful but deadly.

  12. Fascinating. Clouds are such beautiful and varied things. Lenticular clouds are quite common down here but I never seem to have my camera with me when I see one.
    Alen

    • I know – usually it’s a case of not being quick enough, but these stayed around for at least an hour. I still can’t believe we saw them (plenty of others did too, going by Twitter etc!) Love lenticular clouds, especially because they usually happen in fine weather (I think!) Dreaming of fine weather at present!

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