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    Nacreous clouds

    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 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…

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    Fog bows

    The only time I have ever seen a fog bow is very early one summer’s morning, as we were driving towards Loch Awe and Taynuilt in Argyll.    The mist was lifting quickly against a brilliant blue sky, and suddenly we saw it hovering there in front us, ghost-like.   Less than a minute later, it was gone. Fog bows follow same laws of physics as rainbows, with a few vital differences.  They require a combination of mist and bright sunshine, and the sun must be less than 40 degrees above the horizon. Because the water droplets in the mist are so tiny, they are unable to split the rays of sunlight…