Sun dog over the Channel

I saw a rare and wonderful atmospheric display yesterday: a sun dog. If you are unfamiliar with the term, allow me to explain. Sun dogs are caused by the refraction of light through ice crystals in the high atmosphere. These crystals have to be hexagonal in shape in order to work their magic. But if they form, and when they do it is generally in high, thin sheets of cirrus cloud, a bright, rainbow like spot appears 22 degrees out from the sun- about a stretched hand away. Unlike rainbows, which experience a double internal reflection before the light from the raindrops reaches our eyes, in sun dogs they are refracted only once, hence they are much brighter and the red is on the inside, the opposite to a rainbow. Because they are sun-ward, unlike rainbows which of course are opposite the sun, they can be difficult to see, but if you shade your eyes from the direct glare of the sun you will sometimes find them if there is wispy cirrus about. As it was yesterday.

And it was more than just a blob. It was a broad strip, stretching up towards the zenith, where an entire halo was beginning to form. And directly above the sun an even more unusual phenomenon had formed: a "Parry's arc" which requires the ice crystals be aligned at a very specific angle to our eyes. A little wedge of brilliant light sat there, forming part of the whole wonderful display.

I was visiting my Mum at the time, and pointed it out to her. Her eyes are, even at the age of 92, are at least as good as mine, and she could see it clearly. She loved it, though with her dementia, it is unlikely she retained the memory for more than a minute.

Sun dogs are a sign of change. They often indicate a weather front is on its way, usually a cold one. Approaching cool air pushes under warmer air, forcing it upwards where the water droplets freeze, sometimes into the magic hexagonal shape. But I have noticed that when I see them it signals some sort of change in my life, and sometimes a good one. It can't signal a good change for my Mum: her life is on an inevitable downward spiral, but it might just indicate a favourable turn for me- God knows I need one.