This week in Cumbria we were lucky enough to see and capture on camera the rare upside-down rainbow. Well we thought it was rare, and we thought we’d find out more about the phenomenon
It was a great meteorolgical event for the lake district, or so we thought, but whatever it was a beautiful site to see the upside-down rainbow.
What is an upside down rainbow.
The correct name is actually a circumzenithal, circumzenith or Bravias – arc and strangely enough isn’t actually a rainbow, but from a family of halos.
Yes, thats right an unside-down rainbow isn’t a rainbow. It looks like a rainbow but it isn’t because rainbows are produced by the bending of light and seraration of colours that come from raindrops.
The circumzenithal arc
However what we call the upside-down rainbow – the circumzenithal arc happens occurs when sunlight refracts through ice crystals that are in a specific type of cloud called cirrus or cirrostratus not raindrops.
This is because cirrus clouds are very thin and wispy. They are the most common form of high-level cloudds. These clouds are typically found at heights greater than 20,000 feet and are composed of ice crystals that originate from the freezing of supercooled water droplets.
So, its very similar to a rainbow, as in the mechanism is the same. It all also depends on the sun, the air and the angles and lots of different effects.
What is surprising is that the circumzenithal arc isn’t that rare. but because it usually happens so high up in the sky we miss it.
You can even get circumzenithal arcs from the light of the moon as well, this is much rarer though.
So next time you are on the lakes in Cumbria, and you see some sundogs, and the cirrus clouds around take a good look up into the sky and look for the upside-down rainbow.