Wednesday, October 22, 2014

The Fire Rainbow An Astonishing and Rare Marvel of Nature

The Fire Rainbow An Astonishing and Rare Marvel of Nature

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fire rainbow 1 The Fire Rainbow An Astonishing and Rare Marvel of NatureNo, it’s not the first of April, the phenomenon known as a “fire rainbow” does exist. Here, read the science behind it and marvel at some amazing photography of this rare beauty, the Circumhorizon Arc, known to its friends as a CHA.
fire rainbow 2 The Fire Rainbow An Astonishing and Rare Marvel of NatureIf you are very lucky you may see a fire rainbow once or twice in your life. It sounds like it could be one of a series of children’s books – “Harry Potter and the Fire Rainbow” has a certain ring to it, but this phenomenon is not fiction. If you are in the right place and at the right time then a fire rainbow is something that you will remember witnessing forever.

fire rainbow 3 The Fire Rainbow An Astonishing and Rare Marvel of Nature

To name it properly, a fire rainbow is a circumhorizontal arc. It is also known as a circumhorizon arc but whichever you chose, scientists (and aficionados) call it a CHA. It is given its name because it looks as if a rainbow has spontaneously combusted as it made its way across the sky. It could even be suspected, perhaps, that some malign fairy or goblin has blown the rainbow up to stop some errant human discovering that elusive pot of gold at its end!

fire rainbow 4 The Fire Rainbow An Astonishing and Rare Marvel of Nature

The real explanation behind a fire rainbow lies more in science text books than in a Brothers Grimm tale. A CHA is a kind of halo – which is an optical phenomenon. These appear around the moon – or in this case the Sun. You have probably seen a halo yourself around a strong light source – take a look at street lights in the fog for example.
fire rainbow 5 The Fire Rainbow An Astonishing and Rare Marvel of NatureAlthough there are many different types of optical halos, a CHA is caused by the refraction though ice crystals in cirrus clouds of light from the sun. Refraction happens when the speed of light is reduced inside a particular medium. This particular refraction happens when light goes from air without cloud to air containing cloud. In this case it is vital that the cloud is cirrus in shape.

fire rainbow 6 The Fire Rainbow An Astonishing and Rare Marvel of Nature

A cirrus cloud is one of those thin, wispy ones, often with tufts sticking out like disheveled hair! They can be huge – covering so much of the sky that you cannot see where one ends and another begins. When they are a massive sheet they are called cirrostratus. They are formed at enormous heights – over eight thousand meters. There is very little moisture at those heights and that’s why they are so skinny!
fire rainbow 7 The Fire Rainbow An Astonishing and Rare Marvel of NatureSo, what happens when light hits a cirrus cloud and what special conditions are needed to form a fire rainbow? The refraction of the light causes it to separate from its “white” form to its different components (which people call wavelengths). The person on the street would say that the light is bent out of shape and split up in to all the different colors that make it up. In other words, a rainbow – or in our case, a fire rainbow!

fire rainbow 8 The Fire Rainbow An Astonishing and Rare Marvel of Nature

So, why don’t we see fire rainbows as often as (its now more mundane!) cousin, the rainbow? For a start the sun has to be at least fifty eight degrees above the horizon for one to occur – and you have to be lucky enough to have cirrus clouds around at the same time! Because of the necessary height of the sun you will not see a fire rainbow north of fifty five degrees – and likewise further south of the magic fifty five degrees. You may occasionally see one if you are high up on a mountain further south or north, but it is not likely!
fire rainbow 9 The Fire Rainbow An Astonishing and Rare Marvel of NatureIt is vital that the crystal is aligned just so as otherwise the light will not separate in to the rainbow like colors we expect. If the alignment is correct then the whole cirrus cloud will “explode” in to a flaming, fire rainbow! The sight is almost as if someone has sprayed the sky with gasoline, thrown a lit match at it and then leant back, arms folded, to take in their handiwork!

fire rainbow 10 The Fire Rainbow An Astonishing and Rare Marvel of Nature

So, if you are lucky enough to see this phenomenon, perhaps it is a good idea to make a wish! The conditions for a fire rainbow are so exact that it means that to see one is a rare sight indeed. When nature does us this sort of favor by giving us a gift such as this, then perhaps it is only right that we make a wish when we encounter it! It may not be very scientific, but to be honest, would you care?


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22 Comments to “The Fire Rainbow An Astonishing and Rare Marvel of Nature”

  • i like it.

  • so what time of day would the 58 eight degrees be?

  • awesome! i see those all the time..love them!

  • I was fortunate to see one last year. I live in the South of England and we were driving in the middle of the day. It was slightly overcast but the fire rainbow was in full view. It seemed to change colours.

  • i’ve seem these multiple times, didn’t know it was a rare event. Ah the clear and uncluttered Oklahoma, USA sky

  • i’ve seen these multiple times, I didn’t know it was rare. ah the clear wide open OklahomaUSA skies.

  • Wow! I’ve never seen rainbow like that. But some people who left comments above obviously have seen it a lot of times!!!! How lucky!

  • Nice ! I only knew what it was called today when a friend told me regarding the pics i posted in my flickr web. So, those i actually witnessed last month were Fire Rainbow! Able to see such beauty of nature in Singapore is considered very very lucky I feel!

  • Wow, I have seen three odd shaped rainbows like these over the past two evenings.
    The one yesterday was actually in a perfect ball.
    One of the “rainbows” I saw today was a thick, smudgy type rainbow going vertical , not arched at all.
    The second one was over my head and was a ribbon shape.
    Horizontal with a dip in the center of it.
    They are so angelic.

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  • We saw this awesome sight in the sky over Barrie, ON, CDA on Sunday afternoon July8th, 2012.

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