Stunning "Fire Rainbow" Captured Over California's Pinnacle National Park

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Photo Credit: Michael Jimenez via National Weather Service Bay Area facebook

Last week, a runner traversing the trails of California’s Pinnacle National Park encountered a mesmerizing sight — a halo of rainbow colors emanating from the single cloud in the clear blue skies. While the phenomenon is commonly referred to as a “fire rainbow,” researchers say the name is misleading since the optical illusion is neither a rainbow, nor does it have anything to do with fire!

Photo Credit: Michael Jimenez via National Weather Service Bay Area Facebook

Instead, the stunning halos are circumhorizon, or circumhorizontal, arcs, which only occur in the summer. They require two conditions — the sun has to be situated 58 degrees or higher in the sky, and there has to be the presence of cirrus clouds. The thin, wispy clouds, which can be found at high altitudes, exist in a low-temperature environment and are therefore filled with ice crystals. As the sun’s light passes through them, the ice particles act like prisms, creating the colorful illusion.

Image Credit: Les Cowley (atopics.co.uk)

Since the sun has to be higher than 58 degrees in the sky for the natural phenomenon to occur, the likelihood of encountering one depends on where you reside. The further away a country is from the equator, the less amount of time the sun remains at the high altitude. Also, the frequency of the sunny days has to coincide with the presence of cirrus clouds. As a result, “fire rainbows” are relatively common in North American cities like Houston and Los Angeles, where they are spotted at least four to five times during summer. However, while they are occasionally seen in European cities such as London and Paris, circumhorizontal arcs do not occur in areas north of Copenhagen.

Resources: atoptics.co.uk, iflscience.com, sfgate.com

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cirruscoincideemanatingencounteredfrequencyhalomesmerizingmisleadingphenomenonprismstraversingwispy
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Reading Comprehension (9 questions)

  1. What did a runner recently see at Pinnacle National Park?
  2. What is the optical illusion commonly called?
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Critical Thinking Challenge

Can you think of the reason the sun has to be so high in the sky for the...

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“While the phenomenon is commonly referred to as a “fire rainbow,” researchers say the name is misleading since the optical illusion is neither a rainbow, nor...

630 Comments
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  • Fran falalalaMonday, April 30, 2018 at 3:54 pm
    I wish I could see it!!!
    • chickinMonday, April 30, 2018 at 3:49 pm
      awsome
      • Lol girlMonday, April 30, 2018 at 3:41 pm
        Lol girl Lol lol lol so cool
        • MakaylaMonday, April 30, 2018 at 3:24 pm
          Wow!!That's cool!Wish I could have seen it!
          • Isaac AsencioMonday, April 30, 2018 at 2:53 pm
            I wish it can show the rainbow by us
            • LawsonMonday, April 30, 2018 at 2:38 pm
              Iv´e heard of this in primary school.It was pretty interesting since I was like 10 years old.Too bad I wouldnt be able to experience this phenomenon since I don´t live by the equator
              • VivMonday, April 30, 2018 at 2:35 pm
                Wow, cool
                • valstrm
                  valstrmMonday, April 30, 2018 at 2:12 pm
                  I like that
                  • goku_sayinultim
                    goku_sayinultimMonday, April 30, 2018 at 2:10 pm
                    So cool bro
                    • ...Monday, April 30, 2018 at 1:30 pm
                      Awh man.. I thought I be like he first one haha.

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