1. occams rusty scissor

    occams rusty scissor Active Member

    Found this interesting cloud formation on our news website:
    [​IMG]

    [​IMG]

    I thought it was pretty spectacular - Im assuming the rainbow pattern is from light refraction through ice crystals?

    The article refers to it as a fallstreak or "punch hole" cloud. I've seen other examples of whispy fallstreak clouds but not in this pattern before.
     
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  2. cloudspotter

    cloudspotter Senior Member

  3. occams rusty scissor

    occams rusty scissor Active Member

    Ah right, cheers. I thought maybe something had disturbed it/caused the streak. Kind of reminds me of the wake left in the ice after an icebreaker passes through.
     
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  4. cloudspotter

    cloudspotter Senior Member

    The guy from the Bureau of Meteorology needs to brush up on his physics a little though

    It's actually a circumhorizontal arc

    http://www.atoptics.co.uk/halo/cha2.htm
     
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  5. Trailspotter

    Trailspotter Senior Member

    This is a combination of two unrelated phenomena: a circumhorizontal arc with a punch hole cloud on the background. The position of the former depends only on the position of the Sun and varies relative the punch hole borders on different photographs.

    I have not figured out the exact time of the photo, but at the place at the present the Sun elevation at noon is much higher than minimal value of 58° required for the observation of circumhorizontal arc.
     
  6. cloudspotter

    cloudspotter Senior Member

    Is the arc not in the fallstreak ice crystals?
     
  7. Trailspotter

    Trailspotter Senior Member

    No, it is not;). Like the rainbow, the arc is not located at a specific distance, but comes from an optical illusion caused by ice crystals viewed from a certain angle relative to a light source. The arc (and other related optical phenomena) is not an object and cannot be physically approached.

    In this case, the ice crystals that caused the arc probably came from the fallstreak cloud.
     
  8. cloudspotter

    cloudspotter Senior Member

    Yes that's what I meant. I thought you were saying that the arc just happened to be there and had nothing to do with the fallstreak, I just read what you posted wrong
     
  9. Mick West

    Mick West Administrator Staff Member

    Very annoying to see stuff like that. The colors in this arc come from refraction - light being bent by tiny prisms and splitting up the colors into different angles. You can tell that what this is, as the colors and the angles match perfectly.

    Iridescence in clouds comes from diffraction - where very small particles scatter certain wavelengths of light. Kind of like the colors of sunset. It's not that - iridescence has a different color spectrum, and a very irregular shape. However the arcs and halos are often described as being iridescent.

    Iridescent in the things he lists comes from thin film interference, where beams of light reflect off the front and the back of something very thin, and certain wavelengths interfere with each other. It's certainly not that.
    [​IMG]

    I think if he wanted to explain it simply, he should have said "kind of like a rainbow, but with ice crystals, so it's a different shape"
     
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  10. TWCobra

    TWCobra Senior Member

  11. Mick West

    Mick West Administrator Staff Member

    This shows how it's a segment of a larger arc, made visible by the presence of ice crystals.
    [​IMG]
     
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  12. Mick West

    Mick West Administrator Staff Member

    Here's a similar cloud, but this time in the position for a sundog.
    [​IMG]

    [​IMG]
     
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  13. Mick West

    Mick West Administrator Staff Member

    This one has a sundog, and more of the 22° halo
    [​IMG]
     
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  14. MikeC

    MikeC Senior Member

    And of course chemmies have seized on it as evidence of geoengineering - eg Clare Swinney in Northland Geo-engineering Watch - complete with this logical impossibility:

    One wonders how moisture falls out of anything if the water molecules have been "broken"! :rolleyes:

    Clare's been panicking about hole punch clouds for a few years now - as witnessed by fellow metabunk member Hemi's old "Conspiracy Nutbarz of New Zealand" blog article from 2010. (also available at his new collaboration here)
     
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  15. occams rusty scissor

    occams rusty scissor Active Member

    Ha... I didn't want to make mention of the inevitable conspiracy theories which would arise, as it was a genuine curiosity. Was fairly certain that it would only be a matter of time before it reared its tin foiled head.
     
  16. Trailspotter

    Trailspotter Senior Member

    Last edited: Nov 5, 2014
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  17. Mick West

    Mick West Administrator Staff Member

    Here's an excellent photo of the Australian Nov 3rd 2014 fallstreak hole that shows both the 22° Halo and the circumhorizon arc

    [​IMG]
     
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