Friday, 3 March 2017

The great 24 February 2017 halo display in Pskov region of Russia

In the evening, I looked at meteoblue's meteogram (like I do everyday), and saw on it plenty of high-level clouds, but at the same time together with middle-level clouds. At 09-30 I woke up that to check whether middle clouds would not allow observing halos.

I came out and saw that the sky indeed was pretty dirty and contained not only cirrus but also low and middle clouds. But above the sun were the central part of UTA and diffuse pillar. I could leisurely to prepare my camera before halos became brighter.

After a few minutes, UTA became seen pretty well. Viewing the sky I was very surprised to detect the supralateral arc to the left of the sun. The arc was not bright but it was clearly visible. It was weird to see such good halos in such dense clouds. Clouds from different levels merged with each other. So at first, I did not understand that it was a big display that penetrated through the gaps of the lower clouds.

After 10-15 minutes came a big gap in those clouds and I saw the full Supralateral arc which was noticeably brighter than previously. I already was very glad because the arc in this form I saw only on my screen when I processed stacks. And at the moment I saw it in the sky with my own eyes. However, this was only a prelude of what was to come.

Wegener arc, subhelic arc, and blue spot on parhelic circle


Around 11-00 the sky started to clear and above the supralateral arc and a nice circumzenithal arc appeared. In that moment I noticed to the west a bright fragment of the parhelic circle which was low over trees. Cirrus arrived from this direction. While I changed the direction of my camera's field of view, I noticed also the anthelion. High clouds arrived quickly, and they were very uniform and smooth. The brightness of halos quick started to accrue. I ran in my home in order to show the current display to my father, and during this couple of minutes the brightness of halos increased even more. I ran back to my camera, and in this moment halos became extremely bright! The upper tangent arc was very perfect and sharp. The supralateral arc was brighter than a common primary rainbow! Probably it reached such extreme brightness not only because crystals were perfect, but also because the sun elevation was almost optimal. The parhelic circle was also incredible and looked like jets of light. Wegener arc was visually visible as well. Its oblique wide lines pointed out on far and weak anthelion. Around anthelion from time to time X-shaped arc was visible.

Near sun there are 9° halo together 9° column arcs
All sky view. Near anthelion there is Tricker arc
Anthelion and some of diffuse anthelic arcs
Upper tangent arc with diffuse upper 23° plate arc and sharp 24° column arcs. Thanks to M.Riikonen for the confirmation
Halos lasted in this bright form around 45 minutes. After the brightness of complex a few decreased, but all details continued were visually visible. I remember that I saw well crossing of Supra/Infra-lateral arcs on the parhelic circle. Also from time to time appeared 120° parhelia.

On the left there is 120° parhelion
At 13-10 was the end of this great display, only halos near the sun remained. Parhelia were most bright in this moment and seemed to me that near them were Lowitz arcs. But stacks showed that is not true.

21 comments:

  1. congratulations Nikita! what a reward for being prepared! this is incredible material, with whole display recorded! i never got any display like that. it feels good when you can anticipate halo displays in advance with meteograms, and be prepared before it happens.
    from my experience with halocamera, it seems that the best displays happen in "young" and growing crystals, and the satellite video of that day seems to show that it was indeed the case with thin cirrus becoming thicker over your area that day, which means fresh growing crystals:
    https://www.youtube.com/watch?v=bFX1SzRgAfw
    congrats again!

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    1. Thank you Nikolas! I use meteograms for a couple of years. Since I saw a post about it in your blog. I advise all observers to use this thing for forecasting of halos and for simplifying of monitoring.

      During the display I had time to save detailed sattelite image. I have created an animation of them: https://3.bp.blogspot.com/-f3nZn4BwVMk/WL6EZp3itGI/AAAAAAAAELo/Oqd0nQr0DKsiefUFYf7usiU2kQIeUhlmgCLcB/s1600/sat24.gif The dark red dot is my location. Bright halo forms started around 11-10. Indeed you are right. It seems over my area in that day fresh cirrus were formed.

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    2. From your animation and the YouTube history, it looks like fresh cirrus clouds sublimating, hence the odd radius. Great data you got!

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  2. Nikita, I would also like to congratulate on this catch. A wonderful display, I've never seen anything like this before, either. And congarts on the superb image processing. Professional work!

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    1. Thank you Agnes. It is nice to hear!

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  3. That anthelion spot is pretty neat. Good symmetry in the all-sky image too. Seems to me those 24° column arcs are rebellious. They don't conform to the usually seen circular trajectory, but are trying to show their true shape. This would talk of small tilts. I haven't checked with simulation though. Kinda odd that in the other image you have only 24° column arcs and in the other only 9° column arcs. I recall, though, there are examples of such behaviour from other displays. Well, you got the equipment and all, let the clouds bring more complex displays to Pskov region!

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    1. Thank you, Marko.

      How do you think, which of diffuse arcs there is in this display? Except for Tricker, which well stands out. Maybe also there is Greenler or Trankle arc?

      Indeed, in penultimate image, 24° column arcs show own true shape. There is not a hint of 24° halo. There is only its tangent arcs. I tried to create a simulation, and can to get such sharp arcs when tilts were 1 degree and less. Note that between 23° plate arcs and UTA something is there. May be is the part of 24° column arcs?

      I agree with you about what is strange to see 9° and 24° column arcs without others odd radius column arcs. Maybe the reason is that the part of cloud which contained pyramidal crystals was narrow?

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  4. That is a super halo! I love the rainbow like supralateral arc, wegener, subhelic and tricker arcs a lot. Here in Ohio USA I have nt had anything yet except the nice display with good upper tangent arcs and supralateral arcs. Hope for some column stuff, odd radius and of course ellipticals

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    1. Thank you, Michael.

      Good luck with that. New season just getting started

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  5. Yesterday I found something new in photos from this display. Seems near parhelia there are Lowitz arcs. I aslo marked some strange halos. I do not know yet what it is. Looks like as middle Lowitz arcs. https://1.bp.blogspot.com/-MvzSDxZEr6I/WL6fNBGxQvI/AAAAAAAAEL4/wYELFT33FO0cgdOE3fZxU08aeKur04yyACLcB/s1600/1155.jpg

    What do you think?

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    1. Looks like middle Lowitz to me. There's also helic arc inside the 22° halo, did you already spot that?
      Congratulations, what a great display this has been!

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    2. To me, middle lowitz should not appear as such an isolated patch... Location matches more 24d upper pkate arc. In this case it would be high cloud pyramid helic arc!
      Can you send me the unprocessed stack so I can br it?

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    3. Reimaa, Nikolas, thank you. I spotted something like the helic arc to the left of the sun, but I did not sure, because this thing is pretty unconvincing. Now I think otherwise. If it is really odd radius helic arc, it would be great.

      Nikolas, maybe you are right about 24° plate arcs. I thought about it, but these arcs seemed to me too oblique. I have sent the stack to your email.

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    4. In spotlight displays you can always distinguish the two diffuse arcs but in high cloud displays it is often more difficult if not downright impossible. Plain "diffuse arcs" is enough for me in this case.

      Yes, the thing between the tangent arc and 23° plate arc is part of the 24° column arc. As for the 9° and 24° not showing together, the unevenness of the high cloud can always be given as an explanation, but still I am a bit uneasy with that. 9° you can get rid of by assuming triangular crystals, but no crystal tweaking get rid of 24° so easily.

      If the br happens to turn out some extra information, please put it somewhere so that we can see it.

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    5. So, I have receive the stack in processing from Nikolas. The assumption about 24 plate arcs and pyramid helic arc is confirme. In this way, we have around 21 different halo forms in this display

      22° halo
      46° halo

      upper tangent arc
      supralateral arc
      infralateral arc
      Wegener arc
      subhelic arc
      diffuse anthelic arcs
      anthelion
      blue spot
      parhelic circle

      circumzenithal arc
      pillar
      parhelia
      120° parhelia

      9° halo
      9° column arcs
      24° column arcs
      23° plate arc
      upper 24° plate arcs
      odd radius helic arc


      Thank you everybody for you help in the definition of forms

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    6. I was wondering Nikita, whether you'd like to put Nicolas's processed version and the finds in a new, separate post, like an update to this one. It would be nice to see the image. Or - if Nicolas agrees - you could add a link to his image here. i'm at least very curious!

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    7. I think Nikolas will not mind if I share it

      https://1.bp.blogspot.com/-Yhk-tdCay7U/WMLsMHJes0I/AAAAAAAAEM0/o61183nKN6wfpfZcH8FUTrz8UrWlfjk-wCLcB/s1600/1155_%25D1%2585515.jpg

      In Nikolas' version pyramidal helic arc became more visible.

      About a separate post, maybe I will do it, because I have a few more photos with which I want to share

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  6. Nikita, it would be really good if you could either update this post or do a separate post including the additional images. This is one of the main functions of Halo Vault, to preserve important halo displays and information relating to halos for posterity. Hopefully, we can get all the relevant images deposited in the Vault rather than linking to them offsite. You only have to look at some of the older halo sites to realise that images are already disappearing as links die or the host site is removed. This is a very worrying trend which this site aims to counter.

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    1. Alec, of course, you are right. I am very familiar with this problem. I will try to do a new separate post

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  7. Good one that pyramid helic arc, we don't see too often photos of them. If it were normal helic arc, it would be rather expected to make (in such a uniform display) fuller loop. But isn't there also upper 9° plate arc visible in Nicolas's edition? One more halo to the list.

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  8. It is possible. I did not pay attention to this area because of there is a speck of dust

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