In an image taken with a 360-degree-view fisheye lens, Ed Stockard stands observing a full-sky show, a circular halo called a parhelic circle along with 22 degree and 46 degree halos. Also present: a circumzenithal arc, an upper tangent arc, and a faint Parry arc. Visit http://www.atoptics.co.uk/halosim.htm and view the frequent and infrequent links on the left. Can you find them all? Photo: Ed Stockard
Marko Riikonen visited South Pole in 1998-1999 to film and study the optical effects of ice crystals in the atmosphere, which manifest visibly as halos across the sky. He was part of a team on an NSF grant led by Walter Tape, a mathematics professor from the University of Alaska, Fairbanks. On January 11th, 1999, the team hit the optical jackpot. An exceptionally bright halo display, which included several frequent and rare halos, appeared in the sky. Marko recalled that it lasted almost an hour—an unusually long time for such a magnificent display—and a good number of station folks came out to watch it. He termed the display an “exhausting experience.”
Riikonen had had his share of discovery prior to his trip to the South Pole; in Chile he witnessed the so-called Lascar display which had at least five new halos, and is still unexplained. Says Marko, “We tried to explain it with cubic ice, but that’s not the answer.”
Meanwhile, in 1999, a few months after Riikonen left South Pole, I found myself heading to Summit Station, Greenland, for the first time. In mid-March four of us went to open the research site after a winter hiatus. Although I had seen some polar halos in Antarctica, I was totally unprepared for what I saw one day while grooming the skiway.
From Oct 15th 2001: Skiway flags salute a nice 22 deg halo with a sunvex parry on top. The wider “v” below is the upper tangent arc. Completing the photo is the partial parhelic circle and associated parhelion or sun dogs. A very faint helic arc is visible to the right. Photo: Ed Stockard
Looking out from the Tucker I saw two halos around the sun and a variety of arcs that I had not a clue about. I stopped the machine and got out. Looking around I could see what I know now is called a parhelic circle encompassing the sky. Literally, turning around in 360 degrees I could see this halo. I started talking to myself. I said words I can’t repeat in this article!
I climbed back in the Tucker but could only drive a short distance before I had to stop, get out and repeat to myself the words of absolute amazement. I didn’t know at the time how the arcs and halos formed. I don’t remember all of the individual sights I saw but that day stuck in my mind.
Fast forward, this time 12 years, to 2011 and I am now spending August to November for the second consecutive year here at Summit. I have spent quite a few years working for PFS/CPS in Kangerlussuaq, which is the logistics hub for the U.S. National Science Foundation’s research program in Greenland. I’ve been a frequent contributor to this blog from my photographic work there. Kanger, as we call it, has remarkable auroras but I’ve rarely seen halos in Kanger like those on top of the ice sheet at Summit.
A typical but beautiful 22 deg halo marks the first phase of 2011-2012 winter operations at Summit Station. Photo: Ed Stockard
A 22 deg halo with faint parahelion or sun dogs. Marko suggested I use a sun blocker, which I made from the lid of a 5-gallon bucket on a 12-ft piece of old bamboo. The blocker keeps the photos from washing out and being over-exposed. Photo: Ed Stockard
Marko Riikonen found my photos in 2010, after they showed up on Atoptics.co.uk and on my flickr.com site. He picked one to include in his new book on halos. He has mentored me in optical photography through this current phase here at Summit, often emailing with obvious enthusiasm. It has been a delight and inspiration having his insight and tips on photographs, as well as his explanations of the phenomena I’m witnessing and documenting.
Halos and arcs can be seen worldwide, but the varied and rare phenomena mostly occur at the higher latitudes. In some remote places in the Arctic and Antarctic, scientists have to rely on the eyes (and cameras) of others. My work here at Summit Station during the early arctic winter has allowed me a unique vantage point to photograph atmospheric optics in detail, for enthusiasts and scientists such as Riikonen to gather more knowledge about them.
Halos can occur by moonlight too. Here, a fairly complex 2010 lunar halo display. Present and easily visible are the 22 deg halo, parahelic circle, parahelion or moon dogs in this case, the upper tangent arc and parry arc along with a lower tangent arc on the horizon. Photo: Ed Stockard
As this correspondence has developed Riikonens’ comments have introduced me to a new vocabulary: Wegener, Schulthess and Kern arcs; Tape infralateral arcs; and all kinds of halos. Riikonen says, “When the temps fall below -30 C, you probably will get some odd radius displays, like last year.” He also says my photos have advanced the field a bit: “The Greenland ice cap halo skies have been a question mark until your photos started coming along. You have already written you name in the halo history.”
Cool.
Riikonen himself is well embedded in halo history, living in Finland in an area that often sees halos. On the night of December 7 /8 2008 in Rovaniemi, Finland, five new halos were revealed. “It was a great night. The display was created with [a] spotlight in diamond dust. The diamond dust was so thick that the moon did not shine through, so the only possibility to see halos was to use the spotlight. The cystals were huge. You could look at them with [the] naked eye. I had never seen a high-quality diamond dust like that.”
Riikonen’s travels in search of halos have taken him to Resolute Bay in Canada and “the pole of cold” in Oymyakon, Siberia. At Oymyakon, in 1997, the optics were found to be rather typical. In his words, “We went to look for halos in the extremely low temps. Well, they were nothing special. When it gets too cold, it is mostly just 22 halo.”
I asked Marko about climate change and the effects it may have on these optical elights. He answered, “The high cloud halos in Finland have gotten markedly poorer soon after we entered new millenium. We used to have a so-called ‘halo spring’ in April-May during which numerous good, high-cloud displays were observed, but now there has been no halo spring for almost a decade. The Finns have been observing halos since the beginning of [the] 1980′s, so it is three decades of data now. That is of course way too small of a sample to say that climate change is responsible for the better quality high-cloud displays famine. Maybe the first two decades were exceptionally high-quality and now we are back to normal. Or maybe that was the norm and due to the climate change high-cloud halos have become poor.”
The above links and the halos mentioned are only a partial list of what Riikonen has seen. Marko hopes others will also photograph the world’s wonderful sky and provide shots of little-seen and possibly never-photographed optics. To all in the Arctic, Antarctic and around the globe: Keep the camera ready. . . Jot down a few facts with the photos—temperature, clouds and winds may help. Share in Marko’s enthusiasm and put forth some good data with remarkable photos. You might even hit that optical jackpot.—Ed Stockard
Sep 29 2011
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