2011. június 1., szerda

Halos 31. May - summary of the month's halos

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Altocumulus virga usually makes pillars. On rare occasions other halos are also seen in it. Yesterday Ac turned into virga for several hours and in the beginning unconventional halos were seen in it: upper tangent arc, circumzenith arc and also short patch of 46° supralateral arc. Parhelion occurred on one shot occasion in contrail. It is getting to look like parhelia in contrail are not that rare after all.

  • parhelion

  • 22° upper tangent arc

  • 46° supralateral arc

  • circumzenith arc

Anyways, this is it. For one month I tried to see every halo possible. I am not going to continue photographing all displays, will just mark up the halos. Next it is time to see what kind of statistics I got for this one month.

Ok, the numbers for May. Halos occurred on 27 days and for individual halos the numbers are:

  • 22° halo - 16 days

  • pillar - 16 days  (including one borderline case)

  • parhelion - 15 days

  • 22° tangent arc - 15 days (upper tangent arc in all and in three also lower)

  • circumzenith arc - 6 days

  • parhelic circle - 2 days

  • 120° parhelion - 2 days

  • 46° lateral arcs - 2 days (supralateral on both, infra on the other)

  • 46° halo - 1 day

  • 9° halo - 1 day

I actually saw cza only on 5 days, but missed pretty certainly one when I was inside. Jari observed that one and I also saw parhelia in that cloud when it had already passed overhead. The numbers above are meant to be absolute numbers of halos, so I added that cza because I most certainly would have seen it had I been outside half and hour earlier or so.

Sofar the halo statistics people have made mostly reflect what they happen to see when they look up. Here I tried to see every halo during the day. I woke up in the morning to see the sunrise and stayed up untill sunset on most days. It became evident that pillars and also parhelia are often seen in very low sun situations in the high cloud bank at the horizon. It may very well be that 22° halo is not the most common halo in Finland, but rather pillar is. 22° halo should have stronger position in the summer when sun spents plenty of time at high elevation when pillar can not be seen, but pillar should gain the upper hand towards the winter when sun is low and when also low level crystals make just pillars. So, as even in the summer month of May the pillar was equal to 22° halo, I would expect in the year's run the pillar be the most numerous halo.

Halos 28. May. 21st day - end of the series of continuous halos days

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In the morning in Tampere about a minute lasting upper tangent arc and in the evening in Artjärvi a parhelion. Also upper tangent arc again, but did not photograph that appearance. 21 days of halos in a row. After this two days without halos commenced.

Halos 26. May

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It would have been nice to say about this display: "I was pretty sure this Ac-virga will make an elliptical halo once they reach the sun and that's what indeed happened". But that did not happen. Only pillar. In Valkealampi, Kontiolahti.

2011. május 21., szombat

Halos 20. May

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In the afternoon the clouds came. Parhelion was blindingly bright. I followed as the same cloud reached the 120° parhelion position and there was an intensity increase which soon attenuated. The last image shows two photos taken 88 seconds apart, the 120° parhelion is seen in the left photo, in the right photo the cloud has already moved further and the distant parhelion is no more seen. I think the best part of the cloud did not pass the 120° parhelion location, or it would have been brighter.

Day's halos:

  • 22° upper tangent arc

  • 22° halo (just a small patch in the second photo)

  • parhelia

  • pillar

  • circumznith arc

  • 120° parhelion

2011. május 2., hétfő

Sun pillar in Stratocumulus virga (and an attempt of fake sun), 1. May

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In the spring, when there is a break of cold air from north and snow showers develop in the daytime, it is good chances for sun pillar in the evening. This is because the snowing cumulonimbus start losing their power and reduce to stratocumulus with icy virga. And the virga of low and middle level clouds often consists of crystals that make decent pillars.

This is what happened on 1. May in Tampere. Above are some photos from the evening. There was also an attempt of fake sun, but for my criteria it was not quite there yet. These low sun pillars and fake suns are difficult to photograph because of the clipping of red. The fifth image (small thumbnail on the right) is a series of the fake sun attempt: the pillar below the sun in the beginning of the series was blindingly bright, even though I was watching with sun glasses (you need welding glass to observe these properly). In the end of the series the true sun is coming visible. The photos were given lowest white balance value possible and highest recovery value in Photoshop. That's how red clipping was gotten rid of. The downside for this realism is unrealistical blue photos. The leftside photo in the gallery on the second row is the same as the first in the blue series, but with more normal white balance values. There is red clipping that masks the true nature of the pillar / fake sun effect.

2011. április 28., csütörtök

Faint odd radius halos

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Now here is an example of a display where you see nothing special visually. Just a faint 22° halo that is a bit brighter from the top. But there was one visual clue, however, that revealed it might be an odd radius display. It was the broadness of the 22° halo. And indeed, in the photos 9° halo is seen as well as 18/20° halo. The outer halo might not contain 22° halo at all, rather, it can be 23/24° halo.

Had I had a convex mirror, the 9° halo would certainly have showed up with it, also the 18/20° halo. The two photos above are versions of one. They are 2 minutes stacks. The date is 28 April 2011.

The display just continued and one could have gotten several hours stack of it. When in the afternoon 9° halo was visible to the naked eye, I took another stack in the middle of tyre changing. The third image has 7 frames taken during about 2 minutes. There is 35° halo (arrow), it is seen also in single images, which means it would have been observable with convex mirror.  Fourth image is a bit longer stack. Now the 35° halo is on the other side.

2011. április 27., szerda

Non-spotted Wegener arc

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Not seeing a colored Wegener when it is there can hollow a halo man up. Just that's what happened today. There was a nice little display little in cirrus and I found Wegener from the photos afterwards. It is actually rather typical for me to not see them.  Curious incidence was that I took a panorama of the same clouds earlier when they were closer to horison and not yet at halo making distance. I did not expect them to show anything special.

Hugin is good now for halo panoramas as it gives 16 bit output. I put here also two different projections of the cirrus cloud panorama. The first is cylindrical and sencond is rectililnear. The rectilinear represents the clouds more like they appeared to the eye, being straight stripes.

2011. április 6., szerda

Lunar diamond dust halo display in Rovaniemi, 7/8 December 2008

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Before the moon halos appeared, diamond dust was so thick that moon did not shine through and I photographed in spotlight beam. As the the diamond dust started thinning, it also lifted up from the ground - there were not much crystals on the ground. The moon elevation is about 30 degrees judging from the circumzenith arc which is slightly separated from the 46 halo.

2011. március 31., csütörtök

South Pole odd radius halo display 6 February 1999

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This was a long lasting display with faint odd radius halos. The scanned slides here only show 9° stuff, but there was more, also the 20° and 24° halos. The crystal orientatation is poorly column oriented as the 9° halo is slightly brighter on the sides. And indeed, in the crystal photos we took with Jarmo Moilanen there were columnar pyramids.

2011. március 27., vasárnap

South Pole halos 5 February 1999

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Basic display at South Pole. The third image is taken by Jarmo Moilanen. The last two images show a contrail display.

2011. március 24., csütörtök

Halo display at South Pole on 4 February 1999

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Just scanned this one from my slides. It is basic South Pole summer season display. In the third and fouth image there is something at the horizon outside the 22° halo. Reflected Lowitz arcs or lower 24° parhelia? Hard to say which one, the clouds mask for example the possible lower 9° parhelia. Maybe there are both. The last heavily usmed image shows faint anthelion / diffuse arcs.

2011. március 22., kedd

Polar stratospheric clouds

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Some photos of polar stratospheric clouds from Lappland. In Finland the PSCs' usually come without irisdescent colours. They occur in winter when there is a deep low pressure over Scandinavia. Thus forecasting their appearance is rather easy. These clouds also are called as mother-of-pearl and nacreous clouds, both names refererring to the irisdescent color in molluscs shells.

The photos above were taken on two occasions, the ones with purple glow on 30 December 1999 and the one with white clouds on 28 November 1999.

2011. március 7., hétfő

C.W.Hissink's ellipse - 9° column arc or an elliptical halo?

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The halo observation by C. W. Hissink 28 June 1901 in Netherland's Zutfen is generally regarded as containing an elliptical halo, and would be thus the second historical record of these rare phomena (the observation is in 1901 Onweders). But could there be a possibility that Hissink did not actually see an elliptical halo, but rather a pyramidal crystal formed 9° column arc, which is an equally rare sight? Hissink measured the halo with an octant and gives 10.5 degree vertical and 7.5 degree horizontal measure for the halo, but it does not say whether these are diameter or radius values. If the former was true, then it would be definitely an ellipse, which are rather small, but in the latter case it would more likely be a 9° column arc.

In the account of the obseravation it is mentioned that the ellipse formed in a lower Ci cloud than the rest of the display (as far as I can understand the text). Elliptical halos never form in high clouds, but rather in middle or low level clouds, typically in the Altocumulus virga. This piece of information would be thus consistent with elliptical halo explanation if we assume there were both high clouds and Ac formed middle level cirrus clouds simultaneously in the sky. Such occurrences of elliptical halos with normal halos have been already photographed at least by Jukka Ruoskanen (the simulations and crystal figures above are made with his HaloPoint software). But then again we have a photographed case by Konstantin Bespalov, where sharply cut segments of odd radius halos with 9° column arc are seen, thus formed in a separate crystal material from the rest of the display (although not separate cloud is really visible). Also the observation of 9° column arc by Martti Perälä in Lapua, Finland, on 27 April 1988 (third image), has a strong resemblance with Hissink's observation. It is identified as "Hissink's halo" in the report, but the estimated 10 and 8 degrees vertical and horizontal sun distances clearly class it as 9° column arc. The sun is at 35-38 degrees elevation, which makes the 9° column arc more elliptical than in Hissink's observation, where the sun was at 47.5 degrees.

Conclusions on the Hissink's observation? Can not really come to any, there is not enough information. Knowing whether it was the diameter or sun distance would give straight answer. Also any piece of additional information about the cloud situation might prove useful, for example if there was a mention of Altocumulus clouds in the sky. If Hissink's halo was indeed a 9° column arc, it would rank again as the second historical record if this halo. There is an earlier display from 5 September 1899, which possibly had a 9° column arc on the other side of the sun, as shown by the fourth image above. But as the display is one sided, one could equally argue that it is just a segment of 9° halo. If, however, it was 9° column arc, Hissink would still get the glory, as he made also this observation.

Afterthought 24 February. The innermost halo lasted 20 minutes. That is long time for an elliptical halo and even longer when we consider that there were simultaneouslyl also halos from normal prismatic crystals. Yeah, if I had to bet, I would definitely go for the 9° column arc now.

2011. március 5., szombat

23° plate arcs from summer 2010

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Some odd radius displays from last summer in Tampere. In most of them there was only 23° plate arc visible. Although the displays were not that impressive, there were plenty of them. In July-August a record breaking heat wave produced many 23° plate arcs, I saw them on 14 days. Stacked images usually revealed more pyramid halos, mostly the 9° halo or 18° plate arcs. 23° plate arc is very easy to identify mistakenly as 22° upper tangent arc.

As a rule, when it is hot weather period, 23° plate arc is more common than 22° upper tangent arc. I am pretty sure they are not limited to Finland and Estonia only (in the latter Marko Krusel has a lot of observations). Hopefully we start getting observations of them coming summer from elsewhere.

The gallery above does not include every odd radius display from last summer. I could not find all them from the hides of my disorganized computer. I'll add them as they come around. Many displays were also not photographed. The dates are given in the file names. In some cases stacking has really made wonders in squeezing out the halos invisible in single frames. In the 15 August display, where there was only solitary 23° plate arc visible to the eye (and nothing more even through a convex "blind spot" mirror), stacking photos taken during about 2 hours unveiled a complex display with 35° halo as shown by the 8 and 9 images in the gallery. The two upper and lower images are single frames, the two in the middle are the same stacked image with different level of unsharp masking. Also the display of 19 August improved markedly by stacking photos taken during only 3 and 13 minutes, the last two images in the gallery. Again comparison with single frames is given.

2011. március 3., csütörtök

Odd radius display in Resolute Bay

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This one occured on 3 April 1998. The spots near the horizon are lower 24° plate arcs. Sometimes is not easy - or even possible - to distinquish them from reflected Lowitz arcs. But this case is obvious, there is also a good lower 9° plate arc. Much fainter are 18°, 23° and upper 24° plate arcs.  The display lasted for several hours, temperature was around -27° C. The source for this display is not known. Maybe it was natural.

2011. március 1., kedd

Diamond dust halo display initiated by a snow blower

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This diamond dust display occurred on 1 April 1998 in Resolute Bay, Canada. The images have been scanned from slides which is why the display has lost its brilliance. But it was not the most brilliant display anyway. What's more interesting here is how it formed. In two photos there is an ice cloud erupting from the Resolute Bay airport. It was caused by a snow blower attached to a tractor that was operating for two hours or so. Most of the snow it blew in the air fell immediately back to the ground, but there also came a cloud of invisible tiny ice particles that started drifting with the wind. These particles acted as a template around which the ice crystals that caused the halo display grew. This happens when air water vapor content exceeds ice saturation, only then can water vapor deposit on these ice nuclei. If the air moisture was below ice saturation, then there would not have been any ice crystal cloud that we see in the photos - and no halos either.

In some of the photos there is rudimentary Moilanen arc, which is not a surprise, since this was a man made display. The photos are in chronological order. As I was running away from the airport the display got constantly better because the crystals had time to grow bigger. After some time Resolute weather station caretaker Wayne Davidson drove by and took me further away from the airport where the display was better defined, though not any brighter, as is seen in the last image.

2011. február 28., hétfő

Fake sun again

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A little longer gap since the last post. The upcoming halo book occupied me during the last days as I made last adjustments before submitting it last night to the publisher for layout.

Anyway, the issue here is fake sun again. The photos above were taken by Olli Sälevä in Rovaniemi. The first two are fresh, from 22 February. After I had written about the fake sun, Olli started to look for it and took these photos. He saw a bright yellow fake sun that day near the sunset, but parking the car and getting the camera ready took 2-3 minutes during which time the real sun already appeared and the fake sun waned. But you still can get the idea here. A bit later the sun got again behind cloud and a spot of light was seen above sun.

The two last Olli's photos are older, from 25 April 2008, showing a beautiful sky with Strato/Altocumulus and pillar. Again here is a situation where fake sun might appear.

Now that I have written already four posts about the fake sun and seen some photos of candidates, it is time to say what I think about the issue. To save some dignity with the phenomenon - so that we would not start reporting every brightening in sun pillar as fake sun - we should only report as fake sun those that have the potential to be taken as real sun. This also takes into an account cases where the real sun is seen, but in which the fake sun is so bright that it could be taken as real sun if the real sun was behind the cloud. By this criteria, I think, the fake sun is a rare phenomenon. And one needs an account from the observer of the sighting, determining it alone from the photos is not enough. The photos by Julie Broson show a true fake sun, because at first for a moment Julie did not know which one was the real sun. Neither was, as the real sun was behind the cloud.

2011. február 25., péntek

More elliptical halos

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Ari Laine photographed this elliptical halo on 24 February in Lahti. It was already third occurrence within two weeks in Finland. This time the ellipse is more like an elliptical glow rather than well defined ring, but outside the glow above the sun there might be a faint ring visible (one has to be cautious about jpg artefacts).  During the last two weeks the conditions have been favourable for ellipses in Finland as it has been clear skies and around -15° C temperatures during the daytime, which is the optimal temperature for the elliptical halo crystal formation. In this case the temperature on the ground was -16° C, but the ellipse formed in an ice crystal layer that slightly above the ground. In Tampere similar crystal layer situation was observed as well, however, the halos were the usual stuff.

2011. február 24., csütörtök

Moon diamond dust odd radius halos in Finland

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On the evening of 17 February Tapio Koski went out on the river ice in Muurola, Rovaniemi, to photograph northern lights. They were not good and he took photos of the moon halos that appeared in the sky. It was an odd radius display and it contained two extremely rare halos: the 20° and 35° lower plate arcs, of which the lower 35° plate arc is even more difficult to catch, as it is never seen much above the horizon. Everything went smoothly for the documentation of the display. The location was optimal with low horizon and Tapio was using wideangle which allowed to capture the whole display and he took series of photos on a tripod for stacking.

First two of Tapio's photos above are single frames with only slight unsharp masking. The next three images are four and five frame stacks and have stronger usm to enhance the lower 35° plate arc at the horizon.  In the fifth image the different radii plate arcs are identified. Moon elevation for the photos is 31-32 degrees. More Tapio's photos are on his site.

Odd radius diamond dust displays are rare in Finland. All together about half a dozen cases have been reported since 1983. The only other lunar odd radius display in Finland was captured by the Finnish meteorological institute automatic aurora borealis camera in Kevo, Northern Finland, on 8 January 1985. Above is a drawing of the display by Jarmo Moilanen.

The odd radius diamond dust displays are formed in urban areas from the power plant and factory plumes at low temperatures. While rare in Finland, in Alaska's Fairbanks they are seen regularly every winter due to the cold weather.

2011. február 23., szerda

Old Dutch halo observations in Onweders, Optische verschijnselen

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The Dutch weather amateurs journal Onweders, Optische verschijnselen, that was published between 1880-1961 contains plenty of observations of atmospheric optical phenomena. Two days ago I visited the Repository library in Kuopio to mark the relevant pages (mainly halos) from the publications for scanning. Pasi Juttula from the library scanned everything yesterday and I have put them here for download. Not all years are there, issues before 1896 are missing from the library collection as well as year 1933. Also I did not mark some of the last issues for scanning, because there seemed to be nothing interesting. Above is a selection of halo drawings from the journals, as well as photos from my visit to the library.

2011. február 21., hétfő

More fake sun photos and drawings

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Fake sun observations are stacking up! There is much more than I thought in the beginning. First, Mike Hollingshead sent some of his old photos which look much like a fake sun. In the first two photos the fake sun is above the sun and in the third photo, where real sun is completely hidden, below. And today I found out, while visiting the repository Library in Kuopio to check the Dutch Weather amateur's journals Onweders, optische verschijnelselen, that there is a regular column devoted to observations of double suns and moons, before rainbows and halos. Plenty of sightings are listed from about two decades starting from the end of 19th century, with two drawing published from years 1897 and 1899, shown in the last two images. Yesterday also one fresh appearance was reported in Finland.

The effect is not really as forgotten as I thought, because it is mentioned in Minnaert's Light and color in the open air, which is not that old book (my Minnaet has been lost for many years). Mike suggests that the effect can't be at all rare. This maybe true. Possibly people just don't look for it because one has to look near the glare of the sun, or even when they look, they don't think it is anything special. And if one lives in a place where low sun can not be seen, this limits the oppotunities to observe the phenomenon.

Some additional issues are worth emphasizing about the fake sun. First, the sun need not be at all hidden for it to be seen. This is seen nicely in Johannes Hevel's draving from 5 February 1674, the fourth image above. Also my observation from 10 May 1987 (fifth image) is a situation where sun is shining unobstructed. The note for the observation says that the fake sun above the real sun was only SLIGHTLY fainter than the real sun. Second point that emerges from many images above is that the fake sun can appear some distance apart from the sun. And finally, not every pillar has a fake sun; there is my other observation (sixth image), from April 1987, where the situation would look fruitful for the fake sun, but only pillar was reported. For me fake sun is something that is or can be potentially mistaken for a real sun. Since I started to write about this, some people have been dubious about fake sun in general or not really understanding how it should look. I can only say that when one sees a true fake sun, there is no need to question anymore.

Two names have been used for this effect, fake sun and double sun. The French use the former (faux soleil) and the Dutch use the latter (dubbele zon). Both have their advantages and disadvantages depending on the situation. The Dutch have also observations of fake moons. I wonder if there are any sightings of fake planets or stars.

2011. február 19., szombat

Diffuse arcs in the spotlight display on November 2007 in Rovaniemi

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These photos have been around and some are still in some blog probably, but I have not made simulations. This was seen in the beginning of November 2007 in Rovaniemi, my second experiment to make halos with portable spotlight. And it was good! Even in the middle of this all light pollution near the center of the city the display was strong.

Different views of the display are given above but the attention here is towards the anthelic arcs in the third and fourth image. There is a combination of diffuse and Tricker anthelic arcs, which together with the subhelic arc make some people see a ruminant skull in the third image. Now a good Tricker arc like this in spotlight displays is quite rare, usually it is the diffuse arcs that dominate and Tricker is almost non-existent. The simulations of this display were made with regular hexagons (with little variation allowed) that had on average aspect ratio 0.9, which is already more plate than column crystal (last image). This created the Tricker and diffuse arc combination as close to the photo as possible. It does not stand close scrutiny, but that's the best I got. Simulations are made with Jukka Ruoskanen's HaloPoint software.

The diffuse arc is mainly composed of two components, diffuse-A and B, which can be called also as Tränkle and Greenler, who found these halos in the computer simulations. But it is known that there is more diffuse arcs components, in sixth image I have dissected them into four components, A, B, C and D. Thusfar we have been only able to distinquish A and B in photos of the spotlight halo displays, the C and D are weak and get mixed with the main components. But perhaps here one can see the influence of diffuse C in the photo. The seventh image gives a comparison with simulations where are all four components and the C component removed. The difference between the simulations is subtle, but maybe there is a slight indication that diffuse C may play here a little part in strenghtening the diffuse A.

2011. február 17., csütörtök

Is here another fake sun?

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A couple of days ago I made a post about the fake sun, showing the excellent photos of Julie Bronson and drawing by Giovanni Cassini. This reminded Mika Aho of his photos of similar looking effect that he took on 19 May 2008 in Korpilahti, Finland. The two photos are shown above and they were shot with an old cell phone camera, which explains the slightly less than optimal quality. The sun is behind the edge of dark Stratocumulus cloud and the fake sun candidate is seen below the sun, with short and fainter extension of pillar further down. The crystal precipitation from the cloud is not visible.

Now it looks like there may be a circular fake sun image of the sun under the cloud edge, but it is not very bright. The cloud edge is actually much brighter.  By strict definition one could say that a genuine fake sun should be so bright that one would take it for a real sun, but of course there is a continuum of intensities, and putting an arbitrary line somewhere along the range is not very fruitful. So, with some reservations due to the images quality, I might say that probably we are looking here at a faint version of a fake sun. In any case it is good that people have started looking for this, be it old photos or fresh displays in the sky.

2011. február 16., szerda

Rare 44° parhelion in Stockholm

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David Åsbrink took these photos of a diamond dust halo display in Stockholm on 8 December 2010. The phenomenon was noticed by many people. In addition to being a bright and beautiful display this one contains also a rarity: inside the 46° lateral arc there is a weak colored spot, the 44° parhelion. It is marked in the third image with an arrow. 44° parhelia are the parhelia of very bright normal parhelia and they were photographed first in 1970 in Canada's Saskatoon. Since then about 13 more photographed cases have accumulated. These days it seems like we are getting at least one photographed case every winter. The solar elevation for these photos was 8 degrees.

2011. február 15., kedd

Another elliptical halo

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Two posts and and three days back there was an elliptical halo in the sky and today ellipse appeared again. It had been a cold night with down to -30° C, and during the daytime as the thin cloud cleared and sun started shining more strongly, also crystal glitter in the air increased. Couple of times I looked out and saw only pillar and poorly defined subsun, but last check came also with faint elliptical halo. Above are different versions of the photos, stacked 13 frame average and lighten images and two single images. Heavily usmed average stack seems to indicate two slightly separate elliptical halos.

This formed in crystals precipitating from very low, almost invisible cloud layer. Temperature at Tampere stations ranged from -15 to -20° C at the time of the observation, the coldest being at Siilinkari on the lake Näsijärvi. I am not sure if heat plant plumes had anything to do with this. The connection was not obvious, at least.

Edit 15 February: Eetu Saarti saw much better ellipse in Kangasala the same day.

2011. február 13., vasárnap

Fake sun

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Julie Bronson's photos above show a largely forgotten effect of a sun pillar, the fake sun. It was photographed on 19 January 2009 in South Central Minnesota, USA.

Sometimes, when low sun is just behind an edge of an opaque cloud that is precipitating ice crystals, an image of the sun can been seen below or above the cloud in the icy virga. The effect is so perfect that one is easily fooled to think it is real sun. It is blindingly bright, circular and about the size of the sun. Only when the true sun comes up from behind the cloud, the cheat is revealed.

Today this optical effect of sun pillar is almost unknown, but in the past sky watchers have made detailed notes on it. Auguste Bravais listed in 1845 five persons who have observed the fake sun, including Johannes Hevel, Pierre Bouguer and Giovanni Cassini. Above is shown the observation by Cassini on 18 January 1693. Unfortunately it is a bit cropped from the left.

Julie Bronson's images of the fake sun may be the only ones existing. Her documentation of the phenomenon is commendably extensive and comparison with Cassini's 300 years old observation is good. I have seen fake sun a couple of times during 25 years of sky watching. Appearances of this effect are short and camera must be handy when the time comes.

2011. február 12., szombat

Possible elliptical halo

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Half an hour ago I was talking with Jari in the phone and monitored the sky at the same time. There was Stratocumulus drifting fast and it was turning into ice. I saw an elliptical halo and eventually got some photos, but I am not so sure about this anymore. Maybe it is an ellipse, maybe not.

Update: the sky got almost completely overcast for a while, but then Stratocumulus receded and I was ready with camera waiting for the ellipse. Which appeared and also shows up clearly in the photos (the second collase). All together this was a beautiful case. Fast moving low clouds, crystals in the air, iridescence... I have seen in similar conditions an elliptical halo in Kilpisjärvi while walking up the Saana mountain. Possibly they are not that rare there in early spring around March.

Update II: it turned out many people saw this in Tampere, Helsinki and Lahti. Best photos took Olli Leivo and Jari Luomanen. If my memory is correct, the temperatures in Tampere stations were between -10 and -14° C.

2011. február 8., kedd

Bishop's rings

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Some Bishop's rings for a change. Bishop's rings are very large coronas that form from very small particles. These are the four Bishops that I have photographed. The first photo shows a "genuine" Bishop: it formed from volcanic eruption particles in stratosphere, ejected there by the cataclysmic eruption of Mt. Pinatubo in June 1991. As there is no cleaning rain in stratosphere, the particles drift around a long time and this Bishop was photographed a year later on 1 May 1992 in Vuontisjärvi, Lappland. The corona was visible for about two years after the Pinatubo eruption. It was seen in the sky pretty much all the time, but its intensity varied from day to day. Stratospheric Bishops are rare because only the largest volcanic eruptions can penetrate the tropopause.

Some photos are also shown from the four days trip to Pinatubo that I made with Holger and Hans in May 1994, three years after the main eruption. Pinatubo was still active, but these were tiny secondary eruptions on the flanks initiated by rainwater seeping to the ground and interacting with the hot pyroclastic material deposited during the main eruption. It was not a safe trip.

Three other Bishop's rings are tropospheric Bishops. First are three images of a Bishop's ring at El Tatio geysir field in Chile at 4300 meters elevation in December 2000. I was watching this with Leena Virta. It was a huge "super-Bishop", with the outer red edge at about 55 degrees from the sun. In one image comparison is also given with 22° halo. Visually this was of course more impressive and between the inner blue disk and broad red outer rim there was also narrower green segment, but that did not catch on film (Ektachrome 100 WS or SV was the film). The corona was seen in some stuff that formed Altocumulus, the developing clouds are seen in the photo.

Then there are two cases of stratospheric Bishops from last summer in Tampere. These ones also formed in "pre-Altocumulus".  For the first case size comparison is given with 22° halo. I have been wondering whether the Islandic volcanic eruption may have had something to do with these, at least in Lappland red volcanic sunsets were observed.  But I have a recollection that the second one could not have been caused by that eruption anymore.

Photographing Bishop's rings is always disappointment, the colors do not reproduce well. Faint Bishops during hot weather (caused by the forest fires in the Russia, for example) are not uncommon in the summer in Finland, but I think it would be hopeless to try to photograph them.

2011. február 6., vasárnap

Halo observations by J. R. Blake in the Antarctic (part II)

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Completing the first post of Roger Blake's halo observations in the Antarctic, here are the rest of his halo drawings together with the written descriptions. The display at midnight between 2 and 3 December 1958 comes as two dravings in Blake's book. It was remarkalbly accurate observation of a complex diplay with all four kaleidoscopic arcs, especially when one takes in to account that it was observed from a moving dog sledge. The display had also its contribution to halo science: both Tricker and Greenler used the observation to support the theoretical considerations of the kaleidoscopic arcs. In the drawing these arcs are 1) helic arc; 2) subhelic arc; 3) subanthelic arc and 4) Tricker arc. The observational account in the above image is not given full, but only from the part concerning these arcs.

2011. február 4., péntek

Diamond dust halos at -2° C from Italy

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Diamond dusts close to freezing point are not common. This display, photographed by Francesco Cadini on 3 February 2011 a few kilometers outside Milano, occurred when Francesco's car thermometer showed values between -1.5 and -2° C. Taking into account a possible inaccuracy, he says that it could not have been colder than -3° C.

The display formed from thick water fog. Cadini tells that in the area where the display was seen there is a phenomenon called the "chemical snow",  which occurs in high pressure situation with fog and clear sky above the fog. The abundant pollutans in the air are supposed to initiate this chemical snowing and in one case 2 cm of snow accumulation has been recorded. There is an Italian language description of the phenomenon.

Most likely the pollutants were also responsible for the transformation of the water fog to observed diamond dust. A quick look at some papers reveals that if certain substance acts as an immersion freezing nuclei and contact freezing nuclei, the latter works at much higher temperatures. So probably the formation of this diamond dust was initiated by pollutant particles colliding with water droplets. Once the process starts, sudden freezing of droplets may produce splinters that further freeze other droplets and chain reaction is created. The water droplets also evaporate and the released water vapor deposits on ice particles, and through this growth we get the crystals with proper faces for halo making.

Supercooled water fog in general has a tendecy to turn into diamond dust locally. If you drive around the city when it is below freezing you are likely to encounter spots of diamond dusts.  Usually only the lower layer of the fog turns into diamond dust and thus you can see halos only at night in the light of streelamps. Sometimes, though, as in Cadini's case, a whole fog column turns into ice crystals and sun or moon halos can be observed. The process punches a hole in the fog and in the photos above the edge of the foggy wall is seen clearly.

Cadini's display has also weak Moilanen arc, which shows best in heavily usmed image. He suspects that this might be the first Moilanen arc photographed in Italy.

2011. február 2., szerda

Old photos of halos from anthelic and subanthelic region

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Alan Clark sent these scans of his old slides. The anthelic arcs in the first two photos were photographed in 1980 in Canada, while the two latter images with subparhelic circle, subanthelion and possible faint arcs upwards from the subanthelion were photographed in 1978 on a flight across the US, en route to NASA Ames. Halos suffer markedly when scanned from slides but it is always nice to see any documents of these rare halos.

2011. február 1., kedd

Halo observations by J. R. Blake in the Antarctic

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There are two books devoted to halo observations in the Antarctic in 1950's. One is by the Swedish meteorologist Göstä Liljequist and another by the Australian glasiologist Roger Blake. The images above are from Blake's book "Solar Halos in Antarctica", which I found for sale in an Australian antikvariat a few years ago. Blake was in a project called the "Souther Seismic Traverse", using the Australian research station Mawson as a base for the trips further south. The time he spent in the Antarctic spanned from 30 September 1958 to 17 January 1959 and halos were a sideline research for him, clearly inspired by the Liljequists's work in the early 50's. Above are shown three displays from Blake's book.

The first display, observed from a field trip at the location 70.1° S and 62.1° E on 21 November 1958, contains 9° halo. Blake wrote the following notes on it: "The parhelic circle extended only about 10° either side of the sun, being rather faint. It formed a closed semicircle with a very faint Hall's halo, the radius of that halo being approximately half that of the 22° halo, but observations being greatly impeded by the sun's brightness."

The second display was seen near the first display's location, on 28 November 1958. It has sunvex Parry arc and halos at the anthelic region: "Through the anthelic point was a bright, white vertical pillar, reaching the ground. Also visible was part of the parhelic circle, the intersection of the two arcs being a 'spot' of greater intensity. The parhelic circle did not exists elsewhere."

The third observation on 29 November 1958 was made in the same area as two previous ones. It has several interesting features: "The 22° and 46° halos were both very brightly coloured, and both 22° and 46° parhelia were present, both pair being very bright. The vertical pillar extended from the horizon to the top of the 22° halo, which was brilliant. From this point extended the upper contact arc which merged smoothly with Parry's Arc; both these arcs were coloured and very bright. [... ] The circumzenithal arc was also present, being very brightly coloured. A fairly bright, coloured arc, passing through or close to the zenith and concave to the sun was visible, the colours being very pure and distinct. Because of its position, it was difficult to obtain any estimates; however, it appeared to have approximately the same curvature as the 22° halo. The full 180° of the parhelic circle was visible on either side of the sun, being intersected approximately 90° from the sun by a pair of white pillars extending from the horizon slightly above the parhelic ring. The points of intersection resembled mock-suns, though white. Also at 180° there existed a somewhat fainter, white pillar extending to just above the horizon, the point of intersection with the parhelic circle again being brighter. The display disappeared as the cloud cover increased."

Now I could go on discussing what Blake really saw in 29th November display, but that would not lead anywhere. Suffice to say: a photograph would have been nice.

2011. január 30., vasárnap

Halo Stamps

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I have never considered myself a stamp collector until Jarmo donated two halo stamps recently. They are beautiful.  See Jarmo's site for more.

2011. január 28., péntek

Double-V above lamps

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Mike Hollingshead photographed these pillars on 26 January 2011 in Blair, Nebraska. The curious thing is that there are two V's above the lamp. Normally only one is seen, the upper tangent arc. While the lower V in Hollingshead's photos is the tangent arc, the upper must be the sunvex Parry arc. Or is it? Lets see if simulations are of any help. Above are two simulations made with Lars Gislen's Streetlight Halo software, which assumes omnidirectional light source. On the right is simulation with column oriented crystals, on the left with Parry oriented crystals. Light source elevation is 2 degrees. The Parry is nothing like the upper arc in Hollingshead's photos, and actually the simulations rather depict what the lower arc should look like. In the lower position Parry and tangent arcs overlap and would be indistinquishable from each other. So, not much help from simulations in identifying the upper arc. But the situation between photos and omnidirectional light simulations is not entirely comparable because even floodlighs give to some extent directed light and this why the upper arc can be seen.

Whathever the upper arc is, it is its classical form, i.e. the form that is similar to what is seen in sun light and which in divergent light situation is formed in crystals near observer. The stronger V below is the divergent light form that shows in Gislen's simulations, made by crystals further away from the observer. The upper arc could be either tangent arc or Parry arc or both, same with the lower arc. The helic arc in two of Hollingshead's images seems to indicate there is Parry population present, so perhaps Parry arc is involved in some way or another. But then again if the lamp is near 0 degrees elevation (the two degrees in the simulation may be overestimate) helic and subhelic arcs overlap, and then the halo would not be sure indication of Parry orientation, because subhelic arc forms also from column oriented crystals. Anyway, usually these displays do have Parry orientation halos and sometimes they even dominate over the column orientation halos.

Mike's photos appeared in Spaceweather.

2011. január 26., szerda

Bottlinger's rings

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The classical form of rarely observed Bottlinger's rings is an elliptical ring around subsun, sighted normally from an airplane. Their occurrences can be very short, just a couple of seconds. This is because suitable crystal areas are often small and pass swiftly under fast the moving aircraft. Bottlinger's rings have been seen twice also in diamond dust with floodlight as a light source. Formed this way, they look very different from the classical Bottlinger's rings. All together about 10 observations of Bottlinger's rings are known.

Above are shown three cases of Bottlinger's rings. First one is from the book "Clouds of the World" by Richard Scorer, published in 1972. The photographer is not known, the photo was taken near Des Moines, Iowa. The phenomenon is well defined and taking into an account that this is a printed photo, it must have been an impressive Bottlinger to look at. (The book by Scorer is a nice item to have in collection. It has 22 halo photos including the famous black and white "76° halo" photo in the Antarctic by Scorer himself. There are plenty of cheap second hand copies available.)

Second photo shows Bottlinger's ring over Cornwallis Island in the Canadian high artic on 16 April 1999. Leena Virta and I had hitchiked a ride on an airplane that carried supplies to magnetic pole skiing expedition. On a way back we were flying under Ac layer which precipitated ice crystals. Subsun was seen first and I adjusted camera exposure, focus and aperture ready for the Bottlinger, which indeed appeared for about 10 seconds, followed by two other equally brief occurrences. Then the airplane turned so that we lost sight of the subsun, but we were already starting landing to Resolute. It was clear skies in Resolute but luckily the Bottlinger cloud movement was in our direction, and after waiting for a while on the ground, the cloud arrived and elliptical halos were seen around the sun (they were photographed as well, but I can't find those slides right now).

The third case in the above gallery was seen from Yakutsk-Moscow -flight on 3 March 1997, 4 hours and 20 minutes after departure, somewhere over Siberia. We were returning from the Oymyakon halo expedition and all of us three were having window seats. First time the Bottlinger flashed we were sort of asking each other "did you see what I think I saw"? We continued looking and the Bottlinger appeared again, and this time it was better. Jarmo was keeping the camera at the window ready and got a photo, though not from the best moment.

Three explanations have been proposed for Bottlinger's rings. One, suggested by Bottlinger himself, is that plate like crystals fall in pendulum motion. The 1910 article by Bottlinger in Meteorologische Zeitschrift is given above. Second theory is that crystals fall in gyrating mode. This was proposed by Lynch, Gedzelman and Frazer in 1994. A figure depicting the pendulum and gyration motions of the crystals and the resulting simulated Bottlinger's rings from their paper is shown. Third model gives low angle pyramidal crystals as an explanation for Bottlinger's rings. This was brought forward by S. W. Visser in 1961 to explain elliptical halos; in 1999 Sillanpää et. al. extended the idea to Bottlinger's rings.

Now which one is right? I go for the Visser-Sillanpää model although low pyramid angles are not theoretically favourable. It is the only one that explains also nicely the elliptical halos. With gyration model multiple scattering should be incorporated, in which elliptical halos would be Bottlinger's rings caused by the subsun. Sillanpää et. al. has shown that elliptical halo shapes and intensities can not be explained by such a model. There are also other considerations which make the gyration model weak, but I leave it at that this time.

2011. január 24., hétfő

The Saskatoon halo display

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A handful of halo displays have been of such an impact that they have become known by the location of occurrence or by the observer’s name. The display in Canada’s Saskatoon on 3 December 1970 belongs in that group – it is simply called ‘the Saskatoon display’. This halo complex was of remarkable intensity but its main merit is that it provided the first photographic documentation of parhelia at about 46 degrees distance from the sun. More precisely, they are 44° parhelia, which are the parhelia of exceedingly bright ordinary 22° parhelia. “Secondary halos” and “multiple scattering halos” are the terms that have been used to describe halos formed in such a way.

Thus far, only one photo of the display’s 44° parhelia has been published, printed in black and white in the June 1972 issue of Weather magazine in an article “Unusual arcs in the Saskatoon halo display” by W. F. J. Evans and R. A. R. Tricker. The cover of that issue is shown above, with a photo of the circumzenithal arc from the display. The cover was originally in color but I have only this black and white scan. Shown also is a drawing from another Weather article “Photometeors at Saskatoon on 3 December 1970″ in the 1971 issue 26 by Earle Ripley and Bernard Saugier.

Of the few people who photographed the Saskatoon display, Earle Ripley was watching it at the University of Saskatchewan campus. Above are two photos of the 44° parhelia that Earle send me a couple of days ago after I had contacted him. He gave permission to go ahead with publication on the internet. The photos were taken about 10:30 am, at which time the sun elevation was about 9 degrees. The intensity of the 44° parhelia in those photos is unparalleled. This is made even more remarkable because of the high sun elevation. No other 44° parhelia photos exist for this high a solar altitude. The higher the sun is, the more extensive the diamond dust cloud has to be vertically in order to have enough crystal mass for the formation of the 44° parhelia. The horizontal extent of the diamond dust in 44° parhelia displays is probably always of the order of kilometres.

After Saskatoon, 30 years passed until the next photos of 44° parhelia were taken. Now it appears that we get one photographed case every year. This year's display came from Sweden, last year from Czech Republic. None have been as great as the Saskatoon, but displays of similar magnitude and style certainly recur - at least in the vast uninhabited expanses of polar areas - and one day someone is bound to be around when that happens, hopefully with a camera.

[25 January: The black and white Weather cover was replaced with colored one, thanks for Walt Tape for sending it]

2011. január 13., csütörtök

Streelight Bottlinger in Kangasala on 9/10 January 2010

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If there is a holy trinity for a halo man, it must be the appearance of streetlight pillar and Bottlinger's ring. The night we saw this with Jari Luomanen we had given alreaydy up the halo hunt at Sappee ski resort and were returning home. But on a way back Jari thought of seeing something resembling 22 tanget arcs in the Kangasala lights and we went to take closer look. It was not tanget arc - the lamp pillar was accompanied by a steep V-figure, of a kind which we had never seen before. We started photographing, although in the beginning we had swells of  suspicions of it being just a lamp artefact. However, as the effect later clearly showed on some other lamps, this was not a worry anymore: it was a halo. But what halo, that was not competely clear until later when the halonight was already over.

The stuff formed from nucleating water fog at -16 C. The area where the nucleation took place was perhaps about a square kilometer and within it, only at a small, say, two hundres square meter area was the Bottlinger seen. Elsewhere it was just pillars (the first photo above shows just pillars, but to the right from the photo a Bottlinger was seen constantly from a lamp only about 100 meters away). And outside that water fog was everywhere. Anyway, the Bottlinger was seen in the same spot for 4 hours at the Kangasal industrial area. We drove a bit around returning always to same place.

Some variation can be seen in the photos in the angle of the V when a time lapse movie is made. I took crystal samples and above are plenty of photos of those crystals. For some reason all turned more or less blurry, but one can still make out details of them.  Is it only me, or are the branches of many crystals slightly sloping towards the ends? That low angle would provide the reflecting surface for the Bottlinger in horizontal crystals.

Now Bottlinger's ring is just a helic arc from crystal angles that do not deviate much from the horizontal, but in this display there was also another helic arc, as shown by two photos above. This one probably has the same angle as the normal helic arc from Parry crystals. Non-Parry helic arcs are common - they have been seen with only a pillar.

2011. január 12., szerda

What is the first record of a halo from Lowitz orientation with 315 / 325 raypath?

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I am wondering what is the first record of halo from Lowitz oriented crystals with raypaths 315 and 325 respectively above and below parhelion? It has been called as "reflected Lowitz arc" and parhelion legs and arms. People are also calling it just Lowitz arcs, but it is not the same halo as Lowitz arcs which have 35 raypath. (From Parry orientation 35 make the Parry arc and 315/325 the Hastings arc and from column orientation you get tangent arc and Wegener arc). Above are some some early observations related to this halo.  First is observation by Gösta Liljequist in the Antarctic on 13. May 1951 of the 315 arc. I have included also simulation (made with HaloSim software) and crystal figures depicting the raypath of this arc. That is a pretty realible looking observation. Second is a photo from the French Greenland expedition, taken on 21.7.1951. These are peculiar looking parhelia and one could argue that there is actually no parhelia at all, but this is less convincing documentation for the 315/325 arcs. The photo is from Readers Digest world map book from the 70's (thanks for Jukka Ruoskanen for scanning it). Third is photo by Emil Schulthess in the antarctic in 1957 from Scientific American 1962 September issue. Here we are seeing the 325 arcs at the horizon, marked with an arrow. And fourth is Paul Schultz photo from 1905-06 in Alaska. I strongly suspect the arcs here were not actually inclining outwards, but it is rather due to camera projection when the display was placed at the top of the frame (and then the photo was cropped). The last photo is mine showing similar projection distortion effect of normal parhelia when the halos are placed at the top of the frame.

So, from all this it looks like Liljequist made the first convincing observation of the Lowitz-orientation 315/325 halo and Emil Schulthess took the first photo. I wonder if anyone knows any earlier photos? I have this strange recollection of a guy named P. Stahl having taken a photo of it in the 1951 French Greenland expedition, other than the one above. And that it would appear in some world map book. The photo would be similar in manner to the Schulthess photo. Possibly I just saw Schulthess photo and  somehow mixed up the names, decade old memories are not to be trusted.