Saturday, 22 October 2011

Helic and Tape arc in Cirrus

In the afternoon of October 14, I observed a large halo display in Bochum, Germany.
It started at 14.25 CET (15.25 CEST) with circumzenithal and supralateral arc. During the following minutes, also the upper tangent arc, a bright Parry arc and the 22°-halo appeared, followed by both sundogs and a faint upper circular Lowitz arc on the left side. ( 1 )

At 14.50 CET, I noticed a conspicuous white arc, forming a circle around the zenith together with the CZA. A closer look showed that this circle was not really circular, but rather had the shape of an American football.

This white arc grew longer and longer, an as ist passed the supralateral arc, it turned out to be the heliac arc, clearly visible in thin cirrus clouds.
At 14.55 CET, also the upper left Tape arc appeared as a bright colourful spot on the supralateral arc. At the same time, the left part of the Parry arc grew very long, almost reaching the supralateral arc, while its upper part faded away. ( 2 )

After 15.00 CET, the halo display slowly vanished, but before it faded away, left Lowitz arc was visible for about 10 minutes, as well as a very bright part of the parhelic circle. The display ended at 15.25 CET, having showed 10 different types of haloes with up to 8 being visible at the same time.


Peter Krämer, Bochum, Germany

Monday, 17 October 2011

Subanthelion and diffuse subanthelic arcs

I took these pictures during the beginning of a flight from Paris to Washington DC on the 18th of September. It shows the subanthelic area. At first the subanthelion appeared alone ( 1 ).

Then a short time later subparhelic circle and diffused arcs appeared too for about 1 minute ( 2 ).

Later on the flight, I could observe some brightening in the subanthelic area but not as conspicuous as in the beginning of the flight

Nicolas Lefaudeux

Saturday, 10 September 2011

Plate Arcs from Japan


These pyramidal crystal halos were observed by Anthelene over Sakaiminato city in West Japan. The most interesting features of this high cloud display are the 9°, 20°and 24° plate arcs. Marko Riikonen has made a simulation with HaloPoint2.0 ( 1 ), according to him, the 20° plate arc had been photographed only once or twice in high clouds before. More of Anthelene's images can be seen on her website: http://bluemomenttime.blog89.fc2.com/blog-entry-442.html

Tuesday, 21 June 2011

Pyramidal halos over Frankfurt am Main

Andreas Zeiske observed a pyramidal halo on 6 June 2011 in Frankfurt am Main. In the images, the 22° halo, 18° halo and the left 18° lateral arc can be seen about the St.-Katharinen-Church. The phenomenon formed on a thin field of Cirrus clouds and lasted for 10 minutes at around 08.00 CET. About 5 hours later a cold front with rain showers and thunderstorms swept across the city of Frankfurt. ( 1 - 2 )

Andreas Zeiske, Germany

Sunday, 12 June 2011

Atmospheric Phenomena Blog

The blog on atmospheric optics has moved to a new address ( 1 ), and has recently been updated with many interesting observations. As a teaser, Michael Großmann's image of a tertiary order rainbow can be seen on the right.

Tuesday, 7 June 2011

Pyramidal halo from Thailand


The above image was photographed by Pitan Singhasaneh on 5 June in Bangkok, Thailand.

Sunday, 5 June 2011

Simultaneous upper tangent arc and rainbows



On 4 June 2011 Pietari Puranen observed these rainbows in Jyväskylä. When he turned around to see the sky around the sun, he observed an upper tangent arc. Remarkably, the arc formed in virga precipitating from the same low clouds around the rainbow forming cumulonimbus. It is rare to see halos in virga so close to rainbows.

As column crystals are formed in temperatures relatively close to 0 degrees Celsius we may assume the Virga has been born in temperatures around, say, -4 to -9 degrees Celcius. At least in those temperatures diamond dust close to the ground seems to most often exhibit column crystals.

Thursday, 2 June 2011

Double sun effect



On May 1st 2011 cumulonimbus clouds precipitating hail were commmon. These clouds exhibited clear praecipitatio and later in the evening they featured prominent virga. In these virga a sun pillar formed and as the sun descended behing stratocumulus a double sun effect was seen. A series of images is provided to see the progression of the effect. The real sun can be seen descending behing the stratocumulus.

The first observation of this effect was by Giovanni Cassini in 1693 (see e.g. Riikonen 2011 (1)). By clicking the above image a larger version can be seen. A full image gallery is available online (2). Marko Riikonen also captured images from the other side of the lake (3).

Monday, 30 May 2011

New book on halos



The Finnish Astronomical Association URSA has just published a new book on halos by Marko Riikonen. This book combines the latest halo science with stunning images from all around the world.

Spanning 168 pages, the book presents, illustrates and analyses all the known (and the less well known!) halo forms in great detail. In addition, the newly made discoveries and methodologies concerning spotlight displays are discussed in depth. Many historical displays are also included as a reference. Particular care has been put into preparing the beautiful computer simulations that are used to explain the ice crystal populations behind each display.

The variety of the images is striking and Riikonen has obviously spent a lot of time in finding great examples. Luckily the quality of printing matches these images: I have rarely, if ever, seen a print job this good. Even the faintest halos can be distinguisted in the images.

As Riikonen is a long-time expert in the field, the substance of the book is solid and provides everybody from beginners to experts with new insights about halo science. Being such a significant contribution to the field of atmospheric optics one can but hope for a quick release of an English language edition.

A few select pages can be previewed online (1). Publisher information (2).

Riikonen, Marko (2011) Halot. Jääkidepilvien valoilmiöt. [Halos. The optical phenomena of ice crystal clouds]. Tähtitieteellinen yhdistys URSA ry, Helsinki.

Liljequist superparhelia & a nucleation agent gun



This Liljequist superparhelia was observed in the spotlight beam on 5 January 2011. The lamp is about a degree or two below the horizon, thus giving the central stage to the Liljequist superparhelia. The Liljequist parhelia can be seen against the snowy ground below the superparhelia.

The halos were seen in diamond dust that was generated by my water ice nucleation agent gun operating ca. 1 kilometer away from the site of the observation. The nucleation agent gun can operate autonomously for hours since the water supply is automated. The temperatures varied between -22 and -27 degrees Celsius.

The image above shows some colour artefacts (the background sky is not even color) as we were also testing Riikonen latest HID lamp (Marko Riikonen accompanied me during this night) that has two high intensity discharge bulbs. Unfortunately we were only able to fire up one bulb. Two bulbs would have produced a more even beam in terms of colours and luminosity.

Full image gallery is available (1). It also contains a lengthier account on the evening.

The nucleation agent gun can be seen in action in a separate photo gallery (2).

Atmospheric optics meeting of 2011 in Finland



Finnish Atmospheric optics enthusiasts met on 27-29 May 2011 in the Artjärvi observation centre. The topics of the presentations varied from the latest scientifical results in NLC research and simulation of higher order rainbows to the polar expeditions and observations of optical phenomena in the 18th century. The full programme is available (<a href="http://www.ursa.fi/wiki/Ilmakeh

Wednesday, 6 April 2011

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.

Thursday, 31 March 2011

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.

Sunday, 27 March 2011

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.

Thursday, 24 March 2011

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.

Monday, 7 March 2011

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.

Saturday, 5 March 2011

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.

Thursday, 3 March 2011

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.

Tuesday, 1 March 2011

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.

Monday, 28 February 2011

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.

Friday, 25 February 2011

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.

Thursday, 24 February 2011

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.

Wednesday, 23 February 2011

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.

Monday, 21 February 2011

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.

Saturday, 19 February 2011

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.

Friday, 18 February 2011

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.

Wednesday, 16 February 2011

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.

Tuesday, 15 February 2011

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.

Sunday, 13 February 2011

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.

Saturday, 12 February 2011

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.

Sunday, 6 February 2011

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.

Friday, 4 February 2011

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.

Wednesday, 2 February 2011

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.

Tuesday, 1 February 2011

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.

Friday, 28 January 2011

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.

Thursday, 27 January 2011

Elliptical halo from 22 January 2011

Midday Altocumulus move thru the area and while passing through, I get a fine corona around the sun and later on lenticular cloud formations pass through showing fine iridescence. With sun getting sort of low, more AC roll in precipating into a layer of ice crystals which forms a tall ellipse that's complete and lasted for over an hour. I got some nice pics of the display and this is a good way to start the new halo year ( 1 - 2 ).

Michael Ellestad

Wednesday, 26 January 2011

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.

Monday, 24 January 2011

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]

Friday, 14 January 2011

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.

Wednesday, 12 January 2011

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


 

















By Marko Riikonen

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.

Sunday, 9 January 2011

Hollow columns halo simulation

I wish you all a very happy year 2011, may it be rich in halos and celestial wonders!

I ran some simulation of halos created by hollow columns. Usually, hollow columns are considered to be poor halo makers, reducing the probability of getting rare arcs. I have simulated hollow columns display using Zemax.

Zemax is commercial software used for optical design. Its primary purpose is design and optimization of optical systems. It allows only static simulation, but I wrote a few macros to simulate halos. The main advantages are that you don’t need to compute yourself all the optics laws, just to concentrate on the halos, and it is very flexible software. I have been able to simulate displays from twinned and complex crystals. Its main disadvantage is that it is very slow compared to dedicated software like Halopoint. I have compared the two software and they give the same halos, so the optics inside is really the same. Crystals used to simulate hollow columns keep their crystalline faces for the hollow parts. In real crystals, the holes appear to be more rounded and smooth. The halos simulated are so from ideal hollow columns. Simulation shows that, quite unexpectedly, hollow columns strongly enhance complex arcs in the anthelic direction. For instance, Tricker and subhelic arcs are much more prominent than with regular columns. Marko Riikonen pointed out a display with samples showing lots of hollow columns that had strong Tricker and subhelic arc. Simulations with hollow columns are quite consistent with the display.

I still don’t really figure how these complex raypaths can have increased probability with hollow columns, but simulations definitely show it.

Nicolas Lefaudeux

Saturday, 8 January 2011

Lowitz arcs from Florida

Nick Beck has sent this high cloud halo display that he observed on Christmas eve in Florida. The sun elevation was 31 degrees when it started and the display ended when the sun was 7 degrees above the horizon, lasting a little over 3 hours. The observed halos include Lowitz, upper sunvex and suncave Parry arcs ( 1 ), possible Wegener ( 2 ) and helic ( 3 ) arcs, and infralateral arc ( 4 ),among others ( 5 - 6 - 7 - 8 - 9 - 10 - 11 )