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

Original post in Ice Crystal Halos

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

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

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

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.

Pyramidal halo from Thailand

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

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.

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).

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

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

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.

Originally published in Submoon

South Pole odd radius halo display 6 February 1999

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.

Originally published in Submoon

 

South Pole halos 5 February 1999

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

Originally published in Submoon

 

Halo display at South Pole on 4 February 1999

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.

Originally published in Submoon

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

 

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 simultaneously also halos from normal prismatic crystals. Yeah, if I had to bet, I would definitely go for the 9° column arc now.

Originally published in Submoon

23° plate arcs from summer 2010

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.

Originally published in Submoon