At about 3:16pm on May 4, 2016, with a sun elevation of 49 degrees, Alan Clark observed pyramidal halos from Calgary, Canada, showing a relatively wide 23deg halo, a distinct 9deg halo, and a hint of an 18.5deg component. A daytime maximum temperature of over 26°C on this day in Calgary broke long-term records. The within which The halo display was formed within cirrus cloud that preceded the arrival of a distinctive cold front.
Alan also produced RGB intensity scans from these halo photos, showing the correct colour separation, with red inner colouring for these halos.
On April 22nd, 2016, I worked on Mt. Fichtelberg (1215 m above sea level) in the German Ore mountains. I noted several interesting phenomena in the sky. An upper air flow from southerly directions had brought in Saharan dust as indicated by a prominent ring of Bishop around the sun, which had already been visible since the day before. On the 22nd, aerosols produced a rather milky sky, with additional thin and high Altocumulus lenticularis clouds due to foehn from the south. These clouds showed a pronounced iridescence when coming close to the sun. This motivated me to investigate the sky in the proximity of the sun in more detail by using dark sunglasses, as it would have been a pity to miss these gorgeous colors.
The common halo observer in Central Europe will associate the term “Lowitz arcs” with short segments below the parhelic circle which connect the parhelia and the 22° halo. These so-called “lower Lowitz arcs” were first documented by T. Lowitz in St. Petersburg in 1790. In 1911, A. Wegener pointed out the hypothesis that these arcs might be caused by plate crystals oscillating around their equilibrium position. This statement is recorded in the classical textbook by J.M. Perter and F.M. Exner . In contrast this, R. Greenler postulated that plate crystals might perform full 360° rotations as they fall, referring to a note from R.A.R. Tricker from 1972 . Even today it is still under discussion which kind of crystal motion does occur in nature, since the Lowitz arc simulations for both assumptions coincide in their celestial position and differ only in their intensity distribution . A couple of years after Greenler´s theoretical predictions, the middle and upper Lowitz arcs were observed and photographed in nature, e.g. 1985 in Knau, Thuringia, East Germany , 1988 in Dover, Delaware, USA  and 1994 in Vaala, Finland . These observations were, however, not inspired by theory, as the arcs were identified only afterwards by comparison with the simulations. In the records of the German “Sektion Halobeobachtungen“ and the later “Arbeitskreis Meteore e.V.“, the upper Lowitz arc was categorized as “unknown halo“ or “abnormal Parry arc“. E. Tränkle presented a simulation of this arc independent from Greenler in 1995 .
On November 1, 2014, Thomas Klein observed in Miesbach/Bavaria a halo phenomenon with multiple appearances. In the morning hours, only the standard halos 22°-ring, both parhelions, upper tangent arc and parry arc were visible. Right after lunch, the first phenomenon was observed in the centre of Miesbach. Beside the halos above, also rare halos were documented, an almost full parhelic arc, both 120° parhelions, left Liljequist parhelion, supralateral arc and cirumzenithal arc. Not be seen but documented on pictures were also helic arc and wegeners arc.
An impressive ice fog halo phenomenon occurred in Bremerhaven at Northern Germany’s North Sea coast on 21 January 2016. It lasted from the morning into the early afternoon. To observe such a halo display in Germany is quite rare by itself, but to have it in ice fog directly at the relatively mild coast is certainly exceptional.
Visually I was able to document the following types of halos:
• 22° halo
• Both parhelions (extremely bright at times)
• Upper and Lower tangent arc
• Upper and Lower sun pillar
• Circumzenithal arc
• 46° halo
• Parhelic circle (near the sun and up to 90° to the sun’s right)
• Supralateral arc
• Parry arc
• Tricker’s anthelic arc
Image processing revealed the following halos:
• Heliac arc
• Moilanen arc (without snow gun!)
More and more ski areas install webcams with a very good image quality. They doesn’t show only the current weather situation, but sometimes also halos. Most interesting are the webcams at the mountain peaks, which also show halo types below the horizon.
Here is divergent light subparhelia flanking the pillar. Spotlight displays are classical displays with little divergenness involved. A way to create truly divergent halos with spotlight is to point it to the ground. The reflection from snow then acts as a divergent light source. Another way that might work is to cover the lamp glass with a layer of snow. That would be a shorter lasting solution, though, as the heat of the lamp will melt the snow.
Most spotlight halos are visibly formed of separate crystal glitter. Not the divergent parhelia. They are solid objects floating majestetically in the air. One feels humbled before their lofty heights, just as a lesser subject might feel in the presence of royalty.
Below is another photo of divergent subparhelia taken some hours later. And also a little lunar display from the same night, which was the 18/19 January night in Rovaniemi.
Nothing out of the ordinary here. Just a plate display and its crystals. Visible are the usual folks: subcza, sub-Kern, sub-120° parhelion. The behaviour of the last one in spotlight displays is a little curious, though: while it comes out well in photos, visually it is cryptic. One has to run along the beam to see that ghostly spot of sub-120°. It is not made of big glitter like the sub-Liljequist parhelia – it does not seem to be made of much glitter at all, just faint diffuse spot of light.
It is difficult to get a matching simulation of pretty much any spotlight display. Some details tend to be always wrong. But one can usually obtain what could be called an acceptable approximation of the real thing.
The shown display is a true rebel in this respect, for it comes with three anomalies too blatant to be swept under the rug. First, the subparhelia were brighter than parhelia (this we noticed also visually). Second, of the Schulthess arcs (the arcs from Lowitz orientation) only the concave component was visible. And third, there is no subparhelic circle opposite to the lamp.
We can not simulate any of these anomalies. The solitary presence of the Schulthess arc concave component is not a new thing, there exists a handful of such displays. The missing of subparhelic circle opposite to the lamp in this level of display is something unheard of, as is the inverted relative brightness of parhelia and subparhelia. In the simulation above (light source elevation -5 degrees) only plate oriented crystals were used. Below is a sample of the simulation crystal shape variation, the “mother shape” shown in the upper corner.
The display had also a weak segment of parhelic circle between subparhelia. The crystal shape shown above struck the right balance between the sub-Kern and the parhelic circle segment inside subparhelia.
The night was 18/19 January, the location the Sieriaapa bog in Rovaniemi. The temperature was – 29° C.
Jarmo Moilanen / Marko Riikonen
Minimum stack of 5 images.
Single image of 30 s exposure. There was light snow falling through the diamond dust, drawing streaks in the photo