“Randomized Moilanen half circle halo“ observed again in Ore Mountain Range diamond dust hotspot

On the evening of November 27th, 2015, a group of German halo observers including myself drove on top of Mt. Klínovec to witness a diamond dust halo display both created by the moon and artificial light sources. In a car headlight beam, I detected the upper half of what seemed to be a circular halo of radius 12°-13° by stacking video frames. Because we could simultaneously observe a (traditional) Moilanen arc at the moon, and experienced a considerable wind strength, I suspected that the orientations of the Moilanen crystals got randomized at eye level due to near-ground turbulences.

More than 3 years later, on December 15th, 2018, several halo enthusiasts were attracted independently by favorable conditions and met by chance on the summit of Mt. Fichtelberg, about 4 km north of Mt. Klínovec. After nightfall, multiple halo species created by car headlights became visible, such as the 22° circular halo, 22° parhelia, upper and lower 22° tangent arcs, 46° circular halo, parhelic circle and traces of the Moilanen arc. About 19:30 CET, Andreas Möller recorded a video of the glittering 22° ring and Moilanen spots. A maximum stack of the individual frames revealed that again not the familiar upward bent V-shape was present here, but a downward-curved segment of (likely) a circle:

photographed and processed by Andreas Möller

In effect, this confirms the earlier observation, though it still is a matter of definition if this phenomenon should be regarded as an individual halo species. So far, visual observations have only given the impression of independent glints, with the circular shape being only accessible through more or less elaborate post-processing of video footage.

The Fichtelberg halo display from December 18th, 2017

Over the past years, the Fichtelberg – Keilberg/Klínovec twin peak region in the German / Czech ore mountains has proven to be an unexpectedly active place for diamond dust halos. As shown in a recent study by Claudia Hinz et al., this high halo activity may have already been present there for decades or even longer, resulting in local myths but sadly few scientific reports in the halo literature up to several years ago.

Another exceptional display was observed on the top of the Fichtelberg (1215 m) on December 18th, 2017, by Gerd Franze, the head of the local meteorological station. He took about 400 photographs from about 12.20 to 13.20 CET (at sun elevations from 16.0° to 14.3°). During the course of the display, the temperature increased from –3.6 °C to its peak value of –1.9 °C at 13:10, followed by a decline down to –5.0 °C over the subsequent hour. Wind was noticed only at very low speeds of about 2-4 m/s coming from between southern and southwestern directions. Fog from the bohemian basin was drifting over the mountain top the whole day. No snow guns were running, as there already was enough natural snow for skiing.


a) view towards the sun, b) view towards the anthelion, c) and d) corresponding simulations using the parameters below


Simulation parameters for HaloPoint 2.0

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Oblique sun pillar at the Mt. Zugspitze

On November, 23rd, 2016, I observed in Altocumulus virga a sun pillar from Mt. Zugspitze which exhibited a certain amount of inclination with respect to the otherwise common vertical direction. At first it appeared rather diffuse, but later on the distinct tilt became clearly visible.

That morning was relatively warm with temperatures around –3°C on the 2963 meter high summit, and a squally foehny wind gusted with peaks up to 80 km/h. Warm air was sucked from the Mediterranean sea by a severe southern air current. I suspect that this wind led to the inclination of the sun pillar by systematically tilting the ice crystal axes into a preferential direction.

There are only a few similar observations that can be found in the literature. On January 1st, 1969, K. Lenggenhager documented a tilted and split lower sun pillar in diamond dust on the Mt. Säntis (2502m). He explained the phenomenon by air currents which were forced to ascend a ridge, and the crystal axes being turned by various amounts on different levels of altitude (see graphic from [1]).

Similar conditions might have prevailed in my observation. The air masses of the Mediterranean sea were forced to ascend the Alps, and therefore they might have tipped the crystal axes increasingly with rising altitude.

Sun pillar in original and with unsharp mask

Another oblique sun pillar was described by Edgar W. Wooland after an observation in Boulder, Colorado [2] on January 10th, 1918, and I myself could also already observe oblique and displaced halos [3]. Unfortunately, there seem to be no further documented cases.

Any appropriate notes on the subject are highly welcome.

References
[1] K. Lenggenhager: “Seitlich verschobene, umschriebene Halostücke, schräg ovaler Halo und schräge Lichtsäulen”, Archiv für Meteorologie, Geophysik und Bioklimatologie, June 1977, Volume 26, Issue 2, pp 275–282
[2] Edgar W. Woolard: “The Boulder Halo Of January 10, 1918”
[3] Claudia Hinz: “Double Halos”

Author: Claudia Hinz

A re-visited 13° halo observation from 2013, and some thoughts about the responsible crystal faces

Circular halos of 12°-13° in radius are named “exotic” because they do not fit in the (nowadays) traditional sequence of well-documented halo radii from pyramidal ice crystals (9°, 18°, 20°, 22°, 23°, 24°, 35°, 46°). The first known photographs of such a halo were obtained at the South Pole, December 11th-12th, 1998, by Walter Tape, Jarmo Moilanen and Robert Greenler. Up to now, there are only few more (Michael Theusner, Bremerhaven, October 28th, 2012; Nicolas Lefaudeux, Paris, May 04th, 2014).

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A possible new halo above Moilanen arc

average3A simple diamond dust display that I photographed on the 6th of this month in Rovaniemi, shows above the Moilanen arc another, weaker V-shape. As I uploaded the photo on Taivaanvahti, I was not conscious of the effect, it caught the sharp eye of Panu Lahtinen and Reima Eresmaa who commented on it. Then some photo processing made it stand out more clearly. The version above was worked by Nicolas Lefaudeux. It is a stack of 13 images taken during 125 seconds.

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Diamond dust halos in spotlight beam in the evening of December 2, 2015

45921_3bfac9da40b093f7ff4ab1552ac073a8Here are shown the rest of the photos from the night that yielded the second capture of the anomalous Wegener/Hastings. From the golf course parking lot, where we took those photos, we walked into the golf course, and were able to place the lamp even lower down.

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Another occurrence of anomalous Hastings/Wegener

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On the left anomalous Wegstings, on the right normal

In an earlier post we showed a photo of a weird downward curving patch of Wegener/Hastings. Here is another case that occurred 9 days later on December 2, 2015. This time we also got a nice comparison to normal “Wegstings” by superposing photos taken from the same camera position.

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An occurrence of anomalous Hastings/Wegener

45820_e662e364876303651b6b4fbc10d66a83The image above shows what looks like a patch of Wegener or Hastings on top of the 22° halo. But instead of having the usual horizontal curvature, it is bending slightly downwards. Because of the view angle, though, the effect is not as evident as it could be. Anyway, if it were standard Hastings or Wegener, it would curve steeper up in the photo.

We have no idea how it formed, our attempts at simulating have come up empty-handed. The display was seen in Rovaniemi on 23 November, 2015, and the arc appeared at a stage when the display was still progressing to reach its peak.

Nine days later, in the beginning of December, we got another, better sighting, suggesting it is not exceedingly rare. In a similar manner, it did not occur when the display was at its best, but when the display was undergoing a momentary low. We will post about this later.

Jarmo Moilanen, Marko Mikkilä, Marko Riikonen

Segments of a circular halo from Moilanen crystals observed Nov 27th, 2015, on Mt. Klínovec (CZ)

During last year’s meeting of the German halo observers, we decided to drive on top of Mt. Klínovec (Keilberg) after dinner on Nov 27th, 2015. We used the car headlights as light sources for glittering diamond dust displays from ice crystals within the first few meters above the ground, while facing temperatures in the range of –5 °C to –6 °C at wind speeds of 5 – 6 bft. Simultaneously, there appeared a non-glittering, but slowly changing moon halo display in crystals higher up, including a “traditional” Moilanen arc:

2015_11_27_2003_30s_imgp3912_usm(20:03 CET, unsharp masked, for the original image see here)

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Presumed Reflection Subsun in Denmark

Bright and defined reflection subsun. Photo: Anders Falk Jensen

On June 5th, 2015, Anders Falk Jensen made a very interesting observation:

“It was very calm, no or very little wind. At 4.20-4.22 local time I observed a red upper pillar around 30 min’s before sunrise in altocumulus virga.

Later on the train at 5.40-5.48 local time, I observed a peculiar looking pillar in front of the altoculumus clouds, while travelling for 12 km from the town of Jelling through Gadbjerg to Give, Denmark. Sunrise had taken place approx. 60 min’s earlier. The solar elevation during the 8 minute observation increased from 5.4 to 6.5 degrees. The azimuth of the Sun changed from 57.1 to 58.6 degrees.

With these data, I later looked on a map and found the lakes Mossø and Skanderborg plus the Bay of Aarhus, located at distances between 44 and 68 km, suitable for providing the reflected sunlight. I then calculated the cloud height for the reflection to be at 2.5 to 3.5 km, appropriate for altocumulus clouds.

So, I believe that sunrays on this morning were reflected off the calm surface of these lakes, then reached ice crystal virga underneath the altocumulus, creating the phenomenon of a reflection subsun/pillar (which actually is like a subsun turned upside down). The sun was hidden by the clouds all the time, which is actually needed for this kind of observation, as a reflection subsun just about coincides with the sun. After years of observing such phenomena, I immediately knew, that this was something extraordinary. The irregularities seen might originate from minor water surface disturbances and the shape of the lake and surroundings. Also of interest are the vertical “pillar slices”. In some of my photos, weak reflection crepuscular rays are also visible.”

It is of note, that for the observation to hold its place as a halo, there must have been ice crystal clouds in about 3 km altitude in June. The ambient ground level temperature was circa 15 degrees centigrade according to the Danish Weather Office. A radiosonde analysis is not available any more from Denmark, but both Norderney in northern Germany and Stavanger in Norway reported rather warm temperatures at the altocumulus cloulds’ height, so this halo came as a surprise in them.

Further examples of reflection subsun: 123

Article about reflection subsun