Author: Claudia Hinz

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Diamond Dust Halos on 13 December 2024 over the Ore Mountain Ridge

In winter, halos can also form directly at ground level when moisture-saturated air crystallizes. This typically occurs at very low temperatures below –10 °C, for example in river valleys. Additional condensation nuclei can strongly influence the temperature at which ice crystals form, as can orographic lifting processes over mountain ridges and passes. Consequently, ice fog halos are frequently observed in ski resorts, where snow cannons provide abundant condensation nuclei, but they can also form on mountain passes where fog enriched with dust from the valleys flows over the highest points, crystallizes into ice particles, and subsequently dissipates.

Similar conditions are found along the crest of the ridge of Ore Mountains (Erzgebirge). This tilted fault-block mountain range rises gradually from the Saxon side and then “drops” abruptly at the ridge into the Eger Valley, which lies up to 1,000 meters lower on the Bohemian side. In the Bohemian Basin, persistent fog often develops during high-pressure weather patterns, sometimes lasting for days or even weeks. Numerous power plants enrich this fog with condensation nuclei. The very cold, moisture-saturated air over the basin is denser and has higher air pressure than the often warmer air mass along the ridge. When this fog flows over the Ore Mountain crest, orographic lifting and pressure equalization cause water vapor within the fog to freeze around the abundant condensation nuclei, forming minute ice crystals. The large number of nuclei promotes ice crystal formation even at comparatively high temperatures, because in this supersaturated air water droplets freeze readily and in significant numbers.

Thus, under south to southeasterly winds, it is sometimes possible to observe spectacular diamond dust halos between the Bohemian Klínovec (Keilberg, 1,244 m) and the Saxon Fichtelberg (1,215 m) at temperatures from –2 °C. This diversity of halo types is unique in Central Europe. Snow cannons play a minimal role here, as the prevailing Bohemian winds carry ice crystals from natural fog across the summit. In the adjacent valleys, however, additional crystals may form from the fine droplets produced by snow cannons when winds are calm. Nevertheless, diamond dust halos have been documented in the Fichtelberg–Klínovec region long before the advent of snowmaking equipment.

Beginning on 11 December 2024, a large high-pressure system in the Bohemian Basin produced dense fog, which in lower elevations of the central and eastern Ore Mountains resulted in freezing drizzle and glaze ice. Webcams occasionally showed brief halo displays, but the fog’s upper boundary was high, allowing little sunlight to penetrate.

Conditions changed on 13 December, when the fog top descended to roughly 1,000 meters. Shortly after sunrise, both webcams and photographs taken by observers on-site captured impressive halo formations. In addition to the 22° halo and sundogs, the upper tangent arc and the Parry arc were visible, the latter appearing just before sunset as a distinctive “double V” shape nestled against the upper tangent arc.

In the early afternoon, we set out for the Ore Mountains’ “diamond dust halo paradise” and descended into the lower fog within the Czech Neklid ski area on Klínovec. What awaited us there was breathtaking—a glittering, three-dimensional halo display featuring 18 distinct halo types and 25 single halos. Ice crystals sparkled in every direction, and near the zenith and antisolar point it was especially difficult to match the dazzling glints to their corresponding halo forms. Only later, upon reviewing the photographs—of which a small selection is presented here—were the arcs clearly identifiable. Altogether, the following halo types were visible to the naked eye:

  • 22° halo
  • Left and right parhelia (sundogs)
  • Upper and lower tangent arcs
  • Upper and lower light pillars
  • Circumzenithal arc
  • 46° halo
  • Parhelic circle
  • Right 120° parhelion
  • Supralateral arc
  • Infralateral arc
  • Concave and convex Parry arcs
  • Subsun
  • Wegener’s anthelic arc
  • Tricker’s anthelic arc
  • Tape arcs
  • Heliac arc
  • Anthelic arc
  • Moilanen arc

For us, this was the second-largest halo display we have ever witnessed, surpassed only by an event in 2014, when 20 halo types and 23 single halos were seen simultaneously. However, the 2014 display was short-lived, whereas this time the halos persisted for more than 30 minutes.

Text and photos: Claudia and Wolfgang Hinz

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Moilanen arc observations from Davos

Moilanen arc in Davos. Photo: Bertram Radelow

This report describes halo displays including Moilanen arcs (MAs) which occurred in Davos from 2005 to 2017, caused by snow gun induced diamond dust. Four of them are discussed in more detail. The MAs are presented in relation to the degree of ripening of the diamond dust crystals, and with respect to the other halo types in the displays.

Davos is a world-renowned winter sport resort. Because of the decreasing amount of natural snow over the past decades, numerous snow guns have been installed. In the winter season 2017/18, more than 150 of them are running.

Snow guns produce artificial snow made from clumps of small ice spheres without any discernible hexagonal crystal structures. However, a part of the water spray is converted into microscopically small ice spheres which drift off. These will serve as condensation seeds for larger crystals, often in column shape, but also plates do occur.

Remarkably, MAs are preferably generated during the first stage of crystal growth. Full-ripe crystals produce only dull MAs or none at all.

Author: Bertram Radelow, Davos, Switzerland

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Diamond dust halos on December 2nd, 2017 at the Fichtelgebirge

Concave and convexe Parry arc. Photos: Ruben Jakob

At the Fichtelgebirge, a low mountain range in northeastern Bavaria, there were similar halo phenomena as in the ore mountains circa 100km away (see article). In the morning, the high fog staunched and dissolved while passing the mountains. From afar, a very interesting cloud edge was seen at Mount Schneeberg (1051m above sea level). Shortly ahead Schneeberg, the temperature fell below -8 °C and rose to -5 °C in the fog. In the valley between the two mountains diamond dust was non-existent. I kept searching and trying to get out of the fog. Just in the village Grassemann (about 700m above sea level) there was a right parhelion and shortly afterwards a Supralateral arc visible above the fog. After 20 minutes, the fog suddenly came up to me and conjured a variety of halos in the sky. When I saw the concave and the convex Parry arc as well as the Moilanen arc distinctly, I was speechless. After that, the halo activity waned slowly. At 10 o’clock there were no more halos seen. The high fog broadened increasingly and the sun couldn’t shine through.

Grassemann 09.17 CET
Grassemann 09.18 CET
Grassemann 09.18 CET
Grassemann 09.21 CET
Grassemann 09.25 CET
Grassemann 09.26 CET
Grassemann 09.31 CET
Grassemann 09.43 CET
Ochsenkopf 11.13 CET
Ochsenkopf 11.16 CET
Ochsenkopf 11.24 CET
Ochsenkopf 11.27 CET
Ochsenkopf 11.38 CET
Ochsenkopf 11.40 CET
Ochsenkopf 11.41 CET

All in all, the following halo types were visible:
– 22°-halo
– Parhelia
– Upper tangent arc
– Upper and lower sun pillar
– Circumzenithal arc
– 46°-halo and Supralateral arc
– Fragment of parhelic circle
– Upper concave and convex Parry arcs
– Upper Tape arcs
– Heliac arc
– Subhelic arc
– Moilanen arc

Afterwards I drove to the top of Mount Ochsenkopf (1024m above sea level). There was a second halo show starting at 11.10 CET. However, expect of the right infralateral arc with the Tape arc, there were no further halo types.

Author: Ruben Jacob, Burgkunstadt, Germany

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Diamond dust halos on December 2nd, 2017 at the rim of the Ore Mountains

Due to the inflow of polar air in the night of december 1st to 2nd there was fog formation in the valleys of the ore mountains. At the top of Fichtelberg (1214m above sea level) Claudia Hinz could observe the lower tangent arc and in parts also the submoon repeatedly in the lower sea of clouds. About 03.45 CET single shreds of clouds rose from the valley and forms an extensive halo phenomenon for 5 minutes as it is rare at the moon certainly. There was the 22°-halo, both parhelia, bright upper and lower tangent arcs, the complete light pillar, 46°-halo, supra- and infralateral arc, parhelic circle, submoon and both subparhelia. The evaluation of the photos revealed the Parry arc, the Lowitz arc on the left side and the upper and lower Tape arcs.

Weather situation

During the day Wolfgang Hinz took over the further observation at the rim of the ore mountains. At the sun the halo types changed quite fast, too. Several times the 16 visual observed halo types formed phenomena including 19 halos. Pictures showed two more halo types. Some halos lasted just for minutes, whereas the 22°-halo and the parhelia were there from 9.30 CET to 13.00 CET. But they appered earlier and continued towards the later afternoon. The Halos were observed on top of Fichtelberg and its surrounding area, at the border to Bohemia and at the Czech ski area Neklid, as well as on the way home in the mountain village Tellerhäuser.

All in all, the following halo types were observed:
– 22°-halo with both parhelia
– Upper and lower tangent arc
– Upper and lower sun pillar
– Circumzenital arc
– 46°-Halo
– Parhelic circle
– The left Lowitz arc shortly
– Left 120°-parhelia
– Supra- and infralateral arcs
– Parry arc
– Subsun
– Tape arc’s
– Trickers’s anthelic arc
– Heliac arc
– Moilanen arc (faint)
– Subhelic arc (Photo)
– Anthelion (Photo)

Author: Claudia and Wolfgang Hinz, Schwarzenberg, Germany

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Moving Ripples in a sundog

On March 26, 2017, I could observe this phenomenon for the second time. The first time I observed it in Munich about 20 years ago, when within a few minutes two boundles of “moving ripples” crossed a left-hand sundog. At that time I did not know what I was seeing. I learned it thereafter, also the name of the phenomenon, that it has been observed several times until then and that it may be related to acustic waves. Later, the video of the “extermination” of a sundog by a rocket launch became well known. But I did not see this phenomen again till March 26, 2017.

It is just a “must” for me to photograph with my pocket camera every halo I see mostly only to get the time mark of its beginning and/or end for the record. On that day I was several times on my balcony to check for halos. The sky had only contrail-cirrus (now officially termed Ci-homomutatus), but no halos. But once I discovered a faint sundog it may have been the only halo-active contrail-cirrus group of that day. I observed the sundog coming and going with the respective cirrus couds resp. the standing sundog against the moving clouds. The sundog was faint the whole time and all but remarcable. But then I surprisingly realized that there were some odd dark strokes crossing part of the sundog diagonally. Remembering the moving ripples, I immediately zoomed in. I could record this phenomenon in some pictures. It did last only about 30 seconds, but visually the dark stripes were much more evident than the photographs suggest.

The exceptionality of this observation was that the otherwise “moving” ripples were in fact “standing”: They moved with the cloud through the sundog. This can be seen very nicely on the photographs: the ripples seem to be a fixed structure of the cloud. But they were only visible in the area of the sundog. Outside this area the ripple pattern did not show up: the dark stripes were not there! Clearly recognizable is also the fact that each ripple began weak and increased its intensity towards a maximum in the centre of the ripple area, and to vanish at the other border of the ripple area.

Remarcable was also the fact that the ripples showed up only in a part of the cloud resp. the sundog area. For me it remains a mystery why (only) a small part of the cloud was “trapped” in these “acustic waves”…

Author: Christoph Gerber, Heidelberg (BW), Germany

Link to the topic: Collection of all known observations

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Halos in pyramidal ice crystals in Ohio

On June 17th, 2017 Michael Ellestad have recorded in Ohio, USA a nice pyramidal crystal halo complex. began in the morning and ended at midday and near evening the halos returned. In all he observed 9, 18, 23, 24deg and faint 35deg halos with upper and lower 9deg tangent plate arcs, 18deg lateral plate arcs, 23deg upper plate arc, upper and lower 24deg plate arcs and maybe the very rare pyramidal helic arc.

The cause was the warm front of a small low pressure area over Lake Michigan. In such small depressions crystals often have only a short lifetime, but have optimal optical properties during this time. Since these small-scale low-pressure areas occur very frequently in the 5 Great Lakes of North America, this could be the reason why pyramidal crystals and haloes occur several times a year, more frequently than in most other parts of the world. But also the jetstream, which runs mstly over Ohio, could have a positive influence on the crystals, as was investigated by Rainer Schmidt in this article.

 

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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

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Diamond dust halos in Jena, Germany

On January 22nd 2017 I had the opportunity to witness a halo phenomenon in my home town for the first time.

The observation took place in Jena-Maua Germany (50°51’59.4″N 11°36’02.0″E) from 8:45-10:45 CET within about one kilometer. The maximum activity was observed between 10:15 and 10:45 CET.

We had a high-pressure weather situation with more and more lifting and dispelling fog (starting with 50m AGL) in the ‘Saale’-valley. Measured temperatures were about -10 to -6 degrees.

After recognizing the lower sun pillar besides the left Subparhelia in front of the fog boundary (seen from 300m height) I drove closer to the fog and found myself standing inside diamond dust (height 150m).

Between 9:45 and 10:45 the following types of halos have been witnessed: 22° halo, left and right parhelia, upper and lower tangent arcs, upper and lower sun pillar, Circumzenithal Arc, parhelic circle, Anthelion, left and right 120° parhelia, Supralateral arc, Parry arc, Subsun, left and right subparhelia, Tricker’s anthelic arc, Tapes arcs, Heliac arc and subhelic arc.

Uncertainties exist concerning the following observations: Lowitz arcs and Moilanen arc.

To sum up the best possibility of seeing this phenomenon was inside or near Jena-Maua – a small district of the city Jena which has some industry chimneys (compare the last photographs with the smoke trail). It seems legit to suppose that industrial fine particules conduced sublimation/condensation nucleus for the diamond dust development.

Author: Marco Rank, Jena, Thuringia, Germany

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Reflection subsun in California

On January 25, 2017 I observed a reflection subsun in Auburn, California. This was my second observation of this phenomenon, the first of which was on February 1, 2008 and is already documented here.

The conditions between the two observations are nearly identical: The observing location, time of day, and time of year. Also of note is that both were seen following a multi-day period of heavy rains, which supplied the water that reflected the sun upward toward the Altocumulus cloud. The water had filled the Yolo Bypass, which is an area that is designed to flood during periods of heavy precipitation and lies along the line of sight between Auburn and the setting sun.

Author: Steve Sumner

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Reflection subsun in Southern Finland

6th January, 2017, I observed quite a clear reflection subsun in the southern Finland.

It was morning,  local time around 11am. I looked outside and saw a nice sun pillar. And clouds, that were about to block the Sun. So I went to take photos of the pillar before it was too late.

I got the pictures and stayed for a while and saw the clouds running over the Sun. Surprisingly, the pillar didnt disappear. I waited for a little while longer but the halo was stubborn. Then I realized, the source was not the Sun, directly, but its reflection! The sea is a couple of miles away and wasnt yet frozen (map).

More pictures can be found here.


Author: Matti Helin, near Turku, Southwest Finland