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

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.

 

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

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

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

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

AKM’s Circumhorizon Arc Seasons 2015 & 2016

Starting in 2015, inscribed members of AKM’s forum were invited to post photographically documented circumhorizon arcs (CHAs). The reach of this mostly German language website and the geographical limit for CHAs at ca. 55° N, restricted the incoming reports to Germany and its surroundings to latitudes between about 47° N and 52° N, in practice. The possible maximum solar elevation angle for these places varies between 61° and 67°, thus not quite attaining the brightness optimum for CHAs, which comes at a little less than 68°. [1]

On the other hand, it has been found that some of the aesthetically more pleasing CHA apparitions occur at 65° solar elevation or less. This is because the CHA gets wider then, therefore increasing the dispersion of spectral colors. Such CHAs are also situated less high in the sky, where they are more easily seen unintentionally. Also then, an interesting landscape in the foreground may add to the scene’s beauty.

The following table contains a summary for the 2015 and 2016 CHA observations. Observations on the same day have been included, if from different places and reported in the said forum or – in just two cases – directly communicated to this author. Chance findings of related CHAs in other public networks and oral reports solicited by an AKM posts are carried separately. For consistency, three CHAs seen in far-away places by a travelling AKM member were not included in the count. The last column contains the count of AKM’s systematic visual observers.

tabelle

It is clear, that the CHA campaigns for 2015 and 2016 were comparably successful, definitely surpassing the counts for any earlier year. The competitive character of a call for CHAs stipulated an increased time log from skilled observers and made them aware of quite inconspicuous CHAs. Although the meteoros.de forum boasts many hundreds of members, the number of those contributing CHAs, was quite low. The CHA reports for 2015 and 2016, respectively, were delivered by 15 and 19 observers, respectively, who lump together to just 26 different persons for both years. So every CHA reporter on the average had 2.3 specimens. Besides different personal noon-day observing options, the more southerly observers were favored, of course. The most successful six of them recorded 34 CHAs (58% of the grand total).

In concluding, some circumhorizon arc images from 2016 are duplicated from our forum. First place goes to a very nice spectrally pure example, seen June 15th at a solar elevation of 64.1o by Daniel Eggert near Neuburg (Danube).

The photo by Isabelle Klein (a) shows a CHA underneath a 22o circumscribed halo, as photographed from the Autobahn A1 near Hermeskeil nine days earlier, on June 6th, at a solar elevation of 63.4o. Unsharp masking of this shot shows an infralateral arc curving upwards from the CHA. Not shown here is the also present complete parhelic circle.

By contrast, Michael Großmann’s photo (b) from Aulendorf, taken June 18th at a solar elevation of 65.3o does not show any hints of a 22o halo.

On July 6th, Elmar Schmidt experienced a long-lasting CHA display in Heidelberg (c). The sky was uniformly covered with cirrus clouds, which washed out the contrast for the halo, which extends for more than 60o of azimuth. To show this better, two portrait oriented wide-angle photos, taken at solar elevation of 63.4o, were stitched together, therefore artificially broadening the circumscribed 22o halo disproportionately w.r. to the CHA.

Karl Kaiser in Schlägl, Austria, took his photo (d) of a delicately colored CHA on July 8th at a solar elevation angle of 63.4o.

[1]        E. Schmidt, A. Haußmann, C. Hinz, P. Zenko: Der Zirkumhorizontalbogen – Teil I: Auftreten und Häufigkeit, VdS-Journal, Nr. 53 (2015), S. 70

Author: Dr. Elmar Schmidt, Bad Schönborn, Germany

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

Pyramidalhalo in Calgary, Canada

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.

Elliptical halos with small radii observed from Mt. Fichtelberg

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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.

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