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
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
In an earlier post I told simulation attempts were not succesful for this display. Well, I really did not put that much effort into it. Now I have given it a fresh look and managed to get some succees.
The problem was the subhelic arc and anthelic arcs that could not be get rid of. In new simulations made with HaloPoint the subhelic arc issue is pretty much resolved and the anthelic arcs also play it low key.
This was a good no-hassle night of diamond dust hunt. The swarm was stationary and I didn’t have to pack up every 20 minutes to follow its whims. During the 6 hours of observing it was necessary to move only once. Also, both two locations were quite good concerning the light pollution. Especially the second place, where I wrapped it up in the morning ours, had a really dark segment which I used to light up the anthelic region.
As for the halos, the start of the night at around midnight was not so inspiring. As I arrived to the snow deposit area near the river, a sneak peek in beam revealed a run-of-the-mill plate display and I though it will just get worse because the temperatures were in the bad range, around -15 C. So I decided I might as well give some minutes for the half-moon display that had a smudge of Moilanen arc. In photographs it was transformed into a nice V-shape.
In snow gun diamond dust displays Parry orientation is often strongly emphasized in relation to column orientation. There may be no signs of column orientation at all, except for perhaps a slight tanget arc brightening on top of 22° halo.
Spotlight displays are great in that almost every time you photograph them, you realize you understand halos less and less. This time the puzzle is: Why Wegener in the image above is so strong in comparison to other reflection halos? No subhelic arc is visible and neither there seems to be diffuse arc – I think the spikes at the subanthelic point are lamp artefacts. Of course I can’t not say that for sure, but around the subanthelic point even weak stuff shows up easily to the eye, so had there been diffuse arcs, I should have noticed it. If we accept this, then, in addition to the Wegener, the only suggestion of column reflection halos is what looks like a short patch of Tricker arc cutting across the sub-Kern arc (see the simulation below for comparison).
Showcasing the last winter’s spotlight displays is still under way, but fresh produce is already coming in. Here is the new crop that I harvested on the evening of 5th November in Rovaniemi. In the image above the lamp is around -6 degrees below the horizon and both parhelic and subparhelic circle are visible. Slight intensity enhancements in them on the side of the sky opposite to the lamp are suggestive of Liljequist parhelia. Included are also Sub-Kern and sub-120° parhelion. I did not spot sub-Kern this time, but the latter was quite discernible when running alongside the beam. As usual, it was a pale pillar of light in which no individual crystals were detectable – very different from the intense subparhelic circle patch towards the subanthelic point, which is always made of pure glitter.
On the fifth of November the diamond dust season opened in earnest, when Esa Palmi photographed a major display at the Kittilä airport. While the sun side is always the attention gatherer, the main attraction of the display is really on the opposite part of the sky, where a strong subanthelic arc dominates the scene.
Here 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.
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.