Saturday, 22 December 2018

Some odd radius column displays from China in 2018

Odd radius column arcs have long been deemed as some of the rarest halo forms. Sighting reports in most parts of the world have indeed been sparse. However, during the past few years in China, we came across a good number of odd radius column displays. Spring monsoon seems to bring them to our country every year.

In 2018 we documented at least a dozen such displays country wide, most of which occurred in April and May over Southern China. Here I’d like to share with the world some of the most noteworthy ones. All photos below are single shots with only minor USM applied.

On April 29, photographer Cui Yongjiang witnessed a long lasting display from Shangri-la, Yunnan Province. Complexity of the display peaked in the afternoon when the sun dropped to around 40° altitude. The 9° and 24° column arcs in this display are rather weak, implying short prism faces among the crystals.

© Cui Yongjiang, shown with permission

Later on May 17 in Sanya, Hainan Province, Weibu captured a short-lived display in which the sun sit at 83° altitude. At such high altitude, most odd radius column arcs turn into circles. The 20° and 35° column arcs have their upper half much brighter than the lower half. The way that the 20° column arc completely outshines other arcs in this display is quite interesting. Crystals with long pyramidal caps and very short prisms might have been responsible for such appearance.

© Weibu, shown with permission

Up until August, all documented column displays took place in Southern China. Such displays have been much rarer in Northern China where monsoon from the Indian Ocean hardly reaches. 

The pattern does get busted sometimes. On August 12, the best display of the year swept across Heilongjiang Province in Northern China. Middle school teacher Mao Xiufang from Daqing noticed this complex display during class break and snapped this amazing shot with her phone. The 20° column arcs in the display are sharp while the 35° column arcs are vividly colored. The 9° column arcs are even displaying their theoretical curly-bracket shapes.

© Mao Xiufang, shown with permission

An hour later, the clouds advanced 200km east with crystals reaching their peak diversity and optical quality. Fang Tongbing grabbed this handphone photo manifesting the display at its best. The sharpness of the 9° , 20° and 24° column arcs are very close to simulations. Had the crystal quality been any better, we might even start seeing traces of odd radius Parry arcs! 

Apart from the column arcs, some plate orientated crystals also joined the party contributing to a weak 23° upper plate arc.

© Fang Tongbing, shown with permission

This high quality display turned out to be the last odd radius column display from China in 2018. Overall we had a big year for odd radius halos. Interestingly all these displays occurred close to noon hours when the sun was higher than 40°. The cause of this pattern could be a meteorological subject worth studying.

Hopefully in the year of 2019 we will be blessed with more displays like these. Stay tuned.

Jia Hao

Monday, 17 December 2018

Complex Halo Display, Borlänge, Sweden

On the 14th December 2018 at 12.30 UTC, Magnus Edbäck photographed an amazingly complex display in his home village of Utendal near Borlänge, Sweden comprising many extremely rare halos with at least one completely new halo form, a multiple scattering halo. Highlights include 46° contact arc, Hastings arc, extremely long Schulthess arcs and the rarely seen in daylight Ounasvaara arc. Like Marko Riikonen's 6th March 2017 Rovaniemi display, this one will go down in the annals of halo history and no doubt will be discussed and analysed for a long time to come. The two faint patches of light on either side of the 22° tangent arc are the new multiple scattering halo which at the time of writing has not been given a name. It is quite possible that the display was caused by snow guns in operation at the Romme Alpin ski centre situated about 12km away from Utendal.

Magnus has very kindly agreed to give an account of how he photographed the display.

"This is the story about my halo picture.

I was having lunch at my parents home when my mother asked me to look out to see how nice the sun was shining. At once I saw that this was not like any halo I had ever seen before. The sight of the sky was amazing. I then went to my home and grabbed the camera. My parents and I live next door to one another in Utendal, a small village outside Borlänge. I quickly checked that I had the appropriate lens, it was Samyang 14mm F2.8 that was on. The camera I used is a Canon 6D which I have modified with a Baader filter, mainly for use when I shoot the starry sky. From what I understand, the filter has no significance when shooting halo.

I went to a place on my parents courtyard where I could see as much of the display as possible. I quickly checked the settings on the camera, adjusted it to ISO200 and set the aperture to F8 to get a good depth of field. The day was quite cold (about 7 degrees below zero) and I was not wearing a jacket so I only took a few quick pictures (4pcs).

I then went back home to look at the pictures. On my way home, I also saw arcs to the north and I'm very sad that I did not take any photos of them. I quickly examined the images in Adobe Lightroom and picked an image that I uploaded to the Swedish astroforum I then went back to my parents to finish lunch.

Quite soon afterwards, I received comments on by both Hans Bengtsson and Timo Karhula, who thought the display appeared to be something out of the ordinary. Hans thought I should send the image to Les Cowley and Timo thought I should publish it on I received answers fairly quickly from both Les and At 15:35 UTC 2018-12-14 I received mail from Marko Pekkola where he wrote:

"Congratulations Magnus of finding a new halo form in the sky in solar display! Several experts analysed this photo and Marko Riikonen identified one of the forms as the first multiple scattering halo of its kind.”  - Magnus Edbäck

Image processed by Nicolas Lefaudeux.
Image processed by Nicolas Lefaudeux.
Nicolas Lefaudeux has analysed and stacked the four raw files with background subtraction and produced these breathtakingly complex and beautiful processed images. The new halo is a multiple scattering [MS] halo, ie a "halo of a halo". These are extremely rare and can only appear in the brightest displays with very bright halos to forms.

This new halo is the uta of parhelion / parhelion of uta and it is the 5th MS halo form (after par of par, uta of uta, uta of pc/pc of uta, and cza of pillar). It requires both a very bright parhelion and a very bright uta to form. 

This uta of par/par of uta was the most likely MS halo form expected to be caught, because of its relative ease to appear in simulation and because it is not overlapped with other bright regular halos.

All images copyright Magnus Edbäck

Friday, 14 December 2018

Spotlight display with diffuse and Tricker arcs

The diamond dust season has begun in the Czech Republic and on the night between 13th and 14th December it showed what it can do. Temperatures were droping below -10°C in many places, and with a fairly strong temperature inversion (+4,5°C with 300 metres), freezing fogs were forecast - humidity was very high.

The pictures were taken in Velké Karlovice near Kyčerka ski centre. A place I've been to a few times already. And it has its reason. There is another ski centre Karolinka located nearly 4 km from Kyčerka, and while Kyčerka is making halos like crazy, Karolinka is as dry as a bone. This time it wasn't any different. Although it took some time, the snow guns were able to create a marvelous display, one I've never seen in the spotlight before.

I arrived at Kyčerka sometime around 21:00 UTC and until 22:00 UTC, the halo making process was at a threshold. Wind was still blowing a little bit and the halos were changing between beautiful tangent arcs and weak light pillars within minutes. Then the wind calmed down and the valley was beginning to be engulfed in an ice fog.

I set up my spotlight and what I see is amazing. Beautiful and bright upper tangent arc with sharp helic arc is visible. I see Tape arcs as well, though not that well defined. But what I saw in the anthelic region amazed me the most. There was a clear and bright arc hovering above my shadow. Clearly, the Parry oriented crystals made sure the Tricker arc is nicely visible. What I didn't realize was that diffuse arcs were there, too. I saw them after I was looking at the photos in my computer.

It was really freezing and my hands and feet started to feel numb from constantly standing in the light beam. After I took the photos, I sped to my car to warm up, circled the valley for a bit to see if things have changed and then made a decision to go home, because I was tired and slowly transforming into a popsicle.

Next time I plan to place the lamp in a higher elevation for more halo forms to show up. And maybe update my spotlight a little bit, it has too wide beam, which illuminates the snow cover. I wasn't able to find a decent spotlight with a tight beam though, so I'll keep looking.

Diffuse arcs with Tricker arc, helic arc and maybe a hint of Wegener

Diffuse arcs with Tricker arc, helic arc and maybe a hint of Wegener (B-R processed)

UTA, Parry arc, helic arc, Tape arcs etc.

Thursday, 13 December 2018

Elliptical halos 12-12-18

Early in the day before leaving for work saw some AC clouds moving over our area and whenever I see AC clouds or altocumulus clouds first thing that comes in mind well you guessed it elliptical halos. While driving down a back country road I slow down and park the car and right there I saw an elliptical glow manifest its self and I watched two halos form both red on inside and blue on the outside. There was no telephone pole for me to use to block the sun. I know if I used the macro lens and try to cover the sun with my hand it would be blurry so I used the wide angle.

This is my second elliptical halo observation for the 2018 halo season and this is a good way to wrap it up.