Unprecedented high-quality 28° arc outbreak in China

The 28° arc outbreak in China just wouldn't stop.  Since my last post ( https://thehalovault.blogspot.com/2022/08/28-arc-spotted-4-times-within-one-week.html ), 16 more sightings were reported across multiple provinces as of Aug 27, meaning that a total of 20 cases occurred within the 20 day period between Aug 7 and 26. Such an intense outbreak is beyond our wildest dreams.

What makes this outbreak more monumental is the high average quality of cases. Multiple observers described the 28° arcs as 'very bright, as bright as the 24° and 35° plate arcs'. Visual detection of color in the arcs was also widely reported, which has been a real rarity in past years.

If we were to identify the climax of the outbreak, it has to be Aug 21 and 22. Within this busy 24 hours, bright and vivid 28° arcs, together with other high quality odd radius plate arcs, popped up every time the sun neared the horizon. The largely low-cloud and haze free skies gave enthusiasts in several provinces a rare opportunity to appreciate odd radius halos at their best.

Aug 21, evening:

The grand show started in Anhui and Jiangsu Province. LIU Qianyu in Anqing grabbed with his DSLR a series of textbook standard photos showcasing a typical sunset odd radius plate arc + 28° arc display.

Taken by LIU Qianyu in Anqing, Anhui Province. Camera photo. Single exposure.

300km away, LI Jiamin in Nanjing witnessed an equally splendid display. She also managed to take a time-lapse video of it.

Taken by LI Jiamin in Nanjing, Jiangsu Province. Mobile phone photo. Single exposure.

Aug 22, morning:

Less than 12 hours later in Nanjing, the 28° arc showed up again in the morning sky, bringing its  recurrence interval record in China from 3 days down to hours.

HAO Yanjun, one of our key community members, contributed by far our most comprehensive camera coverage of a 28° arc display. Despite not having a tripod available at the scene, he managed to follow the display for hours handholding his SONY mirrorless camera. 

Taken by HAO Yanjun in Nanjing, Jiangsu Province. Camera photo. 30 frame stack.

HAO's effort in maintaining a relatively consistent field of view and regular intervals while shooting clearly pays off in post processing. Stacking 30 frames yields a result beating all our past data. The BGR + B-R processed version of the stack turns out buttery smooth, almost like a simulation!

BGR and BGR+B-R version of HAO Yanjun's stack.

HAO's amazing captures have undoubtedly raised the bar to a whole new level, and will likely remain unchallenged for some time.

Aug 22, evening:

Hours later, the crystals drifted southwards to Jiangxi and Hunan Province. CHEN Junzhi in Ganzhou probably never anticipated his first 28° arcs to be this bright.

Taken by CHEN Junzhi in Ganzhou, Jiangxi Province. Mobile phone photo.

TANG Chaowen in Shaoyang was treated with something a bit different. The 28° arc he saw, while also bright and colorful, exhibits a prominent sunvex/comma shape. 

Taken by TANG Chaowen in Shaoyang, Hunan Province. Mobile phone photo.

Such peculiar appearance was first reported in the 2020 Pu'er display ( https://thehalovault.blogspot.com/2020/09/mysterious-sunvex-28arcs-in-yunnan-china.html ). Now TANG's capture provides solid evidence that the Pu'er case isn't a one-off outlier. Given that available theories are facing trouble explaining the shape, fresh ideas are much needed to crack the Chinese 28° arc mystery.

Jia Hao

28° arc spotted 4 times within one week in China

After a two year long no-show, the mysterious 28° arc finally makes its comeback in China, in a very dramatic way.

Between Aug 7 and 14, the arc was observed four times in three provinces, setting a new record.

Aug 14, Ningbo, Zhejiang Province

Photographed by LI Shengyu. Single exposure with no processing. Shown with permission.

BGR and B-R versions of the stacked image.

Very high quality set of capture by LI Shengyu. Stacking, BGR and B-R processing reveal the arc's weird sunvex comma shape, reminiscent of the 2020 Pu'er display ( https://thehalovault.blogspot.com/2020/09/mysterious-sunvex-28arcs-in-yunnan-china.html ).

Aug 13, Xi'an, Shanxi Province

Photographed by Aphelius. Shown with permission.

Enhanced by Aphelius. Shown with permission.

Seasoned sky watcher Aphelius sets China's northernmost (35°N) 28° arc sighting record with his brilliant Aug 13 observation. Xi'an is geographically considered a Northern China city, which means the 28° arc finally makes its debut in Northern China. It remains to be seen how much more north it can push in future.

Aug 10 and Aug 7, Renhuai, Guizhou Province

ZHANG Zhengqiang's second observation on Aug 10. Mobile phone photo. Shown with permission. 

BGR processed version.

ZHANG Zhengqiang's first observation on Aug 7. Mobile phone photo. Shown with permission.

BGR processed version.

Yet another new record, ZHANG Zhengqiang witnessed a repeat event merely two days after his first observation on Aug 7, from exactly the same location! The two displays almost look identical. Atmospheric condition during those few days must have been remarkably consistent.

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At the time of writing, there's still an ongoing odd radius plate arc outbreak in Southern China, which has lasted more than a month and shows no sign of stopping. Plate arcs are spotted almost everyday in (mostly) Southern China since late June. We shall reach well over 50 odd radius days in 2022. More 28° arc occurrences are likely on the way if the outbreak continues.

Jia Hao