A major halo outbreak stunned sky enthusiasts in multiple Southern China provinces between Apr 29 and May 01, with a surprisingly wide variety of high cloud halos. Even though nothing particularly rare were discovered, it's still worth sharing some of the highlights as eye candies to the international community.
(We were completely overwhelmed by the huge number of online records and submissions during the outbreak. Special thanks goes to JI Yun, who spent days going through thousands of cases and identifying the noteworthy ones. All photos in the post are shown with permission. Minimal post processing applied.)
Mid-to-high Sun Parry Arcs
 |
| Likely China's best mid-sun parry arc record to date, taken by PENG Lijuan in Hunan Province on Apr 30. |
 |
Taken by JIANG Simin in Hunan Province on Apr 30. Note how the lower suncave parry arc becomes a full circle under the 70° high sun, and cuts right through the parhelic circle and Wegener arc. What a sight to behold.
|
Helic Arc
Helic arc has been extremely rare in China, both in high clouds and diamond dust. The previous two high cloud cases were forgettable at best - barely visible in heavily processed raw images.
Finally during this outbreak, some good quality high cloud helic arcs were photographed, with mobile phones!
 |
| Taken by PENG Lijuan in Hunan province on Apr 30. There seems to be traces of lower Lowitz arc tangent to the left side of 22° halo too. |
 |
Taken by JIANG Simin in Hunan province on Apr 30.
|
Odd Radius Column Arcs
 |
| Taken by ZHANG Yifei in Sichuan province on May 1. 9°, 20°, 24° and 35° column arcs are all sharp and vivid. Note how the 20° and 35° column arcs differ from their random counterparts by being half circles. |
 |
| Taken by LIANG Yongqiang in Guizhou province on May 1. Column arcs in this one are not as intense as the Sichuan photo. However, look carefully for the 35° column arc which cuts through a weak Wegener arc inside the parhelic circle. Such combo doesn't come easy! |
Airborne Odd Radius Plate Arcs
Upper 20° and 35° plate arcs are very common during summer months in Southern China. Their lower counterparts, on the other hand, are far less frequent. In fact, the number of sightings we logged before this outbreak is zero. The void is now filled, finally.
 |
| Taken by BAC onboard a Zhuhai - Shanghai flight, on May 1. 9°, 20° and 35° lower plate arcs dominate the show. 24° lower plate arcs are probably there too, as well as weak 9°, 20° and 35° column arcs. |
JI Yun & JIA Hao
