Kameron Barge captured this amazing ice halo around the sun at Whitefish Mountain Resort – a ski resort in Whitefish, Montana – on December 7, 2017. He originally posted it at Spaceweather.com’s gallery, saying:
As we rode the chair down into the clouds today, we begin seeing all sorts of halos, and sun dogs!
I wondered about the glittery look of the photo, and, as usual, turned to sky optics expert Les Cowley of the website Atmospheric Optics. Les told me:
This is an exceptional ice halo display made by diamond dust ice crystals. The key is the location, a ski resort. The snow blowers emit small nuclei on which large snowflakes grow. A by-product is tiny almost optically perfect halo-forming crystals that form slowly in the air up to a few miles downwind … these are the diamond dust.
The diamond dust is the reason ski resorts are the best places to see fine halo displays.
Kameron later confirmed to me via email that the snowblowers were hard at work on the day he took the photo:
I think the clouds this day were partially manmade. The lower half of the ski hill had many snow blowers creating vast plumes.
Meanwhile, Les also took the trouble to annotate the photo for us (see below), pointing out some of the optical effects you don’t see on ordinary halos, for example, the illuminated vertical lines or subparhelia below the sundogs. Les wrote:
Thank you, Kameron and Les!
Bottom line: Ski resorts are the best places to see ice halos like this one. Kameron Barge caught it in early December, 2017 at a ski resort in Whitefish, Montana.