The appearance of a "circular rainbow" requires very specific conditions regarding the relative height of the sun, the concentration of mist, and air humidity.
Recently, 33-year-old amateur climber Sam Clack, after climbing Snowdon in northwest Wales, UK, was pleasantly surprised to see a circular rainbow. This phenomenon is formed by the diffraction of sunlight and requires specific conditions related to the relative position of the sun, as well as the concentration and humidity of clouds and mist, making it extremely rare to witness.
The "circular rainbow" was first discovered on Brocken, the highest peak in Germany’s Harz Mountains. When standing on the mountain summit with one's back to the sun and with fog lingering in front and below, sometimes a colorful ring with red on the outside and purple on the inside can be seen in the sky ahead, with the observer's shadow visible in the center — moving as the person moves, and vanishing when the person leaves. This phenomenon is also known as the "Brocken Specter."
Mr. Clack is a radio journalist. On that day, a physics teacher who was climbing with him pointed out the magical sight. Clack said, “I’ve never seen this phenomenon before, and I doubt I’ll ever see it again. It’s truly a miracle of nature.”