The horizontal arc around the ground is also called the phenomenon of daily load or solar load. There are also folk sayings about rainbow clouds and flame rainbows. The circular arc is called the most beautiful of all halo images, and its color sequence from top to bottom is: red, orange, yellow, green, blue, indigo, blue-violet. It is a kind of light.
A horizontal arc around the horizon will only appear when the sun is at least 58 degrees from the horizon, but in mid-latitudes, the sun can only reach this altitude in June and early July, and only within a few hours before and after mid-day.
The formation principle of the circum-horizontal arc phenomenon is similar to that of the circum-zenith arc, and both are caused by the refraction of ice crystals in the upper atmosphere irradiated by sunlight. The difference is that the incident light of the circum-horizontal arc phenomenon enters from above the ice crystal, so the color order of refracted is opposite to the circum-zenith arc.