An atmospheric display known as a circumhorizontal arc, frequently referred to as a "fire rainbow" due to its vibrant, flame-like aesthetic, was captured in a 2021 image near North Fork Mountain, West Virginia. This optical event occurs when sunlight is refracted by ice crystals suspended within high-altitude clouds.
For this phenomenon to manifest, specific atmospheric conditions must be met. The sun must be positioned at an elevation of at least 58 degrees, and the sky must contain cirrus clouds—specifically cirrus fibratus in this instance—located below the sun. The effect is created by flat, hexagonal ice crystals within these clouds that must be aligned horizontally to refract the sunlight in unison.
Because these precise conditions are required, circumhorizontal arcs are considered an uncommon sight. The image serves as a demonstration of how ice crystals can function as floating prisms to manipulate light.
Source: NASA
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