Fire rainbows are a rare phenomenon that only occur when the Sun is higher than 58° above the horizon and its light passes through cirrus clouds made of ice crystals.
These captivating atmospheric displays are scientifically known as circumhorizontal arcs. While the name "fire rainbow" might suggest a connection with fire or rainbows, it's essential to understand that this phenomenon has nothing to do with fire and isn't a true rainbow.
The process behind fire rainbows is intricate. When sunlight interacts with ice crystals in cirrus clouds, the light is refracted, or bent, in a specific way. For a circumhorizontal arc to form, the Sun must be at a relatively high angle in the sky, usually exceeding 58 degrees. This angle allows sunlight to enter the ice crystals at a specific angle, resulting in the stunning array of colors observed in the sky.
The characteristic vibrant hues of fire rainbows are a result of the dispersion of sunlight, similar to the process that occurs in rainbows. However, unlike rainbows, which are formed by the refraction, reflection, and dispersion of sunlight in water droplets, fire rainbows arise from the unique hexagonal shape of ice crystals in cirrus clouds.
Observing a fire rainbow is a rare treat for sky gazers, as specific conditions must align for this phenomenon to take place. Not only does the Sun need to be at the optimal angle, but cirrus clouds must also be present, and their ice crystals must be appropriately oriented to refract the sunlight. These factors contribute to the infrequency of fire rainbows, making each sighting a memorable and mesmerizing experience.
Photographers and weather enthusiasts often eagerly anticipate the chance to capture this rare spectacle. The resulting images, with their vibrant hues stretched across the sky, serve as a testament to the beauty and complexity of the atmospheric phenomena that can grace our world under the right circumstances.
So, the next time you find yourself gazing at the sky and spot these radiant streaks of color, take a moment to appreciate the delicate interplay of sunlight and ice crystals that gives rise to the breathtaking phenomenon known as a fire rainbow.
