Explain the phenomenon of fire rainbow

Fire rainbows appear in the sky with many striking colors, but are only observed in certain areas.

Steve Ackerman, professor of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison, calculates that several variables must coincide for this spectacular phenomenon to occur. Fire rainbows are one of the few types of halos formed by the refraction of light in intermingled plate-shaped ice crystals in the atmosphere, which often appear in cirrus clouds.

A fire rainbow (Circumhorizontal arc) is a colorful halo that appears across the sky, also known as a circumhorizontal arc . When seen in the sky, this colorful halo looks almost like a rainbow. However, it only occurs in cirrus clouds and at certain latitudes.

Explain the phenomenon of fire rainbow
Fire rainbow.

According to the Mother Nature Network, this optical phenomenon forms from the refraction of sunlight , sometimes from the Moon , through ice crystals suspended in the air. The Sun must then be very high, about 58 degrees above the horizon or higher.

On Earth , a fire rainbow cannot appear north of latitude 55 degrees north and south of latitude 55 degrees south. For people living near the poles, observing this phenomenon is impossible.

Fire rainbows only appear when four special conditions are met: Light must pass through the cirrus clouds at a specific angle. The sun must be at least 58 degrees above the horizon. Ice crystals through which light is split into colors should have a hexagonal shape, and their faces run parallel to the ground.

When light passes through these ice crystals, it refracts. This bending of light is equivalent to the bending of light through a prism. If the crystals align, the cirrus clouds will act like a prism, resulting in a rainbow-like shape. In addition, the cirrus clouds have a slender shape, reminiscent of fire, which is why this phenomenon is popularly known as a fire rainbow.

Cloud iridescence is often confused with a fire rainbow, due to their similarity in color and shape. However, iridescent clouds originate from light diffraction, rather than refraction. Diffraction is the bending of light when it encounters an obstacle and is blocked.

Explain the phenomenon of fire rainbow
Iridescent clouds with bands of color that are not in a certain sequence, can be seen in every cloud layer

It is also possible to distinguish these two phenomena with the naked eye: fire rainbows occur only at a fixed location in relation to the Sun or Moon, while iridescent clouds can occur in other locations. each other in the sky. Besides, the color bands in the fire rainbow always run horizontally with the red of the VIBGYOR color spectrum at the top and purple at the bottom. The colors of iridescent clouds do not always show this fixed sequence of colors, i.e., the sequence of colors in them is random.

Explain the phenomenon of fire rainbow
Fire rainbow with colors in sequence from red to purple and running horizontally, only visible
in high-level clouds (clouds of cirrus).

Due to the extreme conditions mentioned above, fire rainbows are very rare. In addition, in the places where it is commonly detected, the frequency and duration of occurrence also varies widely.

In London, for example, the sun is only high enough for a meager 140 hours from May to July. Or like in Los Angeles, the sun is high enough for 670 hours from March to September. In addition, European weather is often cloudy, fire rainbow – phenomenon of high-altitude clouds, which can be obscured by low- and mid-level clouds, making detection of fire rainbows in Europe even more elusive .

Fire rainbow is one of the most beautiful phenomena in nature. Europeans and Americans should feel lucky as they get to witness this rare phenomenon more often than many people in other parts of the world!