Most rainbows are colorful and vibrant, but not this one. A rare white rainbow, also known as a ghost rainbow or a fogbow, was captured on video arcing over the skies of Heihe, Heilongjiang province, China, on June 29.
The vivid fogbow clearly stands out amid the fog bank lingering in the skies over the Chinese city, which is located in the country's north along the Russian border. The bright blue skies contrast against the bright white fogbow, and the partly sunny conditions in the fogbow's backdrop are crucial to its formation.
"Somewhat rare but often overlooked, 'fogbows' are seen opposite the sun, like rainbows, but lack their color because of the tiny size of the water droplets which diffract light," said AccuWeather Meteorologist and Senior Weather Editor Jesse Ferrell.
To spot a fogbow, you should keep your eyes out for a thin bank of fog opposite the sun. Common places to spot fogbows are, unsurprisingly, where it is often foggy: for example, as fog rolls in over the ocean or as fog slides down a hillside into a valley. Like a rainbow, if you happen to catch one while flying or while quite high up in the sky, you might see the fogbow as a full circle in the sky.
— Andrew Hewison (@AndrewHewison2) March 21, 2019
Fogbows are not the only kind of alternative rainbow out there, however. While the moon doesn't emit light like the sun, the reflection of the sun's light on the moon can be strong enough to form a colorful rainbow, even with a dark sky in the background.
They are rare because moonlight simply is not nearly as bright as sunlight, but the mechanism of water droplets reflecting light causes them to form, according to AccuWeather meteorologists.
Most moonbows are white like fogbows, as the light given off by the moon's reflection is typically not strong enough to produce a vivid spectrum of colors when refracted.
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