An ethereal apparition, sometimes known as a fogbow or a white rainbow, is significantly less common than its wet counterpart, the rainbow.

According to photographer Stuart Berman, who resides in San Francisco's Russian Hill area, the shot was taken at Hawk Hill on the Marin Headlands peninsula, and that he observed it for 15 to 20 minutes but it was still there when he left. 

Mysterious 'Fogbow' Weather Phenomenon Appears

(Photo : Stainless Images/Unsplash)

Fogbows, like rainbows, are created by a similar physical phenomenon, with light being refracted by fog droplets rather than rain droplets, as per Newsweek.

Rainbows develop when sunlight travels through droplets in the air and reflects, refracts, and disperses, resulting in a rainbow arc of light in the sky.

To view a rainbow, the observer must be at a 42-degree angle to the light source.

When a fogbow forms, the same refraction happens, but it looks colorless because to the difference in the size of the fog water droplets.

When compared to rain droplets, which are 10 to 1,000 times bigger, these droplets are often less than 0.05 millimeters (0.0020 inches).

According to the Meteorological Office of the United Kingdom, the tiny size of the droplets causes diffraction rather than refraction to have a major influence on the light.

This implies that rather than being divided into its rainbow spectrum, light is simply dispersed and smeared into a white haze.

Brooke Bingaman, a meteorologist for the National Weather Service, told the SFGate news site that the photographer was at the perfect perspective position with the sun behind them.

You may notice the reddish tinge on the outside of the image if you look to the right side of the photograph. It has a hint of color, but the prisms aren't as effective as conventional raindrops.

Also Read: Incredible White Rainbow Caught on Camera in Scotland

Fogbows are rainbows' cousins

Fogbows are also known as white rainbows, cloudbows, and ghost rainbows, as per Earthsky.

They form in the same way as rainbows do, from the same combination of sunshine and moisture.

Rainbows form as raindrops fall into the air. A rainbow always appears in the opposite direction of the sun.

Fogbows are much the same, always opposite the sun, but fogbows are caused by the small droplets inside a fog or cloud rather than larger raindrops.

When the sun is shining brightly, look for fogbows in a thin fog. When the sun breaks through a fog, you could glimpse one.

Or keep an eye out for fogbows over the water.

A fogbow is composed of the same ingredients as a rainbow: sunshine at the observer's back and water droplets in front.

The water droplets that makeup fog are so minute, between 10 and 1000 times smaller than raindrops, that while light still reflects off the droplet back towards the viewer, the process of diffraction of the light by the droplet becomes the primary effect.

Diffraction broadens the reflected beam of light, smearing out the colors that produce the typical ghostly white or very faintly colored fogbow. As a result, the fogbow is far wider than a rainbow.

To allow light to penetrate between the droplets and create the appearance, the fog bank must be somewhat dispersed and thin. Fogbows are enormous, almost as huge as rainbows.

A similar appearance may be observed from airplanes in cloud droplets, which are referred to as cloud bows.

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