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We haven’t had a lot of rain this month so I’ve not been getting my usual lot of rainbow photos.
The other day, while going through the many emails and wonderful photos that I receive, I spotted this beauty. It’s a bow - but not a brilliant bow. The photo was submitted by Levi Bagley. Levi took the picture last Tuesday, while out lobster fishing off Grand Manan Island in the Bay of Fundy. He said it had been quite foggy, and as the fog cleared, this magnificent white rainbow appeared.
While rainbows are quite common around here, fogbows are rarer. Fogbows are generally seen as an arc of dense fog along the edge of a fog bank. The physics behind the fog bow is very similar: the bow is caused by sunlight refracting inside water droplets. However, unlike rainbows, where the raindrops are large enough to refract sunlight into individual colours, the water droplets in a fogbow are much smaller. Droplets in fog are so small (smaller than 0.05 mm) that the colours are much fainter, often with nothing more than a red outer edge and bluish inner edge. The way the light scatters from a fogbow allows for overlapping colour and more of a hazy white bow instead of the colourful rainbow we’re used to seeing following a rain shower.
In some parts of the world, when sailors encounter fogbows through eerie ocean mist, they’re referred to as “seadogs.” I’ve also heard them referred to as ghost rainbows.
To see a fogbow, you should have bright sunshine at your back, illuminating an area of dissipating fog in front of you. You are more likely to see a fogbow in colder areas or over cold water. Very cold air can’t hold as much moisture as warmer air, and therefore fog and subsequently, fogbows, appear.
Last Tuesday, moist tropical air rising over the colder air close to the water resulted in widespread advection fog and this mystical fogbow of Grand Manan.
Levi didn’t mention a pot of gold at the end of this fogbow. I hope he found a pot of lobster!
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Cindy Day is the chief meteorologist for SaltWire Network