A great example of a fogbow captured by member Kevin Smith on the 7th May 2023.
A fogbow is a similar phenomenon to a rainbow but as its name suggests, it appears as a bow in fog rather than rain.
Due to the very small size of the water droplets that cause fog being so much smaller than in rain i.e. smaller than 0.1 mm in diameter; fogbows have very weak colours or no colour at all. Fogbows that have no colour are sometimes called ‘white rainbows’.
A Fog Bow by Kevin Smith
”How do fogbows form?
The elements that make up a fogbow are the same as for a rainbow – sunlight at the observers back, and water droplets in front. The water droplets that make up fog are so tiny compared to raindrops, between 10 and 1000 times smaller, that while the light still reflects from the water droplet back towards the observer, the process of diffraction of the light by the droplet becomes a dominant effect.
The process of diffraction broadens the reflected beam of light which smears out the colours which give the characteristic ghostly white, or very faintly coloured fogbow. This also makes the fogbow much broader than a rainbow.
The fog bank has to be relatively diffused and thin to allow the light to pass through the droplets and create the effect. Fogbows are large, almost as big as rainbows.
A similar effect can also be seen from aircraft in cloud droplets, when they’re known as cloud bows.” ref:https://www.metoffice.gov.uk/weather/learn-about/weather/optical-effects/rainbows/fogbow