Relative Rainbows

One very hot day, my husband and I made plans to go to the beach early to swim. As we got to the coast we realised there was fog hugging the coastline. We decided to go and swim any way. It was one of the most beautiful experiences of my life. The fog was thick but only created a thin layer above the sea. This meant we were bathed in sunlight and blue sky from above but visibility was very low. Across the water, the foghorn called and we could see car headlights on the nearby headland. The water was crystal clear with barely a ripple of waves. We could see tiny fish and even a tiny bright purple jellyfish. We also discovered the fog bow.

We had no idea it was even a possibility but light can produce the same bow shape in fog. The only difference is the bow is completely white, earning it another name, the white rainbow. Apparently they actually do have colours but they are very weak because the water droplets are so tiny. At sea, fog bows were also known as sea-dogs and when seen from above from aircraft they are called cloud bows.

The more I started to read about rainbows, the more I realised that there ae actually a few variations to the rainbow...

When the light of the moon is particularly strong, it can form a moonbow in the same way as the sun forms a rainbow. They are much fainter and harder to see than rainbows, so sometimes appear white as the eye can not pick out the colours. In order to see a moonbow, the sky needs to be very dark and the moon very bright and low in the sky. Water droplets need to be present in the air in the same way as with a rainbow.

If a rainbow occurs at sunset or sunrise, it may appear more red coloured and is known as a redbow. This is because when the sun is at a low angle in the sky it has further to travel through the atmosphere and the blue and green wavelengths of light are more easily scattered, leaving the red and yellow wavelengths.

It is also possible for rainbows to form from water droplets in other situations, such as from dew, sea spray. Dewbows are small, white and always seen as circular. Sea spray bows look very similar to rainbows but have a slightly smaller radius than a rainbow. Sometimes the spray is actually caused by whales or dolphins!

I have not seen a moonbow, redbow or dewbow myself but I have seen bits of rainbow in sea spray, just not from the blowhole of a whale or dolphin. Going to keep looking! I have collected together some pictured on pinterest though....