Atmospheric
Optics
Cloudbow, Netherlands
~ Wiendeld Visser captured this rare cloudbow on the evening of 21st May near Eelde, a small town south of the city of Groningen in the northern Netherlands.
Images ©Wiendeld Visser, shown with permission
Waves refract on entering the droplet, some reflect from the far side, refract again and emerge as a primary rainbow, fogbow or cloudbow. Which one depends on the drop size and source of the drops.
Small water droplets ~0.1mm diameter in the evening air created this cloudbow. Full blown rainbows resplendent with colour come from raindrops ten times that size and larger.
0.1mm drops are sufficiently small that diffraction effects broaden the bow and weaken the colours. Wiendeld’s bow has pastel reds on its outer rim and perhaps a hint of blues inside.
Notice the broad spacing of the supernumerary bows. Another sign of small droplets, the smaller the drops the more widely spaced are the supernumeraries.
Look out for cloudbows when the sun is low, the air is humid and the face pricks with tiny water drops.
