Rainbow caused by rain

For the formation of a rainbow usually require liquid water. Drops falling from the sky, intercepting the rays of sunlight, reflecting them in colorful splashes of red, green and blue. Recently a resident of Finland Valtteri Immonen, I am watching a rainbow over the town of Muonio. But something was missing.

"It was -6 °C, while there was no rain, no snow, but the sky stretches a vast rainbow, says Immonen. — I've never seen a rainbow in winter, and didn't even know that was possible".

According to atmospheric optics expert Les Cowley, the raindrops must have been present.

"The appearance of the rainbow, narrow and compact, indicates that it was formed by drops of water of moderate size, perhaps with a diameter of about 0.5 mm. I'm guessing that had taken place precipitation is the highest level, who could not reach the ground. Drops could also be supercooled below the freezing point of water," — said the scientist.

Supercooled droplets can be formed when drops of liquid water pass through layers of air below freezing temperatures. Drops containing dust particles or even germs, easy to freeze, when there are impurities formed ice crystals. But when the rain is particularly clean, they can remain liquid even in sub-zero temperatures.

Translated by «Yandex.Translator»