Have you seen colored snow: yellow, green, red or even black?
One of the causes of unusual rainfall is industrial emissions from metallurgical or chemical enterprises.
The second reason is related to algae. There are about 350 species of algae on our planet that reproduce well in snow.
Chlamydomonas
One of them is Chlamydomonas snow, a single-celled algae that can secrete the pigment astaxanthin. Algae cells are densely filled with this red pigment, which gives snowdrifts their red or pink color. It is interesting that the snow colored by these algae acquires a specific taste that resembles watermelon and has the same smell. It is dangerous to eat such snow, because some plants are toxic.
Chlamydomonas snowbloom blooms after the dark and cold period of winter, when the water begins to warm. Young algae remains green for some time, snow becomes green due to chlorophyll. And only later, when the weather becomes clearer, it acquires a blood-red or dark crimson color. At a temperature of +4C, the plant dies from the heat. Most often, such piles can be found in the mountains and in the polar regions.
Let’s consider a few more algae that color the snow. Desmidium algae and snow raphidonema give the snow a green color. Ancylonema Nordenskjöld and diatoms color the snow brown. Black snow can be seen in the mountains of the Czech Republic. Its cause is usually snow scotiella.
In addition to snow algae, there are algae that settle on the border between ice and sea water. In winter, they slow down their development in anticipation of warmth. But it is worth warming the sun, as they immediately come to life. The ice begins to bloom, turning brown. Such a phenomenon can be found in the Arctic and Antarctic.
Dust and other particles
The third reason for the unusual color of the snow is dust and other particles. In this case, it most often comes out yellow, gray, pink or red-brown. It is very rare, but it happens that the snow falls in two colors. This happened in 2002 due to sandstorms in China. The cyclone, which came from the Sea of Japan, captured particles of yellow and red sand, which gave the snow certain shades.
The fourth reason is a purple glow, when the snow acquires a color for a short time. When this phenomenon is observed, not only the snow, but everything around turns pink. This is exclusively the play of sunlight scattered by the atmosphere and repeatedly reflected in snow crystals. A purple glow occurs in frosty weather. The ground should be covered with white snow, and the air should be sufficiently moist, saturated with tiny ice particles. In cloudy weather, the effect is enhanced due to the fact that light is repeatedly reflected from clouds and snow cover.
This beautiful optical phenomenon can often be seen at dawn or at sunset. It lasts no longer than 20-30 minutes.
And even under normal daylight, snow can have different shades. For example, it can become gray due to particles of street dust settling on it.