What is the phenomenon of blood-red sky?

The blood-red sky is a burning cloud phenomenon.

When the sun just comes out or is about to set, the clouds on the horizon are often red, like burning. This kind of red cloud is called sunrise and sunset, which is vividly called "flaming cloud".

Then, the sun is a mixture of red, orange, yellow, green, cyan, blue and purple.

In the morning glow, red light has the greatest ability to pass through the air layer, followed by orange, yellow and green light, and cyan, blue and purple light are the worst.

When the weather is clear, there are few raindrops hanging in the air. Almost all the red, orange, yellow and green lights pass through, and only blue, blue and purple light are blocked. Among these lights, blue light reflects the most, so the whole sky is "dyed" blue.

In cloudy morning or evening, the air layer through which sunlight passes is thicker than that at noon. Among them, yellow, green, cyan, blue and purple are exhausted when they "walk" in the air. They can stick their heads out through the air layer and "dye" the horizon red to form burning clouds.