What does this weather sign mean?

morphological character

1, the sand wall stands.

Most of the strong sandstorms on the mainland come from the northwest or west, and a few from the east. When almost all sandstorms come, we can see a black sand wall moving rapidly and getting closer and closer in the direction of the wind. Seen from a distance, the sandstorm wall is towering like a mountain, much like a city wall, and it is the sandstorm Depth Charge.

2. It is already dark.

When a strong sandstorm occurs, due to the strong wind of magnitude 8 or above, the wind is very strong and can roll up stones and sand. As more and more dust flies into the air, the thick dust is overwhelming, blocking the sun and making people see nothing for a period of time, just like at night.

3. Rolling and rushing

When the black wind blows, the air near the ground is very unstable. The heated air below rises and the surrounding air flows to supplement it, which makes the air roll up and down with a lot of dust, forming countless dust clouds of different sizes to meet and rush in the air.

4. smart

The upper layer of sand wall is often yellow to red, the middle layer is gray-black and the lower layer is black. The reason why the upper layer is yellow-red is because the dust on the upper layer is so thin that sunlight can almost shoot down through the dust. The dust in the lower layer has a large concentration and coarse particles, and the sunlight is almost completely absorbed or scattered by the dust, so it is black. Where the sand wall has moved, the sky is flickering and changing.

Extended data

Dust weather is divided into 5 grades from light to heavy:

1. floating dust: a weather phenomenon in which dust and fine sand float evenly in the air, making the horizontal visibility less than 10 km;

2. Sand blowing: the wind blows up the dust on the ground, making the air quite turbid, and the horizontal visibility is within 1 km to1km;

3. Sandstorm: a weather phenomenon in which strong winds blow up a lot of dust on the ground, making the air very turbid and the horizontal visibility is less than 1 km;

4. Strong sandstorm: a weather phenomenon in which strong winds blow up dust on the ground, making the air fuzzy and turbid, and the horizontal visibility is less than 500 meters;

5. Extremely strong sandstorm: a weather phenomenon in which strong winds blow up dust on the ground, making the air particularly turbid and the horizontal visibility is less than 50 meters.

Baidu encyclopedia-sandstorm