What is the sign of blizzard?

The sign of a snowstorm is four snowflakes under a cloud.

The sign of heavy snow is that there are three snowflakes under the cloud.

The symbol of snow is two snowflakes under a cloud.

The symbol of light snow is clouds and snowflakes.

Light snow: It means that the horizontal visual distance is equal to or greater than 1000 m when it snows, the depth of snow on the ground is less than 3 cm, the precipitation level is 24 hours, and the snowfall is between 0. 1 ~ 2.4 mm..

Snow: refers to the horizontal visual distance between 500 ~ 1000m when it snows, the depth of snow on the ground is 3 ~ 5cm, and the snowfall in 24 hours is 2.5 ~ 4.9 mm. ..

Heavy snow: refers to the poor visibility when it snows, the horizontal visual distance is less than 500 meters, the depth of snow on the ground is equal to or greater than 5 cm, and the snowfall in 24 hours reaches 5.0 ~ 9.9 mm.

If there is snowfall without forming snow, it is generally called "sporadic light snow".

When the snowfall reaches 10.0 ~ 19.9 mm in 24 hours, it is a blizzard, 20.0 ~ 29.9 mm is a blizzard, and more than 30.0 mm is a blizzard.

The cause of snow

If water vapor wants to crystallize, two conditions must be met to form snowfall:

One condition is that water vapor is saturated. When saturated air is cooled to a temperature below the dew point, the excess water vapor in the air becomes water droplets or ice crystals. Because the saturated water vapor content of ice surface is lower than that of water surface, the water vapor saturation required for the growth of ice crystals is lower than that of water droplets. That is to say, water droplets can only grow when the relative humidity is not lower than 100%; But when the relative humidity is less than 100%, ice crystals tend to grow.

Another condition is that there must be condensation nuclei in the air. Condensation nuclei are tiny solid particles suspended in the air. The ideal condensation nucleus is the particle that absorbs the most water, such as sea salt, sulfuric acid, nitrogen and other chemicals. So sometimes there are clouds in the sky, but there is no snow. In this case, people often use artificial snowfall.