What does "∞" in the weather stand for?

The weather forecast symbol ∞ stands for haze.

grade

1, mild haze: air relative humidity is less than or equal to 80%, visibility is more than or equal to 5km and less than10km;

2. Mild haze: the relative humidity of the air is less than or equal to 80%, and the visibility is more than or equal to 3 kilometers and less than 5 kilometers;

3. Moderate haze: the air relative humidity is less than or equal to 80%, and the visibility is more than or equal to 2 kilometers and less than 3 kilometers;

4. Severe haze: the air relative humidity is less than or equal to 80%, and the visibility is less than 2 kilometers.

Extended data 1, affecting health. The composition of smog is very complex, including hundreds of atmospheric particles. Among them, aerosol particles with a diameter less than 10 micron are harmful to human health, such as mineral particles, sea salt, sulfate, nitrate and organic aerosol particles.

Aerosol particles with a diameter less than 10 micron include coarse particles, fine particles with a diameter less than 2.5 microns and inhalable particles (inhalable to the lungs), which can directly enter and adhere to the upper and lower respiratory tract and lung lobes of human body.

2. Affect mental health. The gloomy and foggy weather is prone to mental laziness, depression and pessimism due to the weak light and low air pressure, and even it is easy to get out of control at the slightest sign of trouble.

3, affecting traffic safety. When there is haze weather, outdoor visibility is low, pollution continues, traffic jams and accidents occur frequently.

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