What does the weather forecast symbol ∞ stand for

∞ indicates haze in meteorological symbols.

Haze, also known as haze and ash haze, refers to the turbidity phenomenon formed by the suspension of a large number of particles such as unexplained smoke and dust. The core substance of smog is dust particles suspended in the air, which are called aerosol particles in meteorology.

Haze contains hundreds of atmospheric chemical particles, which can cause respiratory diseases, cardiovascular diseases, blood system, reproductive system and other diseases, such as pharyngitis, emphysema, asthma, rhinitis, bronchitis and other inflammation.

Extended data:

As a natural phenomenon, smog has three factors:

1, the horizontal static wind phenomenon increases.

With the rapid development of urban construction, buildings are built higher and higher, which increases the friction coefficient of the ground and obviously weakens the airflow when passing through the urban area. The increase of static wind phenomenon is not conducive to the diffusion and dilution of atmospheric pollutants to the periphery of urban areas, and it is easy to accumulate high-concentration pollution in urban areas.

2. Vertical inversion.

The inversion layer is like a pot cover over a city, which causes the inversion phenomenon that the temperature at high altitude is higher than that at low altitude. Under normal climatic conditions, pollutants diffuse from low altitude with high temperature to high altitude with low temperature and are gradually discharged into the atmosphere. Under the inversion phenomenon, the low-altitude temperature is lower, which leads to the retention of pollutants and cannot be discharged in time.

3. The increase of suspended particles.

With the development of industry, the increase of motor vehicles, the discharge of pollutants and the increase of suspended solids in the city directly lead to the decrease of visibility and make the whole city look gray.

The formation of smog is closely related to the discharge of pollutants. In cities, motor vehicle exhaust and other smoke and dust emission sources emit micron-sized particles, which stay in the atmosphere. When adverse weather such as inversion and still wind appears, smog is formed.

Baidu encyclopedia-smog