What does the wheat in the weather forecast mean?

Haze refers to non-absorbent solid particles such as dust or salts suspended in the air, which cannot be recognized by the naked eye because of their tiny particles. There are three main factors in the formation of haze:

First, the phenomenon of static wind in the horizontal direction has increased. In recent years, with the rapid development of urban construction, buildings are built higher and higher, which increases the friction coefficient of the ground and 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 in urban areas and cause pollution.

The second is the phenomenon of vertical inversion. The inversion layer is like a pot cover over a city, which makes the inversion phenomenon higher than the near-surface temperature. Under normal weather conditions, pollutants diffuse from low altitude with high temperature to high altitude with low temperature and are gradually discharged into the atmosphere. Under the condition of inversion, the low-altitude temperature is lower, which leads to the pollutants staying in the near-surface layer and unable to be discharged.

Thirdly, with the development of industrial production and transportation, the emissions of pollutants and suspended solids in cities have greatly increased, which directly leads to the decrease of visibility and makes the whole city look gray.

According to experts, the composition of smog is very complicated, including hundreds of atmospheric particles, among which aerosol particles with a diameter less than 10 micron are harmful to human health. Particles are easily deposited in the upper and lower respiratory tract and alveoli after being inhaled into the human respiratory tract, causing rhinitis, bronchitis and other diseases, and can also induce lung cancer in this environment for a long time.

Experts believe that smog is even more harmful than dusty weather (floating dust, sand blowing and sandstorm). Therefore, it is suggested that people take necessary protective measures in foggy days, and relevant departments should gradually establish an early warning and defense mechanism for foggy days.