What does wheat in the weather forecast mean?

Haze?

Haze refers to non-absorbent solid particles such as dust or salts suspended in the air. Because their particles are so fine, they cannot be identified by the naked eye. There are three main factors that contribute to the formation of haze:

First, the increase in horizontal static winds. In recent years, with the rapid development of urban construction, buildings have been built higher and higher, which has increased the ground friction coefficient and significantly weakened the wind flow through the urban area. The increase of quiet wind phenomenon is not conducive to the diffusion and dilution of air pollutants to the periphery of the city, and it is easy to accumulate in the city and cause pollution.

The second is the temperature inversion phenomenon in the vertical direction. The temperature inversion layer is like a pot lid covering the sky above the city, causing a temperature inversion phenomenon that is higher in the sky than near the ground. Under normal weather conditions, pollutants diffuse from low altitudes with high temperatures to high altitudes with low temperatures, and are gradually discharged into the atmosphere in cycles. However, under temperature inversion conditions, the temperature at low altitude is actually lower, causing pollutants to stay near the ground and not be discharged.

Third, with the development of industrial production and transportation, pollutant emissions and urban suspended solids have increased significantly, which directly leads to reduced visibility, making the entire city look gray.

According to experts, the composition of haze is very complex, including hundreds of types of atmospheric particles, of which the main ones harmful to human health are aerosol particles with a diameter of less than 10 microns. After such particles are inhaled into the human respiratory tract, they are easily deposited in the upper and lower respiratory tracts and alveoli, causing rhinitis, bronchitis and other diseases. Long-term exposure to this environment can also induce lung cancer.

Relevant experts believe that haze is even more harmful than sand and dust weather (floating dust, blowing sand, sandstorms). Therefore, it is recommended that people take necessary protective measures during haze days, and relevant departments should gradually establish early warning and defense mechanisms for haze days.