In which season does haze weather occur the most?

Haze is also called atmospheric brown cloud. In the ground meteorological observation standard of China Meteorological Bureau, the definition of haze weather is: "A large number of extremely fine dry dust particles float evenly in the air, which makes the air with horizontal visibility less than 10 km generally turbid, making bright objects in the distance slightly yellow and red, and making darker objects slightly blue." At present, there are four areas with serious smog in some parts of China: Huanghuaihai area, Yangtze River basin, Sichuan basin and Pearl River Delta.

Causes of haze

As a natural phenomenon, smog has three factors. 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 high-concentration pollution in urban areas. The second is the phenomenon of 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. The third is the increase of suspended particulate matter. In recent years, with the development of industry, the increase of motor vehicles, the discharge of pollutants and the increase of suspended solids in the city have directly led to the decrease of visibility and made the whole city look gray.