A symbol of haze and sandstorm weather

In the picture, ① means fog, ② means smog, ③ means frost, ④ means sandstorm and ⑤ means hail, so B is chosen.

Haze is a combination of fog and haze. Smog is very common in cities. In many areas of China, fog and haze are combined as disastrous weather phenomena for early warning and forecasting, which are collectively called "haze weather". Haze is the result of interaction between specific climatic conditions and human activities. The economic and social activities of high-density population will inevitably emit a large number of fine particles (PM 2.5). Once the emission exceeds the atmospheric circulation capacity and carrying capacity, the concentration of fine particles will continue to accumulate. At this time, if it is affected by calm weather, it is easy to have a wide range of smog.

climatic factor

"There is a difference between fog and haze. Fog refers to the weather phenomenon that the visibility is lower than 1 km due to the condensation of suspended water vapor in the atmosphere; The formation of smog is mainly the result of a large number of suspended particles in the air and meteorological conditions. There are three reasons:

First, the phenomenon of static wind in the horizontal direction has increased.

The higher the buildings are built in the city, the obstruction and friction of airflow passing through the urban area will be obviously weakened. The increase of static wind phenomenon is not conducive to the diffusion and dilution of suspended particles in the atmosphere, and it is easy to accumulate around urban areas and suburbs.

Second, the vertical direction is reversed.

The inversion layer is like a pot cover over a city. This inversion phenomenon that the upper air temperature is higher than the lower air temperature limits the vertical movement of the lower air, making it difficult for suspended particles in the air to drift to the upper air and be blocked at the lower air and near the ground.

Third, the increase of suspended particulate matter and organic pollutants in the air. With the growth of urban population and industrial development, the number of motor vehicles has surged, resulting in a large increase in pollutant emissions and suspended solids.