What are the main factors that cause extreme weather such as smog, rainstorm and El Nino?

Its formation is mainly the result of the interaction between a large number of suspended particles in the air and meteorological conditions. There are three reasons:

-There are more and more still winds in the horizontal direction. The higher the buildings are built in the city, the more obstacles and frictions make the airflow weaken obviously when passing through the urban area. There are more and more static wind phenomena, which are not conducive to the diffusion and dilution of suspended particles in the atmosphere and are easy to accumulate around urban areas and suburbs.

—— There is inversion in the vertical direction. 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 air in the lower air, so it is difficult for suspended particles in the air to float to the upper air and be blocked at the lower air and near the ground.

The increase of suspended particles in the air. With the growth of urban population, the development of industry and the sharp increase of motor vehicles, the emissions of pollutants and suspended solids have greatly increased, which directly leads to the decrease of visibility.