Where did the fog come from? Why do so many cities in the north have fog, even Xiamen? How come there is fog? I don’t read the news very much, and my answers are often off-putting.

Chemistry

The same thing about fog and haze is that they are visual range obstacles. However, the causes and conditions for the formation of fog and haze are very different. Fog is a large number of tiny water droplets or ice crystals floating in the air. The formation conditions require a high water vapor saturation factor. When fog occurs, the relative humidity of the air often reaches 100% or close to 100%. Fog may become more common or thicker in the morning and evening as the air humidity changes day by day, and become relatively lighter or even disappear during the day. When fog occurs, the effective horizontal visibility is less than 1KM. When the effective horizontal visibility is 1-10KM, it is called light fog.

“There is actually a difference between ‘fog’ and ‘haze’.” Sun Leng, a senior engineer at the Climate System Monitoring Office of the National Climate Center, pointed out that fog refers to the condensation of suspended water vapor in the atmosphere and the visibility is lower than The weather phenomenon at 1 km; the formation of haze is mainly the result of the simultaneous interaction of a large number of particles suspended in the air and meteorological conditions. There are three causes:

——Static wind phenomenon in the horizontal direction increase. Buildings are getting taller and taller in cities, and the blocking and friction effects significantly weaken wind flow through urban areas. The increase in quiet wind phenomena is not conducive to the diffusion and dilution of suspended particles in the atmosphere, and is easy to accumulate around urban areas and suburban areas;

——Temperature inversion occurs in the vertical direction. The inversion layer is like a pot lid covering the city. This inversion phenomenon in which the temperature at high altitudes is higher than that at low altitudes restricts the vertical movement of air at low altitudes in the atmosphere. Suspended particles in the air are difficult to float to high altitudes and are blocked in the atmosphere. Low altitude and near the ground.

——An increase in suspended particulate matter in the air. With the growth of urban population, industrial development, and the surge of motor vehicles, pollutant emissions and suspended solids have increased significantly, directly leading to reduced visibility.

In fact, dust "haze" will also be produced during home decoration. The diffuse indoor dust is not only harmful to the health of workers and users, but also increases the burden of cleaning. When the dust is severe, it also brings many hidden dangers to the decoration project. .