Why is there so much smog in winter?

In winter, the ground is a cold source for the atmosphere, especially at night, the atmospheric temperature near the ground is lower than that in the upper atmosphere, which leads to the stable atmospheric stratification, the air can not convection up and down, and the accumulation of pollutants is difficult to spread. In summer, on the contrary, the ground is the heat source of the atmosphere, and the vertical movement of the atmosphere is active, plus cyclones (temperate cyclones &; Tropical cyclone) is active frequently, so it is not easy to have inversion.

There are two main reasons that affect the change of PM2.5 concentration: pollution source discharge and meteorological conditions. Affected by these two conditions, PM2.5 concentration has obvious seasonal variation characteristics. Although there are differences in specific values between the north and the south due to the different daily and seasonal variation laws of humidity and temperature, the overall trend is roughly the same, which is high in autumn and winter and low in summer.

Extended data:

Smog weather should reduce outdoor activities.

According to the relevant research from 20 13 to 20 15 of the municipal center for disease control and prevention, the indoor PM2.5 concentration is 30% to 40% lower than the outdoor concentration in severe haze weather, so it is suggested to minimize the time and intensity of outdoor activities, especially outdoor activities.

Precautions when wearing a mask

According to the national standards, the protection level of masks is divided into four levels from low to high: D, C, B and A, corresponding to different air quality conditions. Grade A corresponds to "serious pollution" and is used when the concentration of PM2.5 reaches 500 ug/m3; Grade D corresponds to "moderate and below pollution", which is applicable to the situation that the concentration of PM2.5 is less than or equal to 150 ug/m3.

Masks are not suitable for wearing for a long time. On the one hand, pollutants such as particulate matter are adsorbed on the outside of the mask, which leads to increased respiratory resistance; On the other hand, bacteria, viruses, etc. Exhaled gas will also accumulate in the mask. Not breathing fresh air for a long time will reduce your immunity.

People's Network-Don't take it lightly in foggy days.

Baidu encyclopedia-air pollutant concentration