Why is there still foggy weather on snowy days?

In winter, due to the obvious ground radiation cooling at night, the "inversion layer" is easy to appear in the low altitude of the atmosphere, and the exchange and circulation ability of air in the horizontal and vertical directions becomes weak. The pollutants discharged into the air are confined in the shallow atmosphere and gradually gather into smog, leading to air pollution.

At the same time, foggy days appear more frequently in winter. This is because the winter nights are long, there are more opportunities for sunny days and small winds, the ground heat dissipation is faster, and the temperature drop is more significant. When the temperature drops to the lowest in the morning, the water vapor in the air is easy to reach saturation and condense into small water droplets, which accumulate more and more and form fog.

Composition of smoke:

Haze is composed of particles such as dust, sulfuric acid, nitric acid and organic hydrocarbons in the air. It will also make the atmosphere turbid, blur the vision and worsen the visibility. If the horizontal visibility is less than 65,438+00,000 meters, the sight distance obstacle caused by this non-aqueous aerosol system is called haze or dust haze, and the Hong Kong Observatory calls it haze.

Sulfur dioxide, nitrogen oxides and inhalable particles are the main components of smog. The first two are gaseous pollutants, and the last particulate matter is the chief culprit that aggravates smog weather pollution. They combine with fog and instantly turn the sky gray. The abbreviation of particulate matter is PM, and what Beijing monitors is PM2.5, that is, pollutant particles with aerodynamic equivalent diameter less than or equal to 2.5 microns.

Haze is mainly composed of sulfur dioxide, nitrogen oxides and inhalable particles, which combine with fog to make the sky dark and gloomy in an instant. The abbreviation of particulate matter is PM, and Beijing monitors fine particulate matter (PM2.5), that is, pollutant particles with aerodynamic equivalent diameter less than or equal to 2.5 microns. This particle itself is not only a pollutant, but also a carrier of toxic substances such as heavy metals and polycyclic aromatic hydrocarbons.

The distribution of haze particles is relatively uniform, and the size of haze particles is relatively small, ranging from 0.00 1 micron to 10 micron, with an average diameter of about 1 ~ 2 micron. Floating particles are invisible to the naked eye. Because the smog is composed of dust, sulfuric acid, nitric acid and other particles, the longer the scattering wavelength, the more the light ratio, so the smog looks yellow or orange-gray.