What does the smog in the weather forecast mean?

Haze, also known as haze, refers to the turbidity caused by the suspension of a large number of particles such as smoke and dust. The core substance of smog is dust particles suspended in the air, which are called aerosol particles in meteorology.

Particles such as dust, sulfuric acid, nitric acid and organic hydrocarbons in the air can also make the atmosphere turbid, blur the vision and worsen the visibility. If the horizontal visibility is less than 10000 meters, the visual distance obstacle caused by this non-aqueous aerosol system is called haze or dust haze, and the Hong Kong Observatory calls it haze.

The difference between haze and fog

The difference is that the relative humidity is not large when the smog occurs, but it is saturated in the fog (if there are a lot of condensation nuclei, the relative humidity may not reach 100%, which may lead to saturation). Generally speaking, the visibility deterioration caused by atmospheric haze blurred vision is caused by haze when the relative humidity is less than 80%, while the visibility deterioration caused by atmospheric haze blurred vision is caused by fog when the relative humidity is more than 90%. The visibility deterioration caused by atmospheric haze blurred vision is caused by a mixture of haze and fog when the relative humidity is between 80 and 90%, but its main component is haze. The thickness of haze is relatively thick, which can reach about 1-3 km. Haze is different from fog and clouds, and there is no obvious boundary between haze and clear sky. Smog particles are evenly distributed, and the particle size 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.

Fog is an aerosol system composed of a large number of tiny water droplets or ice crystals suspended in the air near the ground, and it is the product of condensation (or sublimation) of water vapor in the air near the ground. The existence of fog will reduce air transparency and worsen visibility. If the horizontal visibility of the target drops below 1000 meters, the weather phenomenon of water vapor condensation (or condensation) suspended in the air near the ground is called fog. The phenomenon that the horizontal visibility of the target is 1000- 10000 meters is called light fog or mist. When fog is formed, the atmospheric humidity should be saturated (if there are a large number of condensation nuclei, the relative humidity may not reach 100%, and saturation may occur). As far as its physical essence is concerned, fog and cloud are the products of condensation (or condensation) of water vapor in the air, so fog becomes a cloud when it rises from the ground, and it is called fog when it falls to the ground or moves to the mountains. Generally, the thickness of fog is relatively small, and the thickness of common radiation fog is between tens of meters and one hundred and two hundred meters. Fog, like clouds, has obvious boundary with clear sky area, and the droplet concentration distribution is uneven. The droplet size is large, ranging from a few microns to 100 micron, with an average diameter of about 10-20 micron. The naked eye can see the droplets floating in the air. Because the light scattered by fog composed of liquid water or ice crystals has little to do with wavelength, the fog looks milky white or bluish white.

doubt

Haze is also called atmospheric brown cloud. In the ground meteorological observation standard of China Meteorological Bureau, the definition of haze weather is: "A large number of extremely fine dry dust particles float evenly in the air, which makes the air with horizontal visibility less than 10 km generally turbid, making bright objects in the distance slightly yellow and red, and making darker objects slightly blue." At present, there are four areas with serious smog in some parts of China: Huanghuaihai area, Yangtze River basin, Sichuan basin and Pearl River Delta.