When is foggy weather mostly?

Haze, as its name implies, is fog and haze. But there is a big difference between fog and haze. The aerosol system composed of dust, sulfuric acid, nitric acid and other particles in the air causes visual impairment, which is called smog. Haze is haze.

Fog is an aerosol system consisting of a large number of tiny water droplets or ice crystals suspended in the air near the ground. It mostly occurs in autumn and winter (which is also one of the reasons for the large-scale haze weather in China in June 20 13), and it is the product of water vapor condensation (or condensation) in the near-surface air. 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.

Haze (mái), also known as haze (smog), dust, sulfuric acid, nitric acid, organic hydrocarbons and other particles in the air can also make the atmosphere turbid. 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). 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 and gray.

Haze weather is a state of air pollution, and smog is a general term for all kinds of suspended particles in the atmosphere, especially PM2.5 (particles with aerodynamic equivalent diameter less than or equal to 2.5 microns) is considered as the "culprit" causing haze weather. With the deterioration of air quality, cloudy days are increasing and the harm is increasing. In many areas of our country, the smog weather phenomenon is combined with fog as an early warning and forecast of disastrous weather. Collectively referred to as "haze weather".

According to the press conference of China Meteorological Bureau in February, 2065438+03, since the winter, smog has occurred frequently in most parts of central and eastern China, and the number of smog days is generally more than five days. Meteorologists said that there are three main reasons for the haze weather:

1. In June, 5438+ 10, the cold air activity affecting China was weaker than normal, and the wind speed was low. The frequency of atmospheric stability conditions in most parts of central and eastern China is obviously high, especially in North China, which is as high as 64.5%, the highest in 10 years, and it is easy to cause pollutants to accumulate in the near-surface layer, thus leading to frequent haze weather;

Second, the high background concentration of aerosols in winter in China is conducive to the formation of smog;

Third, the smog weather will make the near-surface atmosphere more stable and aggravate the development of smog and air pollution. The formation of haze weather is not only affected by meteorological conditions, but also related to the increase of air pollutant emissions. It is suggested to further strengthen the control and protection of the atmospheric environment, especially to strengthen the multi-department consultation and linkage, improve the emergency emission reduction plan of atmospheric pollutants under static weather conditions, and prevent and control the occurrence of heavily polluted weather.

It is reported that since the winter, there have been 10 ~ 20 days in southern Hebei, Beijing, eastern Shanxi, Shandong, Henan, Anhui, Jiangsu, Shanghai, Zhejiang, Fujian, Hubei, Hunan, most of Jiangxi, western Guangdong, eastern Guangxi, Sichuan and Yunnan, among which most of Jiangsu has more than 20 days. Compared with the same period of normal years, there are more days in southern Hebei, Beijing, Tianjin, Shandong, northern Henan, Anhui, Jiangsu, Shanghai, Zhejiang, Guangdong and eastern Guangxi 1 day, including 3-8 days in Beijing, Tianjin, most of Anhui and Shanghai, and 8 days in northern Shandong, northeastern Anhui, most of Jiangsu, northern Zhejiang and southern Guangdong. In southern North China, central Jiangsu, eastern Sichuan, southwestern Chongqing and western Guizhou, the visibility is less than 1000m for 8 ~/5 days, and less than 500m for 5 ~ 12 days in southern Hebei, northwestern Shandong and eastern Sichuan.