[Difference] Is fog smog? Understand these misunderstandings! What's the difference between fog and smog?

Let's talk about the concepts of fog and smog first.

First of all, what is fog? !

Fog is a physical phenomenon that a large number of water droplets live ice crystals suspended in the air near the ground make the horizontal visibility less than 1 km. The basic conditions of fog formation are rich water vapor in the near-surface air, cooling process and the existence of condensation nodules. When the water vapor pressure in the gas layer near the ground is greater than its saturated water vapor pressure, the water vapor condenses or condenses into fog. The most common are radiation fog and advection fog. There are also fog in North China and radiation fog. Radiation fog is caused by ground radiation cooling and air layer cooling near the ground.

The conditions for the formation of radiation fog are: ① sufficient water vapor; ② Cloudy weather between sunny days; ③ Weak wind (1-3m/s); ④ Stable atmospheric structure.

The thickness of radiation fog depends on the cooling degree of air and wind. The high fog is the height increase caused by air cooling. The radiation fog can extend to several hundred meters high and has a wide range, which can last for many days, and then it is slightly weakened during the day. Radiation fog appears in a clear night in a high-pressure area, and its appearance often indicates a sunny day. For example, the mainland of China is mostly controlled by high pressure in winter, and the night is longer, which is conducive to the formation of radiation fog. So it can be seen that North China is foggy in winter. In the city and its vicinity, there are many smoke particles and dust and rich condensation nuclei, which are particularly easy to form dense fog.

(1), there are a lot of water vapor, smoke particles, dust and condensation nuclei.

② Controlled by subtropical high, it is cloudy between sunny days.

③ The wind force is weak (1-3m/s), which is controlled by the subtropical high pressure area, and there is little convection movement.

④ The atmospheric structure is stable. The subtropical high zone has little control over convective motion.

What is smog?

Haze is a mixture of fog and haze. When the humidity is high in the morning and evening, there are many components of fog. When the daytime humidity is low, haze is the main force, and the relative humidity is between 80% and 90%. Among them, fog is a natural weather phenomenon, and the water vapor in the air is dense. Although dust is the condensation core, it is generally non-toxic and harmless; The core substances of smog are substances suspended in the air such as smoke and dust. The relative humidity of the air is below 80% and the color is yellow. Gas can directly enter and attach to human lower respiratory tract and lung lobes, which is harmful to human health. The formation of haze weather is mainly man-made environmental pollution, and natural conditions such as low temperature and little wind make it difficult for pollutants to spread.

Yes, fog and haze are actually two different things. In fact, you can see it from the picture. It is scientific to distinguish fog from haze. Fog is the product of water vapor condensation, which is mainly composed of water vapor. It is a natural phenomenon, and smog is formed by a large number of particles floating in the air, including PM2.5, which is more harmful to health.