Causes of foggy weather

Reasons for the formation of foggy weather: Fog is formed by radiation cooling, which mostly occurs at night and early morning when the sun is shining, the breeze and the water vapor near the ground are rich and stable, or there is an inversion. Meteorology calls it radiation fog.

Warm and humid air moves horizontally and passes through the cold ground or water surface, and the water vapor in the air is gradually liquefied by cold to form fog, which is called advection fog in meteorology; Sometimes the fog formed by two reasons is called mixed fog. It can be seen that it is late autumn and early winter that can meet these conditions, especially in the morning of late autumn and early winter.

The smog in the city is caused by another reason, and that is human activities. Morning and evening are the peak hours of heating boilers. Under the condition of low air pressure and low wind speed, a large number of pollutants such as suspended solids and automobile exhaust are difficult to diffuse, and it is easier to form smoke (fog) when combined with low-altitude water vapor. This kind of smoke (fog) often lasts for a long time, such as London, which is known as the "foggy city" (note: London

Relationship with the weather

Fog is ever-changing and complicated, but it is nothing more than radiation fog and advection fog. Although there are various phenomena, the essence is the same: water vapor condenses when it meets cold, sometimes fog indicates sunny days, and sometimes fog indicates rainy days, which seems chaotic. But as long as we master the characteristics of radiation fog and advection fog, we can accurately grasp the laws of fog, sunny and rainy, and then predict the weather.

Fog is closely related to future weather changes. The working people in China have known this truth since ancient times, which is reflected in many folk proverbs, such as: "There is fog in Huangmei, and you don't ask for directions when you rock the boat." This means that the fog at the turn of spring and summer is a harbinger of rain, so people also have the saying of "summer fog and rain". Another example is: "The fog is too foggy to see people, so wash clothes boldly." This means that winter fog is sunny, and so is autumn fog.