Causes of foggy weather

Causes of foggy weather: Fog is formed by radiative cooling. Most of it occurs at night and early morning when it is sunny, gentle, and the water vapor near the ground is relatively abundant and stable or there is a temperature inversion. Meteorologically, it is called foggy weather. Radiation fog.

Warm and moist air moves horizontally, passing through the cold ground or water surface, and the water vapor in the air is gradually cooled and liquefied to form fog. Meteorologically, it is called advection fog; sometimes it is formed by two reasons. The fog is called mixed fog. It can be seen that the ones that meet these conditions are late autumn and early winter, especially the mornings in late autumn and early winter.

The smog in the city is caused by another reason, that is, human activities. Morning and evening are the peak periods of heating boilers, and a large amount of smoke, dust, suspended matter and car exhaust and other pollutants are emitted in the city. Under conditions of low air pressure and low wind, it is not easy to spread. When combined with water vapor in the lower air, it is easier to form smoke (fog), and this kind of smoke (fog) often lasts for a long time. For example, it is called "fog city". "London (note: London no longer has severe smog).

Relationship with weather

Fog is ever-changing and complex, but it is nothing more than radiation fog and advection fog. Although the phenomena are diverse, the essence is the same: water vapor encounters It is formed by cold condensation. Sometimes the fog is forecast to be sunny, and sometimes the fog is forecast to be rainy. It seems chaotic. However, as long as you master the characteristics of radiation fog and advection fog, observe from many parties, and analyze carefully, you can accurately grasp the differences between fog and sunny weather. The pattern of rain can be used to predict the weather, which is useful for agriculture, transportation, aerospace, and navigation.

Fog is closely related to future weather changes. Since ancient times, the Chinese working people have understood this truth, and it is reflected in many folk proverbs, such as: "There is fog in the yellow plums, and you can rock the boat without asking the way." This means that the fog at the turn of spring and summer is the harbinger of rain, so folk There is also a saying of "summer fog and rain", and another example is: "The fog is thick and no one can be seen, so boldly wash your clothes." This means that winter fog heralds sunny days, and the same is true for autumn fog.