What is the phenomenon of dark clouds pouring into the streets of China, blocking all visibility?

One recent evening, the streets of Shandong Province, China, were covered in a dark, cottony, hazy layer of cloud that blocked all visibility, looking strange and even terrifying. Many people said they had never seen anything like it before. How can this phenomenon be explained?

Anything related to the weather can affect a lot of people, at least in an entire region, so it always makes people everywhere interested.

Here is the video:

According to meteorologists, what people see, although it looks like clouds, is not a cloud but a special type of fog, called stratospheric fog.

According to the UK Met Office, advection fog occurs when warm, moist air moves over a colder surface and is therefore cooled. For example, a warm air mass passes over an area that is covered in snow. Advection fog also commonly occurs over the sea, when warm air moves over cooler water. Depending on the wind, fog from the sea can also be carried inland.

Unlike normal fog which is usually stationary, advection fog can move horizontally, making it more like clouds drifting over the city.

Additionally, advection fog can form at any time of the day , appearing darker in the evening , and can last for several hours to several days, not easily dissipated even when the weather warms up during the day like other types of fog.

Advection fog can look a lot like clouds rolling into a city. (Photo: WHAS).

Regarding the impact on human life, stratospheric fog is often 'thicker' than other types of fog, reducing visibility to near zero (or zero). Therefore, people are advised not to drive during times of stratospheric fog because it is very dangerous.