Is the gloomy weather caused by smog?

Everyone seems to have this experience: when I wake up, I find that the weather outside the window is gloomy, there is no sunshine, and the air seems to be turbid. At this time, many people unconsciously think that it must be caused by smog. But sometimes it's not the smog that "makes trouble", it's just a simple cloudy day. So how to distinguish cloudy days from foggy days?

On the morning of 2065438+06165438+1October 19, strong fog with visibility less than 50 meters appeared in many places in Jiangxi Province, and skyscrapers stood in the fog like "castles in the air".

First of all, from the definition of meteorology, there are essential differences between cloudy days and foggy days. According to the China Meteorological News, Kang Zhiming, director of the Environmental Meteorological Center of China Meteorological Bureau, pointed out that whether it is cloudy or not depends on the amount of clouds. On cloudy days, the sky is basically covered with clouds and there is no sunshine. The judgment of fog and haze mainly depends on "visibility", and the two cannot be confused. Fog is a water vapor condensate composed of a large number of tiny water droplets or ice crystals suspended in the air near the ground, which is often milky white, making the horizontal visibility less than1km; Haze refers to a large number of extremely fine particles floating evenly in the air, which makes the air turbid and the horizontal visibility is less than 10 km. These particles mainly come from nature and human activities. It can be seen that cloudy days are mainly high-altitude weather phenomena, while foggy days are near-surface weather phenomena.

Secondly, cloudy days are not equal to air pollution. In an interview with People's Daily Online, Jianhua of Beijing Environmental Protection Bureau said that many people think that the air is polluted as long as they can't see the blue sky. In fact, this understanding is inaccurate. The air quality depends on the proportion of pollutants in the air, and accurate data can be obtained through instrument detection. People's feelings about air are subjective and abstract, so judging the quality of air should also be based on monitoring data.

As the Xi Evening News once reported, the ancient city of Xi on 2011118 was shrouded in fog all day and looked gray, but the environmental monitoring data showed that the air pollution quality was "good". Xi'an

Relevant personnel of the Municipal Environmental Protection Bureau said that it was a cloudy day dominated by fog after precipitation, not a real haze day, so the air quality was not bad.

Therefore, when judging whether the weather is cloudy or foggy, we should be rational and objective, not just relying on our own abstract feelings about the weather. We can query the air quality index through relevant weather real-time platforms, authoritative media and other channels, and use it as a standard to distinguish cloudy days from foggy days, instead of "relying" on smog as long as the weather is bad. (Yang Xin)

This paper is scientifically checked by Bu Yong, an associate researcher of China Institute of Science Communication.