Why did you seldom see "smog" before the Yuan Dynasty? Small city scale

Nowadays, the pollution of smog on air quality has attracted more and more attention from the whole society, and when did the record of "smog" weather begin?

At present, the earliest records can be traced back to the Yuan Dynasty. According to the records of Yuan history, in March of Yuan (1329), because there was no snowfall in winter and little rain in spring, the weather was unusually dry, which led to "rainy soil and haze" and "it is difficult to see the sun when you are faint, and passers-by hide your face." In the twelfth lunar month in the sixth year of Yuan Dynasty (1340), "most of the fog locks, and the sun is not seen for many days, and the city (city) gate is hidden in the wind." "The wind haze enveloped the capital for several days, and the emperor feared widespread indignation and discontent. He sent the ritual department to burn incense and pray for the gods to drive away the wind and haze. " It can be seen that the two "smog disasters" recorded in the history books of the Yuan Dynasty lasted for a long time and the visibility was very low.

In the Ming dynasty, the records of "haze disaster" gradually increased. In the early spring of the fourth year of Ming Chenghua (1468), the Record of Ming Xianzong recorded: "This year, from spring to summer, the weather was cold and miserable, and the wind was overcast ... The yellow fog covered the sun for two days, and the stars were not seen day and night." ..... the wind and haze in this spring. Haze and dust accumulate outside Xizhimen, making it difficult to see passers-by. The loyalist half-closed the city gate to cover the dust. "There are dozens of similar' haze disasters' records in Beijing in the Ming Dynasty. There were also many "haze disasters" in the Qing Dynasty. Sixty years of Kangxi (172 1) "Today's (test) issue is covered with yellow fog and misty clouds cover the sun. With such a strong wind, the list will be damaged. "

In ancient times when science was underdeveloped, people knew little about smog, so the degree, concentration, scope and harm of smog could only be recorded by feeling, only the disaster situation. There is no record about how to prevent the "smog disaster".

Why did smog, which was rarely seen in historical materials before the Yuan Dynasty, often visit Beijing in the Ming and Qing Dynasties? Some meteorologists believe that: first, there were few records of meteorological data in Beijing before the Yuan Dynasty; Second, it has a lot to do with the geography of Beijing; Third, before the Yuan Dynasty, there were no large-scale cities in Beijing, with a vast territory and few people, and there was less smog weather. Fourth, after the Ming Dynasty, with the expansion of the city scale, the number of buildings increased, the speed of air flow decreased, and the probability of smog increased accordingly.

The ancients' understanding of the smog disaster was superficial. People thought it was a "smog disaster" from God, so they prayed for God's blessing, "in order to touch God and give rain".