What is inversion weather? Great gods, help!

Generally speaking, the atmospheric temperature decreases with the elevation, and the temperature decreases by about 0℃ or 6℃ for every increase of 100m. That is to say, below a few kilometers, the lower atmosphere is always high temperature and low density, and the upper atmosphere is low temperature and high density, which is "top-heavy". This kind of atmospheric stratification is prone to rolling up and down, that is, "convection" movement, which can transport pollutants near the ground to high altitude or even far away, thus reducing the pollution level over the city. Therefore, under normal circumstances, the air over the city is slightly polluted and has little impact on human health. However, under some weather conditions, the atmospheric structure over a certain place will have an abnormal phenomenon that the temperature rises with the increase of altitude, leading to a top-heavy atmospheric stratification, which meteorologists call "inversion" and the atmosphere with inversion is called "inversion layer". It is like a thick quilt covering our city and countryside. The air flow in the upper and lower layers is reduced, and the air pollutants in the near-surface layer "have no way to go", so they have to stay where they are, and air pollution is bound to increase. There are many reasons for the phenomenon of "upside down". In winter in China, the temperature in the surface layer drops rapidly, mainly due to the radiation cooling of the ground. When the cold current strikes, the ground is controlled by the cold air mass, and the weather is clear, the wind is small and the temperature is low. Especially at night, ground heat radiates (radiates) to high altitude, which makes the temperature near the ground drop rapidly, while the temperature in the upper atmosphere drops slowly, resulting in the so-called "inversion" and "phenomenon" of "heating up and cooling down". Sometimes, the sunshine is insufficient during the day, the ground temperature rises slowly, and the "inverse temperature" is maintained for a long time, and air pollution is becoming more and more serious. In winter, the phenomenon of "inversion" occurs from time to time. When the "inversion" causes fog or serious pollution, people should reduce the time of morning exercise and outdoor activities and try to avoid the harm caused by the "inversion".