Many people have the habit of practicing in the morning. Moreover, they think that the morning air is clean. Understanding is not correct.
Fresh or not air is determined by whether the air is heavily or lightly polluted. The main sources of air pollution are factory smoke, car exhaust, residential kitchen smoke, and carbon dioxide from trees at night. According to measurements 24 hours a day, in the morning, noon, and in the afternoon, the air is slightly polluted, so it is relatively fresh, in which it is about 10 am and 3-4 pm the fresh air is newest. In the early morning, early evening, and at night, the air is seriously polluted, of which around 7 am and 7 pm is the polluted peak, at that time the air is worst.
There are different causes of the freshness of the air in a day, mainly meteorological factors. Since the variation of the vertical temperature difference between day and night is very large, when the ground temperature is higher than that of the air, the air layer above the ground rises, pollutants diffuse. Go to the high place; when the ground temperature is lower than the upper air temperature, a retrograde temperature layer (inverse layer) will form in the sky. It is like an upside-down pan on the ground, which prevents pollutants in the air the ground from diffusing. In general, at night, early morning, and early evening, there will be reverse temperature layers, so the atmosphere at these times is the most cloudy.
During the daytime after sunrise, the ground temperature quickly rises, the reverse temperature layer gradually disappears. Hence the pollutants diffuse rapidly. Generally to 10 am, the freshest terrestrial air. So the morning exercise time should be chosen when the sun rises, it is best to exercise between 10 am and 3 – 4 pm, as the air is fresh at that time.