The coldest reason of "March 9th":
Judging from the heat absorbed and emitted by the ground at that time, although the days are short and the ground absorbs the least solar radiation heat at this time in winter, the heat emitted by the ground at this time is more than the heat absorbed, and the temperature near the ground will continue to be low. When the solar heat absorbed by the ground is almost equal to the heat emitted by the ground, the temperature will reach the coldest.
After the "March 9th", the heat absorbed by the ground will be more than the heat lost by the ground, and the temperature near the ground will gradually increase. Therefore, the coldest time of the year generally appears around "March 9" after the winter solstice.
Winter development information and exercises 39
Pay attention to health, and exercise is an important way to keep healthy.
In the cold winter, practicing martial arts can not only enhance physical fitness, but also exercise people's strong will not to be afraid of cold. Enhance the body's adaptability to cold. As the whole body is full of energy, breathing is deepened, digestion is enhanced, metabolism is vigorous, and physical condition is improved, the health level and sports performance will also be improved accordingly.
Baidu Encyclopedia-Midwinter