Natural changes in the severe cold solar terms

The Great Cold is the last solar term among the 24 solar terms and the last solar term in winter, which is just worth 49. As the saying goes, "There is a great cold every year, not March 9 but April 9", and the weather is still dominated by cold.

The great cold solar term is a festival reflecting climate change, and it is colder in the great cold season, which is the general law of climate change. Before and after the slight cold to the severe cold, the heat emitted from the ground surface reached a peak, so the cold was in March 9th.

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This is because after the winter solstice, the direct point of sunlight will gradually move northward, but in the following time, the direct point of sunlight will always be in the southern hemisphere, and the heat in the northern hemisphere will always be lost, and the heat absorbed during the day is still less than the heat released at night. Therefore, after the winter solstice, the temperature in the northern hemisphere will continue to decrease, with the lowest temperature during the severe cold solar term, which is the coldest solar term in a year.

Because China has a vast territory and a large span between the north and the south, the climate between the north and the south is quite different. According to China's long-term meteorological records, there is no slight cold in the great cold solar terms in the northern region; But for most parts of the south, April and September are the coldest, so the big cold solar terms are colder than the small ones. Slight cold and severe cold are the periods with the least rainfall in a year. During the annual cold solar term, the rainfall in South China is only 5 to 10 mm. ..