Great cold is the last of the 24 solar terms, and there is a saying that "Great cold welcomes the New Year". It's ugly, the solar longitude reaches 300, and it's celebrated every year at 65438+1October 20th to 2 1 day. Great cold, like slight cold, is also a solar term indicating the cold weather. Great cold refers to extremely cold weather. During the great cold solar term on March 9 and April 9, cold waves frequently go south, which is the coldest season in a year, with strong wind and low temperature.
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, it is the coldest of the great cold solar terms. In ancient China, the Great Cold was divided into three stages: "One stage is chicken milk; Second, the symptoms of bird disease; Three times, the water is strong. " Among them, the third period can especially show that the temperature of the great cold is extremely low: at this time, the ice in the water can freeze to the center of the water, and it is thick and firm.
The great cold comes at the end of the year, winter goes to spring, and after the great cold, a new cycle begins. In some parts of China, during the period from the Great Cold to beginning of spring, there were many important folk customs, such as taking off old cloth to make bacon, offering sacrifices to stoves and ending sumptuous food. Tail luxury food is also called "making teeth" and "making luxury food". There is a folk custom of "eating tail teeth" after eating luxury food.
Meteorological changes:
During the severe cold solar term, the atmospheric circulation is relatively stable, and the adjustment period of circulation is about 20 days. When this circulation is adjusted, there will often be a wide range of rain and snow weather and strong winds to cool down. When the west of 80 degrees east longitude is a long wave ridge and East Asia is a coastal trough, under the influence of the northwest wind and the constantly supplemented cold air, China will have a sustained low temperature.
Like slight cold, great cold is also a solar term indicating the degree of cold weather. Modern meteorological observation records show that in some areas of China, severe cold is not as good as slight cold, but in some years and a few coastal areas, the annual minimum temperature will still appear in the severe cold solar terms. Therefore, it is necessary to continue to do a good job in the cold protection of crops, especially to protect livestock from wintering.
In the severe cold season, the average temperature in most parts of southern China is 6℃ to 8℃, which is nearly 65438 0℃ higher than slight cold. The proverb "slight cold and cold, cold into a ball" shows that the great cold solar terms are also the cold period of the year. For some crops, a proper low temperature is necessary in a certain growth period. Wheat and rape with strong winterness need lower temperature through vernalization stage, otherwise they cannot grow and develop normally.
Most of southern China is warm in winter all year round. Wheat and rape sown too early often grow too vigorously, bolting in advance, and their cold resistance is greatly weakened, which makes them vulnerable to low temperature frost. It can be seen that selecting crop varieties according to local conditions, sowing and planting in time and taking effective measures to promote and control are important links to win high yield.