According to Jiu Ge's "walk on the ice" we can get that 39 days is the coldest time of the year, and some solar terms just become the coldest solar terms of the year in 39 days, so is the cold the coldest solar term? Learn from Xiaobian.
Is the cold the coldest time
The three or nine days of the year end on January 17, while the cold solar term is around January 20 of the Gregorian calendar. Therefore, the cold solar term has entered the period of '49'. So, is the cold the coldest time? Is it the big cold or the small cold? Obviously, the cold solar term is not the coldest time, the coldest is the small cold solar term, and the period of the small cold solar term is exactly 39 days.
It is generally believed that it is the coldest during the period of 39 days, but in fact, it is also said that 49 days are colder than 39 days. Now let's take a look at the two statements separately.
During the winter solstice, the daytime is the shortest, the angle between the direct sunlight and the ground is the smallest, and the sunlight intensity per unit area of the ground is the smallest. Therefore, the daily solar heat received by the ground is the least, and the daily heat budget deficit on the ground has not reached the maximum.
But after the winter solstice, although the daytime is growing day by day, the growth rate is very slow. From the winter solstice to the period of "three Nineties", the average daily growth is only about one minute. At the same time, the angle between the direct sunlight angle and the ground increases very slowly. The daily heat budget on the ground is still in deficit, so the heat will continue to lose and the ground temperature will continue to decline. The total heat budget deficit on the ground only reached its maximum value in '39'. Because the air temperature is mainly affected by the ground temperature, this leads to the lowest temperature in the '39' season. In addition, the cold air mass in Siberia also developed to a very strong stage around "39", and the frequent invasion of strong cold air is one of the reasons for the low temperature.
Fourth, ninth, colder:
There is a folk saying in China that the first nine days are warm and the ninth is cold. It is found that if the first nine days are warm, the whole winter will be particularly cold. It is said that "first, do not covet the first nine warm, continuous rain and snow to winter.". "When Yanjing is old," it says: 'the winter solstice is three or nine ice. "It means that we have entered the coldest stage in the cold weather since September 9th. The book said: 'after the winter solstice, it is extremely cold on the thirtieth day' and 'the third day after the winter solstice, which is the coldest in the December. '
Later, it was generally believed that 39 days was the coldest, but in fact, 49 days was the coldest time in winter. However, in the first few days of the year of the ninth lunar calendar, there was a great change in the temperature and cold. The body was not very adapted to the sudden cold, which made it extremely cold. In the fourth nine lunar calendar, although the temperature was lower than that of the third nine, the temperature difference changed slightly, so it was not as cold as it was when the ninth lunar calendar entered the third nine lunar calendar.
Climatic characteristics of the great cold solar term
During the cold solar term, the atmospheric circulation is relatively stable, and the circulation adjustment period is about 20 days. When the circulation is adjusted, large-scale rain and snow weather and strong wind often appear. When the long wave ridge is 80 degrees east longitude to the West and the coastal trough is East Asia, the sustained low temperature will appear in China under the influence of the northwest wind flow control and the continuous supplement of cold air. Like Xiaohan, the severe cold is also the solar term indicating the degree of cold weather. Although modern meteorological observation records show that in some parts of China, the severe cold is not as cold as the minor cold, but in some years and a few coastal areas, the annual minimum temperature will still appear in the solar term of severe cold. Therefore, we should continue to do a good job in crop cold prevention, especially pay attention to the protection of livestock safety through the winter.
In the cold season, the average temperature in most parts of southern China is 6 ℃ to 8 ℃, which is nearly 1 ℃ higher than that in the cold season. The proverb "little cold, big cold, cold into a group" shows that the solar term of big cold is also a cold period of the year.
For some crops, it is necessary to have proper low temperature in a certain growth period. In winter wheat and rape, the lower temperature is required through the vernalization stage, otherwise the normal growth and development can not be achieved. In most areas of South China, the wheat and rape planted too early in winter tend to grow too fast, jointing and bolting ahead of time, which greatly reduces the cold resistance and is vulnerable to the damage of low temperature and frost. It can be seen that the selection of crop varieties according to local conditions, timely sowing and planting, and effective promotion and control measures are important to achieve high yield.
Mild and severe cold are the periods with the least rainfall in a year. The rainfall in most areas of South China is only slightly increased compared with that in the earlier stage. The rainfall in most areas of South China is 5-10 mm, and that in the mountainous areas of Northwest Plateau is only 1-5 mm. In South China, the water consumption of overwintering is small, and the contradiction between supply and demand of farmland water is not obvious. In the case of scarce rain and snow, it is undoubtedly good for the growth of wheat crops to irrigate timely in different areas according to different farming habits and conditions.