There are two days left for Xiaohan solar term in 2019. Xiaohan is the 23rd solar term. Between January 5-7 of the Gregorian calendar, the sun is located at 285 & deg; of the Huangjing;. For China, the cold marks the beginning of the coldest day of the year. According to China's meteorological data, Xiaohan is the solar term with the lowest temperature, and only in a few years, the temperature of the big cold is lower than that of Xiaohan.
In ancient China, Xiaohan was divided into three seasons: 'one is Yanbei village, two is magpie, and three is pheasant. The ancients thought that the geese in migratory birds moved along the Yin and Yang, and the Yang has moved, so the geese began to move northward; at this time, magpies can be seen everywhere in the north, and they began to build nests because they felt the Yang; The third is "Robin" of "pheasant robin". Pheasant will feel the growth of Yang when approaching 49.
At this time, the average temperature in Beijing is generally above - 5 ℃, and the extreme minimum temperature is below - 15 ℃; in the north of Northeast China, the average temperature is around - 30 ℃, the extreme minimum temperature can be as low as - 5 ℃, and the average maximum temperature in the afternoon is no more than - 20 ℃, which is really a world of ice carving and jade carving. In Heilongjiang, Inner Mongolia and Northern Tibet Plateau to the north of 45 & deg; N in Xinjiang, the average temperature is above - 20 ℃, and in the west of Hetao near 40 & deg; N, the average temperature is above - 10 ℃, which is a picture of severe winter. To Qinling and Huaihe River, the average temperature is about 0 ℃, there is no seasonal frozen soil in the south of the line, and there is no obvious overwintering period for winter crops. At this time, the average temperature in the south of the Yangtze River is generally above and below 5 ℃, although the fields are still full of life, there are also cold air southward, causing certain harm.
In the light cold season, in addition to the southern region, winter fertilizer should be applied to wheat, rape and other crops, while in Hainan and most of South China, it is mainly to do a good job in cold prevention and antifreeze, composting and fertilizer production, and water conservancy construction. On the basis of pouring frozen water, applying enough winter fertilizer and cultivating soil to back up roots before winter, adopting artificial covering method in cold winter is also an important measure to prevent freeze injury of agricultural and forestry crops. When the cold wave becomes strong and cold air comes, sprinkling the thin dung water and removing the plant ash can effectively reduce the harm of low temperature to the rape. The vegetable land cultivated in the open can be scattered on the vegetable border with crop straw and straw as the long-term winter cover, which not only does not affect the light, but also reduces the wind speed between the vegetable plants, blocks the heat loss of the ground, and plays the effect of heat preservation and antifreeze. In case of low temperature, thicken the cover for temporary coverage, and remove it in time after low temperature. At this time, the vegetables in the shed should be exposed to the sun as much as possible. Even in the rainy and snowy weather, the grass curtains and other coverings outside the shed should not be uncovered for several days in succession, so as to avoid affecting the normal photosynthesis of the plants, causing the lack of nutrition, and causing the plants to wilt and die when the curtains are uncovered in the sunny weather. High mountain tea garden, especially the tea garden which is vulnerable to the cold wind in the northwest, should cover the canopy with straw, weeds or plastic film to prevent the direct damage of dry shoots and sandstorms to the leaves caused by the wind. After snow, the snow on the branches should be shaken as early as possible to avoid the branches breaking due to strong wind.
Climatic characteristics of the mild cold solar term
When the sun's yellow longitude reaches 285 degrees, the small cold solar term begins. Cold means cold, and small cold means the degree of cold.
The East Asian trough is the most powerful and stable in terms of the small cold solar term, the Mongolia cold high and Aleutian low are also the most powerful and stable, the scale of the westerly trough ridge is the largest, and the westerly intensity is the strongest. The cooling process of cold air is frequent, but few of them reach the standard of cold wave.
As the saying goes, 'cold in September'. "39" is mostly from January 9 to 17, which is also just within the small cold solar term. But it's just a general rule. In a few years, the severe cold may be colder than the minor cold. In the winter of 1975, when people remember clearly, the solar term with the lowest temperature was heavy snow!
In the south of China, it is warm in winter. In January in the middle of winter, there is often frost and snow. The lowest temperature is about - 10 ℃. However, the lowest temperature in the north of South China is rarely lower than - 5 ℃, and the low temperature below 0 ℃ in the south of South China is even less. The coldest area in the middle of winter in China is the north of Heilongjiang Province. The lowest temperature is around - 40 ℃. It's freezing and drips into ice. Low altitude River Valley is the warmest place in the winter in most parts of southern China. The average temperature in January is about 12 ℃, and only a very young population may have a low temperature below 0 ℃. In addition, the temperature inversion effect is very significant, so tropical fruits such as banana and mango can grow well.
The lowest winter temperature in South China is not low, which is conducive to production and diversified management. The minimum temperature is no lower than - 5 ℃ and the annual temperature is higher than 15 ℃. Most areas in South China can meet the requirements, and there are almost all kinds of subtropical plants. Only so, the unique climate conditions should be a very important factor.
However, the weather is not completely controlled by solar terms. It's not cold when it's small. The key is that the sound of cold air is not strong. Yesterday's temperature was considered as a "face" for Xiaohan. However, the temperature in most parts of the northern part of the cold area did not drop sharply, but the temperature in some cities in the southern part of the day was below zero.
People should also pay attention to the forecast of strong cold air by the weather station, prevent the influence of strong wind and snow on the Spring Festival transportation, and pay attention to the prevention of cold and antifreeze.