Introduction of knowledge and data of rainwater solar terms
Rainwater information
Rain is the second of the 24 solar terms. Every February 19 or so, when the longitude of the sun reaches 330 degrees, it is the rain of 24 solar terms. At this time, the temperature rises, the snow melts and the precipitation increases, hence the name rain. The rain solar term generally starts from February 18 or 19 and ends on March 4 or 5. Rain, like Grain Rain, light snow and heavy snow, is a solar term reflecting precipitation.
Twenty-four solar terms: "In the first month, water is born every day. Spring belongs to wood, but there must be water for those who grow wood, so there is rain in beginning of spring. If the east wind melts, it will disperse into rain. " It means that everything begins to sprout before and after the rain and solar terms, and spring is coming. For example, Yizhoushu has phenological records such as "Hongyan coming" and "vegetation sprouting" after the rain.
In ancient China, rainwater was divided into three stages: "One stage was that Rex sacrificed fish; Second, wait for Hongyan to come; Third-class grass sprouted. " In this solar term, otters start fishing and put the fish on the shore like sacrifices before eating; Five days later, the geese began to fly back to the north from the south; In five days, in the "moist and silent" spring rain, the spirit of the sun rises everywhere in the vegetation and begins to sprout. Since then, the earth has gradually begun to show a thriving scene.
The rain solar term generally starts from February 18 or 19 and ends on March 4 or 5. The direct point of the sun is also gradually approaching the equator from the southern hemisphere. At this time, in the northern hemisphere, the sunshine hours and intensity are increasing, the temperature is rising rapidly, the warm and humid air from the ocean is becoming active, the spring drought is frequent, and it is gradually advancing northward. At the same time, cold air is not to be outdone in the weakening trend, and it frequently competes with warm air, unwilling to quit its hegemony and refuse to take away the residual cold.
Rainfall and solar terms increase
It began to rain, and it gradually increased. The rainy season means that it begins to rain and the rainfall gradually increases. In the Yellow River valley, the birthplace of the 24 solar terms, it was cold before the rain, but it was snowing and raining unpleasantly. After the rain, the temperature can generally rise above 0℃, with less snow and more rain. However, in the warm southern region, even in the dead of winter, rainfall is not uncommon. The average temperature in most parts of southern China in this period is above 10℃, peaches and plums are in bud, and cherries are in full bloom. It is indeed a climatic spring. Except for a few years, the frost period is over. It is timely to graft fruit trees and plant trees. After a dry winter in South China, the rain is as expensive as oil all the year round, especially in the west of South China. In agriculture, attention should be paid to moisture conservation and timely irrigation to meet the water supply at the jointing and booting stage of wheat and the critical period of bolting and flowering of rape. The mountainous area of the northwest plateau is still in the dry season, with low temperature and high wind speed, which is prone to forest fires. In addition, the invasion of cold wave will cause strong cooling and snowstorm, which will do great harm to the old, weak and young animals. These should pay special attention to prevention.
Rain not only indicates the beginning and increase of rainfall, but also indicates the rise of temperature. It was cold before it rained. After the rain, people obviously feel that spring has returned to the earth, spring is blooming, spring is full, and people's breath is inspiring their body and mind.
The cold and snow time has passed in most parts of the country, and it began to rain, and the rainfall gradually increased, which is conducive to the greening or growth of overwintering crops. It is necessary to pay close attention to the field management of overwintering crops and make good preparations for seed selection, spring ploughing, fertilization and other spring ploughing and sowing. During the fifteen days of rainy solar terms, we went from the sixth day of July to the second day of September. "In July, the river opened, and cattle were plowed everywhere on September 9 and September 19", which means that most areas except the northwest, northeast and southwest plateaus are still in the cold winter, and many other areas are experiencing or have completed the transition from winter to spring. Urged by the spring breeze and rain, the vast rural areas began to show a sense of spring.
However, in the rainy season, cold air activities in the north are still frequent and the weather is changeable. Since we talk about the frequent cold air activities in the next season, we can't help but mention what people often say about "spring cover". This is the principle of dressing and keeping in good health put forward by the ancients according to the characteristics of spring climate change. In early spring, when the sun is shining and the climate is getting warmer, people gradually go to cotton and wear light clothes. But at this time, it is still cloudy and cold in the north, and the temperature changes greatly. Although the rainy season is not as cold as the winter, the human body panel has become relatively loose, and the resistance to the evil of wind and cold will be weakened, so it is easy to get sick by evil. So it makes sense to pay attention to "spring cover" at this time. This changeable weather is easy to cause people's mood swings and even anxiety, which affects people's physical and mental health, especially those with hypertension, heart disease and asthma. In order to eliminate these unfavorable factors, we should not only continue to cover them in spring, but also take active mental health exercise.
After the rain, the spring breeze warms up, and pathogenic bacteria and viruses are easy to spread with the wind, so infectious diseases tend to break out in spring. Everyone should protect themselves, pay attention to exercise, enhance their resistance and prevent diseases.
In the rainy solar terms, the humid atmosphere gradually rises, and dew and frost appear in the morning. Therefore, in view of such climate characteristics, diet recuperation should be based on conditioning the spleen and stomach, expelling wind and removing dampness. Because the climate is cold at this time, it can be supplemented appropriately, such as honey, jujube, yam and tremella, which are all suitable for this solar term.
At this time, the atmospheric circulation is in the adjustment stage, and the general trend of climate characteristics throughout the country is from cold in late winter to warm in early spring.
For example, in the middle and lower reaches of the Yellow River in North China, the confrontation between cold and warm air did not bring about the sudden drop of temperature and the flying of snowflakes, but the arrival of spring breeze and spring rain. At this time, the average temperature in this area has risen above 0℃, and even the extreme maximum temperature during the day can reach above 20℃. There is no condition of snowfall, even if the ancestors named it "rain" after the first spring rain, it is also appropriate.
The influence of rain on agriculture
In rainy season, wheat enters the stage of turning green, and at this time, wheat has higher requirements for water. At this time, it is the least rainy time of the year. According to the surface climate data of China in 197 1 ~ 2000, the average rainfall in Shijiazhuang, Taiyuan and Beijing in February was only 7.4 mm, 5.2 mm and 4.9 mm respectively, which is really "spring rain is as expensive as oil".
In the northwest and northeast regions, during the rainy solar term, the northwest and northeast regions of China are still not out of the winter category. Judging from the average temperature in February, the monthly average temperatures in Lanzhou, Xining, Urumqi and Shenyang are-65438 0.0℃, -3.9℃, -9.7℃ and -6.9℃ respectively. It can be seen that these places have not got rid of the cold in winter, the weather is still dominated by cold, and the precipitation is dominated by snow.
As for the southwest and the south of the Yangtze River, during the rainy season, except for the spring scenery in southern Yunnan, most places in the southwest and the south of the Yangtze River are still the scene of early spring: the sunshine is warm, the morning and evening are wet and cold, the fields are green, and the spring river is warm.
According to the standard of four seasons, spring begins when the average daily temperature is ≥ 10℃-≤22℃ for five consecutive days. Generally speaking, the real "spring" in these places will come in late March, which is the "vernal equinox" season a month later. However, there are some special circumstances, such as Wuhan February 10, Changsha February 1 1, Nanchang February 1 1, and Nanjing February 2004 13, which are a whole month earlier.
According to the multi-year average rainfall of 65438 10 and February, Wuhan is 43.4 mm and 58.7 mm, Changsha is 66. 1 mm and 95.2 mm, Nanchang is 74.0 mm and 100.7 mm, and Fujian is 48.0 mm and 86.6 mm, which shows the rainfall ratio of the above places in February.
Therefore, in South China, every rainy and solar term, South China is full of spring and flowers are in full bloom.
The annual average temperatures in the following cities in South China in February are: Guangzhou 14.5℃, Nanning 14. 1℃, Haikou 18.7℃. The average precipitation in the above cities in February was 69.4 mm, 42.6 mm and 35.0 mm respectively. Although the rainfall is several times more than that in the middle and lower reaches of the Yellow River, there is still water shortage due to high temperature and large evaporation. Especially in southern South China and Hainan Island, the rainfall during this period is still relatively small, and spring droughts often occur. If the average temperature is lower than 10℃ under the influence of strong cold air, it is very unfavorable for early rice seedling raising.
If we say that in these areas, "beginning of spring" is the first movement "sonata" in spring: spring is budding and spring is chilly. After the rain, it entered the second movement of spring "variation": the temperature rose, and it was cold and warm. In the rainy season, "the seven or nine rivers open and the geese come" is a landscape in late winter and early spring.
Rainwater is mainly composed of hydrochemical component H2O, and a small amount of sulfur dioxide and nitrogen dioxide will form acid rain. In thunderstorm weather, the rain will contain a small amount of ozone molecules caused by lightning, as well as various impurities and floating dust in the air.