1, beginning of spring
Beginning of spring has been the beginning of spring in China since the Qin Dynasty. It was once considered as the beginning of a new year. Beginning of spring is divided from astronomy, but in nature and in people's minds, spring is warm and flowers are fragrant. Spring is growth, cultivation and sowing. In climatology, spring refers to the period from the average temperature 10℃ to 22℃. When it comes to beginning of spring, people obviously feel that the days are getting longer and the sun is getting warmer. Temperature, sunshine and rainfall, which are often at the turning point of the year, tend to rise or increase. The growth of crops in early spring is accelerated, and the water consumption of rape bolting and wheat jointing is increased. It is necessary to irrigate topdressing in time to promote growth.
Agricultural proverbs remind people: "When it rains in beginning of spring, get up early and go to bed late." Da Chun has also begun to prepare for farming. Although "spring" has been established, frost will still appear in most areas of the basin, and in a few years, there will be a scene of "snow is too late for spring, so it is flying through the trees".
2. Rain
The meaning of rain solar terms is that the rain begins and the rainfall increases gradually. In the Yellow River Basin, the origin of the 24 solar terms, the weather was cold before the rain, but the snow was falling and the unpleasant rain was falling. After rain, the temperature can generally rise above 0℃, with less snow and more rain. However, in the warm climate of Sichuan Basin, even in the dead of winter, rainfall is not uncommon. During this period, the average temperature in Sichuan Basin is mostly above 10℃, peaches and plums are in bud, and cherries are in bloom, so it is indeed a climatic spring.
Except for a few years, the frost period has also come to an end. Grafting fruit trees and planting trees is the right time. After the dry winter, there are many spring droughts in the basin all the year round, especially in the western part of the basin. In agriculture, attention should be paid to moisture conservation and timely irrigation to meet the water supply in the critical period when wheat is jointing and booting and rape is bolting and flowering. The mountainous area of western Sichuan Plateau is still in the dry season, with low air temperature and high wind speed, which is prone to forest fires.
In addition, the invasion of cold wave can cause strong cooling and snowstorm, which is extremely harmful to old, weak and young animals.
3. Stunned
Solar terms reflect natural phenology, which means that the sudden movement of spring thunder wakes up the animals that are dormant and hibernating in the soil. At this time, the temperature has risen rapidly, and spring thunder has gradually appeared in most areas of the Yangtze River Basin. In the eastern part of Sichuan Basin and the southern part of Liangshan Prefecture, the first sound of spring thunder can also be heard in perennial rain and fright; The northwest of the basin, except for a few years, generally does not have thunder until Qingming, which is the latest area where thunderstorms begin in Sichuan Province.
By the time of the shock, most parts of China entered the busy season of spring ploughing. Really: the season waits for no one, and every moment is worth a thousand dollars. Generally, the average temperature of the solar term in Sichuan Basin is 12℃ to 14℃, which is more than 3℃ higher than that in the rain solar term, and it is the solar term with the fastest annual temperature rise. The sunshine hours have also increased significantly. However, because of the alternating cold and warm air, the weather is unstable and the temperature fluctuates greatly. In the Yangtze River valley area in the southeast of the basin, the temperature is stable above 12℃ during the period of fright in most years, which is conducive to the sowing of rice and corn. In other areas, the daily average temperature is below 12℃ for more than three consecutive days, so it is not allowed to sow early blindly.
Although the temperature rises rapidly, the rainfall increase is limited. The total rainfall in the central and northwestern parts of the basin is only about 10 mm, and after winter drought all the year round, spring drought often begins to emerge. At this time, wheat booting and rape flowering are in a period of high water demand, and they are sensitive to water demand. Spring drought often becomes an important factor affecting the yield of Koharu. Afforestation should also consider this climate feature, and after planting, we should be diligent in watering and strive to improve the survival rate of saplings.
4. vernal equinox
The vernal equinox is one of the solar terms reflecting the changes of the four seasons. In ancient China, beginning of spring, long summer, beginning of autumn and beginning of winter were used to indicate the beginning of the four seasons. The vernal equinox, summer solstice, autumn equinox and winter solstice are in the middle of each season. On the day of the vernal equinox, the sun shines directly on the equator, and the time between day and night is equal in all parts of the earth. Therefore, the ancient vernal equinox and autumnal equinox are also called "day and night equinox", and there is a folk proverb that "the vernal equinox and autumnal equinox are equally divided between day and night". After the vernal equinox, the overwintering crops in most areas of China entered the spring growth stage. There is an agricultural proverb in Central China that "the wheat rises at the vernal equinox, and every moment is worth a thousand dollars".
The temperature in all parts of Sichuan Province continues to rise, but generally it is not as fast as that from rain to vernal equinox. In late March, the average temperature in the north of the basin was mostly 13℃ to 15℃, and in the south of the basin was mostly 15℃ to 16℃. Most of the plateau has been melted by snow, and the ten-day average temperature is about 5℃ to 10℃. The temperature in Jinsha River, Anning River and other valley areas in southwest Sichuan Province is the highest, with an average of 18℃ to 20℃. Except for the marginal mountainous areas, the average daily temperature in the basin has risen steadily to above 12℃ in seven or eight years, which is beneficial to sowing rice, corn and other crops, and is also very suitable for afforestation.
However, there is often a strong cold air intrusion in the basin before and after the vernal equinox, and the temperature drops significantly, and the minimum temperature can be as low as 5℃. Sometimes a small stream of cold air comes one after another, forming a low temperature and rainy weather that lasts for several days, which is not good for agricultural production. According to this characteristic, we should make full use of the weather forecast, grasp the cold tail and warm head and sow in time.
5. Qingming
Qingming is a solar term representing phenology, which means sunny weather and lush vegetation. On Qingming Day, there are folk customs such as hiking, cold food and sweeping graves. As the saying goes, "Snow breaks in Qingming, and frost breaks in Grain Rain." When it is clear, the climate in the basin is warm and the spring is strong. However, before and after the Qingming Festival, cold air still intrudes from time to time, even making the daily average temperature lower than 12℃ for more than three consecutive days, resulting in rotten seedlings of middle rice and dead seedlings of early rice. Therefore, rice planting and transplanting should avoid cold tail and warm head.
In the western Sichuan Plateau, livestock are weak under the influence of severe winter and insufficient forage, so it is necessary to guard against the harm of strong cooling weather after spring to the old, weak and young livestock. "It rains in succession during the Qingming Festival" is a portrayal of the spring rain in the south of the Yangtze River by Du Mu, a famous poet in the Tang Dynasty.
6. Grain Rain
As the saying goes, "Rain gives birth to a hundred valleys". With timely and sufficient rainfall, cereal crops can thrive. Grain Rain solar terms have such a meaning. In Grain Rain season, in Sichuan Basin, "the young flowers are falling, the cuckoo is crying at night, the peony is blooming, and the cherry is ripe. The natural scenery informs people that it is late spring. At this time, the temperature in the basin rises rapidly. Generally, the average temperature in late April has reached 20℃ to 22℃, which is more than 2℃ higher than that in mid-April, except in the northern and western parts of the basin. In the eastern part of the basin, there is often a high temperature of more than 30 degrees in one or two days, which makes people feel hot. Low-altitude valley areas in southwest Sichuan are used to enter summer.
The climate characteristics of high temperature in spring in the basin are beneficial to catch the early crop cultivation measures in Da Chun. The suitable planting temperature of Polygonum cuspidatum is 18℃ to 22℃, which can be satisfied at this time. The experience in the old arid area of the basin has proved that when Osmunda japonica is planted early after Grain Rain, the rattan leaves can be sealed before the summer drought, the drought resistance can be enhanced, and high and stable yield can be obtained.
7. long summer
As the name implies, long summer refers to the beginning of summer. However, the temperature varies from place to place, and the time of entering summer is actually inconsistent. According to the climatological standard that the five-day average temperature is higher than 22℃ in summer, before and after long summer, the southern Sichuan Basin just entered summer; The temperature in the rest of the basin is about 20℃, and it is still in the late spring season of "no one asks the fallen flowers outside the door, and the green shade of Ran Ran is all over the world"; However, the low-altitude valley in southwest Sichuan felt hot in summer as early as mid-April, and the temperature in long summer has reached above 24℃, which can be described as hot in summer.
Yi Wei has long summer's theory of "seeing by electricity". However, as far as Sichuan is concerned, even in the northwest of the basin, where the first thunderstorm is the latest, the perennial thunderstorm begins in the first and middle of April, so it is not necessary to wait until long summer. After long summer, it is the critical period of water demand for large-scale planting of mid-season rice in the basin. The early and late arrival of heavy rain and the amount of rainfall are closely related to agricultural production. At this time, if it doesn't rain heavily, those farmland without water irrigation can't plow and harrow and plant seedlings.
According to the statistics of climate data, the average heavy rain for many years begins in the middle and late April in the east of the basin, in the middle and late May in the middle and late May in the west. The rainfall in May is 100 to 200mm in the southeast and 75 to100mm in the northwest of the basin. In the western and central parts of the basin, the heavy rain started late, and the rainfall was less, so summer drought often appeared. During this period, just as the basin is harvesting crops in early spring and planting crops in Da Chun, special attention should be paid to the influence of changeable weather. Harvesting should be done in time in sunny days, planting should be done in rainy days, even in rainy days, Koharu harvests should be guarded against sprouting and mildew, and seedlings should be protected against drought, and the harm of low temperature below 20℃ to early rice should be guarded against.
8. Xiaoman
Xiaoman means that summer crops such as wheat are filled with milk and the seeds are full. The agricultural proverbs in Sichuan basin give Xiaoman a new meaning: "Xiaoman is dissatisfied, and he thinks about it"; "Small full of dissatisfaction, regardless of the mango." The term "full" is used to describe the surplus and shortage of rain, and it is pointed out that if there is not enough water in the field when it is full, the ridge may be cracked, and even rice cannot be planted when it is planted. Because "long summer Xiaoman is planting seedlings" and "the seedlings rush to Xiaoman Valley for autumn", Xiaoman is the season suitable for rice planting. Whether the summer drought in the basin is serious or not is directly related to the rice planting area. Sooner or later, planting is closely related to the yield of rice.
9. Miscanthus
The awn seed is a symbol of the maturity of awned crops such as wheat, and it is a solar term reflecting agricultural phenology. By the time of awning, the wheat harvest season in Sichuan basin has passed, and the transplanting of mid-season rice and sweet potato is coming to an end. In most areas, the mid-season rice has entered the green stage, and the seedlings are green and full of vitality. The poem "The east wind has dyed 3,000 hectares, and the broken heron has nowhere to stop" vividly depicts the beautiful scenery of the field at this time.
In the season of awning, the mid-season rice that has not been transplanted should be planted quickly; If it is postponed again, the vegetative growth period of rice will be shortened due to the increase of temperature, and the growth stage will be vulnerable to drought and pests and diseases, and the yield will inevitably be low. Osmunda japonica should be transplanted before the summer solstice at the latest; If the planting is too late, not only will the influence of drought be aggravated, but the temperature will drop when it arrives in Qiu Lai, which is not conducive to the expansion of potato pieces and the yield will also be significantly reduced. This is the truth of the agricultural proverb "busy planting".
10, summer solstice
On the summer solstice, the sun shines directly on the Tropic of Cancer, which is the longest day in a year in the northern hemisphere. It takes about fourteen hours from sunrise to sunset in all parts of Sichuan. Although the summer solstice has the longest day and the highest solar altitude, it is not the hottest time of the year. Because the heat in the near-surface layer is still accumulating at this time, and it has not reached the maximum. The summer solstice solar term is the solar term with the largest annual rainfall in the eastern part of the basin, and it is often controlled by subtropical high in the future, resulting in summer drought. In order to enhance drought resistance and win a bumper harvest in agriculture, it is an important measure to grab and store pre-dormant rainwater in these areas. After the summer solstice, the ground is heated strongly, and the air convection is strong, and thunderstorms are often easy to form in the afternoon to evening. This kind of hot thunderstorm suddenly comes and goes, and the rainfall range is small. People call it "summer rain separates the fields".
In Sichuan, Liu Yuxi, a poet in the Tang Dynasty, skillfully used this kind of weather to write a famous poem, "Sunrise in the east and rain in the west, the road is sunny but sunny".
1 1, Xiaoshu
The trees are shaded, and it is light summer. The average temperature in the light summer in Sichuan Basin is about 26℃, which is already midsummer and quite hot, but it has not yet reached the hottest time. In mid-July all the year round, in the low-altitude valley area in the southeast of the basin, there can be a concentrated period when the daily average temperature is higher than 30℃ and the daily maximum temperature is higher than 35℃, which is unfavorable to the heading and flowering of hybrid rice. In addition to fully considering this factor in the layout in advance, corresponding remedial measures should be taken for those that have been planted. In the northern Sichuan Plateau, frost and snow can still be seen at this time, which is equivalent to the scene in the early spring of the basin. Before and after the light summer, the western part of the basin entered the season with the most rainstorm, and the number of rainstorm days in July and August can account for more than 75% of the whole year, usually about 3 days.
In places with large relief, flash floods often occur, even causing mudslides. However, in the eastern part of the basin, after the slight summer heat, it began to enter the summer drought period because it was often controlled by the subtropical high and the weather was sunny and hot. Sichuan Basin, a climatic feature of drought in the east and waterlogging in the west, has a great relationship with agricultural harvest, so it is necessary to take drought and flood control measures as early as possible to minimize the harm. Around the summer heat, all parts of Sichuan Province entered the season with the most thunderstorms. Thunderstorm is a severe weather phenomenon, often accompanied by strong winds, heavy rains, and sometimes hail, which is easy to cause disasters and must be prevented.
12, summer heat
Summer heat means hot. It shows that it is the hottest solar term in a year. Generally speaking, the solar term of summer heat is the period with the most sunshine and the highest temperature in the basin in a year. The hot summer heat is the season when jasmine and lotus flowers are in full bloom. The jasmine with a sweet smell is more fragrant, and the hotter the weather, the more fragrant it is, giving people a clean and fragrant enjoyment. Noble lotus, not afraid of the scorching sun and showers, blooms in the morning and gathers at dusk. The poet praises it as "reflecting the lotus in the sun is different in color", and the vibrant midsummer is gestating a bumper harvest.
13, beginning of autumn
"It's cool on the day of beginning of autumn" clearly connects beginning of autumn with the cool weather. Visible, beginning of autumn is the beginning of the cool autumn. Due to the different latitudes and altitudes, it is actually impossible for all of them to enter autumn at the same time in beginning of autumn. According to the climatological standard that the average temperature for five days is between 10℃ and 22℃, in China, except those places with north latitude and high altitude, beginning of autumn is still in the hot summer, and even in most parts of the northeast, there is no autumn scenery with cool breeze and yellow leaves fluttering. For the Sichuan Basin located in the middle subtropical zone, the summer heat is still heavy in August all the year round.
Statistics of climate data show that the basin will not enter autumn until the middle and late September. It is impossible to say when autumn begins in plateau and mountain areas where winter is all year round or winter is long without summer, and spring and autumn are connected. After beginning of autumn, late rice in Sichuan basin jointing and booting, cotton boll cracking and boll spitting, field management should not be relaxed at all; Mid-season rice and summer corn enter the stage of filling maturity, so we should guard against the harm of hail, strong wind and heavy rain. The eastern and western parts of the basin should continue to do a good job in drought and flood control respectively. In the basin after beginning of autumn, although the season is still midsummer, "beginning of autumn is full of yellow in ten days" and a golden "autumn" is coming.
14, summer heat
Summer is a solar term that reflects the change of temperature. "Chu" means hiding and ending, and "Chu Xia" means that the hot summer day is over. Generally, the average temperature in Sichuan Basin is about 1.5℃ lower than that in beginning of autumn. In late August of some years, there may be a low temperature in the west of the basin with the daily average temperature below 23℃ for more than three consecutive days, which will affect the flowering of hybrid rice. However, because the summer heat in the basin is still basically controlled by the summer monsoon, the highest temperature in the west of the basin is often higher than 30℃ and the highest temperature in the east of the basin is higher than 35℃. Especially in the low-altitude areas along the Yangtze River, in the years when the summer drought continued, the "autumn tiger" was even more felt. The western Sichuan Plateau has entered the summer and autumn, with an altitude of more than 3,500 meters, showing the scene of early winter, grass withering and frost and snow increasing day by day. Summering in summer is the early stage of the transformation of rainfall distribution in Sichuan basin from more in the west and less in the east to less in the east. At this time, the rainfall in the central part of the basin is often the second highest in a year, which is more than that in the summer heat or the white dew.
Therefore, in order to ensure farmland water use in winter and spring, we must seriously do a good job in water storage during this period. There will be continuous rainy and rainy weather in the plateau from summer to autumn equinox, which is unfavorable to the production of agriculture and animal husbandry. Sichuan basin is also a busy time to harvest mid-season rice. Generally, during the summer solar term, the sunshine in the basin is still sufficient, except for the western part of the basin, there are not many rainy days, which is conducive to the cutting and drying of mid-season rice and cotton bolling. However, in a few years, as Du Fu's poems said, "The dog days have passed, and the sun has turned into rain", and the autumn rain will come ahead of time. Therefore, we should pay special attention to the weather forecast, make full preparations, seize every fine weather, and seize the opportunity to do a good job in grabbing harvest and sun.
15, Millennium
Dew is water droplets condensed by water vapor on the ground or near-earth objects due to the decrease of temperature. Therefore, the Millennium actually indicates that the weather has turned cold. In the climate of 24 solar terms in the basin of our province, the White Dew has the obvious characteristics of rapid temperature drop, the beginning of drizzle and the sudden decrease of sunshine, which profoundly reflects the seasonal change from summer to autumn. The average temperature in the basin during the perennial dew period is about 3℃ lower than that in the summer, and the average temperature in most areas (5 days) has dropped below 22℃ successively. According to the standard of dividing the four seasons by climatology, the time series begins to enter autumn. The autumn rain in the basin mostly appeared before Bailu to first frost, with the most in the middle and lower reaches of Minjiang River and Qingyi River, and relatively less in the middle of the basin. The farmer's proverb, "Too much white dew, walking around every day", can't predict the weather by whether there is rain on the day of the white dew, but there is often a period of continuous rainy weather before and after the white dew festival. Moreover, since then, rainfall in the basin has been characterized by low intensity, frequent rainy days and continuous rainfall.
Accordingly, the sunshine in the basin during the white dew period is about half of that in the summer, and the decreasing trend continues until winter. The above-mentioned climatic characteristics of the Millennium season are unfavorable to late rice heading and blooming, and also affect the harvesting and sun-drying of mid-season rice, so there is a saying in the agricultural proverb that "the Millennium is sunny and the rice is as white as silver". Only by fully understanding the climate characteristics of the Millennium and taking corresponding agricultural technology measures can the harm of autumn rain be alleviated or avoided. On the other hand, we should also seize the rain to store water, especially the Bailu in the east of the basin is another solar term with more rainfall after Xiaoman and the summer solstice, so don't miss the good opportunity.
16, autumnal equinox
The autumnal equinox is a solar term representing seasonal changes. On the day of the autumnal equinox, the sun is located at 0/80 degrees of the yellow meridian/kloc, and the sunlight is almost direct to the equator, and the day and night are almost equal. At this time, the waiting temperature in Sichuan basin generally dropped below 22℃, and it entered a cool autumn. "An autumn rain and a cold". The cold air flowing southward meets the warm and humid air that gradually decays, resulting in repeated rainfall and the temperature dropping again and again. In the northern part of the western Sichuan Plateau, the daily minimum temperature has dropped below 0℃, and you can already see the magnificent snow scene of flying all over the sky and the earth wrapped in silver.
After the autumnal equinox, the rainfall in Sichuan province decreased obviously, and heavy rain and heavy rain rarely appeared. However, the number of rainy days has increased, with frequent rainy days and high night rain rate. Li Shangyin, a famous poet in the Tang Dynasty, famously said, "evening rain rises in the autumn pond", which vividly depicts the climate characteristics of rainy nights in autumn in Sichuan. In Sichuan Basin and Liangshan Prefecture, it is rainy and wet in autumn, which has a great influence on autumn harvest, autumn ploughing and autumn planting.
It is necessary to catch the sun, manage soil moisture and prevent waterlogging, and do a good job in the quality and progress of "Sanqiu" production. At the same time, we should make full use of the meteorological conditions with little rain and good soil moisture in autumn, seize the opportunity to do afforestation and strive to improve the survival rate of saplings.
17, cold dew
In ancient times, dew was regarded as a sign that the weather turned cold. The solar term of Mid-Autumn White Dew is "dew condensation and white", and it is already "dew gas is cold, it will condense" into frost when it is cold in the season and autumn. At this time, the temperature in all parts of Sichuan Province continued to drop. The average daily temperature in the basin is less than 20℃. Even in the areas along the Yangtze River, it is difficult for mercury column to rise above 30℃, while the minimum temperature can drop below 10℃.
Except for a few valley lowlands in the western Sichuan Plateau, the average temperature in five days is generally lower than 10℃, which is already winter according to the standard of climatic division of four seasons. Thousands of miles of frost and snow in Wan Li are very different from the autumn colors in the basin. During the perennial cold dew, the rainfall in the basin is also decreasing day by day. The western part of the basin is mostly about 20 mm, and the eastern part is generally about 30 to 40 mm. It rains frequently, day and night, and it is raining, which affects the production of "Sanqiu" and becomes a disastrous weather in the basin of our province. The climatic characteristics accompanied by the drizzle are: high humidity, more clouds, less sunshine, more cloudy days, and the number of foggy days has increased significantly since then.
However, whether the autumn rain is serious or not directly affects the progress and quality of "Sanqiu". To this end, on the one hand, we should use the weather forecast to grab the harvest and sowing in sunny days; On the other hand, according to local conditions, we should take various effective farming measures, such as deep furrows and high compartments, to reduce wet damage and improve sowing quality. In the plateau area, before and after the cold dew is one of the most serious seasons of snow damage. Snow blocks traffic and harms animal husbandry production, so attention should be paid to prevention.
18, first frost
The solar terms in first frost mean that the weather is getting colder and the frost begins to fall. In the south latitude Sichuan Basin, the average temperature is mostly around 16℃, and there are still three solar terms before the first frost date. In the southern valley of the basin, frost can only be seen in the middle of winter. Of course, even at the same latitude, because of the different altitude and topography, the temperature and humidity of the air close to the stratum are different, and the first frost period and frost days are different. From a scientific point of view, the statement that "dew forms frost" is inaccurate. The frozen dew formed by freezing dew drops is hard small ice beads. Frost refers to the phenomenon of crop freezing injury caused by the sudden drop of temperature, and its damage temperature varies with crops, varieties and growth periods. To form frost, the temperature of the ground or ground objects must drop below 0℃, and the moisture content in the air in the ground should reach a certain level. Therefore, frost does not necessarily occur when frost occurs, and frost does not necessarily occur when frost occurs.
However, because the temperature at the time of frost is already relatively low, if it continues to cool, it will easily lead to frost. After first frost, a large number of Dioscorea zingiberensis were collected and dug in our basin. If the harvest is too early and the lump is not fully expanded, it will affect the yield; However, if the harvest is too late, it may be damaged by early frost, and the blocks will be frozen and deteriorated, so it is very important to dig them in time.
Su Shi, a great writer in the Northern Song Dynasty, said in a poem: "Thousands of trees are swept yellow, and only hibiscus is alone." The climate in Sichuan Basin is mild. During the period of first frost, the fields are lush, orange-yellow-orange-green, autumn chrysanthemums are in full bloom, and hibiscus trees are in full bloom, making the rich "Tianfu" more gorgeous.
19, beginning of winter
"Standing, building also" means that winter begins from now on. "On the day of beginning of winter, the water began to freeze and the ground began to freeze". People often take the bitter north wind and cold frost and snow as symbols of winter. Frost and snow are scarce in the basin of our province. Therefore, in climatology, the day of "beginning of winter" is not fixed as the beginning of winter everywhere, but the season is divided by the temperature, that is, the winter is when the average temperature is below 10℃ for five days, which is more suitable for the phenological landscape at that time. Sichuan Basin in beginning of winter season is still in the busy period of Sanqiu, and the average temperature is generally 12℃ to 15℃. The drizzle is over.
Climatic conditions are suitable for rape transplanting. Wheat with short growth period and strong springiness should also be sown, because there are many strong cold air attacks in the later period of beginning of winter, and the temperature often drops greatly. If the temperature is low after sowing, the seedlings will emerge slowly and the yield will be affected. When the daily average temperature is lower than 15℃, the growth of Osmunda japonica has gradually stopped, so it should be harvested in time. Early frost has occurred in beginning of winter in some years in the northwest of the basin, so it is necessary to dig pits early to avoid freezing injury. At this time, the plateau area is already a dry season, the humidity is rapidly decreasing, and the wind speed is gradually increasing, so we must be highly vigilant against forest fire.
20, light snow
Light snow indicates the starting time and degree of snowfall. Snow is the product of cold weather. Light snow solar terms, the northern Sichuan Basin began to enter winter. "The lotus has no rain cover, and the chrysanthemum still has branches in Ao Shuang", which has been a scene of early winter. Because there are barriers in the north of Qinling Mountain and Daba Mountain, which block the invasion of cold air and reduce the severity of the cold wave, the basin is "warm in winter" significantly. The number of snowfall days in the whole year is mostly less than 5 days, which is much less than that in the middle and lower reaches of the Yangtze River at the same latitude. There is little chance of snowfall before heavy snow, and even in the middle of winter, it is rare to see the charming scenery of "blowing open the petals of ten thousand pear trees". Because the temperature in the surface layer of the basin is often above 0℃ in winter, it is more difficult to snow than to snow. Occasionally, although the sky is "buzzing", there is no "broken jade" on the ground.
However, in the cold western Sichuan Plateau, snow usually begins all the year round 10. The number of snowfall days in the northwest of the plateau can reach more than 60 days in a year, and there is the possibility of snowfall in some alpine regions all year round. During the light snow, the first frost can be seen in the northwest of the basin, so it is necessary to prevent the harm of frost to crops. In the northern part of Gansu and Afghanistan, the lowest temperature is mostly around MINUS 15℃, so it is necessary to do a good job of keeping livestock warm and cold.
2 1, heavy snow
The "heavy snow" indicates that the snow began to fall heavily at this time. The winter climate in Sichuan Basin is mild with little rain and snow. The average temperature is about 2℃ to 4℃ higher than that in the middle and lower reaches of the Yangtze River, and the rainfall accounts for only about 5% of the whole year. Occasionally snow falls, mostly in 1 and February; Snow on the ground is hard to see once every three or five years. If you can witness the snow-capped land and the green trees covered with silver and jade, it is often an unforgettable fun.
"Snow indicates a bumper year" is a popular agricultural proverb in China. In the north, a thick and loose layer of snow is like covering wheat with a quilt to keep out the cold. Snow contains four times more nitrogen compounds than rain. After the snow melts slowly, it seeps into the soil, which can increase the nitrogen in the soil and be easily absorbed and utilized by crops. The low temperature of snow water can freeze the overwintering pests on the ground surface and bring benefits to agricultural production.
However, in the south, if the ground heat loses more on sunny nights after snow, there will be freezing damage, which will cause certain losses to crops such as peas and beans.
22, winter solstice
The winter solstice is a solar term divided by astronomy, which is called "short day" and "short day" in ancient times. On the winter solstice, the sun is located at 270 degrees of the yellow meridian, and the sunlight is almost direct to the tropic of Capricorn, which is the shortest day in the northern hemisphere. There is no 10 hour from sunrise to sunset in all parts of Sichuan Province. After the winter solstice, as the earth moves in orbit around the sun, the direct sunlight zone gradually moves northward, making the days in the northern hemisphere gradually grow and the nights gradually shorten. On the winter solstice, although the height of the sun is the lowest, the sunshine time is the shortest, and the heat absorbed by the ground is less than the heat lost, the heat accumulated on the ground for a long time continues to be lost, and the temperature in the near-surface layer has not yet dropped to the minimum, so it is not the coldest time of the year. After the winter solstice, although the days are getting longer and the nights are getting shorter, in the short term, the days are still shorter and the nights are longer. The heat absorbed by the ground every day is still less than the heat lost, so the temperature does not rise immediately. The masses are used to counting nine from the winter solstice, and every nine days is a "nine". Before and after the "March 9th", the heat accumulated on the ground was the least and the weather was the coldest, so it was said that "it was cold in March 9th!
Folk customs say: 1929 is afraid of making moves, 3949 walks on the ice, willows bloom along the banks of May 9 and June 9, the river of July 9 freezes, swallows come in August 9, and cows walk everywhere.
Astronomy regards the winter solstice as the beginning of winter, which is obviously late for most parts of our country. During the winter solstice, the average temperature in the western Sichuan Plateau is generally below 0℃, and that in the Sichuan Basin is only about 6℃ to 8℃. However, in the low-altitude valley area of southwest Sichuan, even in the coldest early month of 1 month, the average temperature is still above 10℃, which really means that autumn has gone to spring, and there is no winter all year round.
23, slight cold
Cold means cold, and slight cold indicates the degree of cold. As the saying goes, "it's cold in March 9th". "Sanjiu" is mostly from 1 9 to 17, which is also within the slight cold solar term. But this is just a general rule. In a few years, the severe cold may be colder than the mild cold. In the winter of 1975 that people still remember, the solar term with the lowest temperature was actually heavy snow! The winter in Sichuan Basin is warm, with midwinter 1 month. Frost and snow to the east of the Three Gorges intrude, often freezing, and the lowest temperature is around-0/0℃. However, the lowest temperature in the northern part of the basin is rarely below MINUS 5℃, and the low temperature below 0℃ in the southern part of the basin is even more rare.
The coldest area in the middle of winter in Sichuan Province is the northern Sichuan Plateau. The lowest temperature can reach about-30℃. It is freezing and dripping into ice. The low-altitude valley in southwest Sichuan is the warmest place in Sichuan Province in the middle of winter, with the average temperature of 1 month around 12℃, and only a few teenagers may have a low temperature below 0℃. In addition, the inversion effect is very significant, so tropical fruits such as bananas and mangoes can grow well. The lowest temperature in winter in the basin is not low, which is beneficial to non-spring production and is also suitable for diversified management. Citrus, which is ordered not to move, grows in the south, generally requires a minimum temperature of not less than minus 5℃ and an annual temperature higher than 15℃, which can be met in most areas of the basin, and there are almost all kinds of subtropical plants.
24. Great cold
Like the slight cold, the great cold is also a solar term representing the degree of cold weather. Although several records of modern meteorological observation show that in most areas of China, severe cold is not as good as mild cold, in some years and a few coastal areas, the lowest temperature in the whole year will still appear in the severe cold solar terms. In the severe cold season, it is necessary to have a proper low temperature in a certain growth period. Wheat and rape with strong winterness require lower temperature through vernalization stage, otherwise they cannot grow and develop normally.
It is warm in winter all the year round in Sichuan Basin, and wheat and rape sown too early often grow too vigorously, jointing and 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 promotion and control measures are important links to win high yield.