What does the twenty-four solar terms mean? How are they divided? What are their influences?

How are the 24 solar terms determined?

The earth revolves around the sun every 365 days at 5: 48: 46 and rotates once every 24 hours. Because the orbital plane of the earth's rotation is different from the equatorial plane and maintains a certain inclination, the position where the sun shines directly on the earth is different all the year round. In the northern hemisphere, when the sun shines directly at 23.5 degrees north latitude, it is called the summer solstice in astronomy. When the sun shines directly at 23.5 degrees south latitude, it is called the winter solstice; The solstice in summer and the solstice in winter mean that it is halfway between summer and winter. When the sun shines directly at the equator twice a year, it is called vernal equinox and autumnal equinox, which means that it is in the middle of spring and autumn, and the day is as long as the night.

There are eight solar terms reflecting the changes of four seasons: beginning of spring, vernal equinox, long summer, summer solstice, beginning of autumn, autumnal equinox, beginning of winter and winter solstice. Among them, beginning of spring, Changsha, beginning of autumn and beginning of winter are called "Li Si", which means the beginning of the four seasons. There are five solar terms reflecting temperature changes: slight summer, great summer, great summer, slight cold and great cold. The weather phenomena are as follows:

The meaning of the twenty-four solar terms

Beginning of autumn: Standing is the beginning. Beginning of spring is the beginning of spring. Rain: It began to rain, and the rainfall gradually increased. Sting: Sting means hiding. Sting refers to the sudden movement of spring thunder, which awakens animals dormant and hibernating in the soil. Equinox means equal division. The vernal equinox means that day and night are equally divided. Qingming: The weather is fine and the vegetation is lush. Grain Rain: Rain makes a hundred valleys. The rainfall is sufficient and timely. Cereal crops can thrive. Long summer: the beginning of summer. Xiaoman: Summer grain such as wheat is full. Tent crops such as wheat have matured. Summer solstice: The hot summer is coming. Hot in summer means hot. The intense heat means the beginning of hot weather. General department: the hottest time of the year. Beginning of autumn: The beginning of autumn. The heat means ending and hiding. Dew is white. Autumnal equinox: divided equally between day and night. Cold dew: Dew is cold and will freeze. First frost: The weather turned cold and began to frost. Beginning of winter: The beginning of winter. Xiaoxue: It's starting to snow. Heavy snow: With the increase of snowfall, the ground may be covered with snow. Solstice of winter: the cold winter is coming. Slight cold: The climate is getting cold. Great cold: the coldest time of the year.

Beginning of Spring

Since the Qin Dynasty, China has always regarded beginning of spring as the beginning of spring. Beginning of spring is divided from astronomy, but in nature and people's minds, spring is warm and flowers are fragrant. Spring is growth, cultivation and sowing. In climatology, spring refers to the period when the average temperature is between 10℃ and 22℃.

Speaking of beginning of spring, people obviously feel that the days are getting longer and the sun is getting warmer. Temperature, sunshine and rainfall are often at the turning point of a year, with a rising or increasing trend. The growth of crops in early spring is accelerated, and the water consumption for bolting rape and jointing wheat is increased. Irrigation and topdressing should be done in time to promote growth. Agricultural proverbs remind people: "When it begins to rain in spring, get up early and go to bed late", and Da Chun has also begun to prepare for agriculture.

Where is the information that people often look for in spring? The buds protruding from the wicker are "softer than gold and softer than silk"; The eager grass in the soil is waiting for "they grow taller in the spring breeze"; And those who have worked hard in the fields and won a new harvest are creating real spring with their hands.

Rain Water

Rain solar term means that it begins to rain and the rainfall gradually increases. The Yellow River valley, the birthplace of the 24 solar terms, was cold before it rained, but there were snowflakes flying and unpleasant raindrops. After the rain, the temperature can generally rise above 0℃, with less snow and more rain. However, in the warm Sichuan Basin, even in the dead of winter, rainfall is not uncommon. The average temperature in this period in our basin is above 10℃, and the average temperature is above 10℃. It is indeed spring in the climate. Except for a few years, the frost period is over. Grafting fruit trees and planting trees is the right time. After the winter drought, there are many droughts in spring all the year round in the basin, especially in the west of the basin, and the "spring rain is as expensive as oil". In agriculture, we should pay attention to moisturizing and watering in time to meet the water supply in the critical period of wheat jointing and heading and rape bolting and flowering. The mountainous areas of the western Sichuan Plateau are still in the dry season.

Time flies, and the seasons remind people. "A year's plan lies in spring." Koharu's governance and Da Chun's land preparation should be carried out quickly, so as to make this year better than previous years.

Awakening of Insects

Surprise, reflecting natural phenology, refers to the sudden movement of spring thunder, which awakens animals that are dormant and hibernating in the soil. At this time, the temperature rises rapidly, and spring thunder has gradually appeared in most areas of the Yangtze River Basin. In the eastern part of the basin and the southern part of Liangshan Prefecture, spring thunder can be heard all year round. Except for a few years, the northwest of the basin usually thunders until Qingming, which is the latest area where thunderstorms begin in our province.

By the time of shock, most parts of China have entered the busy season of spring ploughing. Really, the season waits for no one, and every moment is worth a thousand dollars. The average temperature of the scary solar term in our province is generally 12℃ to 14℃, which is more than 3℃ higher than the rain solar term, and it is the solar term with the fastest annual temperature rise. The sunshine hours also increased significantly. However, due to the alternation of cold and warm air, the weather is unstable and the temperature fluctuates greatly. In most years, the temperature in panic period is stable above 65438 02℃, which is beneficial to the sowing of rice and corn. In other areas, the daily average temperature is often lower than 12℃ for more than three consecutive days, so it is not allowed to broadcast early blindly. Although the temperature rises rapidly, the increase of rainfall is limited. The total rainfall in the central and northwestern parts of the basin during the panic period is only about 10 mm, and after the perennial winter drought, the spring drought often begins to appear. At this time, the booting stage of wheat and flowering stage of rape are at the peak of water demand and are sensitive to water demand. Spring drought often becomes an important factor affecting the output of Koharu. Afforestation should also consider this climate characteristic, plant logistics and water, and improve the survival rate of saplings.

In the season of fright, the spring is bright and everything is new. Careful observation and accumulation of phenological knowledge are helpful to arrange farming activities according to local conditions.

Spring Equinox

The vernal equinox is one of the solar terms reflecting the changes of the four seasons. In ancient China, beginning of spring, Changxia, 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 all over the earth, so 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 divided into equal parts".

After the vernal equinox, the overwintering crops in most parts of China have entered the spring growth stage. There is an agricultural proverb in central China, "Wheat rises at the vernal equinox, and a moment is worth a thousand dollars". The temperature in all parts of our province continues to rise, but it generally rises quickly from the time when there is no rain to the vernal equinox. In late March, the average temperature in the north of the basin was mostly 65438 03℃ to 65438 05℃, and in the south of the basin was mostly 65438 05℃. The ten-day average temperature is about 5℃ to 10℃. The temperature in Jinsha River and Anning River valleys in the southwest of our province is the highest, with an average of about 18℃ to 20℃. Except in marginal mountainous areas, the average daily temperature in the basin has steadily increased to above 65438 02℃ in the past seven or eight years, which is beneficial to planting crops such as rice and corn, and is also very suitable for afforestation. The temperature drops obviously, and the lowest can be as low as 5℃. Sometimes a small stream of cold air comes one after another, causing low temperature and rainy days, which is not good for agricultural production. According to this feature, we should make full use of the weather forecast, grasp the cold tail and warm head, and sow in time.

Qingming Festival

Qingming is a solar term representing phenology, which means sunny weather and lush vegetation.

As the saying goes: "Snow breaks Qingming, frost breaks Grain Rain." From Qingming to Qingming, the basin has a warm climate and strong spring. However, before and after the Qingming Festival, cold air still invaded from time to time, even making the daily average temperature lower than 12℃ for more than three days, resulting in rotten seedlings of middle rice and dead seedlings of early rice. Therefore, rice planting and transplanting should avoid warm tail and cold head. In the western Sichuan Plateau, livestock are affected by severe winter and insufficient feed.

"There are many rains 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. But as far as Sichuan is concerned, this is not the case. Especially in the west of the basin, it is often in the spring drought period, and the rainfall in early April is generally only 10 to 20 mm, which is less than half of that in the south of the Yangtze River. Although there are many spring rains in the eastern part of the basin, the rainfall in early April is generally only 20 to 40 mm, and the natural precipitation is not enough to meet agricultural production. It must be replenished years ago. In addition, April is the month with the most hail in Liangshan Prefecture, so the prevention of hail disaster should be strengthened.

Grain Rain

As the saying goes, "Rain gives birth to a hundred grains". With sufficient and timely rainfall, cereal crops can thrive. Grain Rain solar terms have such a meaning.

In Grain Rain season, Sichuan Basin is full of flowers, willow leaves fall, cuckoos cry at night, peonies bloom and cherries are ripe. The natural scenery tells people that it is late spring. At this time, the temperature in the basin rose 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 for the northern and western parts of the basin. People began to feel hot. The low-altitude valleys in southwest Sichuan can enter summer. The climatic characteristics of high temperature in spring in the basin are conducive to mastering the early crop cultivation measures in Da Chun. The suitable temperature for planting sweet potato is 18℃ to 22℃, which can be satisfied at this time. The experience in the old arid area of the river basin proves that sweet potatoes can be planted early after Grain Rain, and vine leaves can be sealed before summer drought.

At this time, the eastern part of the basin in our province is full of rain. The rainfall in late April of the year is about 30 to 50 mm. The first rainstorm usually occurs in this period, which is beneficial to rice planting and the growth of corn and cotton at seedling stage. However, the rainfall in most other areas of the basin is less than 30 mm, so irrigation measures should be taken to alleviate the impact of drought. The mountainous area of the western Sichuan Plateau is still in the dry season, and the precipitation is generally only 5 to 20 mm, and the rainfall around Grain Rain in the basin often "sneaked into the night with the wind". Moisturize things quietly, and the frequency of "late rain" is the highest in April and May. "It often rains at night in Sichuan and the river sill is clear", which is quite suitable for crop growth and early spring harvest in Da Chun.

Early 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 in summer is higher than 22℃, the southern Sichuan Basin has just entered summer around the long summer. The temperature in the other basins is about 20℃, and it is still in the late spring season of "no one outside the door asks about falling flowers, and Ran Ran is all over the world"; The low-altitude valley in southwest Sichuan felt the heat of summer as early as mid-April, and the temperature in long summer has reached above 24℃, which can be described as hot summer. Yi Wei has a long summer's theory of "seeing with electricity" However, as far as Sichuan is concerned, even in the northwest of the basin where the first thunder occurred at the latest, the perennial thunderstorm began in mid-April, so "seeing by electricity" does not have to wait for a long summer.

After the long summer, it is the critical period of water demand for large-scale cultivation of mid-season rice in the basin. The early and late arrival of rainstorm and the amount of rainfall are closely related to agricultural production. At this time, if there is no rainstorm, those farmland without water irrigation can't grow pears. According to climate statistics, the average beginning period of heavy rain for many years is in the middle and late April in the east of the basin, and in the middle and late May and late May in the west. The rainfall in the southeast of the basin in May was 65438.

During this period, when harvesting and sowing crops in early spring in Da Chun, we should pay special attention to the influence of changeable weather. We should harvest crops in time on sunny days and sow in rainy days. Even in rainy days, we should be alert to the germination and mildew of crops harvested in Koharu, do a good job of drought resistance and seedling protection, and be alert to the harm of low temperature below 20℃ to early rice.

Grain Buds

Most of the 24 solar terms can be defined by their names, but Xiaoman is somewhat puzzling. Originally, Xiaoman refers to summer crops such as wheat, which are full of milk and full of seeds. Agricultural proverbs in Sichuan basin give Xiaoman a new meaning: "Xiaoman is dissatisfied, but it is difficult to think"; Small crops are not satisfied, regardless of awn seeds. The word "full" is used to describe the amount of rain. It has been pointed out that if the field is not full of water, the ridge may crack, and even if it is full of water, rice can't be planted. Because "transplanting rice in long summer and planting rice in small crops" and "seedlings rush to small crops and autumn crops", small crops are a good season for planting rice. Is the summer drought serious in the basin, and what is the rice planting area? Planting sooner or later is closely related to rice yield. The central and western parts of the basin often suffer from winter drought and spring drought, and the rainstorm comes late. In some years, it will not rain until June, or even as late as July. In addition, the annual rainfall in Xiaoman solar term is not much, with an average of only about 40 mm, and the natural rainfall can not meet the water demand for planting seedlings, which makes the summer drought in the middle of the water-deficient basin more serious. As the saying goes, "storing water is like storing grain" and "preserving water is like preserving grain". In order to resist drought, in addition to improving cultivation measures and speeding up afforestation, special attention should be paid to water storage and conservation in the first year. However, we should also pay attention to the influence of possible continuous rainy weather on crop harvest and sunshine in early spring. At this time, most crops in the mountainous areas of western Sichuan Plateau have entered the rainy season.

Grain in Ear

Miscanthus is a solar term, representing the maturity of crops with awns, such as wheat. By the time Miscanthus arrived, the wheat harvest season in Sichuan Basin had passed, and the transplanting of mid-season rice and sweet potato was 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 dyes 3,000 hectares and herons fly everywhere" vividly depicts the beautiful scenery of the fields at this time.

In the awning season, the medium rice that has not been transplanted in the basin 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 period will be easily affected by drought and diseases and insect pests, and the yield will inevitably be low. Osmunda japonica should be transplanted before the summer solstice at the latest; If sowing is too late, not only will the influence of drought be aggravated, but the temperature will also drop in Qiu Lai, which is not conducive to the expansion of potato pieces and the yield will be significantly reduced. This is the truth of the agricultural proverb "busy planting".

Summer solstice

On the solstice of summer, the sun shines directly on the Tropic of Cancer, which is the longest day of the 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 angle, it is not the hottest time of the year, because the heat near the ground is still accumulating and has not reached the maximum.

After the summer solstice, the agricultural production in the basin of our province entered the field management period because of the vigorous growth of crops and the rapid growth and spread of weeds and pests, and the plateau pastoral area began the golden season of flourishing grass, fertilizer and livestock. At this time, the rainfall in the west of the basin increased obviously, which gradually changed the distribution trend of rainfall in the east since the spring. If there is a summer drought, it is generally expected to be lifted at this time. In recent 30 years, large-scale floods in late June rarely occurred in the western part of the basin. However, the degree is serious. Therefore, special attention should be paid to flood control. The solar term from summer solstice is the solar term with the largest annual rainfall in the eastern part of the basin, which 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 rain before the arrival of summer.

After the summer solstice, the ground is heated strongly and the air convection is strong. Thunderstorms often form in the afternoon and evening. This kind of hot thunderstorm comes and goes, and the rainfall range is small. People call it "summer rain separates the ridge". In Sichuan, Liu Yuxi, a poet in the Tang Dynasty, skillfully used this weather as a metaphor and wrote a famous poem "It rains in the east and rains in the west, but it is sunny on the road".

Minor Heat

Trees are thick and shady, sometimes in light summer. The average summer temperature in Sichuan Basin is around 26℃, which is already midsummer and quite hot, but it is not the hottest time yet. In mid-July, the concentration period of daily average temperature higher than 30℃ and daily maximum temperature higher than 35℃ can begin to appear in the low-altitude valley area in the southeast of the basin, which is not conducive to heading and flowering of hybrid rice. Besides, this factor should be fully considered in advance and has been planted.

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. Mountain torrents often occur in places with large relief, and even cause mudslides. The eastern part of the basin, after experiencing a slight summer heat, began to enter the summer drought period because of the subtropical high, sunny weather and high temperature. The climatic characteristics of this basin in our province have a great relationship with the abundance and abundance of agriculture.

Around the summer heat, it is the most frequent season of thunderstorms in all parts of our province. Thunderstorm is a disastrous weather phenomenon, often accompanied by strong winds, heavy rains and sometimes hail, which is easy to cause disasters, so we should pay attention to prevention.

Major Heat

Summer means heat. Explanation is the hottest solar term in a year.

Generally speaking, the summer solar term is the period with the most sunshine and the highest temperature in a year, the period with the most abundant rainfall, the most common thunderstorm and the most concentrated days with high temperature above 30℃ in the west of the basin, and the period with the most frequent occurrence of high temperature above 35℃ in the east of the basin.

The high temperature around summer is a sign of normal climate, because higher temperature is beneficial to the flowering and filling of crops in Da Chun. However, if the temperature is too high, it will inhibit the growth of crops and the seed setting rate of rice will decrease obviously. After the collapse of the western part of the basin, light, heat and water are at the peak of the year, which promote each other and form good climatic conditions for crop growth in Da Chun, but attention should be paid to flood control and drainage. At this time, the long-term high temperature exposure in the eastern part of the basin is often accompanied by little rain. This will not only limit the advantages of light and heat, but also increase the adverse effects of major spring and summer droughts on crops. In order to resist the summer drought, we should not only pay attention to the early water storage, but also improve the crop cultivation measures according to the climate characteristics in the eastern part of the basin, based on "early" and seek advantages and avoid disadvantages.

The sultry summer is the season when jasmine and lotus are in full bloom. The more fragrant jasmine is, the more fragrant it is, giving people a clean and fragrant enjoyment. Noble lotus flowers are not afraid of the sun and showers, and they open and close at dusk. The poet praised it as "another color of lotus", and the vibrant summer is gestating a bumper harvest.

Beginning of Autumn

"It's cool on beginning of autumn Day" obviously associates beginning of autumn with cool weather. It can be seen that beginning of autumn is the beginning of cool autumn. Because of the different latitudes and altitudes, it is practically impossible to enter autumn at the same time in beginning of autumn. According to the climatological standard that the average temperature in China (5 days) is between 10℃ and 22℃, except for north latitude and west longitude. It's still hot in summer, even in most parts of Northeast China, there is no cool breeze and yellow leaves fluttering in autumn scenery at this time. For the Sichuan Basin located in the middle subtropical zone, the summer heat is still heavy in August all the year round. According to the statistics of climate data, the basin will not enter autumn until the middle and late September. It is impossible to say when autumn begins in the plateau and mountainous areas where winter is all the year round or winter is very long without summer and spring and autumn.

After beginning of autumn, at the jointing and booting stage of late rice in our basin, cotton bolls cracked and vomited, which could not relax field management at all; Mid-season rice and summer corn enter the stage of filling maturity, so it is necessary to guard against the harm of hail, strong wind and heavy rain. In the eastern and western parts of the basin, we should continue to do a good job in drought relief and flood control respectively. Although it is still midsummer in the basin after autumn, a golden "autumn" is coming.

The heat is over

Summer is a solar term reflecting the temperature change. "Chu" means hiding from the end, and "Chu" means that the hot summer has passed.

The average temperature in our basin is generally about 65438 0.5℃ lower than that in early autumn. In late August of some years, the average daily temperature in the western part of the basin may be lower than 23℃ for more than three consecutive days, which will affect the flowering of hybrid rice. However, because 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 that in the east of the basin is higher than 35℃. Especially in the low-altitude areas along the Yangtze River, I felt the afterglow of the "autumn tiger" in the years when the summer drought lasted. When summer comes in the western Sichuan Plateau, autumn is strong. It is early winter at an altitude of more than 3,500 meters, with withered vegetation and increasing frost and snow day by day.

Summer is the early stage of the transformation of rainfall distribution in our province from more in the west to less in the east. At this time, the rainfall in the central part of the basin is often the second highest point in a year, which is more than that in summer or the white dew period. Therefore, in order to ensure farmland water use in winter and spring, we must do a good job of water storage in this period. From summer to autumnal equinox, there will be continuous rainy weather in the plateau, which is unfavorable to agricultural and animal husbandry production. At this time, our basin is also a busy season for harvesting mid-season rice. Generally speaking,; In the case that "the dog days pass and the sun turns into rain", the autumn rain will come ahead of time. Therefore, we should pay special attention to the weather forecast, make full preparations, seize every sunny day, seize the opportunity to grab the harvest and the sun.

White Dew

Dew is water droplets formed by condensation of water vapor on the ground or near-earth objects due to temperature drop. Therefore, the Millennium actually indicates that the weather is getting 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 rain in Mao Mao and the sudden decrease of sunshine, which profoundly reflects the seasonal transition from summer to autumn. The average temperature of the basin in the perennial white dew period is about 3℃ lower than that in summer, and the average temperature in most areas (5 days) has been continuously reduced to below 22℃. According to the standard of dividing four seasons by climatology, the time series begins to enter autumn.

The autumn rain in the basin mostly occurs before the white dew reaches the first frost, most in the middle and lower reaches of Minjiang River and Qingyi River, and relatively less in the middle of the basin. Although the agricultural proverb "If it rains every day in the Millennium" cannot be used as a weather forecast, there is always a period of continuous rainy weather before and after the Millennium Festival. Moreover, since then, rainfall in the basin has been characterized by low intensity, frequent rainy days and continuous rainfall. Correspondingly, the sunshine in the basin during the white dew period suddenly decreased by about half compared with that in summer, and this decreasing trend continued until winter.

The above climatic characteristics in the Millennium season are not conducive to heading and flowering of late rice and bursting of cotton peaches, but also affect the harvesting and sunning of mid-season rice. Therefore, there is a saying in agricultural proverbs that "the weather is good for a thousand years, and the rice in the valley is as white as silver". Only by fully understanding the Millennium climate characteristics and taking corresponding agricultural technical measures can the harm of autumn rain be alleviated or avoided. On the other hand, we must catch rainwater to store water, especially in the eastern part of the basin, which is following Xiaoman and summer solstice.

Autumn Equinox

The autumnal equinox is a solar term representing seasonal changes. At the autumnal equinox, the sun is located at 180 degrees, and the sunlight is almost direct to the equator, and the length of day and night is almost equal. At this time, the waiting temperature in Sichuan basin has generally dropped below 22℃, and it has entered a cool autumn. "An autumn rain and a cold". The cold air from the south meets the warm and humid air that gradually decays, resulting in repeated rainfall and the temperature dropping again and again.

After the autumnal equinox, the rainfall in our province is obviously reduced, and heavy rain and heavy rain generally rarely appear; However, rainy days increase, rainy days are frequent, and the night rain rate is high. Li Shangyin, a famous poet in the Tang Dynasty, famously wrote the poem "Autumn Pool Rains at Night", which vividly described the climate characteristics of autumn rainy nights in Sichuan.

There are many rainy days in autumn in our basin and Liangshan Prefecture, and the wet damage is serious, which has a great influence on autumn harvest, autumn tillage and autumn planting. We should seize sunny days to collect sunlight, do a good job in soil moisture and flood prevention, and do a good job in the quality and progress of production in Sanqiu. At the same time, we should make full use of the meteorological conditions of less rain and good soil moisture in autumn, and make great efforts to plant trees and improve the survival rate of saplings.

Cold Dew

In ancient times, dew was considered as a sign that the weather turned cold. The solar term of Mid-Autumn White Dew is "dew condenses white". When it is cold in the season and autumn, it is already "dew is cold and will condense" into frost.

At this time, the temperature in all parts of our province continued to drop. The average daily temperature in the basin is below 20℃. Even in the areas along the Yangtze River, it is difficult for the mercury column to rise above 30℃, while the minimum temperature can be reduced to below 10℃. Except for a few valley lowlands, the five-day average temperature in the western Sichuan Plateau is generally lower than 10℃, which is measured by the four-season climate division standard.

In the cold dew year, the rainfall in the basin is also decreasing day by day. The western part of the basin is about 20 mm, and the eastern part is generally about 30-40 mm, with frequent rainfall, which affects the production of "Sanqiu" and has become a disastrous weather in the basin of our province. The accompanying climatic characteristics are: high humidity, more clouds, less sunshine and more cloudy days. On the other hand, according to local conditions, we should take various effective farming measures such as deep ditch and high compartment 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 hinders traffic and harms animal husbandry production, so we should pay attention to prevention.

People will celebrate the annual traditional festival.

Frost's Descent

The first frost solar term means that the weather is getting colder, and first frost begins. In the south of Sichuan Basin, the average temperature is around 16℃, and there are still three solar terms before the first frost day. In the valley area in the south of the basin, frost can only be seen in the middle of winter. Of course, even at the same latitude, the temperature and humidity of the ground air are different due to different altitudes and topography, and the first frost period and frost day are different.

From a scientific point of view, the saying that "dew becomes frost" is not accurate. The frozen dew formed by dew freezing is hard small ice beads. Frost refers to the phenomenon of crop freezing injury caused by the sudden drop of temperature, and its harmful 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 water vapor content in the air on the ground should reach a certain level. Therefore, frost does not necessarily occur when frost occurs, nor does it necessarily occur when frost occurs. However, due to the low temperature when frosting, if the temperature continues to drop, it is easy to cause frosting. After the first frost, a large number of flat storage were collected and excavated in our basin. If it is collected too early, it is easy to cause frost. But if the harvest is too late, it may be damaged by early frost, and the block will be frozen and deteriorated, so it is very important to dig it out in time.

Su Shi, a great writer in the Northern Song Dynasty, said in a poem: "Thousands of trees are yellow, and only Furong is alone." The climate in Sichuan Basin is mild. In the first frost, the fields are lush, orange, yellow and green, and autumn chrysanthemums are in full bloom, which makes the rich "Tianfu" more gorgeous.

Beginning of Winter

Speaking of "winter", it will naturally be associated with cold. "Stand and start" means that winter has begun. "On that day in beginning of winter, the water began to freeze and the ground began to freeze." Nowadays, people often take the biting north wind and cold frost and snow as symbols of winter. There is little frost and snow in our river basin. Therefore, in climatology, the day of "beginning of winter" is not fixed as beginning of winter everywhere.

In early winter, China's river basins are still in the peak season of "Sanqiu", and the average temperature is generally between 65438 02℃ and 65438 05℃. The rainy season has ended, and the climatic conditions are suitable for rape transplanting. Wheat with short growth period and strong elasticity 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, seedling emergence is slow and isolation is insufficient, the yield will be affected. When the daily average temperature is lower than 15℃, the growth of Osmunda japonica has gradually stopped and should be harvested in time. Early frost has appeared in early winter in some years in the northwest of the basin. In order to avoid freezing injury, the pit should be dug as soon as possible. At this time, the plateau area is already in the dry season, the humidity decreases rapidly and the wind speed increases, so we must be highly alert to forest fire.

snow

Light snow indicates the beginning time and degree of snowfall. Snow is the product of cold weather. Light snow solar terms, the northern Sichuan basin began to enter winter. "Lotus leaves no rain, chrysanthemum leaves frost branches", which has already shown the scene of early winter. Because the northern foot of Qinling Mountain and Daba Mountain have barriers to prevent the invasion of cold air, the severity of the cold wave has been reduced, resulting in an obvious "warm winter" in the basin. The number of snowfall days in the whole year is less than five days. It is much less than the middle and lower reaches of the Yangtze River at the same latitude. There is little chance of snowfall before the heavy snow. Even in the dead of winter, it is rare to see the charming scenery of "blowing open the petals of ten thousand pear trees". Because the temperature near the surface of the basin is often above 0℃ in winter, it is more difficult to snow than to snow. Although the sky buzzes occasionally, there is no "broken jade" on the ground. However, in the cold western Sichuan Plateau, it is 65,430 years old.

During the light snow period, the first frost usually appears in the northwest of the basin, so it is necessary to prevent frost from harming crops. The lowest temperature in Gansu and northern Afghanistan is around-15℃, so it is necessary to keep livestock warm and cold.

Major Snow

"Heavy snow" indicates that the snowfall has begun to increase. 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 it snows, mostly in 1 and February. It is rare to see snow on the ground once every three to five years. It is often an unforgettable pleasure to witness the snow-covered earth and the green trees wrapped in silver.

"Snow will bring good harvest" is an agricultural proverb widely circulated in China. In the north, a thick layer of loose snow is like a quilt covering wheat to resist the cold. There are four times more nitrogen compounds in snow than in rain. Snow slowly melts and penetrates 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 surface and bring benefits to agricultural production. However, in the south, it can also bring benefits to agricultural production.