Climatic characteristics of autumnal equinox

The autumnal equinox is a solar term representing seasonal changes. On the day of the autumnal equinox, the cold air from the south meets the warm and humid air that gradually decays, resulting in continuous rain and continuous temperature drop. In the northern part of the northwest plateau, the daily minimum temperature has dropped below 0℃, and you can already see the magnificent snow scene flying all over the sky and the earth wrapped in silver. After the autumnal equinox, rainfall in most parts of the south decreased significantly, and heavy rain and heavy rain rarely appeared. 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 said, "It rains at night in autumn pond", which vividly describes the climate characteristics of autumn rainy nights in the south.

According to meteorologists, according to the lunar calendar, "beginning of autumn" is the beginning of autumn, and "first frost" is the end of autumn. The "vernal equinox" is exactly half of the 90 days from beginning of autumn to the first frost. From the day of the autumnal equinox, the climate has three main characteristics: the position of direct sunlight continues to move from the equator to the southern hemisphere, and the phenomenon of short days and long nights in the northern hemisphere will become more and more obvious. The days will gradually shorten and the nights will gradually lengthen (until the winter solstice reaches the longest night and the shortest day); The temperature difference between day and night will gradually increase, and the amplitude will be higher than 10℃. The temperature drops day by day, getting colder every day, and gradually entering the late autumn season. The situation in the southern hemisphere is just the opposite.

At the autumnal equinox, the Yangtze River basin and its vast northern area have entered autumn, and the daily average temperature has dropped below 22℃. The cold air mass in the north began to have some influence. In most areas, the rainy season has just ended, with a cool breeze blowing gently, the sky is high and the clouds are light in Wan Liqing, the air is crisp in autumn, the sweet-scented osmanthus is fragrant, the crab is fat and the chrysanthemum is yellow, and the autumn equinox is a beautiful and pleasant season. It is also an important solar term in agricultural production. After the autumnal equinox, the direct sunlight moved to the southern hemisphere, and the northern hemisphere got less and less solar radiation, while the ground lost more heat and the temperature dropped significantly. Agricultural proverbs say: "An autumn rain is a cold", "The white dew is divided into autumn nights, and one night is cold". "In August, the wild goose gate opens, and the foot of the wild goose is frosty." It is not surprising that the temperature in Northeast China drops early and frost appears at the autumnal equinox. The rapid cooling in autumn makes the autumn harvest, autumn ploughing and autumn planting "Sanqiu" particularly nervous. The autumnal equinox is a good time to harvest cotton and tobacco leaves from green to yellow. Winter wheat has been planted in North China, and the Yangtze River basin and vast areas in the south are busy harvesting late rice and ploughing the land to prepare for rape sowing. Drought and lack of rainfall or continuous rainfall in autumn equinox are the main unfavorable factors affecting the normal operation of Sanqiu, especially the continuous rainfall will make the upcoming crops lodging, mildewing or sprouting, resulting in serious losses. "Sanqiu" is a great help, and the word "early" is the key. Timely harvest of crops in autumn can avoid the harm of first frost and continuous rain, and timely sowing of crops in winter can make full use of heat resources before winter, cultivate strong seedlings to survive the winter safely, and lay the foundation for high yield in the coming year. The autumnal equinox doesn't appear, so cut it and feed it to the old cow. Heading and flowering of double-cropping late rice in South China is the key period for yield formation. The "autumnal equinox" weather formed in advance in low temperature and rainy weather is the main threat to the flowering and fruiting of double-cropping late rice, so we must do a good job in forecasting and defense.

It is rainy and humid in autumn in the south and Liangshan Prefecture, which has great influence on autumn harvest, autumn ploughing and autumn planting. We should catch the sun, control soil moisture and prevent waterlogging, and pay special attention to the quality and progress of production in Sanqiu. At the same time, we should make full use of the meteorological conditions of rainy autumn and good soil moisture, seize the opportunity to do a good job in afforestation, and strive to improve the survival rate of saplings.