Four seasons refer to the four seasons that appear alternately in a year, namely, spring, summer, autumn and winter, and each season lasts for three months. All the year round is formed because the earth revolves around the sun.
Due to the existence of the ecliptic angle, the direct point of the sun moves back and forth between 23 26' in the north and south latitudes of the earth, resulting in the change of the height of the sun at noon and the change of the length of day and night, resulting in the change of seasons.
The commonly used methods of seasonal division mainly include "solar terms method" and "temperature method". Traditionally, China takes "Sili, beginning of spring, long summer, beginning of autumn and beginning of winter as the start of spring, summer, autumn and winter respectively.
Zhang Baokun, a modern scholar, put forward a new seasonal standard, which takes the average temperature (the average temperature for five consecutive days) as the beginning of winter and rising to above 22℃ as the beginning of summer. The average temperature in 10-22℃ is spring or autumn.
spring
The four seasons appear alternately in a year, and the change of the four seasons throughout the year is a continuous process. It is also a process of yin-yang transformation, which changes from one side to another, and quantitative change produces qualitative change. In this gradual process, beginning of spring, long summer, beginning of autumn and beginning of winter, also known as the "Four Stands", are the opening of the season.
Spring ranks first among the four seasons, and a new cycle begins. Spring represents warmth and growth. In spring, the qi of Yin and Yang began to change, and everything sprouted and grew with the rising of yang. Spring is the season for everything to grow and sow in spring. The so-called "one year's plan lies in spring".
Spring begins and ends:
According to the method of solar terms: traditionally, the beginning of spring (when the sun reaches 315 of the yellow meridian) is taken as the starting point of spring and ends before long summer.
According to the temperature method: in modern times, the scholar Zhang Baokun's "waiting average temperature" was adopted, which started in spring and ended when the waiting average temperature rose steadily from below 10℃ to above 10℃ for five consecutive days.
summer
Everything is flourishing in summer, which is a season for crops to grow in the peak season. The temperature rises, the weather is hot, the storms are frequent, and everything is prosperous. Summer is the season with the most storms, often accompanied by strong winds and heavy rains.
In summer in the northern hemisphere, the continental heating pressure rises to form a low pressure, and the ocean constant temperature is relatively low to form a high pressure. According to the circulation, the southeast wind blows in summer. In summer, the daytime is the longest in all parts of the northern hemisphere.
Summer start-end:
According to the method of solar terms, it is divided into "long summer" (refers to the southeast, and the sun reaches 45 longitude of the Yellow River) as the starting point of summer and ends before "beginning of autumn". According to the temperature method, the summer begins when the average temperature rises to above 22℃ and ends when the average temperature is below 22℃.
autumn
Autumn is the harvest season, which means that everything begins to grow from lush to mature. In the first two solar terms of autumn, beginning of autumn is in summer, and it is still very hot. Because the heat brought by the sun has not weakened, the so-called "heat is in the dog days". The dog days appear between the summer heat and the summer heat, which is the highest, humid and sultry day of the year.
The reason for the high humidity in dog days is that the southeast wind blows in dog days, while the Pacific Ocean and Indian Ocean are in the southeast, so the air is humid and the humidity of the wind causes the high humidity in dog days. After the late autumn, it is the opposite. The northwest wind blows, and the northwest is dry inland. The dry northwest wind causes the climate to be dry after the late autumn.
The climate characteristics of the first two solar terms in autumn are humid and sultry. Generally, it is really cool in autumn until after the solar term of Bailu, and it gradually tends to be cool and dry from Bailu. As we enter the late autumn, the climate turns from hot to cold, and everything grows with the cold, and gradually falls. This is the season of alternating hot and cold.
Autumn begins and ends:
According to the method of solar terms, it is divided into "beginning of autumn" (refers to the southwest, and the sun reaches the yellow meridian135) as the starting point in autumn and ends before "beginning of winter". According to the temperature method, it is divided into three parts: the autumn begins when the average temperature drops from above 22℃ to below 22℃ and ends when the average temperature drops below 10℃.
winter
In winter, yin and yang change, everything is hidden from receipt, and plants are angry and closed. After entering beginning of winter, it means that the dry climate with little rain in autumn has gradually passed, and it has turned into a rainy and cold winter climate. The height of the sun in the northern hemisphere is small and the daytime is short.
The so-called "cold in March 9" and the winter solstice is "September 19". It was not very cold before the winter solstice. After the winter solstice, strong cold air frequently went south and crossed Nanling, and the temperature plummeted and the weather was cold. Winter is really cold, after the winter solstice.
Winter begins and ends:
According to the method of solar terms, it is divided into "beginning of winter" (the bucket refers to the northwest, and the sun reaches 225 longitude of the Yellow River) as the starting point of winter and ends before the next beginning of spring. According to the temperature method, the winter begins when the average temperature drops to below 10℃ and ends when the average temperature is above 10℃.