On what basis are the seasons of spring, summer, fall and winter divided?

(1), The four seasons are divided according to the length of day and night and changes in the altitude of the sun. In the division of the four seasons, the apparent position of the sun on the ecliptic is used as the basis, and the bifurcation day, the second solstice day, or the fourth risen day is used as the boundary. However, the boundary points used in dividing the seasons are not exactly the same in Eastern and Western countries.

(2), the first classification: China's traditional method of dividing the four seasons is based on the four seasons in the twenty-four seasons as the beginning of the four seasons, and the two minutes and two solstices as the midpoint. Such as the spring spring as the starting point, the sun's ecliptic is 315 °, the spring divided into the midpoint, the summer as the end point, the sun's ecliptic becomes 45 °, the sun in the ecliptic runs 90 °. This is a traditional, common method .

(3), the second classification: astronomical classification (i.e., the Western classification) of the four seasons to emphasize the climatic significance of the four seasons, is to two minutes and two solstices as the starting point of the four seasons, such as spring to spring into the starting point to the end of the solstice for the termination point. This four seasons than China's traditional division of the four seasons respectively one and a half months late.

(4) Shallow theory: '1 spring and fall equinoxes, the length of day and night and the height of the sun across the globe are equal to the average value of the whole year, with the typical characteristics of the transition from the great (or very small) to the great (or very small). Therefore, the vernal equinox as the midpoint of spring, and the autumnal equinox as the midpoint of autumn is very reasonable; in summer, the day is the longest, the night is the shortest, the sun's altitude is the largest summer solstice day, the surface of the earth to obtain the sun's energy is the most. Therefore, the summer solstice as the midpoint of summer is very reasonable; similarly, the winter solstice as the midpoint of winter is also very scientific.

But, from the actual climate, the summer solstice is not the hottest time, the winter solstice is not the coldest time, the extremes of high and low temperatures are delayed for 1 to 2 months. Our country has "hot in three volts", cold in three nine "said. Therefore, the summer solstice and winter solstice are arranged as the beginning of summer and winter respectively, which can better correspond to the actual climate. Therefore, the Western division of the four seasons better reflects the actual climate significance.

Both the astronomical division of the seasons in China and the climatic division of the seasons in the West are astronomical divisions. This is because the two divisions, the two solstices and the four risings all have exact astronomical meanings, and all divide the year into four roughly equal seasons of three months each, with the sun orbiting 90° on the ecliptic. None of them reflect the actual conditions of the climate of each place. The seasons divided by this method are the astronomical seasons.

The astronomical seasons are hemispherically uniform. Within the boundaries of the hemisphere, each season has a uniform beginning and ending moment, and all four of these seasons, each of equal length, exist at every location within the hemisphere.

(5), the third classification: in order to accurately reflect the actual climate of each place, the division of the four seasons often use the climatic method both modern scholars Zhang BaoKun classification, the use of the candidate average temperature division of the four seasons. And the provisions: the average temperature is greater than or equal to 22 ℃ for the period of summer, less than or equal to 10 ℃ for the period of winter, between 10 ℃ ~ 22 ℃ for the spring or fall. By dividing the seasons according to this standard, the seasons and climate in the mid-latitude region are consistent, and the temperature changes in spring, summer, fall and winter in the low-latitude region and near the poles are very inconspicuous. At the same time, in the mid-latitudes, the length of the seasons is not the same. These are the climatic seasons. For example, in Beijing there are 55 days in spring, 103 days in summer, 50 days in fall and 157 days in winter. This method, can be combined with the specific climate of each place, agriculture, so the use of more...

(6), the fourth classification: climate statistics, because January is generally the coldest month, therefore, the spring, for March, April and May. In summer, it is June, July and August. In the fall, it is September, October and November. In winter, it is December, January and February. This classification of seasons is more suitable for temperate regions with four distinct seasons.

(7), astronomical seasons have theoretical significance, climatic seasons have practical value. Astronomical seasons are the basis for the division of climatic seasons. Astronomical seasons are hemispherically unified. The northern hemisphere is summer, the southern hemisphere is winter; the climatic seasons are unified in the local area (mid-latitude). The division of astronomical seasons depends on changes in astronomical phenomena, and the division of climatic seasons depends on changes in temperature. The astronomical seasons are of equal length regardless of the location in either hemisphere, while the climatic seasons are not necessarily of equal length in the same location. This is the main difference between astronomical and climatic seasons.