What is the method and basis for the division of the four seasons?

The division of the four seasons, there are the following methods:

1. Astronomical division method From the astronomical phenomenon, the change of the four seasons is the length of the day and night and the height of the sun seasonal changes. In a year, the longest day, the sun's height is the highest season is summer, the shortest day, the sun's height is the lowest season is winter, winter, summer and the transition season is spring and fall. For this reason, the astronomical division of the four seasons method, that is, the spring equinox (March 21), the summer solstice (June 21), the autumn equinox (September 21), the winter solstice (December 21) as the beginning of the four seasons. That is: spring equinox to summer solstice is spring, summer solstice to autumn equinox is summer, autumn equinox to winter solstice is autumn, and winter solstice to spring equinox is winter.

2. Meteorological divisions in the meteorological department, usually in the solar calendar March to May for the spring, June to August for the summer, September to November for the fall, December to the next year in February for the winter, and often 1, 4, 7, October as the representative months of winter, spring, summer, and autumn.

3. Ancient divisions Spring (February 4 or 5) as the beginning of spring, summer (May 5 or 6) as the beginning of summer, autumn (August 7 or 8) as the beginning of autumn, winter (November 8 or 9) as the beginning of winter.

4. Lunar calendar division method Chinese folk custom to use the lunar month to divide the four seasons. January to March of the lunar calendar for spring, April to June for summer, July to September for fall, October to December for winter. The first day of the first month is the first day of the year and the first day of spring, so it is also called the Spring Festival.

The above methods are simple and convenient, but there is a **** the same shortcomings, that is, all over the country on the same day to enter the same season, which is very different from the actual situation in various regions of China. For example, in accordance with the above method of division, March has been in the spring, when the south of the Yangtze River is indeed red and green, spring is strong; and the northern part of the Heilongjiang River is cold, icy and snowy, no spring; Hainan Island people have been wearing a single coat over the summer. In order to make the four seasons can be divided with the natural scenery and the rhythm of people's lives, the meteorological department to take the temperature division of the four seasons method.

5. Waiting temperature division method

This division method is to wait (five days for a wait). The average temperature as the division of the four seasons of the temperature index. When the average temperature stabilized above 22 ℃ for the beginning of summer, the average temperature stabilized below 10 ℃ for the beginning of winter, the average temperature between 10 to 22 ℃ for the spring and fall. From 10 ℃ to 22 ℃ is spring, from 22 ℃ down to 10 ℃ is fall.