Which region has four seasons?
1, astronomical division method: astronomical division method, with vernal equinox, summer solstice, autumn equinox and winter solstice as the beginning of the four seasons.
2. Meteorological division: March to May is spring, June to August is summer, September to165438+1October is autumn, and June to February is winter.
3. Division of solar terms: beginning of spring, Changxia, beginning of autumn and beginning of winter are four seasons.
The climate season division index is based on the waiting temperature method proposed by Mr. Zhang Baokun in 1934, and it is still used in meteorological operations. In ancient China, five days was called waiting period, and waiting temperature was the average temperature of five days. However, in the division of climate seasons, it is not a fixed five days, but a five-day moving average, that is, the average value is calculated by taking the current day and the first four days as a group.
Periodic change:
In ancient times, the direction of bucket handle determined the alternation of seasons, and the Big Dipper rotated in a circular way, which was closely related to the change of seasons. The current "twenty-four solar terms" come from the "fixed gas method" concluded more than 300 years ago (it has been used since 1645). "Fixed space method" is a method to determine solar terms according to the position of the sun on the ecliptic, that is, on a 360-degree circle "ecliptic" (the apparent path of the sun on the celestial sphere for one year), it is divided into 24 equal parts, once every 60 years.