How to divide the four seasons into spring, summer, autumn and winter?

The four seasons are divided according to the length of day and night and the change of sun height. In the division of the four seasons, based on the apparent position of the sun on the ecliptic, the bisector, the second solstice or four days are the boundaries. However, the dividing points used by eastern and western countries in dividing the four seasons are not exactly the same.

Overview of the first classification method: The traditional method of dividing the four seasons in China takes four solar terms as the starting point of the four seasons and bisects them and bisects them to the midpoint. For example, in spring, starting from beginning of spring, the meridian of the sun is 365,438+05 degrees, with spring as the midpoint and long summer as the end point. The meridian of the sun becomes 45 degrees, and the sun moves 90 degrees on the ecliptic. This is a traditional and common method.

The second classification: astronomical classification (that is, western classification) emphasizes the climatic significance of the four seasons, and takes the vernal equinox of the sun as the starting point of the four seasons, such as spring as the starting point and summer solstice as the end point. These four seasons are one and a half months later than the traditional four seasons in China.

At the equinox, the length of day and night and the height of the sun around the world are equal to the annual average, which has the typical characteristics of transition from maximum (or minimum) to minimum (or maximum). Therefore, it is very reasonable to regard the vernal equinox as the midpoint of spring and the autumn equinox as the midpoint of autumn. In summer, the day is the longest and the night is the shortest, and the height of the sun is the highest on the day of summer solstice, and the surface gets the most solar energy. Therefore, it is very reasonable to take the summer solstice as the midpoint of summer; Similarly, it is very scientific to regard winter solstice as the midpoint of winter.

However, from the actual climate, summer solstice is not the hottest time, and winter solstice is not the coldest time, so the extreme temperature should be delayed by 1 ~ 2 months respectively. In China, there is a saying that "heat is in the dog days, and cold is in the three or nine years old". Therefore, taking summer solstice and winter solstice as the start dates of summer and winter respectively can better conform to the actual climate. Therefore, the division of four seasons in the west can better reflect the actual climate significance.

Whether it is the division of four seasons with astronomical significance in China or the division of four seasons with climatic significance in the west, it is an astronomical division method. This is because dichotomy, dichotomy and quartile all have exact meanings in astronomy. They all divide a year into four roughly equal seasons, each lasting for three months, and the sun moves 90 degrees on the ecliptic. None of them can reflect the actual situation of the local climate. The seasons divided in this way are the four seasons in astronomy.

The astronomical season is hemispherically unified. In the hemisphere, every season has a unified start and end moment. In the hemisphere, there are four seasons everywhere, and the length of each season is equal.

The third classification method: In order to accurately reflect the actual climate situation in various places, climatology is often used to divide the four seasons, that is, the classification method of modern scholar Zhang Baokun, which uses the average climate temperature to divide the four seasons. It is also stipulated that the period of climate average temperature ≥22℃ is summer, the period of average temperature ≤ 10℃ is winter, and the period between 10℃ and 22℃ is spring or autumn. According to this standard, the seasons in mid-latitude areas are consistent with the climate, while the temperature changes in low-latitude areas and near the polar regions are not obvious. At the same time, in mid-latitude areas, the length of each season is also different. These are the four seasons. For example, Beijing has 55 days in spring, 103 days in summer, 50 days in autumn and 157 days in winter. This method can be combined with the specific climate and agriculture in various places, so it is widely used.

The fourth category: climate statistics, because Leng Yue is generally 1 month, so spring is March, April and May; Summer is June, July and August; Autumn is September, 10,11; Winter is 12, 1 and February. This classification of four seasons is more suitable for temperate regions with distinct seasons.

Astronomical seasons have theoretical significance, while climatic seasons have practical value. Astronomical seasons are the basis for dividing climatic seasons. Astronomical seasons are unified in the hemisphere, with summer in the northern hemisphere and winter in the southern hemisphere. Climate seasons are unified in local areas (mid-latitude areas), and the division of astronomical seasons depends on the change of astronomical phenomena, and the division of climate seasons depends on the change of temperature. No matter where in any hemisphere, there are astronomical seasons of equal length; In the same place, the lengths of the four climatic seasons are not necessarily equal. This is the main difference between astronomical season and climate season.