What are the twelve solar terms related to?

By naming 24 solar terms, we can see that the division of solar terms fully considers the changes of natural phenomena such as seasons, weather and phenology. Spring, summer, autumn and winter reflect the beginning of the four seasons. From the astronomical point of view, it is divided into vernal equinox, autumnal equinox, summer solstice and winter solstice, which reflects the turning point of solar height change.

The five solar terms of small tree, big book, straight book, small culvert and adult reflect the change of temperature and are used to express the degree of heat and cold in different periods of the year. The four solar conditions of rainfall, Grain Rain, light snow and heavy snow reflect the phenomenon of precipitation, indicating the time and intensity of rainfall and snowfall; The three solar terms, the Millennium, Coody Leng and the first frost, reflect the condensation phenomenon. But in essence, it reflects the process and degree of gradual temperature decrease: when the temperature drops to a certain extent, water vapor will condense, and the temperature will continue to drop, not only the condensation will increase, but also the temperature will drop. When the temperature drops below zero degrees Celsius, water vapor will condense into frost.

Xiaoman and Miscanthus reflect the maturity and harvest of crops, clearly reflect the natural phenology, and predict the coming of spring with the first thunder and the recovery of underground lobsters. Beginning of spring is the first of the 24 solar terms, which means the beginning of spring.

At this time, it rains, the spring breeze blows, the snow melts, the air is humid, and the rain increases, so it is called rain. People often say, "It's getting hotter and hotter in spring, and it's raining harder and harder." After the festival said "spring", the weather turned warmer and the spring thunder alarmed my mother. Hibernating animals crouch in the mud, wake up and start to move, and insects will also start to hatch.

On this day, the two hemispheres are equal day and night, so it is called vernal equinox. After this day, the position of the sun moves directly to the north, and the northern hemisphere is longer and shorter. Then the vernal equinox began in the northern hemisphere, and most winter crops in China have entered the spring growth period.