Swallows come to Xinhua News Agency. What phenological phenomenon does pear blossom reflect backwards in Qingming?

"When Swallows Come, Information Office, Tomb-Sweeping Day, pear flower falls" reflects the following phenological phenomena:

The Spring Festival society is approaching, and I have come back at the beginning of my life.

During the Qingming Festival, the weather gradually gets warmer, and begonias and pears fall out.

Phenological phenomena are very extensive. In nature, those natural phenomena that are influenced by the environment (climate, hydrology, soil) and have a cycle of years belong to phenological phenomena.

Phenological phenomena include three aspects:

(1) Plant phenology is also called crop phenology, such as germination, leaf spreading, flowering, leaf discoloration and defoliation of various plants, and phenology during crop growth.

(2) Animal phenology, such as migration, first song, last song and hibernation of migratory birds, insects and other animals.

(3) Various hydrometeorological phenomena, such as first frost, last frost, freezing, melting, first snow, last snow and other natural phenomena.

Xinhua News Agency: Social Day is an ancient festival to worship the land god and pray for a bumper harvest. There are two clubs, spring and autumn. The new society is a spring society, and the time is after beginning of spring and before Qingming.

Twenty-four solar terms, spring equinox and Qingming, is the most unforgettable season in spring. Spring is already in the middle, and new swallows are coming. At this time, social day will also come. The ancients called the swallow a gregarious swallow, thinking that it often came from the Spring Society and went to the Autumn Society. The poet's "new society" refers to the society in spring. At that time, there were two social days in spring and autumn every year, especially spring clubs, neighborhood gatherings, food and wine sharing, and games were full of joy. The girls in the boudoir have also "let go" of "fake". As the saying goes, "Please stop sewing in society", even sewing can be put down and sisters can be called to play outside. This is the spirit of the first sentence of this poem.

Reference link:

Phenology _ Baidu Encyclopedia

Breaking ranks, when swallows come, Xinhua News Agency _ Baidu Encyclopedia