What is the phenophase of the Millennium?

Millennium phenology refers to some specific changes and phenomena in environment and biology during the Millennium solar terms.

Millennium is one of the twenty-four solar terms, which usually occurs on September 7th or 8th in the solar calendar. It marks the end of the Qiu Meng season and the beginning of the Mid-Autumn Festival. According to the observation and records of ancient farming society, the phenology of the Millennium mainly includes the following aspects:

1, cooling down: in the Millennium season, the temperature gradually drops, the temperature difference between day and night increases, the heat gradually decreases during the day, and the cold air begins to radiate at night, making the overall temperature feel cool. The cold air turns to attack, and the warm air gradually recedes.

2. condensation: as the temperature drops, the moisture in the air begins to condense into dew. In the early morning or dusk, you can often see a layer of wet dew on the surface of grass, plant leaves and so on.

3. Migratory birds migration: During the Millennium season, migratory birds from the north such as Hongyan and Swan began to migrate to the south. Because the temperature drops gradually, migratory birds such as Hongyan need to fly south to avoid the cold. This is the biological instinct of migratory birds and a strategy to adapt to the environment.

4. Plant harvest: Some crops and fruits begin to mature, such as rice, corn and apples. This is an important period for farmers to harvest and pick.

5. Plants wither: Some plants begin to wither, and the leaves gradually wither and fall off. This is the physiological adjustment of plants to adapt to climate change.

The reason why the weather is cool in autumn is

1. Change of the Earth's rotation angle: Autumn is one of the stages of the Earth's revolution around the sun. When a certain area of the earth leaves the summer solstice, the angle of sunlight gradually decreases, which leads to the decrease of the average temperature and the gradual cooling of the weather.

2. Movement of the direct sunset area in the northern hemisphere: At the autumnal equinox, the direct sunset area in the northern hemisphere moves slowly from north to south, resulting in the overall climate in the northern hemisphere cooling. The long-term direct sunlight decreases, which makes the weather gradually cool.

3. Humidity and rainfall decrease: With the arrival of autumn, the humid climate in summer decreases gradually, and the rainfall decreases accordingly. Dry air gives off heat easily, which makes temperature sense cooler. In autumn, the atmospheric circulation pattern changes, and there are more cold air activities in the northern hemisphere, which makes the temperature gradually drop.