Everyday technical terms

Everyday technical terms | summer solstice

Summer solstice

Definition: The tenth of the 24 solar terms falls on June 2 1 or 22; It means that the heat is coming, with the longest day and the shortest night.

Subject: Atmospheric Science _ Applied Meteorology

Related terms: summer heat, white dew, autumnal equinox and cold dew.

Extended reading

Summer solstice is the tenth of the 24 solar terms, and the fourth solar term in summer is usually on June 2 1 or 22. The summer solstice is the northernmost day of the year, almost pointing to the Tropic of Cancer. The daylight time in all parts of the northern hemisphere is the longest in the whole year, and the farther north it is, the longer it is. In China, the daily length of Haikou is a little more than 13 hour, that of Hangzhou 14 hour, that of Beijing 15 hour, and that of Mohe city, Heilongjiang province can reach more than 17 hour.

After the summer solstice, the sun will "turn back", the direct sunlight point will begin to move south from the Tropic of Cancer, and the days in the northern hemisphere will gradually shorten. Although the daytime from summer solstice is the longest and the angle of the sun is the largest, it is not the hottest time in a year, because at this time, the heat radiated by the sun to the ground is still more than the heat radiated from the ground to the air, and the heat on the ground continues to accumulate, so the temperature will continue to rise in the next period of time, reaching the highest value in a year from mid-July to mid-August, which is also known as "the heat of three volts".

The summer solstice season is the rainy season in the middle and lower reaches of the Yangtze River and the Jianghuai area in China. The air is very humid, and cold and warm air masses meet here to form rainy weather. In addition, after the summer solstice, the ground is heated strongly and the air convection is strong, and thunderstorms often form in the afternoon to evening. This kind of hot thunderstorm comes suddenly, goes quickly, and the rainfall range is small, so it is called "summer rain over the mountains".

The solstice in summer is considered as the watershed of yin and yang in the world. At this time, yang is at its peak and yin is born. The ancients in our country divided the summer solstice into three periods: one was when the antlers were released, the other was when cicadas began to sing, and the third was when Pinellia ternata was born.

Once the antlers were dissolved, the ancients thought that the deer was a mountain animal belonging to Yang. In summer, the yang rose and fell, and the antlers fell off because of Yin.

Second, the cicada begins to sing: after the summer solstice, the male cicada will drum up and sing. Cicada is also called "cicada" because it first senses the change of seasons.

Third-class Pinellia ternata: Pinellia ternata is a wild herb that likes shade. Yin Qi began to rise from summer solstice, and plants such as Pinellia ternata began to grow, while plants that like sunshine began to decline. (Audit: Liu Yunyun, Senior Engineer, National Climate Center, China Meteorological Bureau)