Why is the day when the sun shines on the Tropic of Cancer the summer solstice?

On the day when the sun hits the Tropic of Cancer, the daylight hours in all parts of the northern hemisphere reach the longest in the whole year. People call this day the summer solstice.

The solstice in summer is the turning point when the sun shines on the earth. On this day, the sun was almost direct to the Tropic of Cancer. After this day, the direct position of the sun will move south, the height angle of the sun will begin to decrease day by day at noon, and the day in the northern hemisphere will be shortened day by day.

Extended data:

Weather characteristics after the summer solstice;

1, convective weather

After the summer solstice, the ground is heated strongly and the air convection is strong, and thunderstorms are often easy to form in the afternoon to evening. This kind of hot thunderstorm comes and goes, and the rainfall range is small. People call it "dividing fields in summer and rain". Liu Yuxi, a poet in the Tang Dynasty, skillfully used this weather to write a famous poem, "The east rises and the west falls, and the road is sunny and sunny."

The heavy precipitation brought by convective weather is not always as beautiful as described in the poem, and it often brings local disasters. In his poem It's Rain in Summer, the poet Xu Xinshu also appropriately described the thunderstorm weather in summer: "It's windy in summer, sitting on the stage in summer, frogs chirping and attacking the dust. The golden gongs are ringing in the air, and the cold rain is like money. "

2. Hot weather

Like the winter solstice, the summer solstice is also a solar term reflecting the changes of the four seasons. Astronomy stipulates that the summer solstice is the beginning of summer in the northern hemisphere. From summer to the future, although the direct point of the sun began to move south from the Tropic of Cancer, the daytime in the northern hemisphere began to shorten gradually, and the height of the sun began to decrease day by day for the Tropic of Cancer and its northern area.

However, because the heat radiated from the sun to the ground is still more than the heat radiated from the ground to the air, the temperature will continue to rise in the future, so there is a saying that it is not too hot from summer to the sun.

Although the sunshine duration from summer solstice is the longest, it is not the hottest time of the year. For the Yellow River in China and most of its northern areas, the highest monthly average temperature is July, followed by August and then June.

Baidu encyclopedia-summer solstice