After the east solstice, the sun has moved towards the Tropic of Cancer, but why does it get colder in the north?

If we only consider the position of the sun, then the theory is this: the earth absorbs heat from the sun during the day and radiates heat at night. In winter, the days are short and the nights are long in the north, and the heat emitted is greater than the heat absorbed. The weather It's getting colder and colder. After the winter solstice, the nights begin to get shorter and the days begin to get longer, but the nights are still long and the days are short. Although the heat absorbed by the ground begins to increase, it still does not dissipate as much heat, so it will continue to get colder. The sun's movement toward the Tropic of Cancer only slows down the cooling, but it has not yet reached the point of warming. Regardless of other practical factors, the temperature begins to rise only after the vernal equinox, when the days are longer than the nights.

The actual situation is that the ground can store heat for a period of time after absorbing it, and it will not be dissipated instantly. The ocean will absorb more heat. The air has a thermal insulation effect, which can also prevent the ground from cooling so quickly. , and the air flows, and the global climate affects each other, all of which are conducive to warming, so the temperature has already begun to rise before the vernal equinox. But just after the winter solstice, the temperature continued to drop.