What's the temperature difference between north and south of China?

In winter, the lowest temperature in northern China often drops to-3 ~ 4℃, and there is thick snow everywhere in the fields, while the temperature in southern China is mostly above ℃, and the lowest temperature is only a few degrees below zero. In summer, the temperature difference between the north and the south is very small. What is the reason?

because the temperature on the earth is determined by the amount of solar radiation energy absorbed by the surface and the strength of thermal radiation ability of the surface. If the light intensity is large and the time is long, the ground will receive more heat from the sun, and at the same time, it will release more heat to the air, so the temperature will be high; On the contrary, the temperature is low.

China is located in the northern hemisphere, and the sunlight that hits the northern hemisphere in winter is all oblique. Due to the different degrees of inclination of sunlight to the north and south of China, the north is more inclined than the south, and the solar heat obtained per unit area on the ground is less than that in the south; In other words, the light intensity in the north is smaller than that in the south.

In terms of the length of illumination time, in winter, the illumination time in the south is longer than that in the north. For example, around the winter solstice, the illumination time in Haikou, Hainan Island, China is about 1.9 hours, while that in Harbin, Heilongjiang Province is only about 8.6 hours. In summer, the situation is just the opposite. The illumination time in the north is longer than that in the south. For example, around the summer solstice, the daytime in Harbin is about 15.7 hours, while that in Haikou is only about 13.2 hours.

In addition, in winter, the north is often affected by the prevailing northerly airflow, and the cold current frequently goes south, bringing cold weather that is far from possible in the local latitude; There is little northerly airflow prevailing in the south, and the temperature is still high. In summer, the southeast monsoon prevailing in the south can continuously blow warm air to the north.

It can be seen that in winter, the light intensity in the south of China is greater than that in the north, and the light duration is longer, and the prevailing northerly airflow has little influence, which causes the temperature difference between the north and the south. In summer, although the light intensity in the south is greater than that in the north, the light time is shorter than that in the north, and the prevailing southeast monsoon can continuously blow to the north, which reduces the temperature difference between the two. Therefore, the temperature difference between the north and the south of China is very small in summer, and we can still grow rice in Heilongjiang Province.