What is the temperature difference between north and south in China?

In winter, the lowest temperature in the north of China often drops to -30 ~ 40℃, and there is thick snow everywhere in the fields, while the temperature in the south of China is mostly above 0℃, and the lowest temperature is only a few degrees below zero. In summer, the temperature difference between north and south is very small. What is the reason?

Because the temperature on the earth depends on 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 receives more heat from the sun and releases more heat to the air at the same time, so the temperature is high; On the contrary, the temperature is low.

China is located in the northern hemisphere, and the sunlight hitting the northern hemisphere in winter is 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 per unit area of the ground is less than that of the south; In other words, the light intensity in the north is smaller than that in the south.

Judging from the length of illumination time, the illumination time in the south is longer than that in the north in winter. For example, in winter, the illumination time in Haikou, Hainan Island in China is about 10.9 hours, while that in Harbin, Heilongjiang Province is only about 8.6 hours. In summer, the situation is just the opposite. The light time in the north is longer than that in the south. For example, from summer to around, the daytime in Harbin is about 15.7 hours, while the daytime 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; In the south, the northerly airflow is less, 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, the light duration is longer, and the prevailing northerly airflow has little effect, resulting in a large 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, thus narrowing the temperature difference between the two. Therefore, the temperature difference between north and south of China is very small in summer, and rice can still be planted in Heilongjiang Province.