Why does cold air come from Xinjiang? How is cold air formed?

The weather forecast often mentions that "a cold air front from western Siberia arrived in northern Xinjiang this morning …" and "a cold air from Mongolia entered eastern Inner Mongolia to western Hetao, and the cold air will move eastward and southward …". Is the origin of cold air invading China in Western Siberia or Mongolia? Where is its hometown?

In fact, the distant Arctic Ocean and cold Siberia are the cradles of cold air. The cold air originally came from the Arctic Ocean, and later strengthened through Siberia. These areas have high latitude, long winter nights, short days and few sunshine hours. In the polar regions, there will even be extreme nights, and the sun never shows its face. Therefore, the earth's heat from the sun is very weak; However, at night, the ground radiates a lot of heat into space. With the continuous cooling of the ground, the temperature of the atmosphere near the ground is getting lower and lower, and the accumulation of cold air will increase. Guided by the northwest airflow, this cold air reactor with extremely low temperature will push from north to south, affecting Mongolia, North China, East China or most of China.

The intensity of each cold air intrusion is different, strong or weak, and the cooling rate is also more or less. Cold air, such as tidal surge, affects a wide range, reaching more than 1, 2000 kilometers. Because the moving path is different, the affected area is also different.