20 13, 10, 14- 16, a large-scale cooling process occurred from north to south in China, which caused the weather system of this cooling process in China.

During the movement of the front, the cold air mass plays a leading role, pushing the front to move to the side of the warm air mass, and this front becomes a cold front. A cold front is what people often call a cold air front. It is Depth Charge with cold air heading south, and it is the most common weather system that affects China, especially in winter. Every few days in winter, a cold air invades the inland from northwest and north China. When the cold front crosses the border, it will be accompanied by the increase of northerly wind, the increase of air pressure and the decrease of temperature, which will sometimes cause rain and snow and even cause heavy rain in summer. Generally, after the cold front crosses the border, the local area will be controlled by cold high pressure, and the weather will become sunny.