The cause of the snowstorm

The main reason for the formation of a large-scale rain and snow weather process is the abnormal atmospheric circulation, especially the abnormal flow of Eurasian balloon. As we all know, the atmospheric circulation has its own operating rules, and it maintains a stable circulation state for a certain period of time. There is a low-value system in the southwest of Qinghai-Tibet Plateau, while Siberia maintains a relatively high-value system, namely, meteorological low-pressure system and high-pressure system. These two systems have existed in these two areas for a long time, and the low-pressure system has brought abundant precipitation to the southern part of China, mainly in the southern sea and the Indian Ocean. Cold high pressure from Siberia pushes cold air to the south. Obviously, under normal circumstances, cold air from Siberia is the main controlling factor in winter, which makes most parts of China dry and cold.

In some special years, such as 2008, due to the abnormal climate (influenced by La Ni? a phenomenon), the warm and humid airflow in the southwest affects most parts of China northward, while the high pressure system in the north is stable, and cold air is continuously transported southward from Siberia, so that cold and warm air meet in the middle and lower reaches of the Yangtze River and the south. The density of cold air is relatively high, and warm air will slide upward along the cold air layer, which will condense the rich water vapor carried by warm and humid airflow and form rain and snow weather. Due to the unusually long-term intersection of cold and warm air in this area, the rainy and snowy weather in southern China lasts for a long time.