What is a snowstorm?

Abnormal atmospheric circulation is the "culprit" of snowstorm.

"The direct cause of the recent rain and snow weather is abnormal atmospheric circulation," said Sun Jun, chief forecaster of the Central Meteorological Observatory.

He analyzed that from the evolution of atmospheric circulation in the short and medium term, there have been frequent cold air and active warm and humid airflow since the winter of this year. Especially since June+10 in 5438, the circulation in the middle and high latitudes is mainly meridional, with frequent cold air activities. In addition, the subtropical system is strong, northwest than normal, which is conducive to transporting warm and humid air from the south to the north. On the one hand, the cold air in the north is very active, on the other hand, the warm and humid airflow in the south is constantly transported northward. The intersection of cold and warm air flow is mainly located in the central and eastern regions of China, which creates favorable circulation conditions for large-scale rain and snow weather.

This year's atmospheric circulation anomaly is related to the "La Nina event" that is taking place in the equatorial Middle East Pacific. Li Weijing, deputy director of the National Climate Center, said that from the perspective of climate change, the current low temperature in the equatorial Middle East Pacific is one of the manifestations of the "La Nina" phenomenon. Statistical analysis shows that the meridional dimension of mid-latitude atmospheric circulation may be strengthened in the winter of the year and the spring of the following year when the "Strong La Ni? a Event" occurred, that is, the cold air activity is frequent, which easily leads to low temperature in most parts of northern and eastern China and more precipitation in the area north of the Yangtze River.

Why is this year's heavy snow so slow to "recede"? Experts attribute the reason to the stability of atmospheric circulation. Sun Jun said: "It is precisely because of the stable atmospheric circulation during this period that the warm and humid airflow and cold air in the southwest have been around 30 degrees north latitude, especially in the middle and lower reaches of the Yangtze River, so there will be no obvious turning point in the recent rain and snow weather."