Why is there less snow in the north and more snow in the south in recent years?

In fact, climate is a complex system. The reason why there is more rain and snow this year is precisely that the warm and humid airflow is active, while the cold air is not strong enough, which is inseparable from the cold and warm confrontation, resulting in an increase in low-temperature rain and snow weather in a large area of China. Therefore, the essence is that climate warming is still causing trouble. In the context of global warming, sometimes there will be temporary cooling or even extremely cold weather in some areas. It is not impossible. This is reminiscent of the scene described in the American movie The Day After Tomorrow. The day after tomorrow tells the story that Europe and America suddenly cooled down due to global warming and entered the ice age. Although the film is fictional, it has scientific basis. It turns out that global warming has caused a large number of ice and snow in Greenland and the Arctic to melt, and cold water has flowed into the North Atlantic, changing the balance of the "temperature-salt cycle". Therefore, warm currents cannot reach North America. The relevant areas have become colder than before, causing unprecedented disasters. The film reminds us that climate warming may lead to some extreme events, such as floods, hail attacks, increased typhoons, heavy rains, severe cold arrival and other disastrous consequences.

There are two reasons for the abnormal climate. The first reason is that we are in a La Nina state this year, that is, the SST in the equatorial eastern Pacific is below minus 0.5 degrees lower than normal, which has a very obvious impact on China's climate. Under the influence of La Nina phenomenon, the meridional circulation in East Asia is abnormal, which is very beneficial to the southward movement of cold air in northern China. It has given us a cold winter, so we can see that this cold winter has already appeared this year.

The second reason is that the two conditions that must be met when it snows or rains are 1. It comes from the warm and humid air flow in the tropics. There is cold air from high mountain area. The snowfall area in winter (the same as the rainfall area in summer) is distributed near the front, that is, the intersection of cold and warm air masses. This position is not fixed, but is determined by the strength of the two air masses. The cold air mass is weak, the front and precipitation areas have high latitudes, the cold air mass is strong, and the front and precipitation areas have low latitudes. The land cold high that affects China in winter is the Asian high centered on Mongolia and Siberia (also known as the Mongolian Siberian high), which has a very large sphere of influence and has a great impact on the weather in China, especially in the northern region.

Because the warm air mass in the south is also very active this year, a large number of warm and humid air currents from the Pacific Ocean and the Indian Ocean frequently patronize the south. When the powerful cold air mass from Mongolia and Siberia quickly went south to meet the warm and humid air mass, the cold and warm air just merged into one. Affected by these two air currents, there have been more rainy and snowy weather recently, especially in the Yangtze River basin, and the low temperature weather has lasted for a long time.