Climate of Spring Festival in Hunan Province

This year's Spring Festival circle of friends was screened by waves of goose feather snow, and there was a blizzard in Hunan 16 counties and cities. This is because Hunan is affected by frequent cold air, which leads to continuous low temperature in Hunan. The purple cold air is formed due to the stability of mid-high latitudes in Europe and Asia and the unusually active trough of low pressure in the southern margin of the Qinghai-Tibet Plateau.

1. What caused the cold air in Hunan?

According to the detection of Hunan Climate Center,1From October 23rd to February 7th, the average temperature in Hunan Province was only 3.6℃, 2.5℃ lower than the same period last year. There are two main reasons for the cold air going south to Hunan this time. One is the stable blocking form in the middle and high latitudes of Europe and Asia, which is conducive to the slow infiltration and gradual deepening of cold air to the south. The second factor is that the trough of low pressure in the south branch of Nanyuan in Qinghai-Tibet Plateau has been extremely active, so the water vapor in the Bay of Bengal is continuously transported to China. In this process, a strong warm and humid airflow and cold air are established, and continuous and stable precipitation is formed in the whole southern region. Therefore, the existence of cold air and sufficient water vapor will lead to snowstorms in various parts of Hunan.

2. What caused the snow in the south this year?

In fact, it is because we are in La Nina state this year, that is, the sea surface temperature in the equatorial eastern Pacific is 0.5 degrees lower than in previous years. This phenomenon has a great influence on the climate in China, and under this influence, the meridional circulation in East Asia is abnormal. This abnormal circulation situation is very conducive to the southward movement of cold air in the north, and the warm air mass in the south is also very active this year. Therefore, when a cold air mass and a warm air mass are combined, they will be affected by the same airflow, so there will be more rain and snow in the Yangtze River basin, and the cold weather will last for a long time. However, in the case that there is only a strong cold air mass in the south, but there is no warm moisture mass to provide a lot of water vapor, there will be a big cooling weather in the south, resulting in more snow in the south.