The cold wave hit many places and the temperature "dived". Why is it so cold this winter?

These days, the cold air continues to give force, and many netizens feel that they are cracking! The Central Meteorological Observatory 10 continued to issue a blue warning of cold wave at 06: 65438 on October 6. It is predicted that the cold wave will affect most parts of central and eastern China from June 6th to 7th. The local cooling rate exceeds 10℃, and the temperature in many places may break through the new low since this winter.

According to the statistics of National Climate Center, since winter (65438+February 2020 1? 202 1, 65438+1October 3rd) In June 5438+February, 2020, there were two cold air processes affecting China, namely, from June 5438+February13rd to June 5438+05 (national strong cold air) and from February 29th to June 5th. Compared with the same period in history, the number of cold air (including cold wave) is small, but it is a nationwide cold air process with large influence and strong cold air intensity. Cold wave weather continues to affect the central and eastern regions of China. Affected by strong cold air, the temperature in the eastern and southern parts of Northeast China, the eastern part of Northwest China, most of North China, Huanghuai, Jianghuai, Jianghan, Jiangnan, the eastern part of Southwest China, most of South China and Taiwan Province Island will drop by 6 ~ 8℃ successively from 08: 00 on the 6th to 20: 00 on the 8th. Among them, the temperature drop in southern Shanxi, south-central Shandong, most of Jiangsu, Shanghai and northwestern Jiangxi, northwestern Zhejiang and Fujian can reach 10℃.

Since winter, the middle and high latitudes in Europe and Asia have been controlled by the meridional circulation which is high in the west and low in the east. The winter monsoon in East Asia is strong, and this circulation pattern changed little in June+February, 5438. The continuous meridional circulation high in the west and low in the east and the continuous strong winter wind are the direct reasons for the low temperature in most parts of central and eastern China since June 5438+February 2020. In addition, the recent La Nina phenomenon in the equatorial Middle East and the Pacific Ocean and the decrease of Arctic sea ice in autumn are two signals that cannot be ignored. Historical statistical analysis shows that the latitude of atmospheric circulation in middle and high latitudes in Europe and Asia is larger in most La Nina years, the cold air activity in China is more frequent and stronger than in other years, and the probability that the temperature in most parts of the central and eastern regions is lower than normal is also higher.

The direct reasons for the low temperature in central and eastern China are the meridional circulation with high in the west and low in the east and the strong winter monsoon in East Asia. La Nina in autumn and the lack of Arctic sea ice provide an important background for the strengthening of winter winds this year.