There was more rainfall in many places in June, and the atmospheric circulation anomaly was the main cause

　　◎Our reporter Fu Lili

　　This year seems to have been exceptionally rainy.

　　On July 5, at the regular press conference of the China Meteorological Administration, Wang Yawei, deputy director of the Emergency Disaster Mitigation and Public Service Department of the China Meteorological Administration, announced that the national average precipitation in June was 112.1 mm, 9.1% higher than the same period of the previous year; Jilin and Liaoning , Shandong's precipitation is the largest in the same period in history.

Especially from late May to early June, there were relatively serious rainstorms and floods in southern China, and the public was quite concerned.

What is the reason behind it and is it related to climate warming?

　　"Severe floods in many parts of South China are mainly directly affected by abnormal atmospheric circulation." Xiao Chan, deputy director of the National Climate Center, responded.

　　Xiao Chan explained that since May, the atmospheric circulation in the middle and high latitudes of Eurasia has been large in longitude and direction, resulting in frequent cold air activities in eastern my country.

Especially in the first half of June, the northeast cold vortex was more active, and its development trend to the south strengthened. On the one hand, it guided the cold air to move southward, affecting the southern part of Jiangnan and southern China. Water vapor transport from the Pacific Ocean mainly affects southern China.

　　At the same time, with the onset and establishment of the summer monsoon, the southwest water vapor transport guided by the monsoon circulation continued to be strong.

　　In addition, according to the forecast of the Central Meteorological Observatory, from July 5th to 7th, the residual circulation of "Siamba" will continue to move northward. Affected by it and the westerly belt system, a huge rainfall belt will run through the north and south of my country, from south China to northeast China. There have been heavy rains.

　　"Comprehensive judgment, the rainy season in North China this year is early and the rainfall is high. The most important reason is that it is affected by the La Niña event." Xiao Chan said.

　　For the third year in a row, meteorologists have predicted La Niña, a rare "triple" La Niña climate event.

　　Xiao Chan introduced that La Niña is a manifestation of ocean thermal conditions, that is, the abnormal cooling of sea water in the central and eastern Pacific Ocean.

This phenomenon affects the global climate.

At present, the La Niña phenomenon is still ongoing, and the decay has been slow since spring.

It is expected that from July to August, the cold water in the equatorial central and eastern Pacific will temporarily attenuate, but it will still maintain a La Niña or neutral cold state.

It is expected that the cold water in autumn and winter is more likely to develop and strengthen again.

　　Historically, there have been similar La Niña phenomena for three consecutive years, including 1998-2001, 1983-1986, and 1973-1976.

What impact will it have on our country?

Xiao Chan pointed out that in the summer of the following year after most La Niña events, the East Asian summer monsoon is likely to be stronger, and the western Pacific subtropical high is likely to be northerly, and the northern part of my country is more likely to have more precipitation.

　　However, Xiao Chan also said that the range, center, and intensity of the northern rainy areas are also very different, mainly due to the intensity of the La Niña event itself, the location of its cold SST center, and its different development trends in spring and summer. There are also various factors such as sea temperature in other sea areas (such as the Indian Ocean, the Atlantic Ocean, etc.), plateau snow cover and Arctic sea ice, and atmospheric intraseasonal oscillations.

　　Xiao Chan emphasized that in the case of La Niña events occurring in three consecutive winters, the locations of the main rainy areas in my country in summer are also different, which once again proves the complexity of the impact of La Niña events on my country's summer climate.

Due to the small sample size, there are still few studies on the impact of consecutive La Niña events on my country's climate, and further research is needed.