Experts explain in detail why the rainfall in the pre-flood season in South China was so heavy. Extreme weather events may be more frequent in this year’s flood season – News

China Weather Network News Heavy rains are coming again! Heavy rainfall has occurred frequently in the south since April. The rain in South China during the pre-flood period almost resembled “dragon boat water”. In the three days from now (April 24 to 26), a new round of precipitation will hit Jiangnan and South China again. How strong will this wave of rain be? When does the heaviest rainfall occur? Where is the area with the heaviest rainfall? In response to the recent frequent heavy rainfall in the south, the China Meteorological Administration held a press briefing this morning and invited meteorological experts to give in-depth interpretations.

Where and when will the rain be the strongest during the new round of precipitation?

Rainfall has continued in South China recently. From April 19 to yesterday morning, daily rainfall at 17 national meteorological observation stations in Guangdong and Guangxi exceeded the April extreme value. The heavy precipitation temporarily subsided during the day yesterday, but starting today, a new round of precipitation will hit Jiangnan, South China and other places again.

The Central Meteorological Observatory predicts that in the next three days, there will be heavy rainfall again in Jiangnan, South China and central and eastern Guizhou. Some areas in Guangdong, Guangxi, Fujian, Zhejiang, Jiangxi, Guizhou and other places will have heavy to heavy rains accompanied by thunderstorms. In strong convective weather such as strong winds and hail, the center of heavy rainfall is located from northeastern Guangxi to central Guangdong, with local cumulative rainfall reaching 250 to 300 millimeters.

Tomorrow will be the strongest period of this round of heavy rainfall. There will be heavy rain or heavy rain in some areas in northeastern Guangxi and central and northern Guangdong. The scope of heavy rainfall will shrink from the day after tomorrow. Yang Guojie, chief forecaster of the Guangdong Provincial Meteorological Observatory, said: “The precipitation process in Guangdong has certain similarities with the previous round. In particular, the rainfall areas will overlap and the disasters are relatively high. We must continue to be vigilant about small and medium-sized river floods, mountain torrents, urban and rural areas Secondary disasters such as waterlogging.”

How heavy has the precipitation been in South China since April?

This year’s pre-flood season in South China not only came early, but also rained very frequently. Since Guangdong entered April, it has rained most of the time, especially since the 17th, heavy rains and even heavy rains have appeared frequently.

Zheng Zhihai, chief forecaster of the National Climate Center, said: “Since April this year, precipitation in South China has more than doubled compared to the same period in normal years, the second highest amount since 1961.” Generally speaking, heavy rains and strong convective weather are more common in South China during the pre-flood season. , but at this time, the South China Sea monsoon has not yet fully erupted, and the water vapor conditions in South China are not very abundant, so the heavy rainfall is not large in scope and does not last long. However, water vapor is very abundant in South China this year, and the subtropical high continues to be strong, resulting in heavy rainfall, long duration, and wider impact in the pre-flood season in South China this year.

Why is the precipitation in South China this year so heavy during the pre-flood season?

This year’s excess precipitation in South China is obviously related to El Niño. According to Zheng Zhihai’s analysis: “Under the background of global warming, the temperature in Jiangnan, South China and other places is significantly higher than the same period in normal years. The increase in temperature will increase the moisture content of the atmosphere and enhance the intensity of convection, resulting in more precipitation events; on the other hand, Affected by El Niño, the northwest Pacific subtropical high has continued to strengthen since April, guiding water vapor from the South China Sea and the Bay of Bengal to continue to be transported to southern China. The water vapor is extremely abundant. At the same time, combined with the circulation anomalies in the Tibetan Plateau and South China, multiple heavy rainfall processes have formed. “

As for why central and northern South China has become the center of heavy rains, Zheng Zhihai said that the recent strength and southerly location of the western Pacific subtropical high, coupled with the active plateau trough and southern branch system, have caused the center of water vapor to be mainly located from southern Jiangnan to central and northern South China. , resulting in stronger and more precipitation in this area.

Will the south face greater flood control pressure after entering the main flood season?

Zheng Zhihai said: “my country’s climate conditions are generally biased during this year’s flood season. There are more extreme weather and climate events, and floods are more severe than droughts. The eastern monsoon region has generally more precipitation. Considering regional and periodic flood disasters, it will be more obvious.”

The overall water system conditions in this year’s flood season are still relatively good. The middle and lower reaches of the Yangtze River Basin, Huaihe River Basin, and Taihu Lake Basin in the south will have significantly more precipitation than the same period of the year. The Songhua River Basin and the middle and lower reaches of the Yellow River Basin in the north will also have more precipitation. It is recommended that relevant departments Make preparations for flood prevention in advance. (Text/Yang Xing Design/Liu Hongxin)