Two global teleconnection wave trains converge in Central China, sharpening pressure gradients over northern China and enabling the winds' breadth, strength and persistence in the north of the country, researchers report
For five days in April of 2025, record-breaking winds swept through China, with speeds surpassing 45 meters per second in some areas. That's roughly the same wind speed of a category 2 hurricane. However, a hurricane breezes through in a matter of hours. What caused this extreme wind event — that resulted in five deaths and caused more than $154 million in economic losses, according to the Ministry of Emergency Management — to persist at such strength for so long and across so much of the country?
That's the question a team of researchers in Sun Yat-sen University's School of Atmospheric Sciences set out to understand. In an assessment of global atmospheric configurations, the researchers found that two remote and large-scale patterns related to Rossby wave trains converged to strengthen a pressure gradient over northern China, driving the winds.
The team published their findings, which they said could help inform more reliable forecasting of extreme wind events, on July 7 in the journal Ocean-Land-Atmosphere Research .
"Previous studies had explained the regional weather systems, but the upstream, large-scale forcing was still unclear," said corresponding author Kaiqiang Deng, Associate Professor of Atmospheric Sciences. "So, we traced how the winds evolved across China and examined whether remote Eurasian Rosby waves helped organize the pressure pattern over northern China."
To trace this evolution, the team used the hourly ERA5 data, which had been previously evaluated and found to accurately capture near-surface wind variability in China. They specifically accessed spatial and temporal changes by the hour for April of 2025 and compared it to the averaged climatological reference period for the corresponding days from 1979 to 2024.
They found that a wind flow of northern and northeastern China in April of 2025 had peak average speeds exceeding 9 meters per second, which is more than 4 meters more per second than reference period. This was likely due to an anomalous atmospheric circulation with enhanced winds that the team identified over northern China; however, even that did not explain the force of the wind event from April 10 to April 15.
According to Deng, the existing winds were boosted by two distinct Rossby wave trains — which exist in the upper-air jet stream as alternating patterns of high- and low-pressure areas — converging over Central Asia. One originated over the Barents-Kara Sea, north of Siberia, and the other from the Mediterranean.
"Their combined influence strengthened the ridge — high pressure — over northwestern China and the trough — low pressure — over northeastern China, sharpening the pressure gradient and driving the record-breaking northerly winds," Deng said. "At the event's peak, daily maximum winds exceeded 15 meters per second across northern China and locally surpassed 45 meters per second."
Next, Deng said the team plans to investigate what initiated the two wave trains, which he theorized could be linked to variability in the sea ice in the Barents-Kara and to tropical sea-surface temperatures in the Mediterranean.
"Our longer-term goal is to determine how these wave trains and the East Asian cold vortex may change in a warming climate and to translate the resulting dynamical signals into more reliable forecasts and earlier warnings of high-impact wind events in China," Deng said.
Deng is also affiliated with Sun Yat-sen University's Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, as well as the Southern Marine Science and Engineering Guangdong Laboratory. Other collaborators include first author Jiayi Nie, Xi Chen, Wentian Qiu and Qinghong Zhao, all of whom are also affiliated with Sun Yat-sen University's School of Atmospheric Sciences and the Southern Marine Science and Engineering Guangdong Laboratory.
The National Key R&D Program of China, the Natural Science Foundation of Guangdong Province, and the Southern Marine Science and Engineering Guangdong Laboratory supported this work.
