By Ethan Wang and Ryan Woo
BEIJING, Aug 13 (Reuters) – Typhoon Dolphin unleashed extreme rain across eastern, central and northern China, far from the coast where it made landfall on Sunday following a two-week journey across the Pacific Ocean.
Its longevity and broad circulation made Dolphin one of China’s most significant weather events in recent years, with meteorologists comparing it with the devastating Typhoon Doksuri in 2023.
HOW SEVERE WAS THE RAINFALL?
Single-day rainfall records were smashed at 13 weather stations across the country.
In Zhejiang, average rainfall from August 7 to 11 reached 215 mm (8.46 inches), a record for any typhoon making landfall in the eastern Chinese province.
The city of Taizhou, where Dolphin first came ashore, received an average of 438 mm, setting a new record.
As Dolphin moved inland, it continued to rewrite rainfall records across Hubei and Henan provinces.
The northernmost arc of its rain bands brushed the capital Beijing, where 90.7 mm of rain soaked one district within an hour on Wednesday, the highest hourly total for that area since records began in 1954.
Dolphin’s unusually wide impact stemmed from the scale of its circulation and persistent moisture even after landfall, said Benjamin Horton, dean of the School of Energy and Environment at City University of Hong Kong.
“Many typhoons weaken quickly after landfall because they lose their oceanic heat source and encounter friction over land. Dolphin weakened as a wind storm, but its moisture plume and remnant circulation remained very effective at producing rainfall,” he said.
WHAT HELPED SUSTAIN DOLPHIN’S LONG LIFE CYCLE?
Formed near the International Date Line, about 6,000 km east of Zhejiang, Dolphin was the farthest-origin typhoon ever to make landfall in China.
Its lifespan of 16 days was three times that of a typical typhoon.
El Niño conditions this year can shift tropical cyclone initiation further east in the Pacific, giving storms a longer track over the warm ocean before reaching East Asia, said Xiangbo Feng, a tropical cyclones scientist at the University of Reading in the UK.
“This provides storms more time to organise and intensify, and they are more likely to grow into strong or violent typhoons,” Feng said. “I anticipate there will be more such storms this year.”
IS CLIMATE CHANGE FUELLING STRONGER TYPHOONS?
Scientists warn that typhoons have become more likely to affect East Asia as a result of climate change.
“A warmer atmosphere holds more water vapour, roughly 7% more for each 1 degree Celsius of warming, and that gives tropical cyclones a larger moisture reservoir when the surrounding circulation is favourable,” Horton said.
“In practical terms, this means that the same type of storm today can produce heavier rainfall than it would have in a cooler climate,” he said.
The probability of a typhoon affecting East Asia has significantly increased from 33% to 65%, according to Feng.
Global ocean warming may also be slowing the rate at which storms decay over land.
The rate of post-landfall decay has decreased by roughly 45% between 1967 and 2018, according to Hui Su, chair professor of the Department of Civil and Environmental Engineering at the Hong Kong University of Science and Technology.
“Global warming has enhanced the capacity of holding moisture and energy in the atmosphere, and when precipitation has been triggered, it may pour down more rainfall,” said Wang Fan, a research assistant professor at the Hong Kong Baptist University Academy of Geography, Sociology and International Studies.
HOW DOES DOLPHIN COMPARE TO DOKSURI IN 2023?
Dolphin’s path has drawn comparison to Typhoon Doksuri. In 2023, Doksuri’s remnants brought devastating rain to northern China and Beijing experienced its heaviest rainfall in 140 years.
For Doksuri, meteorologists identified a blocking pattern involving subtropical and continental high-pressure systems, moisture convergence, low-level lifting near the Taihang Mountains and additional moisture input associated with Typhoon Khanun, Horton said.
Dolphin appears to have followed a similar pattern, with a weakening cyclone continuing to carry deep tropical moisture inland, where it interacts with regional circulation and topography to enhance rainfall, he said.
“The common lesson is that a typhoon does not have to remain intense in terms of wind speed to remain dangerous. Once the circulation carries large amounts of moisture inland, the flood risk can persist for days and can shift far from the coast.”
(Reporting by Ethan Wang and Ryan Woo in Beijing; Additional reporting by Xiuhao Chen in Beijing and Joyce Zhou in Hong Kong; Editing by Kate Mayberry)
