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Typhoon Dolphin and climate change: El Nino and Climate Change are the main factors that boosted its intensity

After a two-week trip across the Pacific Ocean, Typhoon Dolphin brought extreme rain to eastern, central, and northern China. Dolphin's long-lasting and wide circulation made it one of China’s most significant weather events in recent times. Meteorologists have compared it to the devastating Typhoon Doksuri that will hit in 2023.

How severe was the rain?

Thirteen weather stations in the country broke their records for a single-day rainfall.

The average rainfall in?Zhejiang from 7 to 11 August was 215 mm (or 8.46 inches), which is a record for a typhoon that made landfall in eastern China.

Taizhou, the city where Dolphin was first spotted, had an average rainfall of 438mm. This is a record.

Dolphin continued to break rainfall records in Hubei and Henan Provinces as it moved inland. In the northernmost arc, its rain bands touched the capital Beijing. On Wednesday, 90.7 mm fell in one district, which was the highest amount of rain recorded for this area since 1954. Benjamin Horton, Dean of City University of Hong Kong's School of Energy and Environment, explained that the Dolphin's wide-ranging impact was due to its high circulation and the persistent moisture it left behind even after landfall.

Many typhoons weakened quickly after landfall due to the loss of their oceanic heat and friction on land. Dolphin was no longer a windstorm, but the moisture plume it produced and its remnant circulation were still very effective in producing rain," said he.

What helped sustain the long life cycle of the dolphin?

Dolphin, the furthest-originating typhoon to ever make landfall in China, formed near the International Date Line, approximately 6,000 km east from Zhejiang.

The typhoon's 16-day lifespan was three times longer than a normal typhoon. El Nino conditions can cause tropical cyclones to move 'further east' in the Pacific this year, allowing storms to travel a longer path over the warm sea before reaching East Asia.

Feng stated that this would give storms more time to intensify and organise, making them more likely to become violent or strong typhoons. "I expect there will be many more storms like this in the coming year."

Is climate change causing more violent criminals?

Scientists warn climate change has made typhoons more likely to hit East Asia. Horton explained that a warmer atmosphere can hold more water vapour. This is roughly 7% higher for every 1 degree Celsius increase in temperature. Tropical cyclones have a bigger moisture reservoir when surrounding circulation conditions are favorable.

He said that in practical terms this meant the same storm type today could produce heavier rain than it would in a cooler climate.

According to Feng, the probability of an East Asian typhoon has increased significantly from 33% up to 65%.

The global warming of the oceans may also slow down the rate that storms degrade on land.

Hui Su is the chair professor of Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology.

"Global warming has increased the ability of the atmosphere to?hold moisture and energy, and it is possible that precipitation will be triggered more often," said Wang Fan. He's a research assistant at the Academy of Geography Sociology and International Studies of the Hong Kong Baptist University.

How does 'DOLPHIN' compare to DOKSURI in 2023?

Dolphin's path is compared to that of Typhoon Doksuri. Doksuri brought heavy rains to Beijing in 2023.

Horton explained that for Doksuri meteorologists had identified a blocking pattern, which involved subtropical high-pressure systems and continental high pressure systems, moisture convergence and low-level lift near the Taihang Mountains, as well as additional moisture input from Typhoon Khanun. Dolphin seems to have followed a pattern similar to Doksuri, as a weakening tropical cyclone continued to bring deep moisture into the interior, where it interacted with topography and regional circulation to increase rainfall.

The common lesson learned is that a storm does not need to be intense in terms wind speed to be dangerous. Flood risk can last for days once the circulation has brought large amounts of water inland. It can also shift away from the coast. Reporting by Ethan Wang in Beijing, Additional reporting by Xiuhao Chan in Beijing and Joyce Zhou from Hong Kong. Editing by Kate Mayberry

(source: Reuters)