Urban areas, particularly in regions in northern China, India, and Bangladesh, could see more extreme rainfall from atmospheric rivers
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Climate change could increase the number of people in Asia exposed to extreme rainfall from atmospheric rivers, a new study funded by China’s National Key R&D Program and China Agricultural University’s 2115 Talent Development Program has found.
Atmospheric rivers are also known as ‘rivers in the sky’, as they appear like bodies of water when viewed from a satellite. They can be anywhere from 402 to 604 kilometres (250 to 375 miles) wide. On average, the Earth has four to five active atmospheric rivers at any one time.
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The new study made two key findings: first, changes in atmospheric circulation could reduce or suppress atmospheric rivers in some lower-altitude areas. Secondly, as warmer air can contain more moisture, atmospheric rivers affecting subtropical and midlatitude regions can become wetter and potentially produce more extreme rainfall.
Across more than half of the parts of Asia affected by atmospheric rivers, more people could be exposed to the extreme rainfall they bring. The biggest increases are expected in cities in northern China, India and Bangladesh. There, exposure could rise by 24 to 59 per cent.
Atmospheric rivers, on average, transport water at more than two times the rate of the Amazon River.
Similar to a conveyor belt, they transport moisture from the tropical and subtropical oceans before releasing it as rain or snow in cooler regions. More than 50 per cent of rainfall in parts of the coasts of North America, France, Spain, Portugal, the United Kingdom, South America, Southeast Asia, and New Zealand is from atmospheric rivers, research shows.
In the US alone, they are responsible for more than 80 per cent of flooding on the West Coast, costing more than $ 1billion in damage every year.
In February 2022, an atmospheric river led to Brisbane experiencing more than 80 per cent of its normal annual rainfall in just six days, inundating more than 15,000 homes and killing nine people.
Moving atmospheric rivers
A 2024 study found that atmospheric rivers have shifted by about 6 to 10 degrees toward the poles over the last 40 years. One reason for this is cooling sea surface temperatures in the eastern tropical Pacific, which push atmospheric rivers toward the poles.
However, during El Niño conditions, warmer sea surface temperatures cause atmospheric rivers to remain closer to the equator, causing the mechanism to operate in the opposite direction.
In the subtropics, atmospheric rivers are becoming less common – meaning longer droughts and a decreased supply of water.
When atmospheric rivers move to either pole, higher-latitude communities – such as the US Pacific Northwest and Europe – could experience more extreme rainfall, flooding and even landslides. Meanwhile in the Arctic, a greater presence of atmospheric rivers could lead to increased sea-ice melting.
