China’s rain belt shifts northwards

Northern China has experienced one of its longest rainy seasons since records began in 1961, reported Jiemian. 

The wet conditions, which began eight days earlier than usual on 10 July, coincide with a northward and westward shift in China’s 400 mm annual rainfall threshold. That line broadly separates the country’s wetter and more humid regions to the south and drier regions to the north.

Over the last decade, it has moved by about 40-45 km on average, Guo Jun, a meteorologist at the Tianjin Climate Centre, told Tianjin Daily. In parts of northern China, the shift may be as much as 200 km, he added. 

The line roughly coincides with another one that reflects China’s uneven population distribution: around 96% of people live to the south-east of the “Hu Huanyong Line” despite that area covering about 36% of the nation’s land, according to China Weather. 

The rainfall threshold also broadly corresponds to transitions between the southeast’s forests and farming and the northwest’s grasslands and grazing. Its movement could therefore affect vegetation and agriculture, expectations for ecological restoration, plus northern China’s urban infrastructure, National Geographic China noted. 

Guo, however, cautioned against interpreting the shift as evidence of long-term regional climate change, which would require data going further back than a decade, he said. 

That said, the observed shift is consistent with research done by the National Climate Centre. Since 1970, the northern edge of the Western Pacific Subtropical High – a major atmospheric system that influences rainfall in China – has moved northwards by roughly 55-110 km every 10 years, Chao Qingchen, director of the centre, told China Newsweek. 

Xu Xiaofeng, former deputy director-general of the China Meteorological Administration, has also previously described a northward shift in China’s rain belt.

Chao Qingchen has linked the shift to global warming. But Wei Ke, a research fellow at the Chinese Academy of Sciences, told Hongxin News that researchers have not yet reached a consensus on its causes.

Read Dialogue Earth’s recent article on how China could cut its emissions using green procurement.