Global warming increases risks in eastern China

image: East China floods in the summer of 2020
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The Western Pacific Subtropical High (WPSH) is an anticyclonic atmospheric system hovering above the middle and lower troposphere of the Pacific Northwest, dominating summer weather extremes in densely populated East Asian countries. East.

In the summer of 2020, an abnormally strong WPSH resulted in catastrophic flooding with hundreds of deaths, 28,000 homes destroyed, and tens of billions of dollars in economic damage in China alone.

Scientists from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences and the Commonwealth Scientific and Industrial Research Organization (CSIRO) have recently found that the frequency of WPSH events as strong as those observed at summer 2020 is likely to increase under the business as usual carbon emissions scenario, based on 32 climate models.

Their study was published in PNAS May 30.

The interannual intensity of the WPSH is influenced by the variability in sea surface temperature (SST) in tropical regions such as the central Pacific and the Indian Ocean. Abnormal SST can affect both local and distant precipitation and atmospheric convection, which in turn modulate atmospheric circulation over the Pacific Northwest.

Under global warming, precipitation and atmospheric convection may be more sensitive to SST variability. Indeed, the saturation vapor pressure increases exponentially with increasing temperature. In a warmer climate, the mean-state moisture content of the atmosphere will increase and the response of tropical humidity and global moist instability associated with SST anomalies will also be greater.

“These changes combined with the non-uniform change in background SST may lead to enhanced responses of atmospheric convection to the central Pacific SST and then to increased variability in atmospheric circulation, including WPSH,” said Dr. YANG Kai of IAP, lead author of the study.

“Increased WPSH variability translates to an increase in the frequency of strong WPSH events, suggesting that greenhouse warming is likely to increase the risk of flooding in eastern China associated with strong WPSH events, as seen in episode 2020,” Professor HUANG Gang said. of the IAP, one of the corresponding authors.

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Teresa H. Sadler