Scientists recently discovered that the frequency of such strong Western Pacific Subtropical High events, as seen in the summer of 2020, can rise under the business-as-usual carbon emission scenario based on 32 climate models.
As indicated in a EurekAlert! report, the WPSH is an anticyclonic atmospheric system that hovers over the middle and lower troposphere of the northwestern Pacific, dominating summer climate extremes in East Asia's densely populated nations.
In the summer of the said year, an anomalously strong WPSH led to catastrophic floods with hundreds of deaths, about 28,000 homes destroyed, and tens of billions of dollars in economic damage in China alone.
Scientists, specifically from the Institute of Atmospheric Physics of the Chinese Academy of Sciences and the Commonwealth Scientific and Industrial Research Organization, led the recently published research.
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A man looks out at vehicles stuck along a flooded street after heavy rains hit the area in Linyi in China's eastern Shandong province on August 14, 2020.
Effect of Global Warming
Essentially, the interannual intensity of WPSH is impacted by the variability of sea surface temperature, or SST, in tropical regions like the central Pacific and the Indian Ocean.
The anomalous SST can impact both local and rainfall and atmospheric convection, modulating atmospheric circulation over the northwestern Pacific.
Under global warming, a related Eurasia Review report said rainfall and atmospheric convection could be more sensitive to SST variability. This is because saturation vapor pressure increases exponentially with temperature rises.
In a warmer climate, the atmosphere's mean-state moisture content will rise, and the response of tropical humidity and linked gross moist instability to SST anomalies will also be more massive.
According to the lead author of the study, published in the Proceedings of the National Academy of Sciences, Dr. Yang Kai from IAP, such changes integrating with the non-uniform change in background SST can result in enhanced responses of atmospheric convection to the central Pacific SST, and then increased variability of the atmospheric circulation which includes the WPSH.
One of the corresponding authors, Professor Huang Gang from IAP, added that the increase in WPSH variability is translating into a rise in the frequency of strong WPSH events, suggesting that greenhouse warming is likely to increase the risk of East China flooding linked to strong WPSH occurrences "as seen in the 2020 episode."
Climate Change and Flooding in China
The burden on dams in China can grow as climate change makes extreme weather occurrences more typical.
More so, as the atmosphere of the Earth gets warmer, it's holding more moisture, making downpours more intense, director of the Earth Observatory of Singapore Benjamin Horton said in an AFP report via Yahoo! News.
As indicated in the report, water levels reached historic highs in more than 50 rivers during the summer of 2021 in China, China's ministry of water resources said, as authorities cautioned that the Three Gorges Dam was facing the largest flood peak since it started operating in 2003.
Climate analyst for Greenpeace East Asia Li Shuo said the floods are ringing an alarm bell for "China that climate change is here."
The country's fast development and breakneck urbanization have also exacerbated flooding. Urban sprawl, in particular, has covered more and more land in impassable concrete, increasing the danger of rapid water buildup on the surface during heavy rain with nowhere to drain into.
Related information about the reason for flooding in China is shown on Spotlight on China's YouTube video below:
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