Fig. 1 Extreme precipitation in China contributed by emissions reductions during COVID-19.
In the early and middle summer of 2020, persistent extreme precipitation events occurred in eastern China. The accumulated rainfall has broken its 50-year record since 1961. Eastern China, as one of the most urbanized and densely populated regions in the world, suffered severe damages and losses from this disaster. Extreme precipitation can induce severe stress on aquatic and terrestrial ecosystems, societal infrastructure, and socioeconomics. From the perspective of climate variability, the strong Indian Ocean Dipole event in 2019, the notably delayed withdrawal of the Meiyu-Baiu front caused by enhanced Arabian Sea warming, and the sub-seasonal phase transition of the North Atlantic Oscillation were postulated as contributors of the unprecedented 2020 extreme summer rainfall in China. In addition to natural variability, human influence may also have a dramatic impact on extreme precipitations.
On February 18, 2022, a study titled "Abrupt emissions reductions during COVID-19 contributed to record summer rainfall in China" was published online in Nature Communications (https://doi.org/10.1038/s41467-022-28537-9). This research was a collaboration between Nanjing University of Information Science & Technology and Pacific Northwest National Laboratory in USA, and other institutions.
The study investigated the impact of COVID-19-induced abrupt emissions reductions on the unprecedented summer precipitation in China and showed that the abrupt emissions reductions during the pandemic strengthened the summer atmospheric convection over eastern China, resulting in a positive sea level pressure anomaly over northwestern Pacific Ocean. The latter enhanced moisture convergence to eastern China and further intensified rainfall in that region. Modeling experiments show that the reduction in aerosols had a stronger impact on precipitation than the decrease of greenhouse gases did. The study concluded that through abrupt emissions reductions, the COVID-19 pandemic contributed importantly to the 2020 extreme summer rainfall in eastern China.
Professor Yang Yang from Nanjing University of Information Science & Technology (NUIST) was the first and corresponding author of this paper, Dr. Lili Ren was the co-first author. Dr. Hailong Wang from the Pacific Northwest National Laboratory in the United States was the co-corresponding author. Other contributing authors include Professor Hong Liao, Associate Professors Pinya Wang and Lei Chen, and Dr. Jiandong Li from the School of Environmental Science and Engineering at NUIST, Dr. Xin Hao from the School of Atmospheric Sciences at NUIST, Dr. Mingxuan Wu from the Pacific Northwest National Laboratory in the United States, Dr. Ruby Leung, a member of the National Academy of Engineering in the United States, Professor Fengfei Song from Ocean University of China, Dr. Jing Wang from Tianjin Institute of Meteorological Sciences, and Associate Researcher Zhenqiang Zhou from Fudan University.
