Cause of Extreme Heavy and Persistent Rainfall over Yangtze River in Summer 2020

• Published in: Advances in atmospheric sciences Vol. 38; no. 12; pp. 1994 - 2009
• Main Authors: Pan, Xiao, Li, Tim, Sun, Ying, Zhu, Zhiwei
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.12.2021; Springer Nature B.V; Key Laboratory of Meteorological Disaster,Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science and Technology,Nanjing 210044,China%National Climate Center,Beijing 100081,China%Key Laboratory of Meteorological Disaster,Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science and Technology,Nanjing 210044,China; State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China; Key Laboratory of Meteorological Disaster,Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science and Technology,Nanjing 210044,China%International Pacific Research Center and Department of Atmospheric Sciences,School of Ocean and Earth Science and Technology,University of Hawaii at Manoa,Honolulu,Hawaii 96822,USA
• Subjects: Anomalies; Anticyclones; Atmospheric Sciences; Confluence; Data analysis; Decay rate; Earth and Environmental Science; Earth Sciences; El Nino; El Nino phenomena; Extreme weather; Geophysics/Geodesy; Heating; Heavy rainfall; La Nina; Meteorology; Original Paper; Planetary waves; Predictability and Impacts; Pressure anomalies; Rain; Rainfall; River valleys; Rivers; Rossby waves; Sea surface; Sea surface temperature anomalies; Summer; Summer 2020: Record Rainfall in Asia — Mechanisms; Surface temperature; Tropical climate; Wave packets; Wave trains; Northeast Asia; Yangtze River; La Niña; 罗斯贝波列; 西北太平洋异常反气旋; CP and EP El Niño; 拉尼娜; Rossby wave train; 中太平洋型和东太平洋型厄尔尼诺; 长江洪涝; anomalous anticyclone over the western North Pacific; 印度洋增暖; Yangtze River floods; Indian Ocean warming; CP and EP El Ni?o; La Ni?a
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/s00376-021-0433-3

Record-breaking heavy and persistent precipitation occurred over the Yangtze River Valley (YRV) in June-July (JJ) 2020. An observational data analysis has indicated that the strong and persistent rainfall arose from the confluence of southerly wind anomalies to the south associated with an extremely strong anomalous anticyclone over the western North Pacific (WNPAC) and northeasterly anomalies to the north associated with a high-pressure anomaly over Northeast Asia. A further observational and modeling study has shown that the extremely strong WNPAC was caused by both La Niña-like SST anomaly (SSTA) forcing in the equatorial Pacific and warm SSTA forcing in the tropical Indian Ocean (IO). Different from conventional central Pacific (CP) El Niños that decay slowly, a CP El Niño in early 2020 decayed quickly and became a La Niña by early summer. This quick transition had a critical impact on the WNPAC. Meanwhile, an unusually large area of SST warming occurred in the tropical IO because a moderate interannual SSTA over the IO associated with the CP El Niño was superposed by an interdecadal/long-term trend component. Numerical sensitivity experiments have demonstrated that both the heating anomaly in the IO and the heating anomaly in the tropical Pacific contributed to the formation and maintenance of the WNPAC. The persistent high-pressure anomaly in Northeast Asia was part of a stationary Rossby wave train in the midlatitudes, driven by combined heating anomalies over India, the tropical eastern Pacific, and the tropical Atlantic.