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Magnitude, Scale, and Dynamics of the 2020 Mei-yu Rains and Floods over China

Abstract

Large parts of East and South Asia were affected by heavy precipitation and flooding during early summer 2020. This study provides both a statistical and dynamical characterization of rains and floods affecting the Yangtze River Basin (YRB). By aggregating daily and monthly precipitation over river basins across Asia, it is shown that the YRB is one of the areas that was particularly affected. June and July 2020 rainfall was higher than in the previous 20 years, and the YRB experienced anomalously high rainfall across most of its sub-basins. YRB discharge also attained levels not seen since 1998/1999. An automated method detecting the daily position of the East Asian Summer Monsoon Front (EASMF) is applied to show that the anomalously high YRB precipitation was associated with a halted northward progression of the EASMF and prolonged mei-yu conditions over the YRB lasting more than one month. Two 5-day heavy-precipitation episodes (12−16 June and 4−8 July 2020) are selected from this period for dynamical characterization, including Lagrangian trajectory analysis. Particular attention is devoted to the dynamics of the airstreams converging at the EASMF. Both episodes display heavy precipitation and convergence of monsoonal and subtropical air masses. However, clear differences are identified in the upper-level flow pattern, substantially affecting the balance of airmass advection towards the EASMF. This study contextualizes heavy precipitation in Asia in summer 2020 and showcases several analysis tools developed by the authors for the study of such events.

摘要

2020 年初夏, 东亚和南亚许多地区均受到暴雨和洪水的强烈影响. 本研究给出此次影响长江流域强降水和洪水的统计学和动力学特征. 通过对亚洲各大流域日降水和月降水资料的分析表明, 长江流域是受此次强降水影响最为明显的区域之一. 2020 年 6-7 月长江流域降水为过去20年间最强, 且强降水覆盖了流域内绝大多数地区. 长江流量为 1998/1999 年以来最大. 利用一种可以自动识别日尺度东亚夏季风锋的方法, 分析东亚夏季风锋与强降水之间的关系, 结果表明长江流域降水异常偏多与东亚夏季风锋北抬过程停滞、 长江流域上空持续超过一个月的梅雨环流背景相关. 选取两个持续 5 天的强降水过程 (2020 年 6 月 12-16 日和 7 月 4-8 日), 利用拉格朗日轨迹追踪法, 分析降水中动力过程, 重点关注与东亚夏季风锋期气流辐合相关的动力特征. 在两段降水过程中, 季风气流和副热带气流的辐合均与强降水相伴出现; 但高层环流型差异明显, 这极大影响了东亚夏季风锋附近水平平流的平衡. 本研究以 2020 年夏季亚洲强降水为例, 展示了作者发展的一系列分析方法在此类强降水事件中的应用方法和前景.

References

  1. Appenzeller, C., and H. C. Davies, 1992: Structure of stratospheric intrusions into the troposphere. Nature, 358, 570–572, https://doi.org/10.1038/358570a0.

    Article  Google Scholar 

  2. Associated Press, 2020: China Blows up Dam on Yangtze River Tributary to Ease Flooding. The Guardian. [Available online from https://twnews.co.uk/gb-news/china-blows-up-dam-on-yangtze-river-tributary-to-ease-flooding.]

  3. Buckley, C., 2016: Widespread flooding in China kills over 160, providing a test for leaders. New York Times. Available from https://www.nytimes.com/2016/07/09/world/asia/china-floods.html.

  4. Burke, C., and P. Stott, 2017: Impact of anthropogenic climate change on the East Asian summer monsoon. J. Climate, 30, 5205–5220, https://doi.org/10.1175/JCLI-D-16-0892.1.

    Article  Google Scholar 

  5. Chen, H. P., and J. Q. Sun, 2013: Projected change in East Asian summer monsoon precipitation under RCP scenario. Meteor. Atmos. Phys., 121, 55–77, https://doi.org/10.1007/s00703-013-0257-5.

    Article  Google Scholar 

  6. Chiang, J. C. H., L. M. Swenson, and W. Kong, 2017: Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation. Geophys. Res. Lett., 44, 3788–3795, https://doi.org/10.1002/2017GL072739.

    Article  Google Scholar 

  7. Davies, R., 2013: Flooding in China, 2010. Flood List. Available from http://floodlist.com/asia/flooding-china-2010.

  8. Ding, Y. H., Y. Y. Liu, and Z.-Z. Hu, 2021: The record-breaking Meiyu in 2020 and associated atmospheric circulation and tropical SST anomalies. Adv. Atmos. Sci., 1–14, https://doi.org/10.1007/s00376-021-0361-2.

  9. Duan, W. L., B. He, D. Nover, J. L. Fan, G. S. Yang, W. Chen, H. F. Meng, and C. M. Liu, 2016: Floods and associated socioeconomic damages in China over the last century. Natural Hazards, 52, 401–413, https://doi.org/10.1007/s11069-016-2207-2.

    Article  Google Scholar 

  10. Gu, L. P., 2017: China Starts Emergency Response for Flood-Stricken Hunan. China News Service. Available from https://www.ecns.cn/2017/06-26/262961.shtml.

  11. Guan, P. Y., G. X. Chen, W. X. Zeng, and Q. Liu, 2020: Corridors of Mei-Yu-season rainfall over eastern China. J. Climate, 33, 2603–2626, https://doi.org/10.1175/JCLI-D-19-0649.1.

    Article  Google Scholar 

  12. Hansen, K, 2020: Yangtze Dams Spill Water. NASA Earth Observatory. Available from https://earthobservatory.nasa.gov/images/147013/yangtze-dams-spill-water.

  13. Harrigan, S., and Coauthors, 2020: GloFAS-ERA5 operational global river discharge reanalysis 1979-present. Earth System Science Data, 12, 2043–2060, https://doi.org/10.5194/essd-12-2043-2020.

    Article  Google Scholar 

  14. He, B. S., X. L. Huang, M. H. Ma, Q. R. Chang, Y. Tu, Q. Li, K. Zhang, and Y. Hong, 2018: Analysis of flash flood disaster characteristics in China from 2011 to 2015. Natural Hazards, 90, 407–420, https://doi.org/10.1007/s11069-017-3052-7.

    Article  Google Scholar 

  15. Hersbach, H., and Coauthors, 2020: The ERA5 global reanalysis. Quart. J. Roy. Meteor. Soc., 146, 1999–2049, https://doi.org/10.1002/qj.3803.

    Article  Google Scholar 

  16. Huffman, G. J., D. T. Bolvin, E. J. Nelkin, and J. Tan, 2020: Integrated Multi-satellitE retrievals for GPM (IMERG) technical documentation. NASA/GSFC Code. Available from https://docserver.gesdisc.eosdis.nasa.gov/public/project/GPM/IMERG_doc.06.pdf.

  17. Jiang, Q., and Coauthors, 2021: Evaluation of the ERA5 reanalysis precipitation dataset over Chinese Mainland. J. Hydrol., 595, 125660, https://doi.org/10.1016/j.jhydrol.2020.125660.

    Article  Google Scholar 

  18. Kaamil, A., 2020: ‘A Critical Situation’: Bangladesh in Crisis as Monsoon Floods Follow Super-Cyclone. The Guardian. Available from https://www.sparkblue.org/content/critical-situ-ation-bangladesh-crisis-monsoon-floods-follow-super-cyc-lone.

  19. Kong, W. W., L. M. Swenson, and J. C. H. Chiang, 2017: Seasonal transitions and the westerly jet in the Holocene East Asian summer monsoon. J. Climate, 30, 3343–3365, https://doi.org/10.1175/JCLI-D-16-0087.1.

    Article  Google Scholar 

  20. Kramer, K., and J. Ware, 2020: Counting the Cost 2020 A Year of Climate Breakdown. Christian Aid. Available from https://christianaid.org.uk/sites/default/files/2020-12/Count-ing%20the%20cost%202020.pdf.

  21. Lehner, B., 2014: HydroBASINS: Global Watershed Boundaries and Sub-Basin Delineations Derived from HydroSHEDS Data at 15 Second Resolution. Technical Documentation Version 1.c (With and Without Inserted Lakes). HydroSHEDS. [Available online from https://hydrosheds.org/images/inpages/HydroBASINS_TechDoc_v1c.pdf.]

  22. Lehner, B., and G. Grill, 2013: Global river hydrography and network routing: Baseline data and new approaches to study the world’s large river systems. Hydrological Processes, 27, 2171–2186, https://doi.org/10.1002/hyp.9740.

    Article  Google Scholar 

  23. Liu, B. Q., Y. H. Yan, C. W. Zhu, S. M. Ma, and J. Y. Li, 2020: Record — breaking meiyu rainfall around the Yangtze River in 2020 regulated by the subseasonal phase transition of the North Atlantic oscillation. Geophys. Res. Lett., 47, e2020GL090342, https://doi.org/10.1029/2020GL090342.

    Google Scholar 

  24. Lyu, H.-M., Y.-S. Xu, W.-C. Cheng, and A. Arulrajah, 2018: Flooding hazards across southern China and prospective sustainability measures. Sustainability, 10, 1682, https://doi.org/10.3390/su10051682.

    Article  Google Scholar 

  25. Muetzelfeldt, M. R., R. Schiemann, A. G. Turner, N. P. Klingaman, P. L. Vidale, and M. J. Roberts, 2021: Evaluation of Asian summer precipitation in different configurations of a high-resolution GCM at a range of decision-relevant spatial scales. Hydrology and Earth System Sciences Discussions, 1–38, https://doi.org/10.5194/hess-2020-652.

  26. Müller, O. V., P. L. Vidale, B. Vannière, R. Schiemann, and P. C. McGuire, 2021: Does the HadGEM3-GC3 1 GCM overestimate land precipitation at high resolution? A constraint based on observed river discharge Journal of Hydrometeorology, 22, 2131–2151, https://doi.org/10.1175/JHM-D-20-0290.1.

    Google Scholar 

  27. Parker, D. J., P. Willetts, C. Birch, A. G. Turner, J. H. Marsham, C. M. Taylor, S. Kolusu, and G. M. Martin, 2016: The interaction of moist convection and mid-level dry air in the advance of the onset of the Indian monsoon. Quart. J. Roy. Meteor. Soc., 142, 2256–2272, https://doi.org/10.1002/qj.2815.

    Article  Google Scholar 

  28. Rodwell, M. J., and B. J. Hoskins, 2001: Subtropical anticyclones and summer monsoons. J. Climate, 14, 3192–3211, https://doi.org/10.1175/1520-0442(2001)014<3192:SAASM>2.0.CO;2.

    Article  Google Scholar 

  29. Sampe, T., and S.-P. Xie, 2010: Large-scale dynamics of the Meiyu-Baiu rainband: Environmental forcing by the westerly jet. J. Climate, 23, 113–134, https://doi.org/10.1175/2009JCLI3128.1.

    Article  Google Scholar 

  30. Schiemann, R., D. Lüthi, and C. Schär, 2009: Seasonality and inter-annual variability of the westerly jet in the Tibetan Plateau region. J. Climate, 22, 2940–2957, https://doi.org/10.1175/2008JCLI2625.1.

    Article  Google Scholar 

  31. Schiemann, R., P. L. Vidale, L. C. Shaffrey, S. J. Johnson, M. J. Roberts, M. E. Demory, M. S. Mizielinski, and J. Strachan, 2018: Mean and extreme precipitation over European river basins better simulated in a 25km AGCM. Hydrology and Earth System Sciences, 22, 3933–3950, https://doi.org/10.5194/hess-22-3933-2018.

    Article  Google Scholar 

  32. Sengupta, S., and J. A. Manik, 2020: A Quarter of Bangladesh is Flooded. Millions Have Lost Everything. The New York Times. [Available from https://chowdhurycenter.berkeley.edu/quarter-bangladesh-flooded-millions-have-lost-everything.]

  33. Sprenger, M., and H. Wernli, 2015: The LAGRANTO Lagrangian analysis tool-version 2. 0. Geoscientific Model Development, 8, 2569–2586, https://doi.org/10.5194/gmd-8-2569-2015.

    Article  Google Scholar 

  34. Tang, S. X., R. Li, J. X. He, H. Wang, X. G. Fan, and S. Y. Yao, 2020: Comparative evaluation of the GPM IMERG early, late, and final hourly precipitation products using the CMPA data over Sichuan Basin of China. Water, 22, 554, https://doi.org/10.3390/w12020554.

    Article  Google Scholar 

  35. Thomson, B., 2020: China goes into ‘Wartime Mode’ to Fight ‘Flood Catastrophe’ as ‘Extraordinarily’ Heavy Rainfalls Leave at Least 141 People Dead or Missing. The Daily Mail. [Available online from https://www.dailymail.co.uk/news/article-8517037/China-goes-wartime-mode-fight-flood-cata-strophe-141-people-dead-missing.html.]

  36. Volonté, A., A. G. Turner, and A. Menon, 2020: Airmass analysis of the processes driving the progression of the Indian summer monsoon. Quart. J. Roy. Meteor. Soc., 146, 2949–2980, https://doi.org/10.1002//j.3700.

    Article  Google Scholar 

  37. Volonté, A., A. G. Turner, R. Schiemann, P. L. Vidale, and N. P. Klingaman, 2021: The interaction of tropical and extratropical air masses controlling East Asian summer monsoon progression. Weather and Climate Dynamics Discussions, 1–29, https://doi.org/10.5194/wcd-2021-12.

  38. Wang, Z. L., R. D. Zhong, C. G. Lai, and J. C. Chen, 2017: Evaluation of the GPM IMERG satellite-based precipitation products and the hydrological utility. Atmospheric Research, 196, 151–163, https://doi.org/10.1016/j.atmosres.2017.06.020.

    Article  Google Scholar 

  39. Webster, P. J., V. O. Magaña, T. N. Palmer, J. Shukla, R. A. Tomas, M. Yanai, and T. Yasunari, 1998: Monsoons: Processes, predictability, and the prospects for prediction. J. Geophys. Res.: Oceans, 103, 14451–14510, https://doi.org/10.1029/97JC02719.

    Article  Google Scholar 

  40. Wernli, H., and H. C. Davies, 1997: A Lagrangian-based analysis of extratropical cyclones. I: The method and some applications. Quart. J. Roy. Meteor. Soc., 123, 467–489, https://doi.org/10.1002/qj.49712353811.

    Google Scholar 

  41. Wu, G. X., Y. M. Liu, B. He, Q. Bao, A. M. Duan, and F. F. Jin, 2012: Thermal controls on the Asian summer monsoon. Scientific Reports, 2, 404, https://doi.org/10.1038/srep00404.

    Article  Google Scholar 

  42. Yu, K., 2020: Wuhan on Alert Again: Flooding Poses Threat to 11 Million People. Al Jazeera. Available from https://theglob-alherald.com/news/wuhan-on-alert-again-flooding-poses-threat-to-11-million-people/.

  43. Yuan, Y., H. Gao, W. J. Li, Y. J. Liu, L. J. Chen, B. Zhou, and Y. H. Ding, 2017: The 2016 summer floods in China and associated physical mechanisms: A comparison with 1998. J. Meteor. Res., 31, 261–277, https://doi.org/10.1007/s13351-017-6192-5.

    Article  Google Scholar 

  44. Zhang, Y. C., F. Q. Zhang, C. A. Davis, and J. H. Sun, 2018: Diurnal evolution and structure of long-lived mesoscale convective vortices along the Mei-Yu front over the East China plains. J. Atmos. Sci., 75, 1005–1025, https://doi.org/10.1175/JAS-D-17-0197.1.

    Article  Google Scholar 

  45. Zong, Y. Q., and X. Q. Chen, 2000: The 1998 flood on the Yangtze, China. Natural Hazards, 22, 165–184, https://doi.org/10.1023/A:1008119805106.

    Article  Google Scholar 

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Acknowledgements

AV, MM, RS, AGT and NPK were supported by the COSMIC project through the Met Office Climate Science for Service Partnership (CSSP) China as part of the Newton Fund, contract number P106301. NPK was supported by a Natural Environmental Research Council (NERC) Independent Research Fellowship (NE/L010976/1) and by the ACREW programme of the National Centre for Atmospheric Science. We thank Omar V. MÜLLER for help with GloFAS-ERA5.

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Authors

Contributions

RS: Abstract and Introduction; AV: Data and Methods, Section 4, and Conclusions; MM: Data and Methods, Section 3 and Conclusions; all: feedback on the manuscript. All authors contributed to the conception and design of the analysis, which was carried out by AV, MM and RS.

Corresponding author

Correspondence to Ambrogio Volonté.

Additional information

Article Highlights

• The YRB experienced its heaviest and most extreme June–July rainfall in the last 20 years.

• The Yangtze River discharge was the highest it has been since 1998/1999.

• The northward progression of the EASMF was halted, with prolonged mei-yu conditions over the YRB.

• Heavy rainfall events are associated with airmass convergence at the EASMF, controlled by the upper-level flow pattern.

This paper is a contribution to the special issue on Summer 2020: Record Rainfall in Asia—Mechanisms, Predictability and Impacts.

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Volonté, A., Muetzelfeldt, M., Schiemann, R. et al. Magnitude, Scale, and Dynamics of the 2020 Mei-yu Rains and Floods over China. Adv. Atmos. Sci. 38, 2082–2096 (2021). https://doi.org/10.1007/s00376-021-1085-z

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Key words

  • East Asian summer monsoon
  • 2020 China floods
  • Yangtze River basin
  • mei-yu front
  • extreme precipitation

关键词

  • 东亚夏季风
  • 2020 年中国洪水
  • 长江流域
  • 梅雨锋
  • 极端降水