Abstract
On 20 July 2021, northern Henan Province in China experienced catastrophic flooding as a result of an extremely intense rainstorm, with a record-breaking hourly rainfall of 201.9 mm during 0800–0900 UTC and daily accumulated rainfall in Zhengzhou City exceeding 600 mm (“Zhengzhou 7.20 rainstorm” for short). The multi-scale dynamical and thermodynamical mechanisms for this rainstorm are investigated based on station-observed and ERA-5 reanalysis datasets. The backward trajectory tracking shows that the warm, moist air from the northwestern Pacific was mainly transported toward Henan Province by confluent southeasterlies on the northern side of a strong typhoon In-Fa (2021), with the convergent southerlies associated with a weaker typhoon Cempaka (2021) concurrently transporting moisture northward from South China Sea, supporting the rainstorm. In the upper troposphere, two equatorward-intruding potential vorticity (PV) streamers within the planetary-scale wave train were located over northern Henan Province, forming significant divergent flow aloft to induce stronger ascending motion locally. Moreover, the converged moist air was also blocked by the mountains in western Henan Province and forced to rise so that a deep meso-β-scale convective vortex (MβCV) was induced over the west of Zhengzhou City. The PV budget analyses demonstrate that the MβCV development was attributed to the positive feedback between the rainfall-related diabatic heating and high-PV under the strong upward PV advection during the Zhengzhou 7.20 rainstorm. Importantly, the MβCV was forced by upper-level larger-scale westerlies becoming eastward-sloping, which allowed the mixtures of abundant raindrops and hydrometeors to ascend slantwise and accumulate just over Zhengzhou City, resulting in the record-breaking hourly rainfall locally.
摘 要
2021 年 7 月 20 日, 中国河南省北部遭遇了由特大暴雨过程导致的灾害性洪涝事件, 其中在北京时间下午 16:00–17:00 (即世界时0800–0900), 郑州市发生了破纪录的每小时达 201.9 毫米的极端强降水, 使得日累计雨量超过 600 毫米 (简称 “郑州7.20暴雨”). 本文基于台站观测和 ERA-5 再分析资料, 揭示了这次特大暴雨过程发生发展的多尺度动力学和热力学机制. 后向水汽轨迹追踪显示, 来自西北太平洋第 6 号强台风 “烟花” 北侧汇合的东南气流是向河南省输送暖湿空气主要载体, 同时, 第7号台风 “查帕卡” 东侧的南风也将水汽从南海向北输送. 在对流层高层的行星尺度波列中, 存在两条向赤道方向伸展的高值位势涡度 (位涡) 带, 河南省北部恰好位于两条高值位涡带之间的高空辐散环流中, 由此激发出较强的局地上升运动. 此外, 在对流层低层, 辐合的暖湿空气被河南省西部的山脉所阻挡而抬升, 从而在郑州市西部诱发了一个深厚的中 β 尺度对流涡旋系统 (MβCV). 位涡的定量诊断表明, 在 “郑州 7.20 暴雨” 期间的较强垂直位涡平流背景下, MβCV 的快速发展主要归咎于与降水相关的非绝热加热和低空高值位涡之间的正反馈. 更重要的是, 受行星尺度高层西风带的影响, MβCV 随高度增加而向东倾斜, 这使得大量混合的雨滴和水凝物倾斜上升, 并在郑州市上空积聚, 导致当地破纪录的小时降雨量.
Similar content being viewed by others
References
Archambault, H. M., D. Keyser, L. F. Bosart, C. A. Davis, and J. M. Cordeira, 2015: A composite perspective of the extratropical flow response to recurving western North Pacific tropical cyclones. Mon. Wea. Rev., 143(4), 1122–1141, https://doi.org/10.1175/MWR-D-14-00270.1.
Bosart, L. F., B. J. Moore, J. M. Cordeira, and H. M. Archambault, 2017: Interactions of North Pacific tropical, midlatitude, and polar disturbances resulting in linked extreme weather events over North America in October 2007. Mon. Wea. Rev., 145(4), 1245–1273, https://doi.org/10.1175/MWR-D-16-0230.1.
CGTN, 2021: China gears up to protect cultural relics during flood season. https://news.cgtn.com/news/2021-07-21/China-gears-up-to-protect-cultural-relics-during-flood-season-125hC1cth16/index.html.
Chen, G., and Coauthors, 2022: Variability of microphysical characteristics in the “21.7” Henan extremely heavy rainfall event. Science China Earth Sciences, 65, 1861–1878, https://doi.org/10.1007/s11430-022-9972-9.
Davis, C. A., and S. B. Trier, 2007: Mesoscale convective vortices observed during BAMEX. Part I: Kinematic and thermodynamic structure. Mon. Wea. Rev., 135(6), 2029–2049, https://doi.org/10.1175/MWR3398.1.
Davis, C. A., and T. J. Galarneau, 2009: The vertical structure of mesoscale convective vortices. J. Atmos. Sci., 66(3), 686–704, https://doi.org/10.1175/2008JAS2819.1.
Ding, Y. H., 2015: On the study of the unprecedented heavy rainfall in Henan Province during 4–8 August 1975: Review and assessment. Acta Meteorologica Sinica, 73(3), 411–424, https://doi.org/10.11676/qxxb2015.067. (in Chinese with English abstract)
Ertel, H., 1942: Ein neuer hydrodynamischer Wirbelsatz. Meteorologische Zeitschrift, 59, 271–281.
Galarneau, T. J., T. M. Hamill, R. M. Dole, and J. Perlwitz, 2012: A multiscale analysis of the extreme weather events over western Russia and northern Pakistan during July 2010. Mon. Wea. Rev., 140(5), 1639–1664, https://doi.org/10.1175/MWR-D-11-00191.1.
Hersbach, H., and Coauthors, 2020: The ERA5 global reanalysis. Quart. J. Roy. Meteor. Soc., 146, 1999–2049, https://doi.org/10.1002/qj.3803.
Hoskins, B., 1997: A potential vorticity view of synoptic development. Meteorological Applications, 4, 325–334, https://doi.org/10.1017/S1350482797000716.
Hoskins, B., 2015: Potential vorticity and the PV perspective. Adv. Atmos. Sci., 32, 2–9, https://doi.org/10.1007/s00376-014-0007-8.
Hoskins, B. J., M. E. McIntyre, and A. W. Robertson, 1985: On the use and significance of isentropic potential vorticity maps. Quart. J. Roy. Meteor. Soc., 111, 877–946, https://doi.org/10.1002/qj.49711147002.
Houze, R. A. Jr., 2012: Orographic effects on precipitating clouds. Rev. Geophys., 50(1), RG1001, https://doi.org/10.1029/2011RG000365.
Hua, S. F., X. Xu, and B. J. Chen, 2020: Influence of multiscale orography on the initiation and maintenance of a precipitating convective system in North China: A case study. J. Geophys. Res.: Atmos., 125(13), e2019JD031731, https://doi.org/10.1029/2019JD031731.
Jiang, Y. Q., Y. Wang, C. H. Chen, H. R. He, and H. Huang, 2019: A numerical study of mesoscale vortex formation in the midlatitudes: The role of moist processes. Adv. Atmos. Sci., 36, 65–78, https://doi.org/10.1007/s00376-018-7234-3.
Lau, K. M., G. J. Yang, and S. H. Shen, 1988: Seasonal and intraseasonal climatology of summer monsoon rainfall over East Asia. Mon. Wea. Rev., 116(1), 18–37, https://doi.org/10.1175/1520-0493(1988)116<0018:SAICOS>2.0.CO;2.
Li, H., and B. Shi, 2021: Death toll from Henan floods rises to 302. China Daily, http://www.chinadaily.com.cn/a/202108/03/WS61087e16a310efa1bd66620d.html.
Meier, F., and P. Knippertz, 2009: Dynamics and predictability of a heavy dry-season precipitation event over West Africa—Sensitivity experiments with a global model. Mon. Wea. Rev., 137(1), 189–206, https://doi.org/10.1175/2008MWR2622.1.
Rolph, G., A. Stein, and B. Stunder, 2017: Real-time environmental applications and display system: READY. Environmental Modelling & Software, 95, 210–228, https://doi.org/10.1016/j.envsoft.2017.06.025.
Stein, A. F., R. R. Draxler, G. D. Rolph, B. J. B. Stunder, M. D. Cohen, and F. Ngan, 2015: NOAA’s HYSPLIT atmospheric transport and dispersion modeling system. Bull. Amer. Meteor. Soc., 96(12), 2059–2077, https://doi.org/10.1175/BAMS-D-14-00110.1.
Su, A. F., X. N. Lü, L. M. Cui, Z. Li, L. Xi, and H. Li, 2021: The basic observational analysis of “7.20” extreme rainstorm in Zhengzhou. Torrential Rain and Disasters, 44(5), 445–454. (in Chinese with English abstract)
Sun, Y., H. Xiao, H. L. Yang, J. F. Ding, D. H. Fu, X. L. Guo, and L. Feng, 2021: Analysis of dynamic conditions and hydrometeor transport of Zhengzhou superheavy rainfall event on 20 July 2021 based on optical flow field of remote sensing data. Chinese Journal of Atmospheric Sciences, 45(6), 1384–1399, https://doi.org/10.3878/j.issn.1006-9895.2109.21155. (in Chinese with English abstract)
Tao, S. Y., and L. X. Chen, 1987: A review of recent research on the East Asian summer monsoon in China. Monsoon Meteorology, C. P. Chang and T. N. Krishnamurti, Eds., Oxford University Press, 60–92.
Wei, P., and Coauthors, 2022: On the key dynamical processes supporting the 21.7 Zhengzhou record-breaking hourly rainfall in China. Adv. Atmos. Sci., https://doi.org/10.1007/s00376-022-2061-y.
Wiegand, L., and P. Knippertz, 2014: Equatorward breaking Rossby waves over the North Atlantic and Mediterranean region in the ECMWF operational ensemble prediction system. Quart. J. Roy. Meteor. Soc., 140, 58–71, https://doi.org/10.1002/qj.2112.
Xu, W. H., Y. Q. Ni, X. K. Wang, and X. X. Qiu, 2012: The evolution of a meso-β-scale convective vortex in the Dabie mountain area. Acta Meteorologica Sinica, 26, 597–613, https://doi.org/10.1007/s13351-012-0505-5.
Yang, L., M. F. Liu, J. A. Smith, and F. Q. Tian, 2017: Typhoon Nina and the August 1975 flood over Central China. Journal of Hydrometeorology, 18(2), 451–472, https://doi.org/10.1175/JHM-D-16-0152.1.
Yin, J. F., D. L. Zhang, Y. L. Luo, and R. Y. Ma, 2020: On the extreme rainfall event of 7 May 2017 over the coastal City of Guangzhou. Part I: Impacts of urbanization and orography. Mon. Wea. Rev., 148(3), 955–979, https://doi.org/10.1175/MWR-D-19-0212.1.
Yin, J. F., H. D. Gu, X. D. Liang, M. Yu, J. S. Sun, Y. X. Xie, F. Li, and C. Wu, 2022: A possible dynamic mechanism for rapid production of the extreme hourly rainfall in Zhengzhou City on 20 July 2021. J. Meteor. Res., 36(1), 6–25, https://doi.org/10.1007/s13351-022-1166-7.
Zhang, G. S., J. Y. Mao, Y. M. Liu, and G. X. Wu, 2021a: PV perspective of impacts on downstream extreme rainfall event of a Tibetan Plateau vortex collaborating with a Southwest China vortex. Adv. Atmos. Sci., 38(11), 1835–1851, https://doi.org/10.1007/s00376-021-1027-9.
Zhang, X., H. Yang, X. M. Wang, L. Shen, D. Wang, and H. Li, 2021b: Analysis on characteristic and abnormality of atmospheric circulations of the July 2021 extreme precipitation in Henan. Transactions of Atmospheric Sciences, 44(5), 672–687, https://doi.org/10.13878/j.cnki.dqkxxb.20210907001. (in Chinese with English abstract)
Zhao, X. F., and Q. Cai, 2021: Better risk management. China Daily, https://www.chinadaily.com.cn/a/202112/07/WS61aea1a8a310cdd39bc79b62.html.
Acknowledgements
This research was supported by the National Natural Science Foundation of China (Grant Nos. 42288101, and 42175076), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB40000000) and the Open Research Fund Program of Plateau Atmosphere and Environment Key Laboratory of Sichuan Province (Project PAEKL-2022-K02).
Author information
Authors and Affiliations
Corresponding author
Additional information
Article Highlights
• Trajectory tracking identified the moisture transport during Zhengzhou 7.20 rainstorm being dominated by typhoons “In-Fa” (2021) and “Cempaka” (2021).
• The upper-tropospheric divergent flow between two PV streamers over Henan Province facilitated development of the MβCV.
• The increasingly sloped MβCV forced by the upper-level larger-scale flow directly produced the extreme hourly rainstorm in Zhengzhou.
This paper is a contribution to the special collection on the July 2021 Zhengzhou, Henan Extreme Rainfall Event.
Rights and permissions
About this article
Cite this article
Zhang, G., Mao, J., Hua, W. et al. Synergistic Effect of the Planetary-scale Disturbance, Typhoon and Meso-β-scale Convective Vortex on the Extremely Intense Rainstorm on 20 July 2021 in Zhengzhou. Adv. Atmos. Sci. 40, 428–446 (2023). https://doi.org/10.1007/s00376-022-2189-9
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00376-022-2189-9
Key words
- extreme rainstorm
- potential vorticity
- trajectory tracking
- planetary-scale disturbance
- meso-β-scale convective system