Abstract
In summer 2020, extreme rainfall occurred throughout the Yangtze River basin, Huaihe River basin, and southern Yellow River basin, which are defined here as the central China (CC) region. However, only a weak central Pacific (CP) El Niño happened during winter 2019/20, so the correlations between the El Niño–Southern Oscillation (ENSO) indices and ENSO-induced circulation anomalies were insufficient to explain this extreme precipitation event. In this study, reanalysis data and numerical experiments are employed to identify and verify the primary ENSO-related factors that cause this extreme rainfall event. During summer 2020, unusually strong anomalous southwesterlies on the northwest side of an extremely strong Northwest Pacific anticyclone anomaly (NWPAC) contributed excess moisture and convective instability to the CC region, and thus, triggered extreme precipitation in this area. The tropical Indian Ocean (TIO) has warmed in recent decades, and consequently, intensified TIO basinwide warming appears after a weak El Niño, which excites an extremely strong NWPAC via the pathway of the Indo-western Pacific Ocean capacitor (IPOC) effect. Additionally, the ENSO event of 2019/20 should be treated as a fast-decaying CP El Niño rather than a general CP El Niño, so that the circulation and precipitation anomalies in summer 2020 can be better understood. Last, the increasing trend of tropospheric temperature and moisture content in the CC region after 2000 is also conducive to producing heavy precipitation.
摘要
2020 夏季在整个长江流域、 淮河流域以及黄河流域南部[本文定义为中国中部 (CC) 地区]均发生了极端强降水事件. 但 2019/20 年冬赤道太平洋仅发生了一次弱的中太平洋型 (CP) El Niño, 因而根据厄尔尼诺–南方涛动 (ENSO) 指数与 ENSO 激发的环流异常间的相关关系难以解释此次极端降水事件. 本研究利用再分析资料和数值模拟试验找出并验证了造成此次极端降水事件与 ENSO 相关的主要因素. 水汽收支和湿静能分析表明: 2020 年夏季异常强烈的西北太平洋反气旋异常 (NWPAC) 西北侧的西南气流异常向 CC 地区输送大量水汽并提供对流不稳定条件, 从而引发了该地区的极端降水. 近几十年来, 热带印度洋 (TIO) 变暖, 使得弱 El Niño 后也能出现强的 TIO 海盆增暖, 进而通过印度–西太平洋电容器效应激发出极端强烈的 NWPAC. 此外, 2019/20 年的 ENSO 事件应被视为一次快速衰减的 CP El Niño, 而不是一次一般的 CP El Niño, 以便更好地理解 2020 年夏季的环流和降水异常. 最后, 2000 年后 CC 区域对流层大气温度和水汽含量的上升趋势也有利于更多降水产生.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Alory, G., S. Wijffels, and G. Meyers, 2007: Observed temperature trends in the Indian Ocean over 1960–1999 and associated mechanisms. Geophys. Res. Lett., 34, L02606, https://doi.org/10.1029/2006GL028044.
Ashok, K., S. K. Behera, S. A. Rao, H. Y. Weng, and T. Yamagata, 2007: El Niño Modoki and its possible teleconnection. J. Geophys. Res. Oceans, 112, C11007, https://doi.org/10.1029/2006JC003798.
Back, L. E., and C. S. Bretherton, 2009: A simple model of climatological rainfall and vertical motion patterns over the tropical oceans. J. Climate, 22, 6477–6497, https://doi.org/10.1175/2009JCLI2393.1.
Barnes, S. L., 1964: A technique for maximizing details in numerical weather map analysis. J. Appl. Meteorol., 3, 396–409, https://doi.org/10.1175/1520-0450(1964)003<0396:ATFMDI>2.0.CO;2.
Chen, W., L. Wang, J. Feng, Z. P. Wen, T. J. Ma, X. Q. Yang, and C. H. Wang, 2019: Recent progress in studies of the variabilities and mechanisms of the East Asian monsoon in a changing climate. Adv. Atmos. Sci., 36, 887–901, https://doi.org/10.1007/s00376-019-8230-y.
Chen, Z. S., Z. P. Wen, R. G. Wu, X. B. Lin, and J. B. Wang, 2016: Relative importance of tropical SST anomalies in maintaining the western North Pacific anomalous anticyclone during El Niño to La Niña transition years. Climate Dyn., 46, 1027–1041, https://doi.org/10.1007/s00382-015-2630-l.
Chen, Z. S., Y. Du, Z. P. Wen, R. G. Wu, and C. Z. Wang, 2018: Indo-Pacific climate during the decaying phase of the 2015/16 El Niño: Role of southeast tropical Indian Ocean warming. Climate Dyn., 50, 4707–4719, https://doi.org/10.1007/s00382-017-3899-z.
Chowdary, J. S., S.-P. Xie, H. Tokinaga, Y. M. Okumura, H. Kubota, N. Johnson, and X.-T. Zheng, 2012: Interdecadal variations in ENSO teleconnection to the Indo-Western Pacific for 1870–2007. J. Climate, 25, 1722–1744, https://doi.org/10.1175/JCLI-D-11-00070.1.
Chowdary, J. S., H. S. Harsha, C. Gnanaseelan, G. Srinivas, A. Parekh, P. Pillai, and C. V. Naidu, 2017: Indian summer monsoon rainfall variability in response to differences in the decay phase of El Niño. Climate Dyn., 48, 2707–2727, https://doi.org/10.1007/s00382-016-3233-l.
Chowdary, J. S., K. M. Hu, G. Srinivas, Y. Kosaka, L. Wang, and K. K. Rao, 2019: The Eurasian jet streams as conduits for East Asian monsoon variability. Current Climate Change Reports, 5, 233–244, https://doi.org/10.1007/s40641-019-00134-x.
Chu, J.-E., K.-J. Ha, J.-Y. Lee, B. Wang, B.-H. Kim, and C. E. Chung, 2014: Future change of the Indian Ocean basin-wide and dipole modes in the CMIP5. Climate Dyn., 43, 535–551, https://doi.org/10.1007/s00382-013-2002-7.
Collins, W. D., and Coauthors, 2004: Description of the NCAR Community Atmosphere Model (CAM 3.0). University Corporation for Atmospheric Research, No. NCAR/TN-464+STR, 214 pp, https://doi.org/10.5065/D63N21CH.
Du, Y., and S.-P. Xie, 2008: Role of atmospheric adjustments in the tropical Indian Ocean warming during the 20th century in climate models. Geophys. Res. Lett., 35, L08712, https://doi.org/10.1029/2008GL033631.
Du, Y., S.-P. Xie, G. Huang, and K. M. Hu, 2009: Role of air-sea interaction in the long persistence of El Niño-induced North Indian Ocean warming. J. Climate, 22, 2023–2038, https://doi.org/10.1175/2008JCLI2590.l.
Efron, B., 1979: Bootstrap methods: Another look at the jack-knife. Annals of Statistics, 7, 1–26, https://doi.org/10.1214/aos/1176344552.
Feng, J., W. Chen, C.-Y. Tam, and W. Zhou, 2011: Different impacts of El Niño and El Niño Modoki on China rainfall in the decaying phases. International Journal of Climatology, 31, 2091–2101, https://doi.org/10.1002/joc.2217.
Feng, J., L. Wang, and W. Chen, 2014: How does the East Asian summer monsoon behave in the decaying phase of El Niño during different PDO Phases? J. Climate, 27, 2682–2698, https://doi.org/10.1175/JCLI-D-13-00015.l.
Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc., 106, 447–462, https://doi.org/10.1002/qj.49710644905.
Hersbach, H., and Coauthors, 2019: ERA5 monthly averaged data on pressure levels from 1979 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS), Available from https://doi.org/10.24381/cds.6860a573.
Huang, B. Y., and Coauthors, 2017: Extended reconstructed sea surface temperature, version 5 (ERSSTv5): Upgrades, validations, and intercomparisons. J. Climate, 30, 8179–8205, https://doi.org/10.1175/JCLI-D-16-0836.1.
Huang, G., K. M. Hu, and S.-P. Xie, 2010: Strengthening of tropical Indian Ocean teleconnection to the Northwest Pacific since the Mid-1970s: An atmospheric GCM study. J. Climate, 23, 5294–5304, https://doi.org/10.1175/2010JCLI3577.1.
Huang R. H., R. H. Zhang, and Q. Y. Zhang, 2000: The 1997/98 ENSO cycle and its impact on summer climate anomalies in East Asia. Adv. Atmos. Sci., 17, 348–362, https://doi.org/10.1007/s00376-000-0028-3.
Jiang, W. P., G. Huang, K. M. Hu, R. G. Wu, H. N. Gong, X. L. Chen, and W. C. Tao, 2017: Diverse relationship between ENSO and the Northwest Pacific summer climate among CMIP5 models: Dependence on the ENSO decay pace. J. Climate, 30, 109–127, https://doi.org/10.1175/JCLI-D-16-0365.1.
Jiang, W. P., G. Huang, P. Huang, R. G. Wu, K. M. Hu, and W. Chen, 2019: Northwest Pacific anticyclonic anomalies during post-El Niño summers determined by the pace of El Niño decay. J. Climate, 32, 3487–3503, https://doi.org/10.1175/JCLI-D-18-0793.1.
Klein, S. A., B. J. Soden, and N.-C. Lau, 1999: Remote sea surface temperature variations during ENSO: Evidence for a tropical atmospheric bridge. J. Climate, 12, 917–932, https://doi.org/10.1175/1520-0442(1999)012<0917:RSSTVD>2.0.CO;2.
Kosaka, Y., J. S. Chowdary, S.-P. Xie, Y.-M. Min, and J.-Y. Lee, 2012: Limitations of seasonal predictability for summer climate over East Asia and the Northwestern Pacific. J. Climate, 25, 7574–7589, https://doi.org/10.1175/JCLI-D-12-00009.1.
Li, T., B. Wang, B. Wu, T. J. Zhou, C.-P. Chang, and R. H. Zhang, 2017: Theories on formation of an anomalous anticyclone in western North Pacific during El Niño: A review. J. Meteor. Res., 31, 987–1006, https://doi.org/10.1007/s13351-017-7147-6.
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.
Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44, 25–43, https://doi.org/10.2151/jmsj1965.44.1_25.
Neelin, J. D., and I. M. Held, 1987: Modeling tropical convergence based on the moist static energy budget. Mon. Wea. Rev., 115, 3–12, https://doi.org/10.1175/1520-0493(1987)115<0003:MTCBOT>2.0.CO;2.
Reynolds, R. W., N. A. Rayner, T. M. Smith, D. C. Stokes, and W. Q. Wang, 2002: An improved in situ and satellite SST analysis for climate. J. Climate, 15, 1609–1625, https://doi.org/10.1175/1520-0442(2002)015<1609:AIISAS>2.0.CO;2.
Tao, W. C., G. Huang, K. M. Hu, X. Qu, G. H. Wen, and H. N. Gong, 2015: Interdecadal modulation of ENSO teleconnections to the Indian Ocean basin mode and their relationship under global warming in CMIP5 models. International Journal Climatology, 35, 391–407, https://doi.org/10.1002/joc.3987.
Wang, B., R. G. Wu, and X. H. Fu, 2000: Pacific-East Asian teleconnection: How does ENSO affect East Asian climate? J. Climate, 13, 1517–1536, https://doi.org/10.1175/1520-0442(2000)013<1517:PEATHD>2.0.CO;2.
Wang, B., J. Li, and Q. He, 2017: Variable and robust East Asian monsoon rainfall response to El Niño over the past 60 years (1957–2016). Adv. Atmos. Sci., 34, 1235–1248, https://doi.org/10.1007/s00376-017-7016-3.
Wei, K., C. J. Ouyang, H. T. Duan, Y. L. Li, M. X. Chen, J. Ma, H. C. An, and S. Zhou, 2020: Reflections on the catastrophic 2020 Yangtze River Basin flooding in southern China. The Innovation, 1, 100038, https://doi.org/10.1016/j.xinn.2020.100038.
Wu, B., T. J. Zhou, and T. Li, 2009: Contrast of rainfall-SST relationships in the western North Pacific between the ENSO-developing and ENSO-decaying summers. J. Climate, 22, 4398–4405, https://doi.org/10.1175/2008JCLI2710.l.
Wu, B., T. Li, and T. J. Zhou, 2010: Relative contributions of the Indian Ocean and local SST anomalies to the maintenance of the western North Pacific anomalous anticyclone during the El Niño decaying summer. J. Climate, 23, 2974–2986, https://doi.org/10.1175/JCLI-D-15-0901.1.
Wu, B., T. J. Zhou, and T. Li, 2017: Atmospheric dynamic and thermodynamic processes driving the western North Pacific anomalous anticyclone during El Niño. Part I: Maintenance mechanisms. J. Climate, 30, 9621–9635, https://doi.org/10.1175/JCLI-D-16-0489.1.
Wu, Z. W., B. Wang, J. P. Li, and F.-F. Jin, 2009b: An empirical seasonal prediction model of the East Asian summer monsoon using ENSO and NAO. J. Geophys. Res. Atmos., 114, D18120, https://doi.org/10.1029/2009JD011733.
Xiang, B. Q., B. Wang, W. D. Yu, and S. B. Xu, 2013: How can anomalous western North Pacific subtropical high intensify in late summer? Geophys. Res. Lett., 40, 2349–2354, https://doi.org/10.1002/grl.50431.
Xie, S.-P., K. M. Hu, J. Hafner, H. Tokinaga, Y. Du, G. Huang, and T. Sampe, 2009: Indian Ocean capacitor effect on Indo-Western Pacific climate during the summer following El Niño. J. Climate, 22, 730–747, https://doi.org/10.1175/2008JCLI2544.1.
Xie, S.-P., Y. Du, G. Huang, X.-T. Zheng, H. Tokinaga, K. M. Hu, and Q. Y. Liu, 2010: Decadal shift in El Niño influences on Indo-Western Pacific and East Asian climate in the 1970s. J. Climate, 23, 3352–3368, https://doi.org/10.1175/2010JCLI3429.1.
Xie, S.-P., Y. Kosaka, Y. Du, K. M. Hu, J. S. Chowdary, and G. Huang, 2016: Indo-western Pacific ocean capacitor and coherent climate anomalies in post-ENSO summer: A review. Adv. Atmos. Sci., 33, 411–432, https://doi.org/10.1007/s00376-015-5192-6.
Yu, J.-Y., X. Wang, S. Yang, H. Paek, and M. Y. Chen, 2017: The Changing El Niño-Southern oscillation and associated climate extremes. Climate Extremes: Patterns and Mechanisms, S.-Y. S. Wang, et al., Eds., AGU, 3–38, https://doi.org/10.1002/9781119068020.chl.
Yuan, Y., and S. Yang, 2012: Impacts of different types of El Niño on the East Asian climate: Focus on ENSO cycles. J. Climate, 25, 7702–7722, https://doi.org/10.1175/JCLI-D-11-00576.1.
Zhang, Q., Y. F. Qian, and X. H. Zhang, 2000: Interannual and interdecadal variations of the South Asia high. Chinese Journal of Atmospheric Sciences, 24, 67–78, https://doi.org/10.3878/j.issn.1006-9895.2000.01.07. (in Chinese with English abstract)
Zhang, R. H., Q. Y. Min, and J. Z. Su, 2017: Impact of El Niño on atmospheric circulations over East Asia and rainfall in China: Role of the anomalous western North Pacific anticyclone. Science China Earth Sciences, 60, 1124–1132, https://doi.org/10.1007/s11430-016-9026-x.
Zheng, F., X.-H. Fang, J.-Y. Yu, and J. Zhu, 2014: Asymmetry of the Bjerknes positive feedback between the two types of El Niño. Geophys. Res. Lett., 41, 7651–7657, https://doi.org/10.1002/2014GL062125.
Zheng, X.-T., S.-P. Xie, and Q.-Y. Liu, 2011: Response of the Indian Ocean basin mode and its capacitor effect to global warming. J. Climate, 24, 6146–6164, https://doi.org/10.1175/2011JCLI4169.1.
Acknowledgements
This study was jointly supported by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS) (Grant No. XDB40000000), the CAS (Grant No. QYZDJ-SSW-DQC021), the National Natural Science Foundation of China (Grant No. 41630531), and the State Key Laboratory of Loess and Quaternary Geology. We thank the supercomputer center of the Pilot Qingdao National Laboratory for Marine Science and Technology and Beijing Super Cloud Computing Center, who offered computing services. We also thank Dr. X. Z. LI, H. LIU, and L. LIU from the Institute of Earth Environment, CAS, who offered suggestions for our numerical experiments.
Author information
Authors and Affiliations
Corresponding author
Additional information
Article Highlights
• The extremely strong Northwest Pacific anticyclone anomaly (NWPAC) is responsible for extreme rainfall in summer 2020.
• The decadal warming trend of the tropical Indian Ocean contributes to the extreme NWPAC that appears after a weak El Niño.
• Considering the 2019/20 event as a fast-decaying El Niño provides a better explanation of the extreme NWPAC and rainfall anomalies.
This paper is a contribution to the special issue on Summer 2020: Record Rainfall in Asia—Mechanisms, Predictability and Impacts.
Rights and permissions
About this article
Cite this article
Fang, C., Liu, Y., Cai, Q. et al. Why Does Extreme Rainfall Occur in Central China during the Summer of 2020 after a Weak El Niño?. Adv. Atmos. Sci. 38, 2067–2081 (2021). https://doi.org/10.1007/s00376-021-1009-y
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00376-021-1009-y
Key words
- extreme rainfall
- Northwest Pacific anticyclone anomaly (NWPAC)
- Indo-western Pacific Ocean capacitor (IPOC)
- Tropical Indian Ocean warming trend
- fast-decaying El Niño