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On the Diurnal Cycle of Heavy Rainfall over the Sichuan Basin during 10–18 August 2020

Abstract

A sustained heavy rainfall event occurred over the Sichuan basin in southwest China during 10–18 August 2020, showing pronounced diurnal rainfall variations with nighttime peak and afternoon minimum values, except on the first day. Results show that the westward extension of the anomalously strong western Pacific subtropical high was conducive to the maintenance of a southerly low-level jet (LLJ) in and to the southeast of the basin, which favored continuous water vapor transport and abnormally high precipitable water in the basin. The diurnal cycle of rainfall over the basin was closely related to the periodic oscillation of the LLJ in both wind speed and direction that was caused by the combination of inertial oscillation and terrain thermal forcing. The nocturnally enhanced rainfall was produced by moist convection mostly initiated during the evening hours over the southwest part of the basin where high convective available potential energy with moister near-surface moist air was present. The convective initiation took place as cold air from either previous precipitating clouds from the western Sichuan Plateau or a larger-scale northerly flow met a warm and humid current from the south. It was the slantwise lifting of the warm, moist airflow above the cold air, often facilitated by southwest vortices and quasi-geostrophic ascent, that released the convective instability and produced heavy rainfall.

摘要

2020 年 8 月 10 日至 18 日, 中国西南四川盆地发生持续性强降水事件, 除第一天外, 降水量呈现显著的夜间峰值和下午谷值的特征. 累积降水最大中心位于盆地西北部, 但夜雨增强首先主要出现在盆地西南部, 随后是盆地西北部. 研究结果表明, 异常强的西太平洋副热带高压西伸, 有利于盆地东南侧偏南低空急流的维持, 从而有利于持续的水汽输送和盆地异常高的可降水量分布. 盆地降水日变化与低空急流风速和风向的周期性变化密切相关, 这种周期性变化由惯性振荡和地形热力强迫共同引起. 夜间增强的降水大多由盆地西南部新生的湿对流带来. 夜间盆地西南部大气具有高的对流有效位能和更湿的近地层空气, 由高原西移到盆地的降水云有关的冷空气/偏北气流带来的冷空气与从南边而来的暖空气相遇有利于对流的触发. 暖湿气流在冷空气之上斜升, 同时有西南涡和准地转抬升的助力, 促进了对流不稳定能量的释放和强降水的产生.

References

  1. Bao, X. H., F. Q. Zhang, and J. H. Sun, 2011: Diurnal variations of warm-season precipitation east of the Tibetan Plateau over China. Mon. Wea. Rev., 139, 2790–2810, https://doi.org/10.1175/MWR-D-11-00006.1.

    Article  Google Scholar 

  2. Blackadar, A. K., 1957: Boundary layer wind maxima and their significance for the growth of nocturnal inversions. Bull. Amer. Meteor. Soc., 38, 283–290, https://doi.org/10.1175/1520-0477-38.5.283.

    Article  Google Scholar 

  3. Buajitti, K., and A. K. Blackadar, 1957: Theoretical studies of diurnal wind-structure variations in the planetary boundary layer. Quart. J. Roy. Meteor. Soc., 83, 486–500, https://doi.org/10.1002/qj.49708335804.

    Article  Google Scholar 

  4. Chen, J., Y. G. Zheng, X. L. Zhang, and P. J. Zhu, 2013: Distribution and diurnal variation of warm-season short-duration heavy rainfall in relation to the MCSs in China. Acta Meteorologica Sinica, 27, 868–888, https://doi.org/10.1007/s13351-013-0605-x.

    Article  Google Scholar 

  5. Du, Y., and R. Rotunno, 2014: A simple analytical model of the nocturnal low-level jet over the Great Plains of the United States. J. Atmos. Sci., 71, 3674–3683, https://doi.org/10.1175/JAS-D-14-0060.1.

    Article  Google Scholar 

  6. Feng, X. Y., C. H. Liu, G. Z. Fan, X. D. Liu, and C. Y. Feng, 2016: Climatology and structures of southwest vortices in the NCEP climate forecast system reanalysis. J. Climate, 29, 7675–7701, https://doi.org/10.1175/JCLI-D-150813.1.

    Article  Google Scholar 

  7. Fu, S.-M., J.-P. Zhang, J.-H. Sun, and X.-Y. Shen, 2014: A fourteen- year climatology of the southwest vortex in Summer. Atmos. Ocean. Sci. Lett., 7, 510–514, https://doi.org/10.3878/AOSL20140047.

    Article  Google Scholar 

  8. Fu, S.-M., Z. Mai, J.-H. Sun, W.-L. Li, Y. Ding, and Y.-Q. Wang, 2019: Impacts of convective activity over the Tibetan Plateau on plateau vortex, southwest vortex, and downstream precipitation. J. Atmos. Sci., 76, 3803–3830, https://doi.org/10.1175/JAS-D-18-0331.1.

    Article  Google Scholar 

  9. Hersbach, H., B. Bill, P. Berrisford, et al, 2020: The ERA5 global reanalysis. Q. J. R. Meteorol. Soc, 146(730), 1999–2049, https://doi.org/10.1002/qj.3803.

    Article  Google Scholar 

  10. Holton, J. R., 1967: The diurnal boundary layer wind oscillation above sloping terrain. Tellus, 19, 200–205, https://doi.org/10.3402/tellusa.v19i2.9766.

    Article  Google Scholar 

  11. Hoxit, L R., 1975: Diurnal variations in planetary boundary-layer winds over land. Bound.-Layer Meteorol., 8, 21–38, https://doi.org/10.1007/BF02579391.

    Article  Google Scholar 

  12. Hu, L., D. F. Deng, S. T. Gao, and X. D. Xu, 2016: The seasonal variation of Tibetan convective systems: Satellite observation. J. Geophys. Res., 121, 5512–5525, https://doi.org/10.1002/2015JD024390.

    Article  Google Scholar 

  13. Huang, Y. J., Y. B. Liu, Y. W. Liu, and J. C. Knievel, 2019: Budget analyses of a record-breaking rainfall event in the coastal metropolitan city of Guangzhou, China. J. Geophys. Res., 124, 9391–9406, https://doi.org/10.1029/2018JD030229.

    Article  Google Scholar 

  14. Jiang, X. N., N.-C. Lau, I. M. Held, and J. J. Ploshay, 2007: Mechanisms of the Great Plains low-level jet as simulated in an AGCM. J. Atmos. Sci., 64, 532–547, https://doi.org/10.1175/JAS3847.1.

    Article  Google Scholar 

  15. Jin, X., T. W. Wu, and L. Li, 2013: The quasi-stationary feature of nocturnal precipitation in the Sichuan Basin and the role of the Tibetan Plateau. Climate Dyn., 41, 977–994, https://doi.org/10.1007/s00382-012-1521-y.

    Article  Google Scholar 

  16. Kuo, Y.-H., L. S. Cheng, and J.-W. Bao, 1988: Numerical simulation of the 1981 Sichuan flood. Part I: Evolution of a mesoscale southwest vortex. Mon. Wea. Rev., 116, 2481–2504, https://doi.org/10.1175/1520-0493(1988)116<2481:NSOTSF>2.0.CO;2.

    Article  Google Scholar 

  17. Li, J., J. Du, D.-L. Zhang, C. G. Cui, and Y. S. Liao, 2014: Ensemble-based analysis and sensitivity of mesoscale forecasts of a vortex over southwest China. Quart. J. Roy. Meteor. Soc., 140, 766–782, https://doi.org/10.1002/qj.2200.

    Article  Google Scholar 

  18. Li, L., R. H. Zhang, and M. Wen, 2017: Genesis of southwest vortices and its relation to Tibetan Plateau vortices. Quart. J. Roy. Meteor. Soc., 143, 2556–2566, https://doi.org/10.1002/qj.3106.

    Article  Google Scholar 

  19. Li, Y. D., Y. Wang, Y. Song, L. Hu, S. T. Gao, and F. Rong, 2008: Characteristics of summer convective systems initiated over the Tibetan Plateau. Part I: Origin, track-2695, https://doi.org/10.1175/2008JAMC1695.1.

    Google Scholar 

  20. Liu, X., Y. L. Luo, Z. Y. Guan, and D.-L. Zhang, 2018: An extreme rainfall event in coastal South China during SCMREX- 2014: Formation and roles of rainband and echo trainings. J. Geophys. Res., 123, 9256–9278, https://doi.org/10.1029/2018JD028418.

    Article  Google Scholar 

  21. Luo, Y. L., M. W. Wu, F. M. Ren, J. Li, and W.-K. Wong, 2016: Synoptic situations of extreme hourly precipitation over China. J. Climate, 29, 8703–8719, https://doi.org/10.1175/JCLI-D-16-0057.1.

    Article  Google Scholar 

  22. Luo, Y. L., and Coauthors, 2020: Science and prediction of heavy rainfall over China: Research progress since the reform and opening-up of new China. Journal of Meteorological Research, 34, 427–459, https://doi.org/10.1007/s13351-020-0006-x.

    Article  Google Scholar 

  23. Markowski, P., and Y. Richardson, 2010: Mesoscale Meteorology in Midlatitudes. John Wiley & Sons, Ltd., 407pp, https://doi.org/10.1002/9780470682104.

    Book  Google Scholar 

  24. Qian, T. T., P. Zhao, F. Q. Zhang, and X. H. Bao, 2015: Rainy-season precipitation over the Sichuan basin and adjacent regions in southwestern China. Mon. Wea. Rev., 143, 383–394, https://doi.org/10.1175/MWR-D-13-00158.1.

    Article  Google Scholar 

  25. Shapiro, A., E. Fedorovich, and S. Rahimi, 2016: A unified theory for the Great Plains nocturnal low-level jet. J. Atmos. Sci., 73, 3037–3057, https://doi.org/10.1175/JAS-D-15-0307.1.

    Article  Google Scholar 

  26. Sugimoto, S., and K. Ueno, 2010: Formation of mesoscale convective systems over the eastern Tibetan Plateau affected by plateau-scale heating contrasts. J. Geophys. Res., 115(D16), D16105, https://doi.org/10.1029/2009JD013609.

    Article  Google Scholar 

  27. Tu, C.-C., Y.-L. Chen, S.-Y. Chen, Y.-H. Kuo, and P.-L. Lin, 2017: Impacts of including rain-evaporative cooling in the initial conditions on the prediction of a coastal heavy rainfall event during TiMREX. Mon. Wea. Rev., 145, 253–277, https://doi.org/10.1175/MWR-D-16-0224.1.

    Article  Google Scholar 

  28. Ueno, K., S. Sugimoto, T. Koike, H. Tsutsui, and X. D. Xu, 2011: Generation processes of mesoscale convective systems following midlatitude troughs around the Sichuan basin. J. Geophys. Res., 116, D02104, https://doi.org/10.1029/2009JD013780.

    Google Scholar 

  29. Wang, C.-C., Chen, G. T.-J., and R. E. Carbone, 2005: Variability of warm-season cloud episodes over East Asia based on GMS infrared brightness temperature observations. Mon. Wea. Rev., 133, 1478–1500, https://doi.org/10.1175/MWR2928.1.

    Article  Google Scholar 

  30. Wang, Q.-W., and Z.-M. Tan, 2014: Multi-scale topographic control of southwest vortex formation in Tibetan Plateau region in an idealized simulation. J. Geophys. Res., 119, 11543–11561, https://doi.org/10.1002/2014JD021898.

    Article  Google Scholar 

  31. Wu, M. W., and Y. L. Luo, 2016: Mesoscale observational analysis of lifting mechanism of a warm-sector convective system producing the maximal daily precipitation in China mainland during pre-summer rainy season of 2015. Journal of Meteorological Research, 30, 719–736, https://doi.org/10.1007/s13351-016-6089-8.

    Article  Google Scholar 

  32. Xia, R. D., D.-L. Zhang, and B. L. Wang, 2015: A 6-yr cloud-toground lightning climatology and its relationship to rainfall over Central and Eastern China. J. Appl. Meteorol. Climatol., 54, 2443–2460, https://doi.org/10.1175/JAMC-D-15-0029.1.

    Article  Google Scholar 

  33. Yuan, W. H., R. C. Yu, M. H. Zhang, W. Y. Lin, H. M. Chen, and J. Li, 2012: Regimes of diurnal variation of summer rainfall over subtropical East Asia. J. Climate, 25, 3307–3320, https://doi.org/10.1175/JCLI-D-11-00288.1.

    Article  Google Scholar 

  34. Zhang, C. H., R. D. Xia, and Y. Q. Wang, 2018: Observational analysis of a local heavy rainfall in Beijing caused by terrain, cold pool outflow and warm moist air interactions. Transactions of Atmospheric Sciences, 41, 207–219, https://doi.org/10.13878/j.cnki.dqkxxb.20160115001. (in Chinese with English abstract)

    Google Scholar 

  35. Zhang, D.-L., and J. M. Fritsch, 1987: Numerical simulation of the meso-β scale structure and evolution of the 1977 Johnstown flood. Part II: Inertially stable warm-core vortex and the mesoscale convective complex. J. Atmos. Sci., 44, 2593–2612, https://doi.org/10.1175/1520-0469(1987)044<2593:NSOTMS>2.0.CO;2.

    Article  Google Scholar 

  36. Zhang, D.-L., S. L. Zhang, and S. J. Weaver, 2006: Low-level jets over the mid-Atlantic States: Warm-season climatology and a case study. J. Appl. Meteorol. Climatol., 45, 194–209, https://doi.org/10.1175/JAM2313.1.

    Article  Google Scholar 

  37. Zhang, Y. H., M. Xue, K. F. Zhu, and B. W. Zhou. 2019: What is the main cause of diurnal variation and nocturnal peak of summer precipitation in Sichuan Basin, China? The key role of boundary layer low-level jet inertial oscillations. J. Geophys. Res., 124, 2643–2664, https://doi.org/10.1029/2018JD029834.

    Article  Google Scholar 

  38. Zhao, Y. C., 2015: A study on the heavy-rain-producing mesoscale convective system associated with diurnal variation of radiation and topography in the eastern slope of the western Sichuan plateau. Meteorol. Atmos. Phys., 127, 123–146, https://doi.org/10.1007/s00703-014-0356-y.

    Article  Google Scholar 

  39. Zhou, T.-J., and R.-C. Yu, 2005: Atmospheric water vapor transport associated with typical anomalous summer rainfall patterns in China. J. Geophys. Res., 110, D08104, https://doi.org/10.1029/2004JD005413.

    Google Scholar 

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Acknowledgements

This study was supported by the National Natural Science Foundation of China (Grant Nos. 41775050, 91937301, 41775002, 42005008) and the Science Development Fund of Chinese of Academy of Meteorological Sciences (2020KJ022).

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Correspondence to Yali Luo.

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Article Highlights

• The diurnal cycle of rainfall with higher nocturnal amount over the basin was closely related to the periodic oscillation of a LLJ.

• The periodic oscillation of the LLJ was caused by the combination of inertial oscillation and terrain thermal forcing.

• The nocturnal rainfall was enhanced by convective storms initiated over the southwest of the basin during evening hours.

• The convective initiation occurred as cold air from either previous precipitating clouds or a larger-scale northerly flow met a warm and humid current from the south.

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

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Cite this article

Xia, R., Luo, Y., Zhang, DL. et al. On the Diurnal Cycle of Heavy Rainfall over the Sichuan Basin during 10–18 August 2020. Adv. Atmos. Sci. 38, 2183–2200 (2021). https://doi.org/10.1007/s00376-021-1118-7

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  • DOI: https://doi.org/10.1007/s00376-021-1118-7

Key words

  • diurnal cycle
  • heavy rainfall
  • low-level jet
  • inertial oscillation
  • terrain
  • Sichuan basin

关键词

  • 日变化
  • 强降水
  • 低空急流
  • 惯性振荡
  • 地形
  • 四川盆地