Record Deluge of July 2021 in Henan, China: Challenges in Understanding, Forecast, and Service
July 2021 has witnessed historically rare, long lasting (> 3 days), and widespread extreme rainfall and severe flooding in central and northern China. This extreme event has left 302 casualties, and direct economic loss of over 100 billion yuan. Zhengzhou, the capital city of Henan Province, received 201.9 mm of rainfall in just one hour on July 20, breaking the record for hourly rainfall rates in the China’s land areas. From July 17 to 22, 39 cities in Henan logged rainfall measurements surpassing half of their annual totals, and 10 cities/counties observed rainfall over the 5-day period equivalent to that of an entire year.
According to the statistics (NCC, 2021), during July 12–18, daily rainfall at 20 national weather stations in Beijing, Inner Mongolia, and provinces of Shanxi, Hebei, Henan, and Anhui reached the extreme precipitation threshold, and 100–250 mm of rainfall occurred over a range of stations in central and northern China. The wide-spread precipitation extremes have brought about massive damage to national economy and safety.
Preliminary investigations suggest that the interactions among the anomalous large-scale (e.g., the western North Pacific high), synoptic-scale (e.g., tropical cyclones In-fa and Cempaka), and mesoscale circulation systems (e.g., the Huanghui vortex) as well as local topography, played significant roles in this deluge.
Overall, the record deluge of July 2021 in Henan, China (the “21.7” event) resembles the torrential rain that ravaged Henan in August 1975 (the “75.8” event), but with changed climate background. Rising weather/climate extremes are widely reported along 40°N of the globe in summer 2021. In late June and early July, extreme heat waves battled Siberia, the western US, and Canada. On July 13–15, unprecedented floods stroke Germany. Multiple indicators of the climate system suggest that climate anomalies are becoming “normal” as global warming continues.
Although weather observing technology and numerical weather prediction (NWP) models have improved considerably in the past 46 years (since “75.8”), challenges remain in understanding the dominant physical mechanisms on multiple timescales; crying needs emerge for refined forecasts of accurate location and amount of such devastating rainfall; and especially, gaps still exist between forecast and service (e.g., warning and response).
This special issue provides a platform to collectively showcase what progress has been made since “75.8”, what the challenges are now, and how to tackle them in a scientific way and in operational settings. It aims to better understand and predict extreme precipitation events, and develop prototype service to better meet the needs of the society in China and beyond.
Submissions covering all aspects of the deluge in Henan and northern China as well as the other associated extreme events occurring in summer 2021 in China and the world are invited. Papers focusing on the following aspects, however, are of special interest,
(1) Contribution of global climate anomalies to the regional precipitation extremes in 2021.
(2) Multiscale interactions among large-, synoptic-, and mesoscale weather systems in sustaining the July 2021 Henan deluge. Particular concerns may include, for example, examination of cloud microphysical processes leading to the exceptionally high efficiency in rainfall production in this event.
(3) Assessment of regional and global NWP models in predicting/simulating this extreme event and improvements in model uncertainty, cloud and precipitation physics representations, and data assimilation using new observations.
(4) Improved and refined forecasting (especially nowcasting) techniques, including but not limited to more forecaster-friendly diagnostic packages or artificial intelligent tools, based on more high-quality observational data.
(5) Development of prototype user service, based on customized needs, to facilitate life-saving responses to extreme event warnings.
(6) New technology including satellite observations and artificial intelligence to advance our understanding of the interactions of multiscale weather systems.
Rucong YU, China Meteorological Administration
Yihong DUAN, Chinese Academy of Meteorological Sciences
Zhemin TAN, Nanjing University
Tim LI, Nanjing University of Information Science & Technology/University of Hawaii
Manuscript submission deadline: December 31, 2022
Submission can be in Chinese first. Authors will be given options to publish in Journal of Meteorological Research in English or Acta Meteorologica Sinica in Chinese.
Papers are published online first soon upon acceptance.
Submission URL: https://mc03.manuscriptcentral.com/acta-e
Please select: “Special issue: July 2021 Henan Deluge”
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Performance of a Global Spectral Model with Dry Air-Mass and Total Air-Mass Conserving Dynamical Cores: A Case Study of the July 2021 Henan Extreme Rainfall Event
2023, 37(1): 20-44. doi: 10.1007/s13351-023-2040-yAbstract Full Text PDF More CitationYang, X. R., W. M. Zhang, J. Peng, et al., 2023: Performance of a global spectral model with dry air-mass and total air-mass conserving dynamical cores: A case study of the July 2021 Henan extreme rainfall event. J. Meteor. Res., 37(1), 20–44, doi: 10.1007/s13351-023-2040-yExport: BibTex EndNote
Record Flood-Producing Rainstorms of July 2021 and August 1975 in Henan of China: Comparative Synoptic Analysis Using ERA5
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Assessing 10 Satellite Precipitation Products in Capturing the July 2021 Extreme Heavy Rain in Henan, China
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A Possible Dynamic Mechanism for Rapid Production of the Extreme Hourly Rainfall in Zhengzhou City on 20 July 2021
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