应用气象学报 (Nov 2022)
Comparative Analysis on Meteorological and Hydrological Rain Gauge Observations of the Extreme Heavy Rainfall Event in Henan Province During July 2021
Abstract
The extreme heavy rainfall event in Henan Province during 17-23 July 2021 with 1-hour rainfall intensity breaking historical record in the inland of China, ranks second among the top 10 weather and climate events in China in 2021. Previous studies have investigated the rain gauge observations collected by the meteorological ground stations to analyze the rainfall situation and count the extreme value of the "21·7" process. Considering the rainfall is uneven in space and time, the observations from a single source has great uncertainty which may miss the actual rainfall extreme value. By comparing the rainfall observations between meteorological and hydrological rain gauge stations, the objectivity and accuracy of the rainfall records from two business systems are analyzed for the "21·7" extreme heavy rainfall event. It is found that the observations exhibit good agreement in the accumulated rainfall distributions of various levels, and the temporal evolution of daily and hourly rainfall. However, the positions and values of accumulated rainfall and hourly rainfall intensity extremum are different in detail according to these two systems. The systematic deviation between the meteorological and hydrological observations is less than 1% in the heavy rainfall area (6-day accumulated rainfall more than 600 mm). These differences are related to the distinctness in the number, location, density of stations, and the accuracy of observation instruments. In addition, the inhomogeneous features of the rainfall in time and space also lead to the deviation of rainfall records between meteorological and hydrological observations.On the other hand, the meteorological and hydrological rainfall data in top 3 accumulated rainfall cities (Zhengzhou, Hebi and Xinxiang) are merged. The results show that merged rainfall data can present more detailed rainfall distributions and more objective rainfall evolution characteristics compared to single source data. Based on the merged rainfall data, the rainfall features in these three cities are summarized. The strongest rainfall period in Hebi and Xinxiang are about 26 hours and 28 hours later than that at Zhengzhou, respectively, while the rainfall events happened in these three cities are characterized by large accumulated amount, extremely strong hourly intensity, concentrated location and sudden increase of rainfall intensity.
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