The variations in summer precipitation according to different grades and their effects on summer drought/flooding in the Haihe River basin were analyzed using the daily precipitation data from 161 meteorological stations from 1972 to 2021. The results showed that the number of rainy days (NRD) in summer in the Haihe River basin significantly declined in the past 50 years, mainly due to the reduction in the number of light-rain days. The precipitation amount (PA) exhibited prominent interdecadal characteristics, showing an upward tendency in the past 20 years accompanied by a remarkable increase in the proportion of torrential rain. The NRD in the northern part of the basin significantly decreased, while the PA in the southeast showed an increasing trend. Summer drought/flooding was strongly linked to the changes in the NRD and was predominantly affected by intense precipitation, with contribution rates of 5.5%, 16.8%, 31.2%, and 46.5% from light, moderate, heavy, and torrential rain, respectively. The effects of torrential rain increased in recent decades, particularly in the flooding scenarios. In addition, July was the critical period for summer drought/flooding, with the major influence of heavy and torrential rain. The most intense summer rainfall event in the Haihe River basin could contribute from 15% to 29% of total precipitation, resulting in changes in the severity and state of summer drought/flooding, which indicated that the precipitation process had a decisive impact on seasonal drought/flooding. Therefore, when predicting summer precipitation in the Haihe River basin, it is necessary to pay attention to the intense rainfall events during critical periods.

中文翻译：

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海河流域夏季降水不同等级的变化及其对夏季旱涝的影响

利用161个气象站1972—2021年的日降水数据，分析了海河流域夏季降水不同等级的变化及其对夏季旱涝的影响。结果表明，雨天数（NRD）近 50 年来海河流域夏季显着下降，主要原因是小雨天数减少。降水量（PA）表现出明显的年代际特征，近20年来呈上升趋势，暴雨占比显着增加。盆地北部NRD显着下降，东南部PA呈上升趋势。夏季干旱/洪水与 NRD 的变化密切相关，主要受强降水的影响，小雨、中雨、大雨和暴雨的贡献率分别为 5.5%、16.8%、31.2% 和 46.5%。近几十年来，暴雨的影响有所增加，特别是在洪水情景中。此外，7 月是夏季旱涝的关键时期，主要受暴雨和暴雨影响。海河流域最强烈的夏季降雨事件可贡献总降水量的15%至29%，导致夏季旱涝的严重程度和状态发生变化，这表明降水过程对季节性干旱具有决定性影响/洪水。因此，在预测海河流域夏季降水时，