Abstract:

The Three Gorges Reservoir area (TGRA), which is located in the hinterland of the Yangtze River Basin, is a typical area with frequent meteorological disasters and fragile ecological environment, especially the hourly heavy rainfall (HHR) in summer is prone to disasters due to suddenness and difficulty in prediction. Based on the hourly precipitation data in summer during 1992-2021 from the National Meteorological Information Center of China Meteorological Administration, the fine spatio-temporal distribution characteristics of HHR and heavy rainfall event (HRE) in the TGRA are investigated. The results show that the summer HHR in the TGRA has strong local features, its intensity is strong, and makes main contribution to total summer precipitation due to its high frequency. The southeastern TGRA is the center of summer HHR precipitation, frequency and intensity. In the past 30 years, the summer HHR precipitation in the TGRA has been non-significant increase. Both the diurnal variations of summer HHR precipitation and frequency in the TGRA show a bimodal pattern, with peaks appearing in the morning and afternoon, respectively, and the peak time phase is related to the terrain. Besides, the summer HREs in the TGRA are mainly short duration (1-6 hours), with precipitation mostly ranging from 20 to 60 mm, while the long duration (>12 hours) HREs seldom occur, with precipitation mostly ranging from 60 to 100 mm. Moreover, the short duration HREs mostly start in the afternoon, and most of their maximum hourly precipitation also occur in the afternoon, while the HREs with medium (7-12 hours) and long durations mostly start at night, and most of their maximum hourly precipitation occur in the morning.

Key words: Three Gorges Reservoir area, hourly heavy rainfall, heavy rainfall event, spatio-temporal distribution, diurnal variation, terrain

摘要：

三峡库区地处长江流域腹地，是典型的气象灾害频发区和生态环境脆弱区，夏季小时强降水（Hourly Heavy Rainfall，HHR）因突发性强、预测难度大等极易致灾。利用中国气象局国家气象信息中心提供的逐小时降水量观测资料，分析1992—2021年三峡库区夏季HHR和强降水事件（Heavy Rainfall Event，HRE）的精细化时空分布特征。结果表明，三峡库区夏季HHR局地性强、强度大，其降水量对夏季总降水量贡献大，且主要源于降水频次的贡献，库区东南部是高值中心。近30 a来，三峡库区夏季HHR降水量呈不显著增加趋势；HHR的降水量和频次日变化均呈双峰型，峰值分别出现在清晨和下午，且日峰值时间位相与地形相关。三峡库区夏季HRE以短历时（1~6 h）为主，其降水量多为20~60 mm，而长历时（>12 h）发生少，其降水量多为60~100 mm。短历时HRE多开始于下午，其最大小时降水量也多发生于下午，而中历时（7~12 h）和长历时HRE多开始于夜间，二者的最大小时降水量均多发生于清晨。

关键词: 三峡库区, 小时强降水, 强降水事件, 时空分布, 日变化, 地形