太湖流域1991—2020年面雨量强降水特征研究

Study on characteristics of heavy rain in 1991—2020 in Taihu Basin based on areal rain

强降水是导致流域洪涝的重要因素之一,了解流域强降水特征有助于提升对洪涝风险的认识。从水文气象角度,利用太湖流域1991—2020年30年面雨量资料,研究强降水(日面雨量≥20 mm)特征,统计强降水日数年变化、日数月分布、出现频次及极端降水空间分布特征,分析产生极端降水的影响天气系统,探讨流域旱涝与总雨量和平均日雨量的关系。结果表明:太湖流域强降水日数年际差异明显,年平均强降水日数为14.9 d;强降水集中出现在6—8月;超过80%的雨强频次分布集中在20~40 mm段,而60 mm以上的频次只占总数的6%。各个水利分区极端降水均超过120 mm,最近10年相比过去20年的极端性增加显著。面雨量极值排名前11次均超过70 mm,为台风或者准静止锋影响。出现极端最大降雨和当年强降水总雨量的大小并不直接相关。强降水降雨总量呈上升趋势,而平均日雨量没有明显趋势。强降水总雨量大小和平均日雨量大小和旱涝关系紧密。

Heavy rainfall is one of the important factors that lead to flood in river basin,understanding of heavy precipitation characteristics helps to improve the understanding of flood risk.The characteristics of heavy rainfall(daily areal rainfall exceeds 20 mm)in Taihu Basin during 1991—2020 were studied from a hydro-meteorological perspective.Annual variation of heavy rain day numbers,monthly variation of heavy rain day numbers,the occurrence frequency and the spatial distribution characteristics of extreme rainfall are analyzed,the relationship between drought and flood and total rainfall and average daily rainfall was discussed.The result show that there are obvious inter-annual differences in day numbers of heavy rainfall.The average heavy rainfall day in Taihu Basin is 14.9 d,and the distribution of heavy rainfall days is from June to August.Almost 80%of the heavy rainfall is concentrated in the 20 to 40 mm range,while the heavy rainfall above 60 mm is only 6%.The extreme rainfall in all sub-regions of Taihu Basin exceeds 120 mm,and the extreme rainfall in the last 10 years has increased significantly compared with that in the past 20 years.In the past 30 years,the top 11 areal rainfall extreme values are over 70 mm,all of which were affected by typhoons or quasi-stationary fronts.The occurrence of extreme maximum rainfall is not directly related to the total rainfall of the year.The total amount of heavy rainfall showed an upward trend,while the average daily rainfall showed no obvious trend.The total rainfall and the average daily rainfall are closely related to drought and flood.