长江上游面雨量低频特征分析

Analysis on low-frequency characteristics of areal rainfall over upper Yangtze River

目前,对长江上游降雨的研究多以过程和影响分析为主,对其低频特征研究较少。基于1961~2017年长江上游276站逐日降水资料,利用泰森多边形法得到长江上游7大流域逐日面雨量,分析了长江上游面雨量低频特征。结果表明:①长江上游面雨量存在着显著的低频振荡,但各流域周期不同,金沙江石鼓以上和金沙江石鼓以下2个流域具有10~40 d周期,而其他流域具有10~25 d周期。②长江上游夏季低频强降水事件在频次、持续天数、降水强度和最大面雨量特征量上排首位,秋季次之,春季最小,但各流域之间特征量存在着较大的差异。③低频强降水过程次数年际差异大,在15~25次之间,随持续时间、流域数量增加,过程次数呈减少趋势。

At present, the research on rainfall in the upper reaches of Yangtze River mainly concentrates on process and influence analysis, but the research on its low frequency characteristics is less. By using the daily precipitation data of 276 stations in the upper reaches of Yangtze River from 1961 to 2017, areal rainfall of seven major basins were calculated with Thiessen Polygons, and its low-frequency characteristics are studied. The results indicated that:(1) Low-frequency oscillation of areal rainfall existed indeed over the upper Yangtze River. But the periods between the seven major basins were different. There existed a 10~40 d oscillation period in the Jinsha River basin, while a 10~25 d oscillation period in other major basins.(2)In the aspect of frequency, continuous days, intensity and maximum areal rainfall, the low-frequency heavy rainfall events in summer were the first, autumn the second, and spring the last. But the differences among these major basins existed obviously.(3)The frequency of the low-frequency heavy processes had great inter-annual variance between 15 to 25 times. The frequency had a decreasing tendency with the increasing of time duration and basins.