关键词: 面雨量, 低频特征, 低频强降水过程, 长江上游

Abstract: 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 10-25d 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.

Key words: areal rainfall, low-frequency characteristic, low-frequency heavy rainfall process, the upper reaches of Yangtze River