近50年四川盆地汛期极端降水事件的时空演变

Temporal and Spatial Variations of Extreme Precipitation Events of Flood Season over Sichuan Basin in Last 50 Years

利用四川盆地1961-2006年145个台站汛期的逐日降水资料,分析了该地区汛期极端降水事件的时空演变特征,结果表明:该地区汛期极端降水事件的发生频次分布与降水量分布差异较大,由西向东呈阶梯状递减趋势;川西高原与四川盆地之间以及盆地东西部之间的反位相变化是川渝地区汛期极端降水事件发生频次最主要的两个空间异常模态;该地区汛期极端降水事件发生频次的空间分布可以分为8个区;分别是四川盆地中部区、东部区、南部区、西部区、川西高原西部区、中部区、川西南山地区和重庆东部区;从长期变化趋势来看,汛期极端降水事件发生频次除在四川盆地西部区和重庆东部区分别呈较弱的减少和增长趋势以外,在其余各区的线性趋势都较为明显,其中四川盆地东部区、川西南山地区、川西高原西部和中部区表现为增长,四川盆地中部和南部区表现为减少;从气候因子分析看,汛期西太平洋副高位置的南北变化、东亚以及南亚季风的强弱变化分别对四川盆地东部区、中部区以及西部区的极端降水事件存在显著影响。

Based on the daily precipitation data of flood season in 1961-2006 from 145 stations over Sichuan Basin, we analyzed the temporal and spatial variations of extreme precipitation events. Results indicate that the extreme precipitation event frequency of flood season shows a gradual decreasing trend from west to east, which is remarkably different from the precipitation distribution. The anti-phase changes between Western Sichuan Plateau and Sichuan Basin, as well as west and east Sichuan Basin, are the main spatial models of extreme precipitation event frequency in flood season. The spatial distribution of extreme precipitation event frequency in flood season over Sichuan Basin can be identified into eight regions： central Sichuan Basin, east Sichuan Basin, south Sichuan Basin, west Sichuan Basin, west of Western Sichuan Plateau, central Western Sichuan Plateau, southwest Sichuan and east Chongqing. In terms of long-term trend, there is an apparent linear trend in extreme precipitation event frequency for all the regions, with the exception of a slight decrease and increase for west Sichuan Basin and east Chongqing. Among the eight regions, east Sichuan Basin, southwest Sichuan, western and central parts of Western Sichuan Plateau show an increasing trend, whileas central and southem Sichuan Basin show a decreasing trend. The fluctuating West Pacific Subtropical High and the varying intensities of East and South Asian monsoons have significant impact on extreme precipitation events over eastern, central and western parts of Sichuan Basin, respectively.