松辽流域降水集中指数的时空变化特征

Temporal and Spatial Variation Characteristics of Precipitation Concentration Index from 1961 to 2017 in Songliao Basin

为了科学防控松辽流域旱涝灾害,利用1961—2017年松辽流域196站逐日降水资料,以候为时间尺度计算降水集中指数(PCI),采用趋势分析、合成分析、Mann-Kendall检验等方法分析该流域及各子流域PCI的时空变化特征。结果表明:松辽流域降水集中程度较高,PCI平均为7.1;PCI及其标准差均呈东低西高的空间分布格局,且在多、少雨年PCI差异较大,少雨年降水普遍集中,多雨年则降水相对均匀,表明西北部PCI高值区发生干旱的概率较大,尤其在少雨年表现得更为突出。近57 a来,松辽流域PCI存在明显的年代际变化特征,流域北部和东部PCI整体呈显著下降趋势,且整个流域和额尔古纳河子流域的PCI发生显著突变,突变年份分别为2003年和1991年,且突变后的变差系数有所增大。近年来,尽管松辽流域PCI处于偏低阶段,但突变后变差系数的增大说明降水的不稳定性增强,旱涝发生的概率增大,易出现降水极端集中的年份。

In order to prevent and control drought and waterlogging disasters scientifically in Songliao Basin,the pentad precipitation concentration index(PCI)was calculated based on daily precipitation data at 196 weather stations of Songliao Basin from 1961 to 2017.And on this basis the temporal and spatial variation characteristics of PCI in Songliao Basin and its sub-basins were analyzed by using trend analysis,composite analysis and Mann-Kendall test,etc.The results show that the precipitation concentration degree in Songliao Basin was higher,and the average value of PCI during 1961-2017 was 7.1.The PCI and its standard deviation increased gradually from east to west in Songliao Basin,and the precipitation generally concentrated in less rain years,while that was relatively uniform in more rain years,which indicated that the probability of drought in PCI higher value area of northwestern Songliao Basin was larger,especially in less rain years.The decadal change characteristic of PCI in Songliao Basin was obvious from 1961 to 2017,and the PCI had significant downward trend in the north and east of Songliao Basin as a whole.The mutation of PCI in Songliao Basin and Erguna river sub-basin was significant from 1961 to 2017,it happened in 2003 and 1991,respectively,and their variation coefficients of PCI increased after the mutation.Although PCI in Songliao Basin was in a lower stage in recent years,the variation coefficients of PCI after the mutation increased and the instability of precipitation strengthened,which indicated that the probability of drought and waterlogging tended to increase,and the precipitation was easily to concentrate extremely.