1960-2010年渭河流域旱涝时空分布特征

Spatiotemporal Variations of Droughts/Floods Distributions in Weihe River Basin From 1960 to 2010

利用1960—2010年渭河流域12个气象站5—9月降水量资料,采用Z指数作为划分旱涝等级的标准,分析了渭河流域近50a旱涝时空特征。结果表明,近50a来,流域范围内大旱大涝年份各出现过至少6次。大旱出现最多的站点为环县和平凉两站。大涝出现最多的站点为长武和西吉两站。发生大涝的站点基本位于渭河干流的中下游。受大涝(大旱)影响范围较广的年份主要发生在1965—1970年和1980—1985年(1970—1975年和1985—2000年),尤其是1964,1975,1983,1984和2003年(1972,1994,1995和1997年)受大涝(大旱)影响的站点数超过了50%。1960—2010年大旱站点比例有明显增加趋势,大涝站点比例有降低趋势。根据累积距平曲线可以看出,全流域在1960—1968年和1977—1985年年降水量高于均值,在1970—1974年和1992—2001年年降水量低于均值;对渭河流域区域Z指数进行经验正交函数分析,发现渭河流域旱涝主要受流域中心地带(洛川—长武—宝鸡)的旱涝气候控制。受地面高程差异影响,北偏西方向发生旱灾机会增大,而南偏东方向发生涝灾的概率增大。东西差异为东部洛川地区旱灾概率加大,流域西部来水概率增强等,表明渭河流域旱涝分布除受大尺度的气候系统影响和控制外,还受地面高程、局地地形等多种因子影响。

Spatial and temporal distributions of droughts/floods were investigated using the precipitation data collected at 12 meteorological stations in the Weihe River basin during the period of 1960-2010. The drought index（Z index） is used to describe the characteristics of droughts/floods. Six large-scale droughts or floods were detected within the whole catchment during the last 51 years. Droughts occurred more frequently at Huanxian and Pingliang station, while more floods events were found at Changwu and Xiji stations. In general, there were more floods in the mid and lower reaches of the Weihe River Basin. The majority of floods were observed in the period of 1965-1970 and 1980-1985, and the droughts were detected mostly in 1970-1975 and 1985-2000. Relative wet period were 1960-1968 and 1977-1985 with higher than average annual precipitation, which was less than average during 1970-1974 and 1992-2001. The Z indices were analyzed by empirical orthogonal function（EOF） method at the climate stations. The results showed that spatial distributions of droughts and floods were mainly influenced by the center of the basin. Due to the topographical effects, the frequency of droughts was higher in the northwest, and that of floods was higher in the southeast. The heterogeneities of droughts/floods were influenced by not only climate changes and largescale weather system, but also other factors such as geographical location, topography and so on.