Based on the annual precipitation data from 51 weather stations from 1964 to 2008 in Liaoning province,the characteristics of drought and flood were analyzed with Z index for a single station and HL index for a region.The results indicate that the occurrence frequencies of drought and flood in a single station are higher in the westem,northern and southeastern regions than in the middle and eastern regions of Liaoning province.The regional flood index decreases gradually, while the regional drought index increases gradually.Z indices of 51 weather stations are analyzed by empirical orthogonal function (EOF) and rotated empirical orthogonal function (REOF)methods.It shows that spatial distributions of drought and flood are influenced by not only rainfall change brought by large-male weather system, but also different factors such as geographical location, land and sea distributions and so on.The study areas can be divided into 4 regions by REOF method,namely, I region is the western Liaoning province; Il region is the northern and northwestern Liaoning province; Ill region is the central and eastern Liaomg province and 1Vregion is the southeastern Liaoning province.%利用1964-2008年辽宁51站降水量资料,采用Z指数和区域旱涝HL指数分析了全区近45a旱涝变化.结果表明:近45 a辽西、辽北以及辽东南地区单站旱涝发生频率均明显高于辽中、辽东地区;区域性洪涝指数逐渐减小,区域性干旱指数逐步增大.对辽宁51站Z指数进行了EOF和REOF分析,可知辽宁旱涝的空间分布特征除受大尺度天气系统所带来的降水量变化影响外,同时还受地理位置、海陆分布等多种因子影响.通过REOF方法可将全区分为4个区域,即I辽西地区,Ⅱ辽北、辽西北地区,Ⅲ辽中、辽东地区和Ⅳ辽东南地区.
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