汾河流域降水及旱涝时空结构特征

利用汾河流域39个测站1956-2000年各月降水资料,采用经验正交函数(EOF)分解技术分析年降水的空间结构特征与变化.结果表明:汾河流域年降水主要有3种典型分布类型,即"全体一致型"、"南北反相型"、"上下游与中游反相型".其中,第1种分布型占主导作用,其相应的时间序列和年均降水序列形状基本相似,趋势皆减少.此外,采用Z指数旱涝指标划分了汛期旱涝状况和等级,结果显示,汛期异常旱涝主要发生在8月和6月.

Analysis on the Spatiotemporal Change of Precipitation, Flood and Drought in the Fenhe River Basin

In this paper,the spatial structural characteristics and change of precipitation in the Fenhe River Basin are analyzed with empirical orthogonal function(EOF)method using the monthly precipitation data from 39 stations during the period of 1956-2000.The results show that there are three typical distribution patterns of annual precipitation in the basin,and they are the "all-consistent pattern","north-south reversal pattern" and "upper and lower reachesmiddle reaches reversal pattern",in which the first distribution pattern is dominant and its variance contribution rate is 59.96%,the shape of corresponding temporal series is basically similar to that of annual precipitation and in a reduction trend.Moreover,the grades of flood and drought during different periods in flood season from June to September are analyzed using Z index method.The results reveal that the abnormal flood or drought in flood season occurs mainly in August and June,and an abnormal flood or drought occurs about every two years. The study results also reveal that the annual precipitation was high in the 1950s and 1960s,and flood occurred frequently;the annual precipitation decreased in the 1980s and 1990s,and drought occurred frequently.