【摘要】 使用长江流域142个站1960~2009年逐日降水量资料,通过定义度量极端降水过程时空聚集程度的参数——极端降水过程事件聚集度和聚集期,并采用主成分分析、Morlet小波分析方法,研究了长江流域极端降水过程事件的年内分布特征。结果表明:长江流域上游极端降水过程事件主要聚集在7月上旬,出现相对比较集中,且聚集度和聚集期年际变化小;中下游则主要聚集在5月中旬至6月下旬,出现比较分散,聚集度和聚集期年际变化相对较大。极端降水过程事件聚集度和聚集期的主要空间异常模态分别表现为东南与西北反向和南北反向的变化特征;其区域平均序列分别呈上升和下降趋势,并分别在13a和10a尺度上周期震荡明显,表明长江流域极端降水过程事件的发生有趋于集中和提早趋势。更多还原

【Abstract】 The spatial-temporal distributions of extreme precipitation events,particularly the durative extreme precipitation events,play an important role in flood disasters.Through introducing the parameters that reflect the temporal distribution of extreme precipitation process events:concentration degree(EPCD) and concentration period(EPCP),the inner-annual inhomogeneity distribution characteristics of extreme precipitation process events over the Yangtze River Basin(YRB)are analyzed.The analyses were based on daily rainfall data of 142 Meteorological stations from 1960to 2009over YRB,using the wavelet and the principal component analysis methods.The results show that extreme precipitation process events over the upper reaches of YRB occur mainly in early July,and their occurrence is relatively intensive.While those over the middle and lower reaches of YRB occur mainly in middle May through late June,and their occurrence is relatively dispersive.Variations of EPCP and EPCD over the middle and lower reaches of YRB are more obvious than those over the upper reaches of YRB.The primary eigenvector represents the reverse EPCD and EPCP variation in the southeast area to the northwest area and the southern area to northern area over the YRB,respectively.Extreme precipitation process events have the trend of concentration and exhibit tendency of shifting to earlier age in the YRB.Furthermore,the EPCD and EPCP have main periodic oscillation of 13years and 10years,respectively.更多还原