长江流域近51a来日降水时空变异的多尺度特征

基于长江流域115个雨量站1963~2013年的日降水数据,应用小波多分辨分析结合信息论的方法,揭示长江流域近51 a来日降水时空变异的多尺度特征。结果表明:空间上,流域日降水序列的变异性具有明显的局部聚集性;并沿纬向呈现出显著的非均质性,而沿经向呈现出拟均匀性;并于103°E附近存在一条明显的分界线,界线以西的日降水变异程度显著高于界限以东的;且日降水变异性与高程之间存在较强的线性相关性,而与年降水量和年降水天数之间则存在较弱的相关性。时间上,流域各站点日降水子序列对原始序列总变异的相对贡献的大小于103°E附近也存在一条明显的分界线,界线以西,各时间尺度下子序列的贡献均大于界线以东;且这种相对贡献的谱图于256 d处呈现出突变现象。此外,流域降水变异的时间尺度可分为3个不同的区间:短期的(2~16 d)、年内的(16~256 d)和年际的(大于256 d)。

MULTISCALE CHARACTERISTICS OF SPATIAL AND TEMPORAL VARIABILITY OF DAILY PRECIPITATION IN YANGTZE RIVER BASIN DURING 1963-2013

Based on the daily precipitation data of 115 rain gauging stations from 1963 to 2013 in the Yangtze River Basin, the multi-scale characteristics of spatial-temporal variability of precipitation in Yangtze River Basin during 1963-2013 are revealed by combining the wavelet multi-resolution analysis and the information entropy theory. The results show that, spatially, the variability of daily precipitation series exists obvious local clustering, significant heterogeneity along the latitudinal direction, and quasi uniformity along the longitudinal direction. There exists an obvious dividing line at approximately 103° longitude, and the variability in the west of this line is significantly higher than that in the east. The variability of daily precipitation has a strong linear correlation with elevation, and a weak linear correlation with mean annual precipitation and average number of rain days. Temporally, an obvious dividing line can be observed at approximately 103° longitude from the spectra of the relative contribution of each subseries to the total variability of the original daily precipitation series. In the west of the line, the contribution of each subseries at different temporal scales is higher than that in the east. And there exists an abruptness at the time scale of 256 days in the mutual information spectra. In addition, the time scale of the precipitation variability can be divided into three distinct scaling regions:(1) synoptic (2-16 days), (2) monthly to annual times (16-256 days) and (3) inter-annual (more than 256 days).