Abstract In this study, with the use of a multiple linear regression approach, the tree-ring chronologies of eight sampling sites in the upper Lancang-Mekong River Basin were developed to provide a 449-year (CE 1557–2005) reconstruction of the annual runoff, thus placing recent changes in annual runoff into a long-term context. These eight tree-ring chronologies have recently been archived in publicly available databases through the International Tree-Ring Data Bank. Reconstruction results showed a good correlation coefficient of 0.662 (n = 39, p-value 2 ) for the degrees of freedom is 42.3%, which meets the precision requirements of reconstruction. The reconstructed runoff displays a trend toward more moist conditions: there were 37 extremely wet years and 23 extremely dry years, exceeding the mean ±1 standard deviation, during the past 449 years. Empirical mode decomposition (EMD) was used to fully analyze and understand the multi-scale variation of the reconstructed runoff. Six intrinsic mode function (IMF) components with different scales were obtained and the sum of all components can be reverted to the original variable sequence. The first and second IMF mainly reflect the change characteristics of the interannual scale of reconstructed sequence. Both are likely controlled by the Quasi-Biennial Oscillation (QBO) and the El Nino-Southern Oscillation (ENSO), respectively. The third IMF showed a 10–13 year scale fluctuation, which is very similar to the solar activity of an 11-year cycle. The fourth and fifth IMF mainly represents multidecadal and centennial oscillations, and they have shown coherent variations with predecessors’ reconstructed May-September precipitations in the same time domain. The lowest frequency component (the residue IMF) represents the trend term of the original signal.

中文翻译：

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使用年轮年表重建澜沧江-湄公河流域上游自公元 1557 年以来的年径流

摘要 在这项研究中，使用多元线性回归方法，开发了澜沧江-湄公河流域上游 8 个采样点的树轮年表，以提供 449 年（CE 1557-2005）的年度重建。径流，从而将年度径流的近期变化置于长期背景下。这八个年轮年表最近已通过国际年轮数据库存档在公开可用的数据库中。重建结果显示，自由度为42.3%的相关系数为0.662（n=39，p值2），满足重建精度要求。重建的径流显示出更潮湿的趋势：在过去的 449 年中，有 37 个极端潮湿的年份和 23 个极端干燥的年份，超过平均值 ±1 标准偏差。经验模态分解（EMD）用于充分分析和理解重建径流的多尺度变化。得到了六个不同尺度的本征模态函数（IMF）分量，所有分量的总和可以恢复为原始变量序列。第一、二阶 IMF 主要反映重构序列年际尺度的变化特征。两者都可能分别受准双年振荡 (QBO) 和厄尔尼诺-南方涛动 (ENSO) 控制。第三次IMF表现出10-13年的尺度波动，这与11年周期的太阳活动非常相似。第四和第五次IMF主要代表了几十年和百年的振荡，并且它们与前人在同一时域内重建的 5 月至 9 月降水显示出一致的变化。最低频率分量（残差 IMF）代表原始信号的趋势项。