基于EMD北海道地区50年降水及南方涛动的分析

Analysis of the Precipitation in Hokkaido Island over 50 Years and Its Southern Oscillation Based on Empirical Mode Decomposition Method

[目的]树木年轮δ^18O资料有助于重建过去降水情况；利用EMD法分析北海道地区50年的降水情况及南方涛动指数（SOI）。[方法]利用北海道大学地球环境科学学院实验室的橡树树轮资料和NCEP公布的1953-2002年的SOI资料，采用EMD法对北海道地区的树轮的δ^18O进行分析。[结果]该地区的降水存在着3、6、11、22、33年的周期。时SOI进行EMD的分析发现，南方涛动同样存在着3,6、22、33、50年的周期；而SOI指数能够反映南方涛动现象。通过对比这两个EMD结果，在相同的时间范围内，北海道地区的降水与南方涛动的周期尺度基本上是相同的，进而推测，北海道地区的降水在很大程度上受到南方涛动的影响。[结论]通过分析得到的北海道地区降水多时间尺度周期，对分析我国的降水资料有一定的启示作用。

[ Objective] The data about 81SO values of tree rings are useful to reconstruct the precipitation in the past. This research was to analyze the precipitation in Hokkaido Island over 50 years and its southern oscillation index （SOI） based on empirical mode decomposition （EMD） method. [ Method] The data about the oak tree rings fetched from Lab. of Globosity Evirornent Science College of Hokkaido Island University and the data of SO1 publicized by NCEP were used to analyze the 3-80 values of tree rings from Hokkaido Island by EMD method. [ Result] There are 3a, 6 a, lla, 22a, 33a precipitation cycles in Hokkaido island. The analysis on the SOI data with EMD showed that 3a, 6a, 22a, 33a, 50a cycles also existed in SOI, while the SOI could reflect SO. By the contrast of the two results about EMD of the two data, it was found that the cycle scale of precipitation was nearly the same with that of SOI in Hokkaido island in same time range, As a result, it was guessed that the precipitation in Hokkaido Island was affected by SO to large extend. [ Conclusion] The precipitation cycles with more time scales in Hokkaido Island were gained by this analysis, which enlightened somewhat on analysis of the precipitation data in China.