树轮记录的长江源区近412年以来3-5月降水量变化

利用采自长江源区青海省治多县立新乡夏日寺的大果圆柏建立树轮宽度标准年表.通过与气候要素的分析发现,该地区树木生长主要受干旱限制,树轮年表与3-5月降水量相关较好(r=0.67).由此重建了长江源区412年以来的3-5月降水量变化,重建方程稳定可靠,方差解释量为44.9%.重建结果显示,重建序列大体经历了10个湿润时期和10个干旱时期,并显示研究区近10年有显著的变湿趋势.采用经验模态分解(EMD)方法对重建序列进行分析,重建降水序列可分解为7个IMF分量,其中,2~4年和6~10年的主要分量表明了降水量与ENSO等海气环流的相关联系,11~28年的分量则显示了区域降水与太阳活动的可能联系.与邻近地区的重建结果对比发现,其变化趋势比较一致.通过时空相关分析,表明重建序列具有较好的时空代表性.此外,重建结果还得到了气象灾害历史记录的验证.

A 412-year March-May precipitation series reconstructed from tree-ring records in the source regions of the Yangtze River

Tree-ring width standardized chronology was established through study of Sabina tibetica in Lixin Town in the source regions of the Yangtze River.Correlation analysis showed that moisture is the main factor controlling tree growth in the regions.It is found that the standardized chronology is significantly correlated with precipitation in the regions from March through May,with a correlation coefficient of 0.69.Thus,precipitation from March through May in the Yangtze River source regions during 1602-2013 was reconstructed.The reconstruction captures 44.9％ of the instrumental precipitation variance.There are 10 wet periods and 10 dry periods in the reconstructed precipitation series over the past 412 years.The reconstruction indicates that there is a remarkably wetting in the last 10 years.Empirical mode decomposition of the series shows that the series can be decomposed into 7 IMF components.Among them,2-4 year and 6-10 year fundamental components indicate the relation between precipitation and atmosphere (such as ENSO);11-28 year fundamental component indicate the possible link between regional precipitation and solar activity.According to analysis of temporal and spatial correlation,it is found that the reconstructed series has good temporal and spatial representation.In addition,the reliability of the reconstruction could be confirmed by some documents and historical records.