近千年青藏高原中南部年代际气候变化的树轮记录与机制研究

In the context of global warming, decadal-scaled climatic change is of significance to global change. Development of long-time-spanned climatic series using proxy data with precise dating and annual resolution to indicate decadal-scaled climatic changes is under great demand. The project aimed at the middle-south Tibetan Plateau (TP) for the study area, which is sensitive to climatic changes and lack of dendroclimatological network. Including the traditional detrending technique (STD), the RCS (Regional Curve Standardization）method is designed to establish chronologies with large sample depth and great reliability on the basis of newly collected tree-ring-width data sets. Local climatic series will be developed then and quantitative analysis will be made to indicate decadal-scaled climatic changes with the application of periodic and abrupt-change techniques. A regional millennial-long climatic series for the middle-south TP will be developed and climate variations will be indicated using principal component analysis on the combination of the newly established tree-ring records by the evaluation of common climatic signal and significant correlation. Meanwhile, the newly developed regional millennial-long climatic series will be discussed in order to indicate the characteristics of climate changes in centennial scale and mechanism of climate variations will finally be discussed by tele-connection with monsoon or sea surface temperature (SST). The project is of importance to solve several key scientific problems, specifically, it is not only essential to strengthen the tree-ring network in the middle-south TP, but also to play an important role to indicate the performance of decadal-scaled climatic changes to regional climate as well as adjustment of atmospheric circulation (such as monsoon and SST) to globally climatic changes.

现代气候变暖背景下，年代际气候波动对全球气候变化具有重要作用。揭示年代际气候变化有赖于选取高分辨率代用指标建立长气候序列来实现。本项目以具有年分辨的树轮为资料，以对气候变化敏感、树轮网络相对薄弱的青藏高原中南部为研究区域，采用STD方法、RCS方法分别建立长度近千年、大复本、可靠性强的年表，重建局地气候序列，并定量分析局地气候的周期、突变等特征。结合区域内已发表的由树轮资料重建的气候序列，应用主成分分析方法，重建区域近千年气候序列，分析区域气候年代际尺度的波动特征。同时，兼顾百年低频尺度的气候变化，识别近千年内区域气候特点及与季风、海温的相互关系，探讨近千年影响高原中南部气候的驱动机制。本项目对加强青藏高原中南部树轮网络研究、探讨年代际气候波动对区域气候变化的作用及辨识季风、海温等因子对全球气候调节作用等重大科学问题的研究具有重要意义。

本项目以具有年分辨的树轮为资料，以对气候变化敏感、树轮网络相对薄弱的青藏高原中南部为研究区域，建立长度近千年、大复本、可靠性强的年表，分别建立了谢通门过去644年（公元1360-2013年）降水序列和朗县过去917年（公元1100-2016年）降水序列。重建结果揭示了高原中南部过去降水的阶段性干湿变化特征。与区域内已发表的由树轮资料重建的气候序列对比发现，过去600年内青藏高原中南部地区经历了相同的干湿变化过程，在年代际尺度上变化一致，可能受到相同的气候驱动因子控制。空间相关性分析也表明，新建的年降水变化具有一定的空间代表性，可以反映青藏高原中南部地区的降水变化。本项目对加强青藏高原中南部树轮网络研究、探讨年代际气候波动对区域气候变化的作用及辨识季风、海温等因子对全球气候调节作用等重大科学问题的研究具有重要意义。