树轮记录的甘肃山丹近224年降水变化

Reconstruction of Annual Precipitation in Shandan Based Tree-Ring since 1783 A.D.

根据山丹大黄沟的树轮样本,建立树轮宽度年表。相关分析发现,大黄沟树轮宽度差值年表与山丹上年8月至当年6月的降水存在显著的正相关,相关系数为0.654(P<0.00001)。利用大黄沟的树轮宽度差值年表,可重建山丹近224年来上年8月至当年6月的降水变化。交叉检验表明降水重建结果稳定可靠。通过对降水重建序列与周边地区树轮降水重建序列和树轮年表资料的对比分析,发现该重建序列与周边地区的树轮重建降水的干湿阶段变化具有一定的同步性,并对西北地区极端干旱历史事件有良好的响应。多窗谱分析发现,重建降水序列具有4.2a、3.4 a、3.2 a、2.6 a的准周期变化;滑动T检验法发现,重建降水序列在1887年、1908年发生过降水突变。

The tree-ring chronologies were established according to samples from Shandan.Single correlation calculation indicated that the correlations were significant between the tree-ring chronologies and previous year′s August to present year′s June（A to J） total precipitation,and the correlation coefficient was 0.654.Using DHG（RES）tree-ring chronology,the previous year′s August to present year′s June precipitation during the last 224 years was reconstructed,with an explained variance of 42.8%.The reconstructed equation was stable by crossing-test.The reconstruction precipitation is compared to historical archives and other tree-ring reconstructions in Northwest China.The results reveal common climatic extremes and change over much of Northwest China.Many of these events have had profound impacts on the peoples over the past several centuries.The reconstructed precipitation series for Middle Hexi Corridor during the last 224 a had significant period cycles of 4.2 a,3.4 a,3.2 a,2.6 a.The abrupt change of precipitation occurred in 1887,1908.