用树轮灰度重建乌孙山北坡4—5月平均最低气温

利用2006年采自新疆伊犁乌孙山北坡3个采点的树轮样本,建立了树轮宽度年表,采用树轮图像分析法进一步建立了3种宽度年表和5种灰度年表。相关分析发现,在所有参数年表中乌孙山北坡3个树轮标准化全轮灰度年表序列与该地区4—5月平均最低气温显著相关,相关系数最大可达-0.552。经多方面检验可知,利用树轮标准化全轮灰度年表重建该地区过去324 a 的4—5月最低气温是可信的。通过对重建最低气温序列进行功率谱分析发现乌孙山北坡4—5月最低气温具有31 a、36 a和48 a的变化准周期;小波分析证实,31~32 a的低频变化周期最为显著,1800年以前,震荡随时间推移逐渐减弱,周期逐渐缩短,19世纪后期震荡加强,进入20世纪,震荡减弱,逐渐趋于稳定。4—5月平均最低气温经历了11高11低的变化阶段。

Mean Minimum Temperature Series of April to May Reconstructed by Tree-ring Gray Chronology in Northern Slope of Wusun Mountains, North Xinjiang

The tree-ring samples of Picea schrenkiana Fisch. et Mey collected from three sites in northern slope of Wusun Mountains in North Xinjiang in 2006, are used to developed tree-ring width chronologies by using standard dendrochronological method. Further, three kinds of width chronologies and five kinds of gray chronologies are established by using image analysis of tree-ring. Single correlation calculation indicated that the three tree-ring standardization gray chronologies in northern slope of Wusun Mountains are all significantly related with the mean minimum temperature of April to May in this area, whose maximum correlation coefficient is -0.552. A 324 years' mean minimum temperature series is well reconstructed by means of the tree-ring mean gray chronology series and its explain variance was 40.5%. Many tests prove that the reconstruction is credible. Power spectrum analysis on the reconstructed series shows that the April-May mean minimum temperature series in northern slope of Wusun Mountains has 32-year, 36-year and 48-year quasi-periodic changes. Wavelet analysis has confirmed the obvious low-frequency change period of 31-year or 32-year cycle. Before 1800, the change extent of April-May mean minimum temperature weakened gradually and the period shortened with time elapse; from then on the temperature vibration strengthened; entering the 20th Century, the temperature vibration returned weak and tended to be stable. The reconstructed temperature series has experienced 11 low and 11 high change stages over the 324 years.