利用2006年采自西藏东部昌都地区的树轮样本,建立了该区域3个树轮年表,相关计算表明,昌都树轮标准化年表与该区域上一年10月到当年1月的平均最低气温相关最为显著,单相关系数高达0.657。利用该年表较好地重建了昌都气象站过去413年上一年10月到当年1月的平均最低气温序列,经多方面验证,表明其具有较好的可信性。过去400年中,西藏东部昌都地区秋、冬季平均最低气温经历了6个偏暖和6个偏冷的变化阶段,并有明显的6个持续变暖和5个持续变冷阶段,变暖缓慢,而变冷迅速。变冷、变暖阶段中以20世纪60年代的迅速降温和70~80年代的升温最为典型。昌都地区秋、冬季节平均最低气温以5年、11年、102~103年的准周期变化最为显著。比较发现,近百年青藏高原东部地区秋、冬季平均最低气温与北半球平均气温具有较好的一致性:20世纪初到30年代,青藏高原东部地区秋、冬季平均最低气温缓慢上升,40年代急剧下降,50年代气温回升,60年代初期气温再次下降,60年代末以后气温逐步升高。
Using the tree-ring samples of Picea likiangensis collected from three stations in Qamdo region of eastern Tibet in 2006,the three tree-ring width chronolgies have set up.The correlation calculation indicated that the correlation coefficient is 0.657 between CHD tree-ring chronologies and mean minimum temperature from autumn to winter.The mean minimum temperature series from last October to January in the past 400 years at Qamdo meteorological station can be better reconstructed using the tree-ring standardized chronologies.The reconstructed series is credible through some significant tests of the tree physiology.Some results is obtained by analyzing the 400-year reconstructed series:(1) the mean minimum temperatures of Qamdo region from autumn to winterin in the past 400 years have significantly quasi-periodic changes of 5,11 and 102~103 years;(2) the mean minimum temperatures from autumn to winter in the past 400 years have six warm stages and six cold stages,six obviously continued warming and five continuous cooling stages,it is warming slowly,and cooling rapidly;the compared analyses showed that the mean minimum temperature from autumn to winter in past 400 years on the eastern Qinghai-Tibet Plateau and the mean temperature of Northern Hemisphere have a good consistency: From early 20th centuries to 1930s,the temperature slowly rise,a sharp decline in 1940s,rise in 1950s,drop again in the early 1960s,it gradually increase after the late 1960s.