基于贺兰山青海云杉(Picea crassifolia)树轮对过去202 a最低气温的重建OA北大核心CSTPCD

Under the influence of global warming,profound changes are occurring in the global hydroclimatic system.Understanding the long-term climate patterns in monsoon and nonmonsoon transitional zones is crucial owing to their complex and diverse climates.Utilizing 66 tree-ring cores from 36 Picea crassifolia trees,a den-drochronological chronology from 1798 to 2016(219 years)was established for a typical area in the transitional zone(Helan Mountains region,northwest China).The Pearson correlation method was used to analyze the rela-tionship between tree-ring widths and local climatic factors.The results show that:(1)The radial growth of Picea crassifolia closely correlates with the area's annual average minimum temperature(R2=0.638,P<0.001).A linear regression equation was used to reconstruct the annual average minimum temperature series for Helan Mountains from 1815 to 2016,with a reduction error and coefficient of efficiency of 0.808 and 0.482,respectively.(2)The reconstructed series generally indicates lower temperatures in the 19th century,consistent with the globally recog-nized"Little Ice Age".From the late 19th century,temperatures gradually increased,showing significant warm periods and extremely warm years,with three abrupt temperature shifts in the 1850s,1890s,and 1990s.(3)Mor-let wavelet analysis shows the periodic distribution characteristics of 6 a,21 a and 46-56 a.Southern Oscilla-tion,Pacific Decadal Oscillation,and Atlantic Multidecadal Oscillation are the driving factors behind these peri-odic changes.(4)Large-scale spatial correlation analysis indicates that the reconstructed temperature series repre-sents the temperature variations well in large regions like most of Inner Mongolia and Ningxia.The reconstructed annual average minimum temperature series for this typical monsoon and nonmonsoon transitional zone reveals its climatic characteristics,providing a reference for global climate change research.