Analysis of reconstructed annual precipitation from tree-rings for the past 500 years in the middle Qilian Mountain  

作　　者：TIAN QinHua ZHOU XiuJi GOU XiaoHu ZHAO Ping FAN ZeXin Samuli HELAMA 

机构地区：[1]National Climate Center,Beijing 100081,China [2]Center for Arid Environment and Paleoclimate Research(CAEP),Key Laboratory of Western China's Environment Systems MOE,Lanzhou University,Lanzhou 730000,China [3]Chinese Academy of Meteorological Sciences,Beijing 100081,China [4]National Meteorological Information Center,Beijing 100081,China [5]Xishuangbanna Tropical Botanical Garden,Chinese Academy of Sciences,Kunming 650223,China [6]Arctic Centre,University of Lapland,Rovaniemi 96101,Finland

出　　处：《Science China Earth Sciences》2012年第5期770-778,共9页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 41001058, 41001009, 40971119 and 40890052);the China Postdoctoral Science Foundation (Grant Nos. 201003194)

摘　　要：The ring-width chronology of a Juniperus przewalskii tree from the middle of the Qilian Mountain was constructed to estimate the annual precipitation (from previous August to current July) since AD 1480.The reconstruction showed four major alternations of drying and wetting over the past 521 years.The rainy 16th century was followed by persistent drought in the 17th century.Moreover,relatively wet conditions persisted from the 18th to the beginning of 20th century until the recurrence of a drought during the 1920s and 1930s.Based on the Empirical Mode Decomposition method,eight Intrinsic Mode Functions (IMFs) were extracted,each representing unique fluctuations of the reconstructed precipitation in the time-frequency domain.The high amplitudes of IMFs on different timescales were often consistent with the high amount of precipitation,and vice versa.The IMF of the lowest frequency indicated that the precipitation has undergone a slow increasing trend over the past 521 years.The 2-3 year and 5-8 year time-scales reflected the characteristics of inter-annual variability in precipitation relevant to regional atmospheric circulation and the El Ni?o-Southern Oscillation (ENSO),respectively.The 10-13 year scale of IMF may be associated with changing solar activity.Specifically,an amalgamation of previous and present data showed that droughts were likely to be a historically persistent feature of the Earth's climate,whereas the probability of intensified rainfall events seemed to increase during the course of the 19th and 20th centuries.These changing characteristics in precipitation indicate an unprecedented alteration of the hydrological cycle,with unknown future amplitude.Our reconstruction complements existing information on past precipitation changes in the Qilian Mountain,and provides additional low-frequency information not previously available.The ring-width chronology of a Juniperus przewalskii tree from the middle of the Qilian Mountain was constructed to estimate the annual precipitation （from previous August to current July） since AD 1480.The reconstruction showed four major alternations of drying and wetting over the past 521 years.The rainy 16th century was followed by persistent drought in the 17th century.Moreover,relatively wet conditions persisted from the 18th to the beginning of 20th century until the recurrence of a drought during the 1920s and 1930s.Based on the Empirical Mode Decomposition method,eight Intrinsic Mode Functions （IMFs） were extracted,each representing unique fluctuations of the reconstructed precipitation in the time-frequency domain.The high amplitudes of IMFs on different timescales were often consistent with the high amount of precipitation,and vice versa.The IMF of the lowest frequency indicated that the precipitation has undergone a slow increasing trend over the past 521 years.The 2-3 year and 5-8 year time-scales reflected the characteristics of inter-annual variability in precipitation relevant to regional atmospheric circulation and the El Ni？o-Southern Oscillation （ENSO）,respectively.The 10-13 year scale of IMF may be associated with changing solar activity.Specifically,an amalgamation of previous and present data showed that droughts were likely to be a historically persistent feature of the Earth＇s climate,whereas the probability of intensified rainfall events seemed to increase during the course of the 19th and 20th centuries.These changing characteristics in precipitation indicate an unprecedented alteration of the hydrological cycle,with unknown future amplitude.Our reconstruction complements existing information on past precipitation changes in the Qilian Mountain,and provides additional low-frequency information not previously available.

关 键 词：Qilian Mountain tree-ring reconstruction empirical mode decomposition multi-scale precipitation variability not previously available 

分 类 号：P467[天文地球—大气科学及气象学] TM76[电气工程—电力系统及自动化]