Regional decadal precipitation reconstructions for the arid and semi-arid zones of northern China were established by the use of different palaeoclimate archives such as ice-cores, tree-rings, lake sediments and writt...Regional decadal precipitation reconstructions for the arid and semi-arid zones of northern China were established by the use of different palaeoclimate archives such as ice-cores, tree-rings, lake sediments and written his-torical documents. Local rainfall reconstructions from single sites were averaged to obtain regional precipitation records for western and eastern regions of an arid and semiarid zone of northern China, respectively. All established regional pre-cipitation curves display 5 dry periods, each lasting about 50 years. Meanwhile, precipitation reconstructions show re-gional dissimilarities. During the last 500 years, the trends of precipitation change in the eastern arid region are basically consistent with those in the western and eastern regions of the semiarid zone. Precipitation variations in the western arid region are unique, showing significant local patterns of rainfall variability. Maximum entropy method (MEM) spec-tral estimates show that each regional precipitation series contains stationary century-scale periodicities of about 120 a. Singular spectrum analysis was applied to isolating the cen-tury-scale oscillation signals from the regional proxy pre-cipitation series. Significant periods with wavelengths of 121.4a, 154.6a, 124.3a, 118.6a, 108.5a and 121.4a were found 26.56%, 26.44%, 28.87%, 18.67%, 33.48% and 34.04% of the variances of the original series for the western arid zone, the eastern arid zone, the whole arid zone, the western semi-arid zone, the eastern semiarid zone and whole northern China, respectively.展开更多
The paleoclimate data recovered from ice cores, tree rings and lake sediments indicate regional features of climatic change on the Tibetan Plateau (TP) during the last 2000 years. The composite temperature reconstruct...The paleoclimate data recovered from ice cores, tree rings and lake sediments indicate regional features of climatic change on the Tibetan Plateau (TP) during the last 2000 years. The composite temperature reconstructions indicate that several main climatic episodes, such as the 揕ittle Ice Age?between 1400 and 1900, the 揗edieval Warm Period?in 1150—1400, a less warm period in 800—1100, and an earlier cold period between the 3rd and 5th centuries, occurred in the TP. In addition, temperature varied from region to region. The period from AD 800 to 1100, which was warm in northeastern TP, was contemporaneous with cooling in the western and southern TP. The southern TP experienced warming between 1150 and 1400. For western TP, the d 18O records of the Guliya ice core indicate that the period 1250—1500 witnessed a clear warming. Large-scale trends in the temperature history from northeastern TP are more similar to those in eastern China than are the trends from the Guliya ice cap far to the west and southern TP. The most prominent similarities between the temperature variations of the TP and eastern China are such cold phases as 1100—1150, 1500—1550, 1650—1700 and 1800—1850, and the latter three cold events match with three widespread glacial advances which occurred on the TP during the Little Ice Age.展开更多
文摘Regional decadal precipitation reconstructions for the arid and semi-arid zones of northern China were established by the use of different palaeoclimate archives such as ice-cores, tree-rings, lake sediments and written his-torical documents. Local rainfall reconstructions from single sites were averaged to obtain regional precipitation records for western and eastern regions of an arid and semiarid zone of northern China, respectively. All established regional pre-cipitation curves display 5 dry periods, each lasting about 50 years. Meanwhile, precipitation reconstructions show re-gional dissimilarities. During the last 500 years, the trends of precipitation change in the eastern arid region are basically consistent with those in the western and eastern regions of the semiarid zone. Precipitation variations in the western arid region are unique, showing significant local patterns of rainfall variability. Maximum entropy method (MEM) spec-tral estimates show that each regional precipitation series contains stationary century-scale periodicities of about 120 a. Singular spectrum analysis was applied to isolating the cen-tury-scale oscillation signals from the regional proxy pre-cipitation series. Significant periods with wavelengths of 121.4a, 154.6a, 124.3a, 118.6a, 108.5a and 121.4a were found 26.56%, 26.44%, 28.87%, 18.67%, 33.48% and 34.04% of the variances of the original series for the western arid zone, the eastern arid zone, the whole arid zone, the western semi-arid zone, the eastern semiarid zone and whole northern China, respectively.
基金This work was jointly supported by the National Key Basic Research Project“The Process of Desertification and Its Control in Northern China”(Grant No.G2000048701)the Knowledge Innovation Fund of the Chinese Academy of Sciences(Grant No.KZCXl-10-02)the National Natural Science Foundation of China(Grant Nos.40201011,40272123 and 90102005)
文摘The paleoclimate data recovered from ice cores, tree rings and lake sediments indicate regional features of climatic change on the Tibetan Plateau (TP) during the last 2000 years. The composite temperature reconstructions indicate that several main climatic episodes, such as the 揕ittle Ice Age?between 1400 and 1900, the 揗edieval Warm Period?in 1150—1400, a less warm period in 800—1100, and an earlier cold period between the 3rd and 5th centuries, occurred in the TP. In addition, temperature varied from region to region. The period from AD 800 to 1100, which was warm in northeastern TP, was contemporaneous with cooling in the western and southern TP. The southern TP experienced warming between 1150 and 1400. For western TP, the d 18O records of the Guliya ice core indicate that the period 1250—1500 witnessed a clear warming. Large-scale trends in the temperature history from northeastern TP are more similar to those in eastern China than are the trends from the Guliya ice cap far to the west and southern TP. The most prominent similarities between the temperature variations of the TP and eastern China are such cold phases as 1100—1150, 1500—1550, 1650—1700 and 1800—1850, and the latter three cold events match with three widespread glacial advances which occurred on the TP during the Little Ice Age.
