Using Lanczos filtered simulation results from the ECHO-G coupled ocean-atmosphere model,this study analyzes the spatiotemporal structure of temperature and precipitation on centennial time scale to examine how climate change in eastern China responded to external forcing during the last millennium.The conclusions are (1) eastern China experienced a warm-cold-warm climate transition,and the transition from the warm period to the cold period was slower than the cold to warm transition which followed it.There was more rainfall in the warm periods,and the transitional peak and valley of precipitation lag those of temperature.The effective solar radiation and solar irradiance have significant impacts on the temporal variation of both temperature and precipitation.Volcanic activity plays an important role in the sudden drop of temperature before the Present Warm Period (PWP).There is a positive correlation between precipitation and volcanic activity before 1400 A.D.,and a negative relationship between the two thereafter.The concentration of greenhouse gases increases in the PWP,and the temperature and precipitation increase accordingly.(2) The spatial pattern of the first leading empirical orthogonal function (EOF) mode of temperature on centennial time scale is consistent with that on the inter-annual/inter-decadal (IA-ID) time scales;namely,the entirety of eastern China is of the same sign.This pattern has good coherence with effective solar radiation and the concentrations of greenhouse gases.The first leading EOF mode of precipitation on centennial time scale is totally different from that on the IA-ID time scales.The first leading mode of centennial time scale changes consistently over the entirety of eastern China,while the middle and lower reaches of the Yangtze and Yellow Rivers are the opposite to the rest of eastern China is the leading spatial pattern on IA-ID time scale.The distribution of precipitation on centennial time scale is affected by solar irradiance and greenhouse gas concentrations.
WANG HongLiLIU JianWANG ZhiYuanWANG SuMinKUANG XueYuan
This paper investigates the interannual variation of the West Pacific Subtropical High(WPSH) intensity based on the data compiled by the Chinese National Climate Center.Monthly reanalysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research(NCEP/NCAR) are also used to study the lead-lag relationship between WPSH intensity and surface heat flux anomalies.The three major findings are as follows:First,WPSH intensity presents good seasonal persistence,especially from winter to the ensuing summer.Persistence is more significant after 1977,especially from spring to summer,and from summer to autumn;persistence of anticyclonic anomalies are significantly better than cyclonic anomalies.Second,surface heat flux tends to present opposite anomalous patterns between the strong and weak years of the WPSH intensity,which is especially valid at the latent heat flux over the ocean.Simultaneous correlations between surface heat flux and WPSH intensity in each of the seasons are marked by similar key areas.Finally,surface heat flux from the preceding winter of a strong summer WPSH is quite similar to strong spring WPSH,but the positive anomalies over the northwest Pacific and south of Japan are notably stronger.The situations in the weak years are similar except for those over the northwest Pacific:winter surface heat flux shows negative anomalies for a weak spring WPSH,but positive anomalies for a weak summer WPSH.It is suggested that surface heat flux in the previous winter plays an important role in maintaining the WPSH intensity in the ensuing spring and summer.
A 475-cm long sediment core (QH-2005) from Lake Qinghai was used to carry out multi-proxy analysis of δ18O and body length of ostracod valves and redness and grain size of sediments, in order to reconstruct environ-mental changes during the past 13500 cal. a BP. The age model was based on 6 14C dates for bulk orgnic carbon (BOC) and 2 14C dates for lignin. The lignin 14C dates are apparently younger than the corresponding layers' BOC 14C dates, indicating that the reservoir age varied from 728 to 1222 a since the Late Glacial and from 2390 to 2490 a immediately before the pre-bomb era. Hence, the 14C age model for Core QH-2005 was corrected by the changing reservoir age. Ostracod δ18O values were primarily related to dilution and evaporative enrichment of the lake water. The reconstructed salinity based on ostracod body length coincides well with ostracod δ18O values. High redness and mean grain size (MZ) values indicate increased riverine supply to Lake Qinghai associated with increasing monsoon rainfall. Multi-proxy results show that climate during 13500-10900 cal. a BP was relatively cold and dry with fre-quent short-term fluctuations; a warm and wet climate began at about 10900 cal. a BP and culminated around 6500 cal. a BP as a result of monsoon strengthening; the climate became cold and dry afterwards and has remained rela-tively stable since 3400 cal. a BP. Our data also reveal short-term (millennial/centennial timescales) climatic fluctua-tions including: Younger Dryas events, ice-rafting events 8 and 1 (by ～11000 cal. a BP and ～1600 cal. a BP respec-tively), 8200 cal. a BP cold event, Little Ice Age and the Medieval Warm Period.
WANG YongSHEN JiXU XingnaLIU XingqiSIROCKO FrankZHANG EnlouJI Junfeng
