The isotope-equipped GCMs （general circulation models） are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spat...The isotope-equipped GCMs （general circulation models） are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spatial distribution and seasonal variation of precipitation isotopic composition in arid central Asia, several isotope-equipped GCMs are applied, and the long-term observations in two stations are used to verify the GCM-simulated results. Generally, seasonality of isotopic composition can be well simulated in each GCM, and the values of 6180 in precipitation are larger in summer months （from April to October） and lower in winter months （from November to March）. Higher latitude usually shows lower values of 6180 in precipitation, and lower latitude has higher values. The values of 5180 are relatively low in the eastern section, and higher in the western section. Among these simulations, ECHAM is good at describing the isotopic composition in the study region, which can be seen from the mean absolute error （MAE） and root-mean-square error （RMSE）. The ECHAM-derived values of 5180 in precipitation positively correlate with the observed series, and the correlation coefficient based on ECHAM is the largest among these GCMs.展开更多
Foliar and root carbon isotope composition(δ13C) of grassland communities on the Qinghai-Tibet Plateau,China,was obtained by the biomass weighting method and direct measurement.We investigated the characteristics and...Foliar and root carbon isotope composition(δ13C) of grassland communities on the Qinghai-Tibet Plateau,China,was obtained by the biomass weighting method and direct measurement.We investigated the characteristics and altitudinal patterns of foliar and root δ13C and determined which environmental factors influenced foliar δ13 C most.Foliar δ13 C of alpine steppe was significantly higher than that of alpine meadow and temperate steppe.For alpine meadow,root δ13C was significantly higher than of foliar δ13C.Foliar δ13C increased with altitude at an average rate of 0.60‰ km 1 for the whole grassland ecosystem.This rate was lower than that at species level.However,there were no significant relationships between root δ13C and altitude.Atmospheric pressure was a more important factor than temperature and precipitation in its influence on the altitudinal pattern of foliar δ13C at the community level.展开更多
We present the first quantitative estimation of monsoon precipitation during the late glaciaI-Holocene in the sandy land of northern China, based on organic carbon isotopic composition data from a loess-sand sequence ...We present the first quantitative estimation of monsoon precipitation during the late glaciaI-Holocene in the sandy land of northern China, based on organic carbon isotopic composition data from a loess-sand sequence at margin of the Mu Us sandy land. We use the relationship between monsoon precipitation and the carbon isotopic composition of modern soils as an analogue, with a minor modification, to reconstruct precipitation back to c. 47 ka ago. The preliminary results indicate that annual monsoon precipitation was high after 8 ka, with an average of 435 mm; and it decreased during 18 and 8 ka with a mean value of 194 mm. The precipitation value of 47-18 ka varied between the two. We compare the recon- structed precipitation with other records and paleoclimatic modeling results, showing that our record agrees with reconstructions of the monsoon precipitation from other sources, even capturing short climatic events such as the Younger Dryas. We suggest that solar irradiance, high-latitude temperature/ice volume and local evaporation have together modified moistures in the sandy land.展开更多
The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional preha...The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.展开更多
基金National Natural Science Foundation of China,No.41161012,No.41461003National Basic Research Program of China,No.2013CBA01801
文摘The isotope-equipped GCMs （general circulation models） are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spatial distribution and seasonal variation of precipitation isotopic composition in arid central Asia, several isotope-equipped GCMs are applied, and the long-term observations in two stations are used to verify the GCM-simulated results. Generally, seasonality of isotopic composition can be well simulated in each GCM, and the values of 6180 in precipitation are larger in summer months （from April to October） and lower in winter months （from November to March）. Higher latitude usually shows lower values of 6180 in precipitation, and lower latitude has higher values. The values of 5180 are relatively low in the eastern section, and higher in the western section. Among these simulations, ECHAM is good at describing the isotopic composition in the study region, which can be seen from the mean absolute error （MAE） and root-mean-square error （RMSE）. The ECHAM-derived values of 5180 in precipitation positively correlate with the observed series, and the correlation coefficient based on ECHAM is the largest among these GCMs.
基金supported by National Key Basic Research Program of China (Grant No.2010CB950902)National Natural Science Foundation of China(Grant No.31070427)National High-tech R&D Program of China(Grant No.2009BAC61B01)
文摘Foliar and root carbon isotope composition(δ13C) of grassland communities on the Qinghai-Tibet Plateau,China,was obtained by the biomass weighting method and direct measurement.We investigated the characteristics and altitudinal patterns of foliar and root δ13C and determined which environmental factors influenced foliar δ13 C most.Foliar δ13 C of alpine steppe was significantly higher than that of alpine meadow and temperate steppe.For alpine meadow,root δ13C was significantly higher than of foliar δ13C.Foliar δ13C increased with altitude at an average rate of 0.60‰ km 1 for the whole grassland ecosystem.This rate was lower than that at species level.However,there were no significant relationships between root δ13C and altitude.Atmospheric pressure was a more important factor than temperature and precipitation in its influence on the altitudinal pattern of foliar δ13C at the community level.
基金National Natural Science Foundation of China, No.41321062 No.41371203+1 种基金 The Global Changes Program of China, 2010CB950203 The Priority Academic Program Development of Jiangsu Higher Education Institu tions, The Fundamental Research Funds for the Central Universities, No. 1082020904
文摘We present the first quantitative estimation of monsoon precipitation during the late glaciaI-Holocene in the sandy land of northern China, based on organic carbon isotopic composition data from a loess-sand sequence at margin of the Mu Us sandy land. We use the relationship between monsoon precipitation and the carbon isotopic composition of modern soils as an analogue, with a minor modification, to reconstruct precipitation back to c. 47 ka ago. The preliminary results indicate that annual monsoon precipitation was high after 8 ka, with an average of 435 mm; and it decreased during 18 and 8 ka with a mean value of 194 mm. The precipitation value of 47-18 ka varied between the two. We compare the recon- structed precipitation with other records and paleoclimatic modeling results, showing that our record agrees with reconstructions of the monsoon precipitation from other sources, even capturing short climatic events such as the Younger Dryas. We suggest that solar irradiance, high-latitude temperature/ice volume and local evaporation have together modified moistures in the sandy land.
文摘The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.
