The spatial distribution and population dynamics of Quercus liaotungensis Koidz., Fraxinus rhynchophylla Hance and Acer mono Maxim. were studied in three warm temperate deciduous forests in Dongling Mountain, Beijing....The spatial distribution and population dynamics of Quercus liaotungensis Koidz., Fraxinus rhynchophylla Hance and Acer mono Maxim. were studied in three warm temperate deciduous forests in Dongling Mountain, Beijing. Clumped distributions appeared in most seedlings (≤0.4 m), short saplings (0.4-1 m) and tall saplings (1-2 m). Random distributions appeared in adults of Q. liaotungensis in Plot 1, F. rhynchophylla in Plot 3. The LSD method was used to discern the differences of different aged population. The class distribution of Q. liaotungensis was nearly a reverse-J shape for Plot 1 and Plot 3, suggesting that the population regenerates continuously. The age-structures of F. rhynchophylla and A. mono in Plot 1 and the test results indicated that they would increase continuously. In Plot 2, the class distribution and the test results showed that all populations would not regenerate continuously.展开更多
A phylogenetic hypothesis for the Asian newts of the Tylototriton asperrimus group was generated using data from two mitochondrial fragments including COI and the ND1-ND2 regions. Four distinct clades (A, B, C, D) w...A phylogenetic hypothesis for the Asian newts of the Tylototriton asperrimus group was generated using data from two mitochondrial fragments including COI and the ND1-ND2 regions. Four distinct clades (A, B, C, D) were resolved with high nodal support within this monophyletic group. Clade A included T. asperrimus, T. hainanensis, T. notialis, "T. vietnamensis", and two unnamed salamander populations from Vietnam. Clade A, constituted the sister group of clades B + C. Newly identified clade C likely represents a new cryptic species. Clade C was the sister group of T. wenxianensis. The true 7: vietnamensis exclusively constituted clade D. Our results bring into question some previous taxonomic decisions, and a revision is required. This study illustrates the necessity to include samples from type localities in taxonomic studies, and highlights the importance of fine-grained geographical sampling.展开更多
Global warming has become an increasing concern, and using soil as a carbon sink to sequester carbon dioxide has attracted much attention in recent years. In this study, soil organic carbon (SOC) content and organic c...Global warming has become an increasing concern, and using soil as a carbon sink to sequester carbon dioxide has attracted much attention in recent years. In this study, soil organic carbon (SOC) content and organic carbon density were estimated based on a soil survey of a small landscape in Dongguan, South China, with spatial heterogeneity of SOC distribution and the impacts of land-use patterns on soil organic carbon content assessed. Field sampling was carried out based on a 150 m×150 m grid system overlaid on the topographic map of the study area and samples were collected in three 20-cm layers to a depth of 60 cm. Spatial variability in the distribution of SOC was assessed using the Kruskal-Wallis test. Results showed that SOC in the topsoil layer (0-20 cm) was not much higher or even lower in some sites than the underlying layers, and except for the two sites covered with natural woodland, it did not exhibit a pronounced vertical gradient. The difference in both horizontal and vertical distribution of SOC was not statistically significant. However, in the topsoil layer among land-use/land-cover patterns, significant differences (P≤0.05) in SOC distribution existed, indicating that management practices had great impact on SOC content. SOC storage in the study area to a depth of 20, 40, and 60 cm was estimated as 2.13×106 kg, 3.46×106 kg, and 4.61×106 kg, respectively.展开更多
Using long term observation data in the main part of East China Sea Kuroshio, variations of Kuroshio upper layer temperature and salinity, their relationships with surface temperature and precipitation in east China a...Using long term observation data in the main part of East China Sea Kuroshio, variations of Kuroshio upper layer temperature and salinity, their relationships with surface temperature and precipitation in east China are studied. Results reveal that the Kuroshio upper layer temperature experienced slight rise while salinity decreased in the past 50 years. In winter, Kuroshio upper layer temperature is closely related to the surface temperature in east China, and large area in east China shows positive correlation to the Kuroshio upper layer temperature, which might be related to the mass temperature reduction as a result of the cold air activities in winter. In summer, the increase of the precipitation causes the increase of diluted Yangtze River water into the shelf sea, thereby results in the salinity decrease of Kuroshio in the upper layer.展开更多
Batch experiments were conducted to study the effects of low-molecular-weight organic acids(LMWOAs) on desorption of Hg from two kinds of soils in the eastern Shandong Province,China.Of all LMWOAs,oxalic and citric ac...Batch experiments were conducted to study the effects of low-molecular-weight organic acids(LMWOAs) on desorption of Hg from two kinds of soils in the eastern Shandong Province,China.Of all LMWOAs,oxalic and citric acids were chosen as the representatives in this experiment because they are most common in soils.Desorption of Hg increases with the increase of extracting time,until the highest desorption amount at 6-8 h,and then declines.It indicates that timeliness is very important when organic acids are used for phytoremediation in contaminated soils.When the concentrations of organic acids increase from 1.0 mmol/L to 10.0 mmol/L,Hg desorption increases significantly regardless of oxalic or citric acid.Compared with oxalic acid,citric acid is more effective to enhance the desorption of Hg,especially from fluvo-aquic soil.With the increase of initial pH value from 3 to 8,Hg desorption decreases directly in the presence of oxalic acid.However,Hg desorption first decreases,then increases,and eventually decreases again in the presence of citric acid due to the variation of competitive ability between chelating of citric acid and adsorption of soil in different pH values.Citric acid showed greater ability to release Hg from soils than oxalic acid.According to the results of the present study,it is found that the bioavailabilities of heavy metal can be improved with selecting suitable types and concentrations of organic acid amendment and reasonable soil condition.展开更多
The output of 25 models used in the Coupled Model Intercomparison Project phase 3 (CMIP3) were evaluated,with a focus on summer precipitation in eastern China for the last 40 years of the 20th century.Most mod-els fai...The output of 25 models used in the Coupled Model Intercomparison Project phase 3 (CMIP3) were evaluated,with a focus on summer precipitation in eastern China for the last 40 years of the 20th century.Most mod-els failed to reproduce rainfall associated with the East Asian summer monsoon (EASM),and hence the seasonal cycle in eastern China,but provided reasonable results in Southwest (SW) and Northeast China (NE).The simula-tions produced reasonable results for the Yangtze-Huai (YH) Basin area,although the Meiyu phenomenon was underestimated in general.One typical regional phe-nomenon,a seasonal northward shift in the rain belt from early to late summer,was completely missed by most models.The long-term climate trends in rainfall over eastern China were largely underestimated,and the ob-served geographical pattern of rainfall changes was not reproduced by most models.Precipitation extremes were evaluated via parameters of fitted GEV (Generalized Ex-treme Values) distributions.The annual extremes were grossly underestimated in the monsoon-dominated YH and SW regions,but reasonable values were calculated for the North China (NC) and NE regions.These results suggest a general failure to capture the dynamics of the EASM in current coupled climate models.Nonetheless,models with higher resolution tend to reproduce larger decadal trends and annual extremes of precipitation in the regions studied.展开更多
High-resolution seismic profiles and surface samples were studied in detail in order to determine the structures, provenance, and dynamic mechanisms of a fine-grained deposit in the southeast coastal area of the Liaod...High-resolution seismic profiles and surface samples were studied in detail in order to determine the structures, provenance, and dynamic mechanisms of a fine-grained deposit in the southeast coastal area of the Liaodong Peninsula, China. Results indicate that there is a prominent fine-grained deposit distributed alongshore up to 14 m thick, which thins out to less than 2 m in both seaward and landward directions, forming an fl-shaped pattern of cross-section. The deposit is 180-300 km away from the Yalu River mouth and extends along the southeast coast of the Liaodong Peninsula between the northeast of Dalian Bay and southwest of the Changshan Islands, in water depths of 20-40 m. The deposit, which is mainly derived from the Yalu River, represents a Holocene Highstand System Tract sequence formed since the highest sea level around 7.0 ka. The Yalu River-derived sediments were redeposited in the area off the southeast coast of the Liaodong Peninsula after resuspension and transportation by the Liaonan Coastal Current.展开更多
Evaluation on the population pressure in the mountainous areas is a necessary condition for the protection and good governance. The evaluation depends on accurate population density assessment. Traditional methods use...Evaluation on the population pressure in the mountainous areas is a necessary condition for the protection and good governance. The evaluation depends on accurate population density assessment. Traditional methods used to calculate population density often adopt the administrative region as a scale for statistical analysis. These methods did not consider the effects of the relief degree of land surface(RDLS) on the population distribution. Therefore they cannot accurately reflect the degree of population aggregation, especially in mountainous areas. To explore this issue further, we took the mountainous areas of China as the research area. China has A total area of 666 km2 can be classified as mountainous area,accounting for 69.4% of the country's total landmass. The data used in this research included the digital elevation model(DEM) of China at a scale of 1:1,000,000, National population density raster data, the DEM and the national population density raster data. First, we determined the relief degree of land surface(RDLS). Next, we conducted a correlation analysis between the population distribution and the RDLS using the Statistical Package for Social Science(SPSS). Based on the correlation analysis results and population distribution, this new method was used to revise the provincial population density of themountainous areas. The revised results were used to determine the population pressure of different mountainous areas. Overall, the following results were obtained:(1) The RDLS was low in most mountainous areas(with a value between 0 and 3.5) and exhibited a spatial pattern that followed the physiognomy of China;(2) The relationship between the RDLS and population density were logarithmic, with an R2 value up to 0.798(p<0.05), and the correlation decreased from east to west;(3) The difference between the revised population density(RPD) and the traditional population density(PD) was larger in the southeastern region of China than in the northwestern region;(4) In addition, compared with traditional results, the revised result indicated that the population pressure was larger. Based on these results, the following conclusions were made:(1) the revised method for estimating population density that incorporates the RDLS is reasonable and practical,(2) the potential population pressure in the southeastern mountainous areas is substantial,(3) the characteristics of the terrain in the high mountainous areas are important for the scattered distribution of the population, and(4) the population distribution of mountainous areas in China should be guided by local conditions, such as social, economic, and topographic conditions.展开更多
In this study, the authors simulate the East Asian climate changes in the mid-Pliocene (~3.3 to 3.0 Ma BP) with the Community Atmosphere Model version 3.1 (CAM3.1) and compare the simulated East Asian monsoon with pa...In this study, the authors simulate the East Asian climate changes in the mid-Pliocene (~3.3 to 3.0 Ma BP) with the Community Atmosphere Model version 3.1 (CAM3.1) and compare the simulated East Asian monsoon with paleoclimate data. The simulations show an obvious warming pattern in East Asia in the mid-Pliocene compared with the pre-industrial climate, with surface air temperature increasing by 0.5 4.0°C. In the warm mid-Pliocene simulation, the East Asian Summer Monsoon (EASM) becomes stronger, while the East Asian Winter Monsoon (EAWM) is similar relative to the pre-industrial climate. Compared with the paleoclimate data, our simulations depict the intensified EASM well but cannot reproduce the weakened EAWM. This model-data discrepancy may be attributed to the uncertainty in the reconstructed mid-Pliocene sea surface temperature.展开更多
It is well known that precipitation anomalies in the tropical western North Pacific (WNP) significantly affect circulation and rainfall in East Asia during summer. In this study, the authors further investigated thi...It is well known that precipitation anomalies in the tropical western North Pacific (WNP) significantly affect circulation and rainfall in East Asia during summer. In this study, the authors further investigated this relationship, by examining the anomalies associated with positive and negative precipitation anomalies in the tropical WNP. The results suggest these anomalies are asymmetric between the enhanced and suppressed WNP rainfall. Positive precipitation anomalies over the WNP, in comparison with their negative counterparts, are more closely related to the meridional teleconnection pattern and rainfall anomalies along the East Asian rain belt. The implications of the results are discussed.展开更多
Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley...Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.展开更多
This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asi...This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asia. Related to the dipole mode, with the heavier sea ice in the north and lighter sea ice in the southeast Barents Sea in spring, the East Asian summer subtropical rainy belt tends to move northward. The significant relationship is established through a wave train over northern Eurasia in the lower troposphere in June. The wave train enhances the northern East Asian low, which induces more rainfall to the north of the East Asian subtropical rainy belt and then attracts the subtropical rainy belt to move northward. This study suggests that the dipole mode of spring sea-ice anomalies in the Barents Sea may be a good precursor for the prediction of East Asian summer rainfall.展开更多
The characteristics of the summer precipitation diurnal cycle over South Asia and East Asia during 2001–13 are investigated based on the high spatiotemporal resolution estimates of the CPC(Climate Prediction Center) ...The characteristics of the summer precipitation diurnal cycle over South Asia and East Asia during 2001–13 are investigated based on the high spatiotemporal resolution estimates of the CPC(Climate Prediction Center) Morphing(CMORPH) technique. The results show that summer precipitation over South Asia and East Asia possesses a remarkable diurnal cycle, with obvious regional differences. Over the coastal areas, plateau, and high mountains, summer precipitation peaks in the late afternoon; while over low altitude areas, such as valleys, basins, and inshore seas, it peaks during midnight to early morning. In addition to these general features consistent with previous studies, the high resolution CMORPH technique can depict finer regional details, such as the less coherent phase pattern over a few regions. Besides, through comparative analysis of the diurnal cycle strength and precipitation fields, the authors find that for humid areas the summer precipitation diurnal cycle is especially significant over Southeast China, the Sichuan Basin, Hainan Province, Taiwan Province, the Philippines, and Indonesia. And it is relatively weak over the south of Northeast China, central East China, Yunnan Province, the central Indian Peninsula, and most oceanic areas. Comparisons between two satellite datasets—those of the CMORPH and Tropical Rainfall Measuring Mission(TRMM) 3B42 products—are also presented. For summer precipitation and the main diurnal cycle features, the results from both products agree over most regions, except a few areas, e.g., the Tibetan Plateau.展开更多
The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO streng...The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China's 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.展开更多
Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months.This study investigates the tropical P...Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months.This study investigates the tropical Pacific sea surface temperature (SST) anomalies associated with meridional displacement of the monthly EAJS during the summer.The meridional displacement of the EAJS in June is significantly associated with the tropical central Pacific SST anomaly in the winter of previous years,while displacements in July and August are related to tropical eastern Pacific SST anomalies in the late spring and concurrent summer.The EAJS tends to shift southward in the following June (July and August) corresponding to a warm SST anomaly in the central (eastern) Pacific in the winter (late spring-summer).The westerly anomaly south of the Asian jet stream is a result of tropical central Pacific warm SST anomaly-related warming in the tropical troposphere,which is proposed as a possible reason for southward displacement of the EAJS in June.The late spring-summer warm SST anomaly in the tropical eastern Pacific,however,may be linked to southward displacement of the EAJS in July and August through a meridional teleconnection over the western North Pacific (WNP) and East Asia.展开更多
Using the monthly mean reanalysis data of height, wind and vertical velocity of NCEP/NCAR from 1958 to 2003, the characteristics of 500hPa height anomalies in the Northern Hemisphere, convergence and divergence on the...Using the monthly mean reanalysis data of height, wind and vertical velocity of NCEP/NCAR from 1958 to 2003, the characteristics of 500hPa height anomalies in the Northern Hemisphere, convergence and divergence on the levels of 200hPa and 925hPa and vertical stream over the Shandong province were studied and compared with that over North China. The study shows that the teleconnection pattern called East Asia-Pacific pattern (EAP) plays important roles in the summer rainfall of Shandong. Weaker Okhotsk sea high, stronger upward stream over tropical areas and Shandong and northward location of subtropical high and stronger Indian low, are likely to lead to more rain in Shandong province in summer, but there are some flood (drought) years in which these characteristics such as the location and intensity of subtropical high change with the least extent. The difference between Shandong and North China in 500hPa height is that there is a teleconnection pattern called Europe / Asia pattern in North China, while there is a negative East Asia Pattern in Shandong during drought years. There is a teleconnection relation between Shandong summer rainfall and convective activities happening in tropical areas in spring and summer accomplished by the Rossby waves. During the flood years in Shandong, the convective activities happening in tropical India Ocean and tropical west Pacific and Walker circulation are much stronger than that during the drought years, but the convective activities happening in tropical east Pacific are weaker than those during the drought years.展开更多
文摘The spatial distribution and population dynamics of Quercus liaotungensis Koidz., Fraxinus rhynchophylla Hance and Acer mono Maxim. were studied in three warm temperate deciduous forests in Dongling Mountain, Beijing. Clumped distributions appeared in most seedlings (≤0.4 m), short saplings (0.4-1 m) and tall saplings (1-2 m). Random distributions appeared in adults of Q. liaotungensis in Plot 1, F. rhynchophylla in Plot 3. The LSD method was used to discern the differences of different aged population. The class distribution of Q. liaotungensis was nearly a reverse-J shape for Plot 1 and Plot 3, suggesting that the population regenerates continuously. The age-structures of F. rhynchophylla and A. mono in Plot 1 and the test results indicated that they would increase continuously. In Plot 2, the class distribution and the test results showed that all populations would not regenerate continuously.
基金supported by grants from the Ministry of Science and Technology of China(MOST Grant 2011FY120200)the National Natural Science Foundation of China(31090100,30870281)+1 种基金the Chinese Academy of Sciences(KSCX2-YW-Z-0807,KSCX2-EW-Z-2)the Bureau of Science and Technology of Yunnan province
文摘A phylogenetic hypothesis for the Asian newts of the Tylototriton asperrimus group was generated using data from two mitochondrial fragments including COI and the ND1-ND2 regions. Four distinct clades (A, B, C, D) were resolved with high nodal support within this monophyletic group. Clade A included T. asperrimus, T. hainanensis, T. notialis, "T. vietnamensis", and two unnamed salamander populations from Vietnam. Clade A, constituted the sister group of clades B + C. Newly identified clade C likely represents a new cryptic species. Clade C was the sister group of T. wenxianensis. The true 7: vietnamensis exclusively constituted clade D. Our results bring into question some previous taxonomic decisions, and a revision is required. This study illustrates the necessity to include samples from type localities in taxonomic studies, and highlights the importance of fine-grained geographical sampling.
基金Project supported by the Key Research Program of Guangdong Province (No. 2002C20703)the Key Research Program of the Forestry Administration of Guangdong Province (No. 2002-12).
文摘Global warming has become an increasing concern, and using soil as a carbon sink to sequester carbon dioxide has attracted much attention in recent years. In this study, soil organic carbon (SOC) content and organic carbon density were estimated based on a soil survey of a small landscape in Dongguan, South China, with spatial heterogeneity of SOC distribution and the impacts of land-use patterns on soil organic carbon content assessed. Field sampling was carried out based on a 150 m×150 m grid system overlaid on the topographic map of the study area and samples were collected in three 20-cm layers to a depth of 60 cm. Spatial variability in the distribution of SOC was assessed using the Kruskal-Wallis test. Results showed that SOC in the topsoil layer (0-20 cm) was not much higher or even lower in some sites than the underlying layers, and except for the two sites covered with natural woodland, it did not exhibit a pronounced vertical gradient. The difference in both horizontal and vertical distribution of SOC was not statistically significant. However, in the topsoil layer among land-use/land-cover patterns, significant differences (P≤0.05) in SOC distribution existed, indicating that management practices had great impact on SOC content. SOC storage in the study area to a depth of 20, 40, and 60 cm was estimated as 2.13×106 kg, 3.46×106 kg, and 4.61×106 kg, respectively.
基金supported by National Natural Science Foundation Project ‘Multi-core Structure of Antarctic Circumpolar Current and a Dynamic View of Its Spatial-temporal Variation’ (No. 40506011)The key project of the National Natural Science Foundation of China ‘Diagnostic Analysis and Numerical Simulation of the Inter-decadal Variations of East Asian Summer Monsoon and Summer Precipitation in East of China’ (No. 40331010)The key project of the Major Natural Fundamental Researches of Universities in Jiangsu Province ‘Research of development and prediction theory of Drought and Flood in the mid-lower reaches of Yangtze River’ (No. 05KJA17002)
文摘Using long term observation data in the main part of East China Sea Kuroshio, variations of Kuroshio upper layer temperature and salinity, their relationships with surface temperature and precipitation in east China are studied. Results reveal that the Kuroshio upper layer temperature experienced slight rise while salinity decreased in the past 50 years. In winter, Kuroshio upper layer temperature is closely related to the surface temperature in east China, and large area in east China shows positive correlation to the Kuroshio upper layer temperature, which might be related to the mass temperature reduction as a result of the cold air activities in winter. In summer, the increase of the precipitation causes the increase of diluted Yangtze River water into the shelf sea, thereby results in the salinity decrease of Kuroshio in the upper layer.
基金Under the auspices of Natural Science Foundation of Shandong Province (No. 2009ZRB019E5)National NaturalScience Foundation of China (No. 41101094)
文摘Batch experiments were conducted to study the effects of low-molecular-weight organic acids(LMWOAs) on desorption of Hg from two kinds of soils in the eastern Shandong Province,China.Of all LMWOAs,oxalic and citric acids were chosen as the representatives in this experiment because they are most common in soils.Desorption of Hg increases with the increase of extracting time,until the highest desorption amount at 6-8 h,and then declines.It indicates that timeliness is very important when organic acids are used for phytoremediation in contaminated soils.When the concentrations of organic acids increase from 1.0 mmol/L to 10.0 mmol/L,Hg desorption increases significantly regardless of oxalic or citric acid.Compared with oxalic acid,citric acid is more effective to enhance the desorption of Hg,especially from fluvo-aquic soil.With the increase of initial pH value from 3 to 8,Hg desorption decreases directly in the presence of oxalic acid.However,Hg desorption first decreases,then increases,and eventually decreases again in the presence of citric acid due to the variation of competitive ability between chelating of citric acid and adsorption of soil in different pH values.Citric acid showed greater ability to release Hg from soils than oxalic acid.According to the results of the present study,it is found that the bioavailabilities of heavy metal can be improved with selecting suitable types and concentrations of organic acid amendment and reasonable soil condition.
基金supported by the National Basic Research Program of China 2009CB421401/2006CB400503the Chinese Meteorological Administration ProgramGYHY200706001
文摘The output of 25 models used in the Coupled Model Intercomparison Project phase 3 (CMIP3) were evaluated,with a focus on summer precipitation in eastern China for the last 40 years of the 20th century.Most mod-els failed to reproduce rainfall associated with the East Asian summer monsoon (EASM),and hence the seasonal cycle in eastern China,but provided reasonable results in Southwest (SW) and Northeast China (NE).The simula-tions produced reasonable results for the Yangtze-Huai (YH) Basin area,although the Meiyu phenomenon was underestimated in general.One typical regional phe-nomenon,a seasonal northward shift in the rain belt from early to late summer,was completely missed by most models.The long-term climate trends in rainfall over eastern China were largely underestimated,and the ob-served geographical pattern of rainfall changes was not reproduced by most models.Precipitation extremes were evaluated via parameters of fitted GEV (Generalized Ex-treme Values) distributions.The annual extremes were grossly underestimated in the monsoon-dominated YH and SW regions,but reasonable values were calculated for the North China (NC) and NE regions.These results suggest a general failure to capture the dynamics of the EASM in current coupled climate models.Nonetheless,models with higher resolution tend to reproduce larger decadal trends and annual extremes of precipitation in the regions studied.
基金Supported by the National Natural Science Foundation of China(No.41106043)the China Geological Survey(Nos.GZH200800501,GZH200900501)the Open Fund of State Key Laboratory of Marine Geology(No.MG0903)
文摘High-resolution seismic profiles and surface samples were studied in detail in order to determine the structures, provenance, and dynamic mechanisms of a fine-grained deposit in the southeast coastal area of the Liaodong Peninsula, China. Results indicate that there is a prominent fine-grained deposit distributed alongshore up to 14 m thick, which thins out to less than 2 m in both seaward and landward directions, forming an fl-shaped pattern of cross-section. The deposit is 180-300 km away from the Yalu River mouth and extends along the southeast coast of the Liaodong Peninsula between the northeast of Dalian Bay and southwest of the Changshan Islands, in water depths of 20-40 m. The deposit, which is mainly derived from the Yalu River, represents a Holocene Highstand System Tract sequence formed since the highest sea level around 7.0 ka. The Yalu River-derived sediments were redeposited in the area off the southeast coast of the Liaodong Peninsula after resuspension and transportation by the Liaonan Coastal Current.
基金supported by a grant from the Major State Basic Research Development Program of China (973 Program) (Grant No. 2015CB452706)National Natural Science Foundation of China (Grant No. 41471469)provided by the national scientific datasharing project Earth System Science Data Sharing Network
文摘Evaluation on the population pressure in the mountainous areas is a necessary condition for the protection and good governance. The evaluation depends on accurate population density assessment. Traditional methods used to calculate population density often adopt the administrative region as a scale for statistical analysis. These methods did not consider the effects of the relief degree of land surface(RDLS) on the population distribution. Therefore they cannot accurately reflect the degree of population aggregation, especially in mountainous areas. To explore this issue further, we took the mountainous areas of China as the research area. China has A total area of 666 km2 can be classified as mountainous area,accounting for 69.4% of the country's total landmass. The data used in this research included the digital elevation model(DEM) of China at a scale of 1:1,000,000, National population density raster data, the DEM and the national population density raster data. First, we determined the relief degree of land surface(RDLS). Next, we conducted a correlation analysis between the population distribution and the RDLS using the Statistical Package for Social Science(SPSS). Based on the correlation analysis results and population distribution, this new method was used to revise the provincial population density of themountainous areas. The revised results were used to determine the population pressure of different mountainous areas. Overall, the following results were obtained:(1) The RDLS was low in most mountainous areas(with a value between 0 and 3.5) and exhibited a spatial pattern that followed the physiognomy of China;(2) The relationship between the RDLS and population density were logarithmic, with an R2 value up to 0.798(p<0.05), and the correlation decreased from east to west;(3) The difference between the revised population density(RPD) and the traditional population density(PD) was larger in the southeastern region of China than in the northwestern region;(4) In addition, compared with traditional results, the revised result indicated that the population pressure was larger. Based on these results, the following conclusions were made:(1) the revised method for estimating population density that incorporates the RDLS is reasonable and practical,(2) the potential population pressure in the southeastern mountainous areas is substantial,(3) the characteristics of the terrain in the high mountainous areas are important for the scattered distribution of the population, and(4) the population distribution of mountainous areas in China should be guided by local conditions, such as social, economic, and topographic conditions.
基金supported by the National Basic Research Program of China(2009CB421406)the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-Q1-02)the National Natural Science Foundation of China(4090205 and 40975050)
文摘In this study, the authors simulate the East Asian climate changes in the mid-Pliocene (~3.3 to 3.0 Ma BP) with the Community Atmosphere Model version 3.1 (CAM3.1) and compare the simulated East Asian monsoon with paleoclimate data. The simulations show an obvious warming pattern in East Asia in the mid-Pliocene compared with the pre-industrial climate, with surface air temperature increasing by 0.5 4.0°C. In the warm mid-Pliocene simulation, the East Asian Summer Monsoon (EASM) becomes stronger, while the East Asian Winter Monsoon (EAWM) is similar relative to the pre-industrial climate. Compared with the paleoclimate data, our simulations depict the intensified EASM well but cannot reproduce the weakened EAWM. This model-data discrepancy may be attributed to the uncertainty in the reconstructed mid-Pliocene sea surface temperature.
基金supported by the National Natural Science Foundation of China[grant number 41320104007]
文摘It is well known that precipitation anomalies in the tropical western North Pacific (WNP) significantly affect circulation and rainfall in East Asia during summer. In this study, the authors further investigated this relationship, by examining the anomalies associated with positive and negative precipitation anomalies in the tropical WNP. The results suggest these anomalies are asymmetric between the enhanced and suppressed WNP rainfall. Positive precipitation anomalies over the WNP, in comparison with their negative counterparts, are more closely related to the meridional teleconnection pattern and rainfall anomalies along the East Asian rain belt. The implications of the results are discussed.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q11-03)
文摘Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.
基金supported by the National Natural Science Foundation of China[grant numbers 41375086 and 41775062]the National Natural Science Foundation of China[grant number 41630530]+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS)supported by the Youth Innovation Promotion Association of CAS
文摘This study reveals a significant relationship, on the interannual timescale, between a dipole mode, the second leading mode, of spring sea-ice anomalies in the Barents Sea and the following-summer rainfall in East Asia. Related to the dipole mode, with the heavier sea ice in the north and lighter sea ice in the southeast Barents Sea in spring, the East Asian summer subtropical rainy belt tends to move northward. The significant relationship is established through a wave train over northern Eurasia in the lower troposphere in June. The wave train enhances the northern East Asian low, which induces more rainfall to the north of the East Asian subtropical rainy belt and then attracts the subtropical rainy belt to move northward. This study suggests that the dipole mode of spring sea-ice anomalies in the Barents Sea may be a good precursor for the prediction of East Asian summer rainfall.
基金supported by the National Basic Research Program of China(Grant No.2013CB430201)the China Meteorological Administration Special Fund for Scientific Research in the Public Interest(Grant No.GYHY201206008)
文摘The characteristics of the summer precipitation diurnal cycle over South Asia and East Asia during 2001–13 are investigated based on the high spatiotemporal resolution estimates of the CPC(Climate Prediction Center) Morphing(CMORPH) technique. The results show that summer precipitation over South Asia and East Asia possesses a remarkable diurnal cycle, with obvious regional differences. Over the coastal areas, plateau, and high mountains, summer precipitation peaks in the late afternoon; while over low altitude areas, such as valleys, basins, and inshore seas, it peaks during midnight to early morning. In addition to these general features consistent with previous studies, the high resolution CMORPH technique can depict finer regional details, such as the less coherent phase pattern over a few regions. Besides, through comparative analysis of the diurnal cycle strength and precipitation fields, the authors find that for humid areas the summer precipitation diurnal cycle is especially significant over Southeast China, the Sichuan Basin, Hainan Province, Taiwan Province, the Philippines, and Indonesia. And it is relatively weak over the south of Northeast China, central East China, Yunnan Province, the central Indian Peninsula, and most oceanic areas. Comparisons between two satellite datasets—those of the CMORPH and Tropical Rainfall Measuring Mission(TRMM) 3B42 products—are also presented. For summer precipitation and the main diurnal cycle features, the results from both products agree over most regions, except a few areas, e.g., the Tibetan Plateau.
基金Joint Project of Natural Science Foundation of China and Yunnan Province (U0833602)
文摘The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China's 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.
基金supported by the National Natural Science Foundation of China (Grant No. 40810059005)
文摘Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months.This study investigates the tropical Pacific sea surface temperature (SST) anomalies associated with meridional displacement of the monthly EAJS during the summer.The meridional displacement of the EAJS in June is significantly associated with the tropical central Pacific SST anomaly in the winter of previous years,while displacements in July and August are related to tropical eastern Pacific SST anomalies in the late spring and concurrent summer.The EAJS tends to shift southward in the following June (July and August) corresponding to a warm SST anomaly in the central (eastern) Pacific in the winter (late spring-summer).The westerly anomaly south of the Asian jet stream is a result of tropical central Pacific warm SST anomaly-related warming in the tropical troposphere,which is proposed as a possible reason for southward displacement of the EAJS in June.The late spring-summer warm SST anomaly in the tropical eastern Pacific,however,may be linked to southward displacement of the EAJS in July and August through a meridional teleconnection over the western North Pacific (WNP) and East Asia.
基金Dedicated Research Fund for Public Interest from the Ministry of Science and Technology (2001DIB20104) "Relationship Between Subtropical Monsoon Circulation and Summer Precipitation in Shandong", a key science project for 2002 in the Shandong province.
文摘Using the monthly mean reanalysis data of height, wind and vertical velocity of NCEP/NCAR from 1958 to 2003, the characteristics of 500hPa height anomalies in the Northern Hemisphere, convergence and divergence on the levels of 200hPa and 925hPa and vertical stream over the Shandong province were studied and compared with that over North China. The study shows that the teleconnection pattern called East Asia-Pacific pattern (EAP) plays important roles in the summer rainfall of Shandong. Weaker Okhotsk sea high, stronger upward stream over tropical areas and Shandong and northward location of subtropical high and stronger Indian low, are likely to lead to more rain in Shandong province in summer, but there are some flood (drought) years in which these characteristics such as the location and intensity of subtropical high change with the least extent. The difference between Shandong and North China in 500hPa height is that there is a teleconnection pattern called Europe / Asia pattern in North China, while there is a negative East Asia Pattern in Shandong during drought years. There is a teleconnection relation between Shandong summer rainfall and convective activities happening in tropical areas in spring and summer accomplished by the Rossby waves. During the flood years in Shandong, the convective activities happening in tropical India Ocean and tropical west Pacific and Walker circulation are much stronger than that during the drought years, but the convective activities happening in tropical east Pacific are weaker than those during the drought years.