Zinc(Zn),a widespread metal in the Earth’s crust,serves as a crucial nutrient in the Southern Ocean’s primary production.Studies on Zn in Antarctic snow and ice offer insights into the origins of this metal and its ...Zinc(Zn),a widespread metal in the Earth’s crust,serves as a crucial nutrient in the Southern Ocean’s primary production.Studies on Zn in Antarctic snow and ice offer insights into the origins of this metal and its transport routes,as well as its impact on the biogeochemical processes within the Antarctic atmosphere–land–ocean system.This review examines research on the spatial and temporal distribution of Zn in Antarctic snow and ice,as well as in Southern Ocean waters.It includes an overview of advanced methods for sampling and analyzing Zn,along with explanations for the observed variations.The review also discusses various sources of Zn as a nutrient to the Southern Ocean.Finally,it addresses prospective issues related to the use of Zn isotopes in identifying atmospheric sources and their biogeochemical effects on the development of the Southern Ocean ecosystem.展开更多
With the rapid development of population and urbanization and the progress of lighting technology, the influence of artificial light sources has increased.In this context, the problem of light pollution has attracted ...With the rapid development of population and urbanization and the progress of lighting technology, the influence of artificial light sources has increased.In this context, the problem of light pollution has attracted wide attention.Previous studies have revealed that light pollution can affect biological living environments, human physical and mental health, astronomical observations and many other aspects.Therefore, organizations internationally have begun to advocate for measures to prevent light pollution, many of which are recognized by the International Dark-Sky Association(IDA).In addition to improving public awareness, legal protections, technical treatments and other means, the construction of Dark Sky Reserves(DSR) has proven to be an effective preventive measure.So far, as a pioneer practice in this field, the IDA has identified 11 DSRs worldwide.Based on the DA requirements for DSRs, this paper utilizes NPP-VIIRS nighttime light data and other multi-source spatial data to analyze possible DSR sites in China.The land of China was divided into more than ten thousand 30 km × 30 km fishnets, and constraint and suitable conditions were designated, respectively, as light and cloud conditions, and scale, traffic and attractiveness conditions.Using a multiple criteria evaluation, 1443 fishnets were finally selected as most suitable sites for the construction of DSRs.Results found that less than 25% of China is not subject to light pollution, and less than 13% is suitable for DSR construction, primarily in western and northern areas, including Tibet, Xinjiang, Qinghai, Gansu and Inner Mongolia.展开更多
In recent decades,the continuously changed glaciers in the Himalayas not only affected process of atmospheric flow and water cycle in the plateau but also increased the frequency of secondary disasters,such as ice col...In recent decades,the continuously changed glaciers in the Himalayas not only affected process of atmospheric flow and water cycle in the plateau but also increased the frequency of secondary disasters,such as ice collapse and outburst floods.Therefore,the monitoring of Himalayas glacial change is of great significance in the aspects of climate change and disaster prevention and reduction.The Himalayas glacier outlines in China were extracted by ratio threshold and visual interpretation based on the Landsat TM/ETM+/OLI data and glacier catalogue data.Based on the ASTER GDEM data,the distribution and change characteristics at different altitudes were studied,and the surface moraine was identified to study the influence of glacial area variations.In addition,Glaciers were divided into marine and continental glaciers in this study,and the distribution and changes of the two types of glaciers were analyzed.Also,a comprehensive analysis of a long time series was performed.The results showed that:(1)From 1990 to 2015,the glaciers in the study area showed an overall trend of melting;the annual melting speed gradually accelerated from 0.48%/a to 0.75%/a.The total melting glacial area was 828.16 km,and the melting rate of the glaciers in the western section was the highest,at 0.63%.(2)The total area of continental glaciers was larger than that of marine glaciers,and its reduction was relatively larger,too.(3)The average size of debris-covered glaciers was 10 times that of debris-free glaciers,but their rate of change(8.1%)was 1/2 of that of debrisfree glaciers(17.8%).(4)The number of glaciers gradually decreased as the size of glaciers increased.The glaciers with grades of>50 km,0.5~1 km,and 1~2 kmhad large change rates,which were 20.1%,19.1%,and 18.5%,respectively.In summary,the Himalayas glaciers in China were melting at an accelerated rate and their numbers were gradually decreasing from 1990 to 2015.The location,type,elevation,size and debris cover of a glacier are all important factors influencing glacier change.It has been found that the lower the elevation or the smaller the size of the glacier,the greater the likelihood of glacier ablation,and the debris can inhibit the melting of glaciers to a certain extent.展开更多
A better knowledge of aerosol properties is of great significance for elucidating the complex mechanisms behind frequently occurring haze pollution events.In this study,we examine the temporal and spatial variations i...A better knowledge of aerosol properties is of great significance for elucidating the complex mechanisms behind frequently occurring haze pollution events.In this study,we examine the temporal and spatial variations in both PM_(1)and its major chemical constituents using three-year field measurements that were collected in six representative regions in China between 2012 and 2014.Our results show that both PM_(1)and its chemical compositions varied significantly in space and time,with high PM_(1)loadings mainly observed in the winter.By comparing chemical constituents between clean and polluted episodes,we find that the elevated PM_(1)mass concentration during pollution events should be largely attributable to significant increases in organic matter(OM)and inorganic aerosols like sulfate,nitrate,and ammonium(SNA),indicative of the critical role of primary emissions and secondary aerosols in elevating PM_(1)pollution levels.The ratios of PM_(1)/PM2.5 are found to be generally high in Shanghai and Guangzhou,while relatively low ratios are seen in Xi’an and Chengdu,indicating anthropogenic emissions were more likely to accumulate in forms of finer particles.With respect to the relative importance of chemical components and meteorological factors quantified via statistical modeling practices,we find that primary emissions and secondary aerosols were the two leading factors contributing to PM_(1)variations,though meteorological factors also played important roles in regulating the dispersion of atmospheric PM.展开更多
The complex network theory provides an approach for understanding the complexity of climate change from a new perspective.In this study,we used the coarse graining process to convert the data series of daily mean temp...The complex network theory provides an approach for understanding the complexity of climate change from a new perspective.In this study,we used the coarse graining process to convert the data series of daily mean temperature and daily precipitation from 1961 to 2011 into symbol sequences consisting of five characteristic symbols(i.e.,R,r,e,d and D),and created the temperature fluctuation network(TFN)and precipitation fluctuation network(PFN)to discover the complex network characteristics of climate change in the Tarim River Basin of Northwest China.The results show that TFN and PEN both present characteristics of scale-free network and small-world network with short average path length and high clustering coefficient.The nodes with high degree in TFN are RRR,d RR and Re R while the nodes with high degree in PFN are rre,rrr,eee and err,which indicates that climate change modes represented by these nodes have large probability of occurrence.Symbol R and r are mostly included in the important nodes of TFN and PFN,which indicate that the fluctuating variation in temperature and precipitation in the Tarim River Basin mainly are rising over the past 50 years.The nodes RRR,DDD,Re R,RRd,DDd and Ree are the hub nodes in TFN,which undertake 19.71%betweenness centrality of the network.The nodes rre,rrr,eee and err are the hub nodes in PFN,which undertake 13.64%betweenness centrality of the network.展开更多
Under the Paris Agreement framework, many developing countries call for low-carbon technology transfers from developed countries as a critical element in the global partnership for carbon emissions abatement. Such a p...Under the Paris Agreement framework, many developing countries call for low-carbon technology transfers from developed countries as a critical element in the global partnership for carbon emissions abatement. Such a partnership may be disrupted as the U.S. walks away from the agreement. Based on CIECIA-TD model, this paper examines effects of the U.S. exit on global low-carbon technology transfers under various scenarios and simulates the effects on low-carbon technology transfer, climate change, countries' emissions abatement results, and economic development. Our findings suggest that lowcarbon technology has significant emissions abatement and temperature rise mitigation effects. Low-carbon technology transfer among developed countries offers huge emissions abatement potentials, but patent protection system presents a significant barrier to further carbon emissions abatement. In this sense, the U.S. exit from the Paris Agreement will significantly impede developed countries' carbon emissions abatement through technology transfer. With limited knowhow, R&D and learning capacity, developing countries will suffer more to cut carbon emissions under the chain effects of a more challenging technology sharing environment that may result from the U.S. exit from the Paris Agreement. As a gradualist emissions abatement approach, low-carbon technology transfer cannot reduce emissions substantially within a short time, but its climate welfare is conducive to global economic growth and of great significance to carbon governance.展开更多
Monitoring and predicting highly localized weather events over a very short-term period,typically ranging from minutes to a few hours,are very important for decision makers and public action.Nowcasting these events us...Monitoring and predicting highly localized weather events over a very short-term period,typically ranging from minutes to a few hours,are very important for decision makers and public action.Nowcasting these events usually relies on radar observations through monitoring and extrapolation.With advanced high-resolution imaging and sounding observations from weather satellites,nowcasting can be enhanced by combining radar,satellite,and other data,while quantitative applications of those data for nowcasting are advanced through using machine learning techniques.Those applications include monitoring the location,impact area,intensity,water vapor,atmospheric instability,precipitation,physical properties,and optical properties of the severe storm at different stages(pre-convection,initiation,development,and decaying),identification of storm types(wind,snow,hail,etc.),and predicting the occurrence and evolution of the storm.Satellite observations can provide information on the environmental characteristics in the preconvection stage and are very useful for situational awareness and storm warning.This paper provides an overview of recent progress on quantitative applications of satellite data in nowcasting and its challenges,and future perspectives are also addressed and discussed.展开更多
The advent of a mobile society has led to profound changes in China’s traditional rural-urban pattern and called for new strategies for urban and rural governance.Based on a macro perspective of temporal and spatial ...The advent of a mobile society has led to profound changes in China’s traditional rural-urban pattern and called for new strategies for urban and rural governance.Based on a macro perspective of temporal and spatial evolution,this study analyzes the historical logics of rural-urban governance,explores the geographical patterns of challenges in China’s rural-urban governance,and finally puts forward targeted strategies for rural-urban governance toward integrated and sustainable development in China.From the historical perspective,the urban originates from the rural,and the connotation of rural,that is,a regional-scale outlook,rural-urban relations,and sociocultural interaction,forms the traditional approach to rural-urban governance.China’s rural-urban governance has evolved from antagonism toward integration.In terms of theoretical development,the turn toward mobility is an important driving factor shaping and promoting the transformation of research focus on rural-urban governance.The mobility of urban and rural factors has especially in recent decades brought extensive challenges for governance,which are highlighted by the disintegration of the stability of rural and urban structures,growing regional disparities in rural education levels,and serious aging and hollowing crises in rural areas.We therefore propose that rural-urban governance should give sufficient consideration to the convergence of wider interests;realize social potential through institutional,cultural and spatial restructuring;and attach importance to collaborative development and governance.And the transfer of rural problems to urban areas should be paid attention to by rural-urban governance.This research enriches the knowledge regarding the logics and patterns of China’s rural-urban governance from an interdisciplinary perspective.It is also helpful in the promotion of rural-urban integration and sustainable development,especially at a time when the mobility of social factors between rural areas and urban areas increasingly challenges traditional urban and rural governance and drives its evolution.展开更多
Antarctic trace metal records provide important information for grasping the influence of human activities on the environment over the last centuries.The CA2016-75 ice core is located along the East Antarctic Zhongsha...Antarctic trace metal records provide important information for grasping the influence of human activities on the environment over the last centuries.The CA2016-75 ice core is located along the East Antarctic Zhongshan Station-Dome A,enhances the record of metals research in the East Antarctic region,and its high-resolution supplies data support for the study of high-frequency climatic drivers and the effect of human activities on the Antarctic environment.A thorough dataset on seven trace metals(Al,Fe,Mn,Cu,Zn,Ba and Pb)in a coastal ice core in eastern Antarctica during the previous 102 years(1915-2016)is presented in this study.Pb has the lowest concentration(9.51±20.95 pg g^(-1)),and Ba has the highest concentration(36.57±51.35 ng g^(-1)).Notable variations are observed between the pre-1968 AD and post-1968 AD phases for Mn,Zn and Ba.The abrupt,remarkable increase in the concentrations coincided with the change of metal smelting production in the southern hemisphere.In addition to this,it may also be related to local Antarctic scientific research activities.Al and Fe,the primary crustal elements,are essentially obtained from soil dust;Cu shows high crustal enrichment factors(EFc,>10),indicating that it is notably affected by anthropogenic activities.Moreover,the anthropogenic activities in the Southern Hemisphere have had an impact on lead deposition in Antarctica.This study not only enriches the trace metal historical record along the Zhongshan Station-Dome A but also provides a high-resolution ice core record,which is very crucial for the reconstruction of trace metal concentration changes in the last 100 years.展开更多
With rapid globalization,industrial parks are playing an increasingly important role in the national and regional development.Since the Belt and Road Initiative(BRI)was put forward,national-level overseas industrial p...With rapid globalization,industrial parks are playing an increasingly important role in the national and regional development.Since the Belt and Road Initiative(BRI)was put forward,national-level overseas industrial parks of China have emerged with new development features and trends.It is of great importance to carry out a comparative study on domestic and overseas industrial parks of China.Based on the perspective of spatiotemporal evolution,this paper compares and analyzes national-level overseas industrial parks along the Belt and Road(B&R)and domestic industrial parks of China.In time,China’s industrial parks have experienced four stages with distinctive state-led characteristic.There are different development paths and modes for overseas industrial parks along the B&R and domestic industrial parks.In space,the national-level overseas industrial parks are invested and constructed by Chinese enterprises(mostly from the coastal developed cities),and mainly distributed in the countries along the B&R.Through typical cases comparison of Thai-Chinese Rayong Industrial Zone and Tianjin Economic-Technological Development Area,the paper finds that national-level overseas industrial parks are basically market-driven and concentrated in traditional advantageous industries,while domestic industrial parks are mainly government-led high-tech industries.Localization of overseas industrial parks and remote coupling with domestic industrial parks become very important.展开更多
Quantitative characterization of environmental characteristics of cropland(ECC)plays an important role in maintaining sustainable development of agricultural systems and ensuring regional food security. In this study,...Quantitative characterization of environmental characteristics of cropland(ECC)plays an important role in maintaining sustainable development of agricultural systems and ensuring regional food security. In this study, the changes in ECC over the Songnen Plain, a major grain crops production region in Northeast China, were investigated for the period 1990–2015. The results revealed significant changes in climate conditions, soil physical properties and cropland use patterns with socioeconomic activities. Trends in climate parameters showed increasing temperature(+0.49°C/decade, p < 0.05) and decreasing wind speed(–0.3 m/s/decade, p < 0.01) for the growing season, while sunshine hours and precipitation exhibited non-significant trends. Four topsoil parameters including soil organic carbon(SOC), clay, bulk density and pH, indicated deteriorating soil conditions across most of the croplands, although some do exhibited slight improvement. The changing amplitude for each of the four above parameters ranged within –0.052 to 0.029 kg C/kg, –0.38 to 0.30,–0.60 to 0.39 g/cm^3, –3.29 to 2.34, respectively. Crop production significantly increased(44.0 million tons) with increasing sown area of croplands(～2.5 million ha) and fertilizer application(～2.5 million tons). The study reveals the dynamics of ECC in the Songnen Plain with intensive cultivation from 1990 to 2015. Population growth, economic development, and policy reform are shown to strongly influence the spatiotemporal changes in cropland characteristics.The study potentially provides valuable scientific information to support sustainable agroecosystem management in the context of global climate change and national socioeconomic development.展开更多
Urban green volume is an important indicator for analyzing urban vegetation structure, ecological evaluation, and green-economic estimation. This paper proposes an object-based method for automated estimation of urban...Urban green volume is an important indicator for analyzing urban vegetation structure, ecological evaluation, and green-economic estimation. This paper proposes an object-based method for automated estimation of urban green volume combining three-dimensional （3D） information from airborne Light Detection and Ranging （LiDAR） data and vegetation information from high resolution remotely sensed images through a case study of the Lujiazui region, Shanghai, China. High resolution airborne near-infrared photographs are used for identifying the urban vegetation distribution. Airborne LiDAR data offer the possibility to extract individual trees and to measure the attributes of trees, such as tree height and crown diameter. In this study, individual trees and grassland are identified as the independent objects of urban vegetation, and the urban green volume is computed as the sum of two broad portions： individual trees volume and grassland volume. The method consists of following steps： generating and filtering the normalized digital surface model （nDSM）, extracting the nDSM of urban vegetation based on the Normalized Difference Vegetation Index （NDVI）, locating the local maxima points, segment- ing the vegetation objects of individual tree crowns and grassland, and calculating the urban green volume of each vegetation object. The results show the quantity and distribution characteristics of urban green volume in the Lujiazui region, and provide valuable parameters for urban green planning and management. It is also concluded from this paper that the integrated application of LiDAR data and image data presents an effective way to estimate urban green volume.展开更多
This article describes a global consistency check of CO2 satellite retrieval products from the Atmospheric Infrared Sounder （AIRS） and Infrared Atmospheric Sounding Interferometer （IASI） using statistical analysis...This article describes a global consistency check of CO2 satellite retrieval products from the Atmospheric Infrared Sounder （AIRS） and Infrared Atmospheric Sounding Interferometer （IASI） using statistical analysis and data from the World Data Centre for Greenhouse Gases （WDCGG）. We use the correlation coefficient （r）, relative difference （RD）, root mean square errors （RMSE）, and mean bias error （MBE） as evaluation indicators for this study. Statistical results show that a linear positive correlation between AIRS/IASI and WDCGG data occurs for most regions around the world. Temporal and spatial variations of these statistical quantities reflect obvious differences between satellite-derived and ground-based data based on geographic position, especially for stations near areas of intense human activities in the Northern Hemisphere. It is noteworthy that there appears to be a very weak correlation between AIRS/IASI data and ten ground- based observation stations in Europe, Asia, and North America. These results indicate that retrieval products from the two satellite-based instruments studied should be used with great caution.展开更多
Estuarine and intertidal wetlands are important sites for nitrogen transformation and elimination.However,the factors controlling nitrogen removal processes remain largely uncertain in the highly dynamic environments....Estuarine and intertidal wetlands are important sites for nitrogen transformation and elimination.However,the factors controlling nitrogen removal processes remain largely uncertain in the highly dynamic environments.In this study,continuous-flow experiment combined with 15 N isotope pairing technique was used to investigate in situ rates of denitrification and anaerobic ammonium oxidation(anammox)and their coupling with nitrification in intertidal wetlands of the Yangtze Estuary.The measured rates varied from below the detection limit to 152.39μmol N/(m^2·hr)for denitrification and from below the detection limit to 43.06μmol N/(m^2·hr)for anammox.The coupling links of nitrogen removal processes with nitrification were mainly dependent on nitrate,organic carbon,sulfide,dissolved oxygen and ferric iron in the estuarine and intertidal wetlands.Additionally,it was estimated that the actual nitrogen removal processes annually removed approximately 5%of the terrigenous inorganic nitrogen discharged into the Yangtze Estuary.This study gives new insights into nitrogen transformation and fate in the estuarine and intertidal wetlands.展开更多
Patterns of biomass allocation among organs in plants are important because they influence many growth processes.The Yunnan-Guizhou Plateau(YGP)is considered to be one of the most sensitive areas in China to climate c...Patterns of biomass allocation among organs in plants are important because they influence many growth processes.The Yunnan-Guizhou Plateau(YGP)is considered to be one of the most sensitive areas in China to climate changes,but we know little about how current climatic gradients on the plateau influence plant biomass allocation.Gentiana rigescens and G.rhodantha,on the YGP,are important species because they are used in traditional Chinese medicines.We therefore analyzed the biomass allocation patterns of the two species across an elevation gradient(1000–2810 m a.s.l.)on the YGP to understand and predict the impact of climate change on these plant species.We found that the total biomass,reproductive biomass,vegetative biomass,aboveground biomass,and belowground biomass in G.rigescens were all significantly larger than those in G.rhodantha(p<0.05).However,for both species the aboveground biomass was nearly isometrically related to belowground biomass,regardless of elevation,mean annual temperature(MAT)ranging from 8.4℃t to 18.8℃t,and mean annual precipitation(MAP)ranging from 681 to 1327 mm,while the reproductive biomass was allometrically related to vegetative biomass.Intriguingly,there was a significant positive relationship(p<0.05)between the slope of the allometric scaling of reproductive and vegetative biomass and elevation among G.rigescens populations,i.e.plants growing at high elevationsallocate proportionately more biomass to reproduction at larger sizes and less at smaller sizes than plants growing at lower elevations.However,for G.rhodantha the reproductive allocation was negatively correlated with latitude.The results suggested different strategies in reproductive allocation in the two Gentiana plants on the YGP.Further studies are needed to investigate other environmental factors,such as nutrients and light,and genetic factors,in order to understand the trend of reproductive allometry along the environmental gradients.Our study has implications for the management and conservation practices of the two Gentiana species.展开更多
Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau(TP)help to reveal basin-scale hydrological cycle characteristics under the interactions between the we...Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau(TP)help to reveal basin-scale hydrological cycle characteristics under the interactions between the westerlies and Indian summer monsoon(ISM) systems and to improve our understanding on the mechanisms of water resource changes in the ‘Asian Water Tower' under climate changes. Based on a Eulerian moisture tracking model(WAM-2) and three atmospheric reanalysis products(ERA-I, MERRA-2, and JRA-55), the contributions of moisture sources to the precipitation in six major sub-basins in the TP were tracked during an approximately 35-year period(1979/1980–2015). The results showed that in the upper Indus(UI),upper Tarim River(UT), and Qaidam Basin(QB), the moisture sources mainly extended westward along the mid-latitude westerlies to the western part of the Eurasian continent. In contrast, in the Yarlung Zangbo River Basin(YB), inner TP(ITP), and the source area of three eastern rivers(TER, including the Nujiang River, Lancang River, and Yangtze River), the moisture sources extended both westward and southward, but mainly southward along the ISM. In winter and spring, all of the sub-basins were dominated by western moisture sources. In summer, the western sources migrated northward with the zonal movement of the westerlies, and simultaneously the southern sources of the YB, ITP, and TER expanded largely toward the Indian Ocean along the ISM. In autumn, the moisture sources of the UI, UT, and QB shrank to the western sources, and the moisture sources of the YB, ITP, and TER shrank to the central-southern TP and the Indian subcontinent. By quantifying the moisture contributions from multiple sources, we found that the terrestrial moisture dominated in all of the sub-basins, particularly in the UT and QB(62–73%). The oceanic contributions were relatively high in the UI(38–42%) and YB(38–41%). In winter, evaporation from the large western water bodies(such as the Mediterranean, Red Sea, and Persian Gulf) was significantly higher than that from the continental areas. This contributed to the peak(valley) values of the oceanic(terrestrial) moisture contributions to all of the subbasins. In summer, the terrestrial moisture contributions to the UI, UT, and QB reached their annual maximum, but the abundant oceanic moisture transported by the ISM restrained the appearance of land source contribution peaks in the YB, ITP, and TER,resulting in almost equal moisture contributions in the YB from the ocean and land.展开更多
Digital Elevation Models(DEMs)play a critical role in hydrologic and hydraulic modeling.Flood inundation mapping is highly dependent on the accuracy of DEMs.Various vertical differences exist among open access DEMs as...Digital Elevation Models(DEMs)play a critical role in hydrologic and hydraulic modeling.Flood inundation mapping is highly dependent on the accuracy of DEMs.Various vertical differences exist among open access DEMs as they use various observation satellites and algorithms.The problem is particularly acute in small,flat coastal cities.Thus,it is necessary to assess the differences of the input of DEMs in flood simulation and to reduce anomalous errors of DEMs.In this study,we first conducted urban flood simulation in the Huangpu River Basin in Shanghai by using the LISFLOOD-FP hydrodynamic model and six open-access DEMs(SRTM,MERIT,CoastalDEM,GDEM,NASADEM,and AW3D30),and analyzed the differences in the results of the flood inundation simulations.Then,we processed the DEMs by using two statistically based methods and compared the results with those using the original DEMs.The results show that:(1)the flood inundation mappings using the six original DEMs are significantly different under the same simulation conditions—this indicates that only using a single DEM dataset may lead to bias of flood mapping and is not adequate for high confidence analysis of exposure and flood management;and(2)the accuracy of a DEM corrected by the Dixon criterion for predicting inundation extent is improved,in addition to reducing errors in extreme water depths—this indicates that the corrected datasets have some performance improvement in the accuracy of flood simulation.A freely available,accurate,high-resolution DEM is needed to support robust flood mapping.Flood-related researchers,practitioners,and other stakeholders should pay attention to the uncertainty caused by DEM quality.展开更多
We use the aerosol optical depth （AOD） measured by the moderate resolution imaging spectrometer （MOD1S） onboard the Terra satellite, air pollution index （API） daily data measured by the Shanghai Environmental Mo...We use the aerosol optical depth （AOD） measured by the moderate resolution imaging spectrometer （MOD1S） onboard the Terra satellite, air pollution index （API） daily data measured by the Shanghai Environmental Monitoring Center （SEMC）, and the ensemble empirical mode decomposition （EEMD） method to analyze the air quality variability in Shanghai in the recent decade. The results indicate that a trend with amplitude of 1.0 is a dominant component for the AOD variability in the recent decade. During the World Expo 2010, the average AOD level reduced 30% in comparison to the long-term trend. Two dominant annual components decreased 80% and 100%. This implies that the air quality in Shanghai was remarkably improved, and environmental initiatives and comprehensive actions for effective. AOD and API reducing air pollution are variability analysis results indicate that semi-annual and annual signals are dominant components implying that the monsoon weather is a dominant factor in modulating the AOD and API variability. The variability of AOD and API in selected districts located in both downtown and suburban areas shows similar trends; i.e., in 2000 the AOD began a monotonic increase, reached the maxima around 2006, then monotonically decreased to 2011 and from around 2006 the API started to decrease till 2011. This indicates that the air quality in the entire Shanghai area, whether urban or suburban areas, has remarkably been improved. The AOD improved degrees （IDS） in all the selected districts are （8.6±1.9）%, and API IDS are （9.2±7.1）%, ranging from a minimum value of 1.5% for Putuo District to a maximum value of 22% for Xuhui District.展开更多
The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite （OMPS） flying onboard the Suomi...The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite （OMPS） flying onboard the Suomi National Polar-orbiting Partnership satellite （S- NPP） launched as a part of the Joint Polar Satellite System （JPSS） program between NOAA and NASA. Since NOAA is already operationally processing OMPS nadir total ozone products, evaluations were made in this study on the total column ozone research products generated by NASA＇s science team, utilizing the latest version of their Backscatter Ultraviolet （BUV） retrieval algorithms, to provide insight into the performance of the operation system. Comparisons were made with globally distributed ground-based Brewer and Dobson spectrophotometer total column ozone measurements. Linear regressions show fair agreement between OMPS and ground-based total column ozone measurements with a root-mean-square error （RMSE） of approximately 3% （10 DU）. The comparison results indicate that the OMPS total column ozone data are 0.59% higher than the Brewer measurements with a standard deviation of 2.82% while 1.09% higher than the Dobson measurements with a standard deviation of 3.27%. Additionally, the variability of relative differences between OMPS and ground total column ozone were analyzed as a function of latitude, time, viewing geometry, and total column ozone value. Results show a 2% bias over most latitudes and viewing conditions when total column ozone value varies between 220 DU and 450 DU.展开更多
Wetland vegetation is intimately related to floodplain inundations,which can be seriously affected by dam operation.Poyang Lake is the largest floodplain wetland in China and naturally connected with the Yangtze River...Wetland vegetation is intimately related to floodplain inundations,which can be seriously affected by dam operation.Poyang Lake is the largest floodplain wetland in China and naturally connected with the Yangtze River and the Three Gorges Dam(TGD)upstream.To understand the potential impacts of TGD on Poyang Lake wetlands,we collected remote sensing imagery acquired during dry season from 1987 to 2020 and extracted vegetation coverage data in the Ganjiang Northern-branch Delta(GND)and the Ganjiang Southern-branch Delta(GSD),using the Object-oriented Artificial Neural Network Regression.Principal components analysis,correlation analysis,and the random forest model were used to explore the interactions between vegetation extent in the two deltas and 33 hydrological variables regarding magnitude,duration,timing,and variation.The implementation of the TGD advanced and extended the low-flow periods in Poyang Lake.Vegetation coverage in the GND and GSD increased at the rates of 0.39 and 0.22 km2/year,respectively.The reservoir storage at the end of September accelerated the runoff recession in the GND and the GSD,making low-flow events more influential for vegetation dynamics and shortening the response time of vegetation to the water regime.This study provides an important reference for evaluating the impacts of dam engineering on downstream wetlands.展开更多
基金supported by the National Natural Science Foundation of China(Grant nos.42176240 and 42101142).
文摘Zinc(Zn),a widespread metal in the Earth’s crust,serves as a crucial nutrient in the Southern Ocean’s primary production.Studies on Zn in Antarctic snow and ice offer insights into the origins of this metal and its transport routes,as well as its impact on the biogeochemical processes within the Antarctic atmosphere–land–ocean system.This review examines research on the spatial and temporal distribution of Zn in Antarctic snow and ice,as well as in Southern Ocean waters.It includes an overview of advanced methods for sampling and analyzing Zn,along with explanations for the observed variations.The review also discusses various sources of Zn as a nutrient to the Southern Ocean.Finally,it addresses prospective issues related to the use of Zn isotopes in identifying atmospheric sources and their biogeochemical effects on the development of the Southern Ocean ecosystem.
基金Under the auspices of the National Natural Science Foundation of China(No.41871162)
文摘With the rapid development of population and urbanization and the progress of lighting technology, the influence of artificial light sources has increased.In this context, the problem of light pollution has attracted wide attention.Previous studies have revealed that light pollution can affect biological living environments, human physical and mental health, astronomical observations and many other aspects.Therefore, organizations internationally have begun to advocate for measures to prevent light pollution, many of which are recognized by the International Dark-Sky Association(IDA).In addition to improving public awareness, legal protections, technical treatments and other means, the construction of Dark Sky Reserves(DSR) has proven to be an effective preventive measure.So far, as a pioneer practice in this field, the IDA has identified 11 DSRs worldwide.Based on the DA requirements for DSRs, this paper utilizes NPP-VIIRS nighttime light data and other multi-source spatial data to analyze possible DSR sites in China.The land of China was divided into more than ten thousand 30 km × 30 km fishnets, and constraint and suitable conditions were designated, respectively, as light and cloud conditions, and scale, traffic and attractiveness conditions.Using a multiple criteria evaluation, 1443 fishnets were finally selected as most suitable sites for the construction of DSRs.Results found that less than 25% of China is not subject to light pollution, and less than 13% is suitable for DSR construction, primarily in western and northern areas, including Tibet, Xinjiang, Qinghai, Gansu and Inner Mongolia.
基金funded by the National Natural Science Foundation of China(Grant Nos.41907396,42001388 and 42071277)Chongqing Research Program of Basic Research and Frontier Technology(No.cstc2019jcyj-msxm X0515)the Science Foundation of the Chongqing Normal University(22XLB002,22XLB003)。
文摘In recent decades,the continuously changed glaciers in the Himalayas not only affected process of atmospheric flow and water cycle in the plateau but also increased the frequency of secondary disasters,such as ice collapse and outburst floods.Therefore,the monitoring of Himalayas glacial change is of great significance in the aspects of climate change and disaster prevention and reduction.The Himalayas glacier outlines in China were extracted by ratio threshold and visual interpretation based on the Landsat TM/ETM+/OLI data and glacier catalogue data.Based on the ASTER GDEM data,the distribution and change characteristics at different altitudes were studied,and the surface moraine was identified to study the influence of glacial area variations.In addition,Glaciers were divided into marine and continental glaciers in this study,and the distribution and changes of the two types of glaciers were analyzed.Also,a comprehensive analysis of a long time series was performed.The results showed that:(1)From 1990 to 2015,the glaciers in the study area showed an overall trend of melting;the annual melting speed gradually accelerated from 0.48%/a to 0.75%/a.The total melting glacial area was 828.16 km,and the melting rate of the glaciers in the western section was the highest,at 0.63%.(2)The total area of continental glaciers was larger than that of marine glaciers,and its reduction was relatively larger,too.(3)The average size of debris-covered glaciers was 10 times that of debris-free glaciers,but their rate of change(8.1%)was 1/2 of that of debrisfree glaciers(17.8%).(4)The number of glaciers gradually decreased as the size of glaciers increased.The glaciers with grades of>50 km,0.5~1 km,and 1~2 kmhad large change rates,which were 20.1%,19.1%,and 18.5%,respectively.In summary,the Himalayas glaciers in China were melting at an accelerated rate and their numbers were gradually decreasing from 1990 to 2015.The location,type,elevation,size and debris cover of a glacier are all important factors influencing glacier change.It has been found that the lower the elevation or the smaller the size of the glacier,the greater the likelihood of glacier ablation,and the debris can inhibit the melting of glaciers to a certain extent.
基金This work was financially supported by National Key R&D Plan(Grant No.2017YFC0210000)National Natural Science Foundation of China(Grant No.41701413)+1 种基金National Key R&D Plan(Grant No.2017YFC0212703)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB05020401).Meteorological data were acquired from the Meteorological Information Comprehensive Analysis and Process System(air temperature,relative humidity,and wind speed),and ERA-Interim reanalysis(boundary layer height)that was provided by the European Centre for Medium-Range Weather Forecasts.
文摘A better knowledge of aerosol properties is of great significance for elucidating the complex mechanisms behind frequently occurring haze pollution events.In this study,we examine the temporal and spatial variations in both PM_(1)and its major chemical constituents using three-year field measurements that were collected in six representative regions in China between 2012 and 2014.Our results show that both PM_(1)and its chemical compositions varied significantly in space and time,with high PM_(1)loadings mainly observed in the winter.By comparing chemical constituents between clean and polluted episodes,we find that the elevated PM_(1)mass concentration during pollution events should be largely attributable to significant increases in organic matter(OM)and inorganic aerosols like sulfate,nitrate,and ammonium(SNA),indicative of the critical role of primary emissions and secondary aerosols in elevating PM_(1)pollution levels.The ratios of PM_(1)/PM2.5 are found to be generally high in Shanghai and Guangzhou,while relatively low ratios are seen in Xi’an and Chengdu,indicating anthropogenic emissions were more likely to accumulate in forms of finer particles.With respect to the relative importance of chemical components and meteorological factors quantified via statistical modeling practices,we find that primary emissions and secondary aerosols were the two leading factors contributing to PM_(1)variations,though meteorological factors also played important roles in regulating the dispersion of atmospheric PM.
基金supported by the Science and Technology Project of Jiangxi Provincial Department of Education (No. GJJ161097)the Open Foundation of the State Key Laboratory of Desert and OasisEcology (No. G2014-02-07)+2 种基金the National Natural Science Foundation of China (41630859)the Open Research Fund of Jiangxi Province Key Laboratory of Water Information Cooperative Sensing and Intelligent Processing (No. 2016WICSIP012)the Key Project of Jiangxi Provincial Department of Science and Technology (No. 20161BBF60061)
文摘The complex network theory provides an approach for understanding the complexity of climate change from a new perspective.In this study,we used the coarse graining process to convert the data series of daily mean temperature and daily precipitation from 1961 to 2011 into symbol sequences consisting of five characteristic symbols(i.e.,R,r,e,d and D),and created the temperature fluctuation network(TFN)and precipitation fluctuation network(PFN)to discover the complex network characteristics of climate change in the Tarim River Basin of Northwest China.The results show that TFN and PEN both present characteristics of scale-free network and small-world network with short average path length and high clustering coefficient.The nodes with high degree in TFN are RRR,d RR and Re R while the nodes with high degree in PFN are rre,rrr,eee and err,which indicates that climate change modes represented by these nodes have large probability of occurrence.Symbol R and r are mostly included in the important nodes of TFN and PFN,which indicate that the fluctuating variation in temperature and precipitation in the Tarim River Basin mainly are rising over the past 50 years.The nodes RRR,DDD,Re R,RRd,DDd and Ree are the hub nodes in TFN,which undertake 19.71%betweenness centrality of the network.The nodes rre,rrr,eee and err are the hub nodes in PFN,which undertake 13.64%betweenness centrality of the network.
基金supported by the National Natural Science Foundation of China (NSFC) Study on Regional Carbon Governance for China’s Response to Climate Change under the Effect of Global Economic Integration, Project Code: 41501130
文摘Under the Paris Agreement framework, many developing countries call for low-carbon technology transfers from developed countries as a critical element in the global partnership for carbon emissions abatement. Such a partnership may be disrupted as the U.S. walks away from the agreement. Based on CIECIA-TD model, this paper examines effects of the U.S. exit on global low-carbon technology transfers under various scenarios and simulates the effects on low-carbon technology transfer, climate change, countries' emissions abatement results, and economic development. Our findings suggest that lowcarbon technology has significant emissions abatement and temperature rise mitigation effects. Low-carbon technology transfer among developed countries offers huge emissions abatement potentials, but patent protection system presents a significant barrier to further carbon emissions abatement. In this sense, the U.S. exit from the Paris Agreement will significantly impede developed countries' carbon emissions abatement through technology transfer. With limited knowhow, R&D and learning capacity, developing countries will suffer more to cut carbon emissions under the chain effects of a more challenging technology sharing environment that may result from the U.S. exit from the Paris Agreement. As a gradualist emissions abatement approach, low-carbon technology transfer cannot reduce emissions substantially within a short time, but its climate welfare is conducive to global economic growth and of great significance to carbon governance.
基金Supported by the National Natural Science Foundation of China(U2142201 and 42175086).
文摘Monitoring and predicting highly localized weather events over a very short-term period,typically ranging from minutes to a few hours,are very important for decision makers and public action.Nowcasting these events usually relies on radar observations through monitoring and extrapolation.With advanced high-resolution imaging and sounding observations from weather satellites,nowcasting can be enhanced by combining radar,satellite,and other data,while quantitative applications of those data for nowcasting are advanced through using machine learning techniques.Those applications include monitoring the location,impact area,intensity,water vapor,atmospheric instability,precipitation,physical properties,and optical properties of the severe storm at different stages(pre-convection,initiation,development,and decaying),identification of storm types(wind,snow,hail,etc.),and predicting the occurrence and evolution of the storm.Satellite observations can provide information on the environmental characteristics in the preconvection stage and are very useful for situational awareness and storm warning.This paper provides an overview of recent progress on quantitative applications of satellite data in nowcasting and its challenges,and future perspectives are also addressed and discussed.
基金Major Program of National Social Science Foundation of China,No.19ZDA086。
文摘The advent of a mobile society has led to profound changes in China’s traditional rural-urban pattern and called for new strategies for urban and rural governance.Based on a macro perspective of temporal and spatial evolution,this study analyzes the historical logics of rural-urban governance,explores the geographical patterns of challenges in China’s rural-urban governance,and finally puts forward targeted strategies for rural-urban governance toward integrated and sustainable development in China.From the historical perspective,the urban originates from the rural,and the connotation of rural,that is,a regional-scale outlook,rural-urban relations,and sociocultural interaction,forms the traditional approach to rural-urban governance.China’s rural-urban governance has evolved from antagonism toward integration.In terms of theoretical development,the turn toward mobility is an important driving factor shaping and promoting the transformation of research focus on rural-urban governance.The mobility of urban and rural factors has especially in recent decades brought extensive challenges for governance,which are highlighted by the disintegration of the stability of rural and urban structures,growing regional disparities in rural education levels,and serious aging and hollowing crises in rural areas.We therefore propose that rural-urban governance should give sufficient consideration to the convergence of wider interests;realize social potential through institutional,cultural and spatial restructuring;and attach importance to collaborative development and governance.And the transfer of rural problems to urban areas should be paid attention to by rural-urban governance.This research enriches the knowledge regarding the logics and patterns of China’s rural-urban governance from an interdisciplinary perspective.It is also helpful in the promotion of rural-urban integration and sustainable development,especially at a time when the mobility of social factors between rural areas and urban areas increasingly challenges traditional urban and rural governance and drives its evolution.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(42176240,41671063,41701071,42101142 and 41671073)the self-dependent project of the State Key Laboratory of Cryospheric Science Supporting Fund in China(SKLCS-ZZ-2023)+1 种基金the Innovative Research Group Project China(1110000001)CAS Pioneer Hundred Talents Programme in China(X.-X.Wang).
文摘Antarctic trace metal records provide important information for grasping the influence of human activities on the environment over the last centuries.The CA2016-75 ice core is located along the East Antarctic Zhongshan Station-Dome A,enhances the record of metals research in the East Antarctic region,and its high-resolution supplies data support for the study of high-frequency climatic drivers and the effect of human activities on the Antarctic environment.A thorough dataset on seven trace metals(Al,Fe,Mn,Cu,Zn,Ba and Pb)in a coastal ice core in eastern Antarctica during the previous 102 years(1915-2016)is presented in this study.Pb has the lowest concentration(9.51±20.95 pg g^(-1)),and Ba has the highest concentration(36.57±51.35 ng g^(-1)).Notable variations are observed between the pre-1968 AD and post-1968 AD phases for Mn,Zn and Ba.The abrupt,remarkable increase in the concentrations coincided with the change of metal smelting production in the southern hemisphere.In addition to this,it may also be related to local Antarctic scientific research activities.Al and Fe,the primary crustal elements,are essentially obtained from soil dust;Cu shows high crustal enrichment factors(EFc,>10),indicating that it is notably affected by anthropogenic activities.Moreover,the anthropogenic activities in the Southern Hemisphere have had an impact on lead deposition in Antarctica.This study not only enriches the trace metal historical record along the Zhongshan Station-Dome A but also provides a high-resolution ice core record,which is very crucial for the reconstruction of trace metal concentration changes in the last 100 years.
基金Major Program of National Social Science Foundation of China,No.19ZDA086。
文摘With rapid globalization,industrial parks are playing an increasingly important role in the national and regional development.Since the Belt and Road Initiative(BRI)was put forward,national-level overseas industrial parks of China have emerged with new development features and trends.It is of great importance to carry out a comparative study on domestic and overseas industrial parks of China.Based on the perspective of spatiotemporal evolution,this paper compares and analyzes national-level overseas industrial parks along the Belt and Road(B&R)and domestic industrial parks of China.In time,China’s industrial parks have experienced four stages with distinctive state-led characteristic.There are different development paths and modes for overseas industrial parks along the B&R and domestic industrial parks.In space,the national-level overseas industrial parks are invested and constructed by Chinese enterprises(mostly from the coastal developed cities),and mainly distributed in the countries along the B&R.Through typical cases comparison of Thai-Chinese Rayong Industrial Zone and Tianjin Economic-Technological Development Area,the paper finds that national-level overseas industrial parks are basically market-driven and concentrated in traditional advantageous industries,while domestic industrial parks are mainly government-led high-tech industries.Localization of overseas industrial parks and remote coupling with domestic industrial parks become very important.
基金National Natural Science Foundation of China,No.41571410,No.41571199,No.41401589
文摘Quantitative characterization of environmental characteristics of cropland(ECC)plays an important role in maintaining sustainable development of agricultural systems and ensuring regional food security. In this study, the changes in ECC over the Songnen Plain, a major grain crops production region in Northeast China, were investigated for the period 1990–2015. The results revealed significant changes in climate conditions, soil physical properties and cropland use patterns with socioeconomic activities. Trends in climate parameters showed increasing temperature(+0.49°C/decade, p < 0.05) and decreasing wind speed(–0.3 m/s/decade, p < 0.01) for the growing season, while sunshine hours and precipitation exhibited non-significant trends. Four topsoil parameters including soil organic carbon(SOC), clay, bulk density and pH, indicated deteriorating soil conditions across most of the croplands, although some do exhibited slight improvement. The changing amplitude for each of the four above parameters ranged within –0.052 to 0.029 kg C/kg, –0.38 to 0.30,–0.60 to 0.39 g/cm^3, –3.29 to 2.34, respectively. Crop production significantly increased(44.0 million tons) with increasing sown area of croplands(～2.5 million ha) and fertilizer application(～2.5 million tons). The study reveals the dynamics of ECC in the Songnen Plain with intensive cultivation from 1990 to 2015. Population growth, economic development, and policy reform are shown to strongly influence the spatiotemporal changes in cropland characteristics.The study potentially provides valuable scientific information to support sustainable agroecosystem management in the context of global climate change and national socioeconomic development.
文摘Urban green volume is an important indicator for analyzing urban vegetation structure, ecological evaluation, and green-economic estimation. This paper proposes an object-based method for automated estimation of urban green volume combining three-dimensional （3D） information from airborne Light Detection and Ranging （LiDAR） data and vegetation information from high resolution remotely sensed images through a case study of the Lujiazui region, Shanghai, China. High resolution airborne near-infrared photographs are used for identifying the urban vegetation distribution. Airborne LiDAR data offer the possibility to extract individual trees and to measure the attributes of trees, such as tree height and crown diameter. In this study, individual trees and grassland are identified as the independent objects of urban vegetation, and the urban green volume is computed as the sum of two broad portions： individual trees volume and grassland volume. The method consists of following steps： generating and filtering the normalized digital surface model （nDSM）, extracting the nDSM of urban vegetation based on the Normalized Difference Vegetation Index （NDVI）, locating the local maxima points, segment- ing the vegetation objects of individual tree crowns and grassland, and calculating the urban green volume of each vegetation object. The results show the quantity and distribution characteristics of urban green volume in the Lujiazui region, and provide valuable parameters for urban green planning and management. It is also concluded from this paper that the integrated application of LiDAR data and image data presents an effective way to estimate urban green volume.
基金Acknowledgements This project was supported by the National Basic Research Program of China （No. 2010CB951603） and the Major Program of National Social Science Foundation of China （No.13＆ZD161）. We thank Prof. Jietai Mao of the Department of Atmospheric ＆ Oceanic Sciences, Peking University, China for providing expert advice and assistance. We also thank the WDCGG for providing the CO2 data. Many thanks to NASA for providing AIRS CO2 data and NOAA for providing IASI CO2 data.
文摘This article describes a global consistency check of CO2 satellite retrieval products from the Atmospheric Infrared Sounder （AIRS） and Infrared Atmospheric Sounding Interferometer （IASI） using statistical analysis and data from the World Data Centre for Greenhouse Gases （WDCGG）. We use the correlation coefficient （r）, relative difference （RD）, root mean square errors （RMSE）, and mean bias error （MBE） as evaluation indicators for this study. Statistical results show that a linear positive correlation between AIRS/IASI and WDCGG data occurs for most regions around the world. Temporal and spatial variations of these statistical quantities reflect obvious differences between satellite-derived and ground-based data based on geographic position, especially for stations near areas of intense human activities in the Northern Hemisphere. It is noteworthy that there appears to be a very weak correlation between AIRS/IASI data and ten ground- based observation stations in Europe, Asia, and North America. These results indicate that retrieval products from the two satellite-based instruments studied should be used with great caution.
基金supported by the National Natural Science Foundation of China(Nos.41725002,41671463,41601530,41761144062,and41730646)the Fundamental Research Funds for the Central UniversitiesChinese National Key Programs for Fundamental Research and Development(Nos.2016YFA0600904,2016YFE0133700)。
文摘Estuarine and intertidal wetlands are important sites for nitrogen transformation and elimination.However,the factors controlling nitrogen removal processes remain largely uncertain in the highly dynamic environments.In this study,continuous-flow experiment combined with 15 N isotope pairing technique was used to investigate in situ rates of denitrification and anaerobic ammonium oxidation(anammox)and their coupling with nitrification in intertidal wetlands of the Yangtze Estuary.The measured rates varied from below the detection limit to 152.39μmol N/(m^2·hr)for denitrification and from below the detection limit to 43.06μmol N/(m^2·hr)for anammox.The coupling links of nitrogen removal processes with nitrification were mainly dependent on nitrate,organic carbon,sulfide,dissolved oxygen and ferric iron in the estuarine and intertidal wetlands.Additionally,it was estimated that the actual nitrogen removal processes annually removed approximately 5%of the terrigenous inorganic nitrogen discharged into the Yangtze Estuary.This study gives new insights into nitrogen transformation and fate in the estuarine and intertidal wetlands.
基金sponsored by the National Natural Science Foundation of China(81760684)the CAS 135 Program(2017XTBGF05)。
文摘Patterns of biomass allocation among organs in plants are important because they influence many growth processes.The Yunnan-Guizhou Plateau(YGP)is considered to be one of the most sensitive areas in China to climate changes,but we know little about how current climatic gradients on the plateau influence plant biomass allocation.Gentiana rigescens and G.rhodantha,on the YGP,are important species because they are used in traditional Chinese medicines.We therefore analyzed the biomass allocation patterns of the two species across an elevation gradient(1000–2810 m a.s.l.)on the YGP to understand and predict the impact of climate change on these plant species.We found that the total biomass,reproductive biomass,vegetative biomass,aboveground biomass,and belowground biomass in G.rigescens were all significantly larger than those in G.rhodantha(p<0.05).However,for both species the aboveground biomass was nearly isometrically related to belowground biomass,regardless of elevation,mean annual temperature(MAT)ranging from 8.4℃t to 18.8℃t,and mean annual precipitation(MAP)ranging from 681 to 1327 mm,while the reproductive biomass was allometrically related to vegetative biomass.Intriguingly,there was a significant positive relationship(p<0.05)between the slope of the allometric scaling of reproductive and vegetative biomass and elevation among G.rigescens populations,i.e.plants growing at high elevationsallocate proportionately more biomass to reproduction at larger sizes and less at smaller sizes than plants growing at lower elevations.However,for G.rhodantha the reproductive allocation was negatively correlated with latitude.The results suggested different strategies in reproductive allocation in the two Gentiana plants on the YGP.Further studies are needed to investigate other environmental factors,such as nutrients and light,and genetic factors,in order to understand the trend of reproductive allometry along the environmental gradients.Our study has implications for the management and conservation practices of the two Gentiana species.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant Nos. 2019QZKK0201 & 2019QZKK020705)the National Natural Science Foundation of China (Grant Nos. 41988101 & 41871057)"Strategic Priority Research Program" of Chinese Academy of Sciences (Grant No. XDA20060202)。
文摘Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau(TP)help to reveal basin-scale hydrological cycle characteristics under the interactions between the westerlies and Indian summer monsoon(ISM) systems and to improve our understanding on the mechanisms of water resource changes in the ‘Asian Water Tower' under climate changes. Based on a Eulerian moisture tracking model(WAM-2) and three atmospheric reanalysis products(ERA-I, MERRA-2, and JRA-55), the contributions of moisture sources to the precipitation in six major sub-basins in the TP were tracked during an approximately 35-year period(1979/1980–2015). The results showed that in the upper Indus(UI),upper Tarim River(UT), and Qaidam Basin(QB), the moisture sources mainly extended westward along the mid-latitude westerlies to the western part of the Eurasian continent. In contrast, in the Yarlung Zangbo River Basin(YB), inner TP(ITP), and the source area of three eastern rivers(TER, including the Nujiang River, Lancang River, and Yangtze River), the moisture sources extended both westward and southward, but mainly southward along the ISM. In winter and spring, all of the sub-basins were dominated by western moisture sources. In summer, the western sources migrated northward with the zonal movement of the westerlies, and simultaneously the southern sources of the YB, ITP, and TER expanded largely toward the Indian Ocean along the ISM. In autumn, the moisture sources of the UI, UT, and QB shrank to the western sources, and the moisture sources of the YB, ITP, and TER shrank to the central-southern TP and the Indian subcontinent. By quantifying the moisture contributions from multiple sources, we found that the terrestrial moisture dominated in all of the sub-basins, particularly in the UT and QB(62–73%). The oceanic contributions were relatively high in the UI(38–42%) and YB(38–41%). In winter, evaporation from the large western water bodies(such as the Mediterranean, Red Sea, and Persian Gulf) was significantly higher than that from the continental areas. This contributed to the peak(valley) values of the oceanic(terrestrial) moisture contributions to all of the subbasins. In summer, the terrestrial moisture contributions to the UI, UT, and QB reached their annual maximum, but the abundant oceanic moisture transported by the ISM restrained the appearance of land source contribution peaks in the YB, ITP, and TER,resulting in almost equal moisture contributions in the YB from the ocean and land.
基金the National Natural Science Foundation of China(42001096,41730646)the Shanghai Sailing Program(19YF1413700)+2 种基金the China Postdoctoral Science Foundation(2019M651429)East China Normal University Institute of Belt and Road&Global Development(ECNU-BRGD-202106)the National Key R&D Program of China(2017YFC1503001,2017YFE0100700).
文摘Digital Elevation Models(DEMs)play a critical role in hydrologic and hydraulic modeling.Flood inundation mapping is highly dependent on the accuracy of DEMs.Various vertical differences exist among open access DEMs as they use various observation satellites and algorithms.The problem is particularly acute in small,flat coastal cities.Thus,it is necessary to assess the differences of the input of DEMs in flood simulation and to reduce anomalous errors of DEMs.In this study,we first conducted urban flood simulation in the Huangpu River Basin in Shanghai by using the LISFLOOD-FP hydrodynamic model and six open-access DEMs(SRTM,MERIT,CoastalDEM,GDEM,NASADEM,and AW3D30),and analyzed the differences in the results of the flood inundation simulations.Then,we processed the DEMs by using two statistically based methods and compared the results with those using the original DEMs.The results show that:(1)the flood inundation mappings using the six original DEMs are significantly different under the same simulation conditions—this indicates that only using a single DEM dataset may lead to bias of flood mapping and is not adequate for high confidence analysis of exposure and flood management;and(2)the accuracy of a DEM corrected by the Dixon criterion for predicting inundation extent is improved,in addition to reducing errors in extreme water depths—this indicates that the corrected datasets have some performance improvement in the accuracy of flood simulation.A freely available,accurate,high-resolution DEM is needed to support robust flood mapping.Flood-related researchers,practitioners,and other stakeholders should pay attention to the uncertainty caused by DEM quality.
文摘We use the aerosol optical depth （AOD） measured by the moderate resolution imaging spectrometer （MOD1S） onboard the Terra satellite, air pollution index （API） daily data measured by the Shanghai Environmental Monitoring Center （SEMC）, and the ensemble empirical mode decomposition （EEMD） method to analyze the air quality variability in Shanghai in the recent decade. The results indicate that a trend with amplitude of 1.0 is a dominant component for the AOD variability in the recent decade. During the World Expo 2010, the average AOD level reduced 30% in comparison to the long-term trend. Two dominant annual components decreased 80% and 100%. This implies that the air quality in Shanghai was remarkably improved, and environmental initiatives and comprehensive actions for effective. AOD and API reducing air pollution are variability analysis results indicate that semi-annual and annual signals are dominant components implying that the monsoon weather is a dominant factor in modulating the AOD and API variability. The variability of AOD and API in selected districts located in both downtown and suburban areas shows similar trends; i.e., in 2000 the AOD began a monotonic increase, reached the maxima around 2006, then monotonically decreased to 2011 and from around 2006 the API started to decrease till 2011. This indicates that the air quality in the entire Shanghai area, whether urban or suburban areas, has remarkably been improved. The AOD improved degrees （IDS） in all the selected districts are （8.6±1.9）%, and API IDS are （9.2±7.1）%, ranging from a minimum value of 1.5% for Putuo District to a maximum value of 22% for Xuhui District.
文摘The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite （OMPS） flying onboard the Suomi National Polar-orbiting Partnership satellite （S- NPP） launched as a part of the Joint Polar Satellite System （JPSS） program between NOAA and NASA. Since NOAA is already operationally processing OMPS nadir total ozone products, evaluations were made in this study on the total column ozone research products generated by NASA＇s science team, utilizing the latest version of their Backscatter Ultraviolet （BUV） retrieval algorithms, to provide insight into the performance of the operation system. Comparisons were made with globally distributed ground-based Brewer and Dobson spectrophotometer total column ozone measurements. Linear regressions show fair agreement between OMPS and ground-based total column ozone measurements with a root-mean-square error （RMSE） of approximately 3% （10 DU）. The comparison results indicate that the OMPS total column ozone data are 0.59% higher than the Brewer measurements with a standard deviation of 2.82% while 1.09% higher than the Dobson measurements with a standard deviation of 3.27%. Additionally, the variability of relative differences between OMPS and ground total column ozone were analyzed as a function of latitude, time, viewing geometry, and total column ozone value. Results show a 2% bias over most latitudes and viewing conditions when total column ozone value varies between 220 DU and 450 DU.
基金Open Research Fund of State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing,Wuhan University(20R01)East China Normal University Excellent Doctoral Students’Academic Innovation Ability Improvement Plan Project,No.YBNLTS2021-028。
文摘Wetland vegetation is intimately related to floodplain inundations,which can be seriously affected by dam operation.Poyang Lake is the largest floodplain wetland in China and naturally connected with the Yangtze River and the Three Gorges Dam(TGD)upstream.To understand the potential impacts of TGD on Poyang Lake wetlands,we collected remote sensing imagery acquired during dry season from 1987 to 2020 and extracted vegetation coverage data in the Ganjiang Northern-branch Delta(GND)and the Ganjiang Southern-branch Delta(GSD),using the Object-oriented Artificial Neural Network Regression.Principal components analysis,correlation analysis,and the random forest model were used to explore the interactions between vegetation extent in the two deltas and 33 hydrological variables regarding magnitude,duration,timing,and variation.The implementation of the TGD advanced and extended the low-flow periods in Poyang Lake.Vegetation coverage in the GND and GSD increased at the rates of 0.39 and 0.22 km2/year,respectively.The reservoir storage at the end of September accelerated the runoff recession in the GND and the GSD,making low-flow events more influential for vegetation dynamics and shortening the response time of vegetation to the water regime.This study provides an important reference for evaluating the impacts of dam engineering on downstream wetlands.
