Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and ...Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and reanalysis data(MERRA-2)from March 2007 to February 2015(eight years).The horizontal distribution reveals lower cirrus fraction values in the northern SCS and higher values in the southern region,with minima observed in March and April and maxima sequentially occurring in August(northern SCS,NSCS),September(middle SCS,MSCS),and December(southern SCS,SSCS).Vertically,the cirrus fraction peaks in summer and reaches its lowest levels in spring.Opaque cirrus dominates during summer in the NSCS and MSCS,comprising 53.6%and 55.9%,respectively,while the SSCS exhibits a higher frequency of opaque cirrus relative to other cloud types.Subvisible cirrus clouds have the lowest frequency year-round,whereas thin cirrus is most prominent in winter in the NSCS(46.3%)and in spring in the MSCS(45.3%).A case study from September 2021 further explores the influence of ice crystal habits on brightness temperature(BT)over the SCS.Simulations utilizing five ice crystal shapes from the ARTS DDA(Atmospheric Radiative Transfer Simulator Discrete Dipole Approximation)database and the RTTOV 12.4 radiative transfer model reveal that the 8-column-aggregate shape best represents BT in the NSCS and SSCS,while the large-block-aggregate shape performs better in the SSCS.展开更多
The promotion of energy efficiency(EE)helps address energy constraints and promote environmental sustainability.This study comprehensively explores the spatiotemporal variations,influencing factors,and configuration p...The promotion of energy efficiency(EE)helps address energy constraints and promote environmental sustainability.This study comprehensively explores the spatiotemporal variations,influencing factors,and configuration promotion paths of EE in 284 Chinese cities during 2003‒2019 using the global super-efficiency minimum distance to strong efficient frontier(G-S-MinDS),exploratory spatial data analysis(ESDA),multiscale geographically weighted regression(MGWR),and fuzzy set qualitative comparative analysis(fsQCA)methods.The findings are:①China’s cities have an annual average EE of 0.658 with a growth rate of 0.53%,showing considerable promotion potential.②Industrial structure optimization,population agglomeration,economic development,and increased green coverage contribute positively,while government intervention and openness hinder China’s urban EE.③Four configurational promotion paths for enhancing China’s urban EE are identified,where among those paths population density is a core condition,while government intervention is not.This study provides valuable insights into substantially improving urban EE,emphasizing the need for targeted policies to address energy and environmental crises in China.展开更多
The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of ISWs.The spatiotemporal variations of the...The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of ISWs.The spatiotemporal variations of the dynamic parameters of the ISWs in the northern South China Sea(SCS)were studied based on the reanalysis of long-term temperature and salinity datasets.The results for spectrum analysis show that there are definite geographical differences for the periodic variation of the parameters:in shallow water,all parameters vary with a wave period of one year,while in deep water wave components of the parameters at other frequencies exist.Using wavelet analysis,the wavelet power spectral densities in deep water exhibited an inter-annual variation pattern.For example,the wave component of the dispersion coefficient with a wave period of about half a year reached its power peak once every two years.Based on previous work,this inter-annual variation pattern was deduced to be caused by dynamic processes.In further work on the regulatory mechanisms,empirical orthogonal function(EOF)decomposition was performed.It was found that the modes of the dispersion coefficient have different geographical distributions,explaining the reason why the wave components in different frequencies appeared in different locations.The numerical simulation results confirm that the variations in the parameters of the ISWs derived from the eKdV equation could affect the waveforms significantly because of changes in the polarity of the ISWs.Therefore,the periodic variations of the dynamic parameters are related to the geographical location because of dynamic processes operating.展开更多
Rapid industrialization and urbanization have led to the most serious habitat degradation in China,especially in the loess hilly area of the Yellow River Basin,where the ecological environment is relatively fragile.Th...Rapid industrialization and urbanization have led to the most serious habitat degradation in China,especially in the loess hilly area of the Yellow River Basin,where the ecological environment is relatively fragile.The contradiction between economic development and ecological environment protection has aroused widespread concern.In this study,we used the habitat quality of Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST-HQ)model at different scales to evaluate the dynamic evolution characteristics of habitat quality in Lanzhou City,Gansu Province of China.The spatiotemporal variations of habitat quality were analyzed by spatial autocorrelation.A Geographical Detector(Geodetector)model was used to explore the driving factors that influencing the spatial differentiation of habitat quality,including natural factors,socio-economic factors,and ecological protection factors.The results showed that the habitat quality index of Lanzhou City decreased from 0.4638 to 0.4548 during 2000-2018.The areas with reduced the habitat quality index were mainly located in the Yellow River Basin and Qinwangchuan Basin,where are the main urban areas and the new economic development areas,respectively.The spatial distribution of habitat quality presented a trend of high in the surrounding areas and low in the middle,and showed a significant positive spatial autocorrelation.With the increase of study scale,the spatial distribution of habitat quality changed from concentrated to dispersed.The spatial differentiation of habitat quality in the study area was the result of multiple factors.Among them,topographic relief and slope were the key factors.The synergistic enhancement among these driving factors intensified the spatial differentiation of habitat quality.The findings of this study can provide a scientific basis for land resources utilization and ecosystem restoration in the arid and semi-arid land.展开更多
The process of habitat degradation varies in habitat type and driving force which shows certain spatial and temporal heterogeneity on regional scales. In the present study, a new diagnostic model for enclosed bay habi...The process of habitat degradation varies in habitat type and driving force which shows certain spatial and temporal heterogeneity on regional scales. In the present study, a new diagnostic model for enclosed bay habitat degradation was established, with which the spatial and temporal variation patterns of habitat degradation during 1991–2012 in Sansha Bay, Fujian, China was investigated. The results show that anthropogenic disturbance is the major controlling factor for the habitat degradation in large temporal heterogeneity in the bay. On the other hand, the habitat degradation experienced signifi cant spatial variations among six sub-bays. Under the joint action of temporal and spatial heterogeneity, the degradation trend in growing scale shows a more signifi cant correlation with the distribution of local leading industries along shorelines. Therefore, we quantifi ed the main characters of habitat degradation in Sansha Bay, and have understood the relationship between the status of habitats spatio-temporal variation value and the main controlling factor leading to the changes. However, a defi ciency of this research is the lack of or inaccessible to the detailed data, which shall be better solved in the future study for accessing more data from more sources.展开更多
Investigation on spatiotemporal variations of maximum seasonal freeze depth （MSFD） over the Heihe River Basin is of great importance for systematic understanding of regional climate and environmental change, ecologi...Investigation on spatiotemporal variations of maximum seasonal freeze depth （MSFD） over the Heihe River Basin is of great importance for systematic understanding of regional climate and environmental change, ecological-hydrological processes, water resources assessment, construction and resource development. Based on soil and air temperatures at the meteorological stations of the China Meteorological Administration （CMA） over the Heihe River Basin, MSFDs time series are structured into a composite time series over the 1960-2007 period. Evaluating the averaged MSFD time series for 1960 2007 reveals a statistically significant trend of 4.0 cm/decade or a net change of-19.2 cm for the 48-year period over the basin. The MSFD had significantly negative correlation with mean annual air temperature （MAAT）, winter air temperature, mean annual ground surface temperature （MAGST）, degree days of thawing for the air （DDTa） as well as for the surface （DDTs）, and degree days of freezing for the surface （DDFs）. While there was significantly positive correlation between DDF,. and MSFD time series, MSFD was deeper and changed greatly in the Heihe River source area. It was shallower in the east-central basin and gradually deepened in other sections of the basin. The MSFD distribution pattern in 2003-2005 is consistent with that of averaged degree days of freezing for air （DDFa） in 1960-2007. However, the maximum of MSFD may not be accurate, because there is no long term observation data in the deep seasonally frozen ground regions near the lower boundary of permafrost. With increasing elevation, averaged DDFa increased at a rate of 51.6 ℃-day/100m, therefore, the MSFG and the date reaching MSFG became deeper and later, respectively.展开更多
River hydrogeochemistry offers necessary guidance for effective water environmental management.However,the influence of cascade reservoirs on river hydrogeochemistry remains unknown.In this study,the Jinsha River,the ...River hydrogeochemistry offers necessary guidance for effective water environmental management.However,the influence of cascade reservoirs on river hydrogeochemistry remains unknown.In this study,the Jinsha River,the headwaters of the Yangtze River of China,was selected to investigate the spatiotemporal variations of hydrogeochemistry after the construction of six cascade reservoirs.Major ions,total dissolved solids,electrical conductivity,and pH values of sampled water in the upper natural reaches and lower reservoir-regulated reaches were analyzed in both flood and dry seasons.The results of Piper diagram and Gibbs plots showed that the hydrogeochemistry of the Jinsha River was naturally controlled by both evaporation-crystallization and carbonate weathering processes,but it was also artificially affected by reservoirs.The impoundment of cascade reservoirs affected the hydrodynamic condition of the river.The river flow in the flood season was reduced by approximately 24.5%,altering the proportions of water sources and leading to notable hydrogeochemical alterations in reservoir-regulated reaches.Conversely,river hydrogeochemistry generally remained unchanged in the dry season,owing to the insignificant effect of cascade reservoirs on river flow.In contrast to what has been observed in previous studies of individual reservoirs,the cumulative influence of cascade reservoirs on the Jinsha River flow regime did not cause abrupt hydrogeochemical changes between the upstream and downstream areas of each reservoir.Moreover,the water quality assessments revealed that the impoundment of cascade reservoirs improved downstream irrigational water quality,with lower Naþratio values in the flood season.This study provides the earliest evaluation of cascade reservoir influence on the hydrogeochemistry of the Jinsha River.The findings of this study can be used as a reference for scientific guidelines for future environmental management of cascade reservoirs in large rivers.展开更多
Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species.In this study,we evaluated changes in microbial comm...Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species.In this study,we evaluated changes in microbial communities in soil samples from C.fargesii forests.The phospholipid fatty acid(PLFA)biomarker method was used to obtain bacteria,fungi,actinomycetes,gram-positive bacteria(G?),gram-negative bacteria(G-),aerobic bacteria,and anaerobic bacteria to investigate spatiotemporal changes in microbial communities during the growing season.The results show that soil microorganisms were mainly concentrated in the upper 20-cm layer,demonstrating an obvious surface aggregation(P<0.05).Large amounts of litter and heavy rainfall during the early growing season resulted in the highest PLFA contents for various microorganisms,whereas relatively low and stable levels were observed during other times.The dominant species during each period were bacteria.G+ or aerobic bacteria were the main bacterial populations,providing insights into the overall trends of soil bacterial PLFA contents.Due to the relative accumulation of refractory substances during the later stages of litter decomposition,the effects of fungi increased significantly.Overall,our findings demonstrate that the main factors influencing microbial communities were litter,rainfall,and soil field capacity.展开更多
Spatiotemporal variations of anthropogenic heat flux(AHF)is reported to be associated with global warming.However,confined to the low spatial resolution of energy consumption statistical data,details of AHF was not we...Spatiotemporal variations of anthropogenic heat flux(AHF)is reported to be associated with global warming.However,confined to the low spatial resolution of energy consumption statistical data,details of AHF was not well descripted.To obtain high spatial resolution data of AHF,Defense Meteorological Satellite Program/Operational Linescan System(DMSP/OLS)nighttime light time-series product and Moderate Resolution Imaging Spectroradiometer(MODIS)satellite monthly normalized difference vegetation index(NDVI)product were applied to construct the human settlement index.Based on the spatial regression relationship between human settlement index and energy consumption data.A 1-km resolution dataset of AHF of 12 selected cities in the eastern China was obtained.Ordinary least-squares(OLS)model was applied to detect the mechanism of spatial patterns of AHF.Results showed that industrial emission in selected cities of the eastern China was accountable for 63%of the total emission.AHF emission in megacities,such as Tianjin,Jinan,Qingdao,and Hangzhou,was most significant.AHF increasing speed in most areas in the chosen cities was quite low.High growth or extremely high growth of AHF were located in central downtown areas.In Beijing,Shanghai,Guangzhou,Jinan,Hangzhou,Changzhou,Zhaoqing,and Jiangmen,a single kernel of AHF was observed.Potential influencing factors showed that precipitation,temperature,elevation,normalized different vegetation index,gross domestic product,and urbanization level were positive with AHF.Overall,this investigation implied that urbanization level and economic development level might dominate the increasing of AHF and the spatial heterogeneousness of AHF.Higher urbanization level or economic development level resulted in high increasing speeds of AHF.These findings provide a novel way to reconstruct of AHF and scientific supports for energy management strategy development.展开更多
Mangroves can not only provide multiple ecosystem service functions,but are also efficient carbon producers,capturers,and sinks.The estimation of the organic carbon accumulation rate(OCAR)in mangrove sediments is fund...Mangroves can not only provide multiple ecosystem service functions,but are also efficient carbon producers,capturers,and sinks.The estimation of the organic carbon accumulation rate(OCAR)in mangrove sediments is fundamental for elucidating the role of mangroves in the global carbon budget.In particular,understanding the past changes in the OCAR in mangrove sediments is vital for predicting the future role of mangroves in the rapidly changing environment.In this study,three dated sediment cores from interior and fringe of mangroves in the Yingluo Bay,China,were used to reconstruct the spatiotemporal variations of the calculated OCAR since 1900 in this area.The increasing OCAR in the mangrove interior was attributed to mangrove flourishment induced by climate change characterized by the rising temperature.However,in the mangrove fringe,the strengthening hydrodynamic conditions under the sea level rise were responsible for the decreasing OCAR,particularly after the1940 s.Furthermore,the duration of inundation by seawater was the primary factors controlling the spatial variability of the OCAR from the mangrove fringe to interior,while the strengthened hydrodynamic conditions after the 1940 s broke this original pattern.展开更多
In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)wer...In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)were conducted in two core sites,i.e.,Huangcuo(HC)and Nanxian-Shibaxian(NX),in the Xiamen Amphioxus Nature Reserve in China.A total of 155 species of macrofauna were recorded,therein,polychaetes were dominant in terms of species number and density.Significant spatiotemporal variations of macrofaunal communities were observed.The density of polychaetes and the biomass of molluscs in the HC site were higher than those in the NX site.Macrofauna were more diverse and abundant in the cold seasons(winter and spring)than that in the warm seasons(summer and autumn).The annual variations of macrofaunal communities may be attributed to the changes in sediment texture among the three years of the survey.The variations in macrofaunal communities were mainly related to the proportion of polychaetes within the community.In addition,the density of amphioxus(include Branchiostoma japonicum and B.belcheri)was negatively correlated to that of polychaetes,bivalves,and crustaceans.Amphioxus was less likely to be found in the sediments with higher silt and clay content.Five biotic indices including Margaref’s richness index(d),Peilou’s evenness index(J′),Shannon-Wiener diversity index(H′),AMBI and M-AMBI were calculated in the present study.AMBI seems suitable in assessing benthic health at the"Amphioxus Sand"habitat,and a potential risk of ecological health in Xiamen Amphioxus Nature Reserve should be aware.展开更多
Benzene,toluene,ethylbenzene,and xylene(BTEX)pollution poses a serious threat to public health and the environment because of its respiratory and neurological effects,carcinogenic properties,and adverse effects on air...Benzene,toluene,ethylbenzene,and xylene(BTEX)pollution poses a serious threat to public health and the environment because of its respiratory and neurological effects,carcinogenic properties,and adverse effects on air quality.BTEX exposure is a matter of grave concern in India owing to the growing vehicular and development activities,necessitating the assessment of atmospheric concentrations and their spatial variation.This paper presents a comprehensive assessment of ambient concentrations and spatiotemporal variations of BTEX in India.The study investigates the correlation of BTEX with other criteria pollutants andmeteorological parameters,aiming to identify interrelationships and diagnostic indicators for the source characterization of BTEX emissions.Additionally,the paper categorizes various regions in India according to the Air Quality Index(AQI)based on BTEX pollution levels.The results reveal that the northern zone of India exhibits the highest levels of BTEX pollution compared to central,eastern,and western regions.In contrast,the southern zone experiences the least pollution with BTEX.Seasonal analysis indicates that winter and postmonsoon periods,characterized by lower temperatures,are associated with higher BTEX levels due to the accumulation of localized emissions.When comparing the different zones in India,high traffic emissions and localized activities,such as solvent use and solvent evaporation,are found to be the primary sources of BTEX.The findings of the current study aid in source characterization and identification,and better understanding of the region’s air quality problems,which helps in the development of focused BTEX pollution reduction and control strategies.展开更多
Coastal ecosystems are plagued by high levels of microplastic pollution.Conducting baseline surveys is crucial to comprehend the distribution and influencing factors of this pollution.The present study investigates th...Coastal ecosystems are plagued by high levels of microplastic pollution.Conducting baseline surveys is crucial to comprehend the distribution and influencing factors of this pollution.The present study investigates the spatiotemporal variation and diversity of microplastic on the coastal beaches in Xiamen City,China,considering the combined effects of seasons,human activities,and physicochemical properties of sediments.It is detected that the abundance of microplastics in Xiamen beaches was 0.271±0.01 items/g.The abundance of microplastics in dry season was significantly higher than in rainy season.In terms of spatial variation,the beaches that attracted a larger number of tourists exhibited significantly higher microplastic abundance.The temporal pattern of microplastic distribution on different beaches varied greatly due to region-specific human activities(e.g.,mangrove restoration project)and sedimentary properties(e.g.,bulk density).When the assemblage of microplastics in the coastal area was viewed as a biological community,the Shannon-Wiener index and Pielou's index were higher in rainy season and in the beaches with high intensity of tourist activities,which suggests that the human activities and the surface runoff may contribute to the diversity of microplastics on coastal beaches.Future investigations are encouraged to combine controlled experiments and long-term monitoring at multiple scales to elucidate the underlying mechanisms and factors associated with microplastic pollution in coastal zone.展开更多
The Yellow River Basin in Sichuan Province(YRS)is undergoing severe soil erosion and exacerbated ecological vulnerability,which collectively pose formidable challenges for regional water conservation(WC)and sustainabl...The Yellow River Basin in Sichuan Province(YRS)is undergoing severe soil erosion and exacerbated ecological vulnerability,which collectively pose formidable challenges for regional water conservation(WC)and sustainable development.While effectively enhancing WC necessitates a comprehensive understanding of its driving factors and corresponding intervention strategies,existing studies have largely neglected the spatiotemporal heterogeneity of both natural and socio-economic drivers.Therefore,this study explored the spatiotemporal heterogeneity of WC drivers in YRS using multi-scale geographically weighted regression(MGWR)and geographically and temporally weighted regression(GTWR)models from an eco-hydrological perspective.We discovered that downstream regions,which are more developed,achieved significantly better WC than upstream regions.The results also demonstrated that the influence of temperature and wind speed is consistently dominant and temporally stable due to climate stability,while the influence of vegetation shifted from negative to positive around 2010,likely indicating greater benefits from understory vegetation.Economic growth positively impacted WC in upstream regions but had a negative effect in the more developed downstream regions.These findings highlight the importance of targeted water conservation strategies,including locally appropriate revegetation,optimization of agricultural and economic structures,and the establishment of eco-compensation mechanisms for ecological conservation and sustainable development.展开更多
As the Arctic undergoes rapid warming and sea ice continues to decline,Ocean-to-Ice Heat Flux(OIHF)plays a crucial role in regulating sea ice dynamics.This study investigates the seasonal variations in ocean-to-ice he...As the Arctic undergoes rapid warming and sea ice continues to decline,Ocean-to-Ice Heat Flux(OIHF)plays a crucial role in regulating sea ice dynamics.This study investigates the seasonal variations in ocean-to-ice heat flux in north of the Fram Strait using the regional Arctic Ocean/sea ice reanalysis product from 1991 to 2020.The analysis reveals that the OIHF exhibits significant seasonal variability,with a pronounced peak during winter in north of the Fram Strait,driven by inflows of Atlantic water.Warm Atlantic water intrusion begins in October,reaches its peak in January and February,and results in a delayed increase in OIHF,with maximum flux observed 2−3 months later.These results highlight the significant role of Atlantic water inflows in influencing Arctic sea ice dynamics and emphasize the need for further investigation into the coupled ocean-atmosphere processes that govern seasonal fluctuations in OIHF.展开更多
Methane(CH_(4))is the second greenhouse gas and has a profound impact on global climate change due to its high global warming potential and concentration.By 2022,the CH_(4)concentration was approximately 1.9 ppm,which...Methane(CH_(4))is the second greenhouse gas and has a profound impact on global climate change due to its high global warming potential and concentration.By 2022,the CH_(4)concentration was approximately 1.9 ppm,which was 264%of the pre-industrial level.The spatiotemporal distribution of CH_(4)was investigated by a portable CH_(4)detector on an unmanned aerial vehicle and electric bicycles in Shaoxing,a city situated in the Yangtze River Delta,China.The vertical distribution revealed CH_(4)concentration generally decreased slowly with height.However,the inversion condition and low atmospheric boundary layer height(ABLH)leaded to the enhancement of CH_(4)with height.The highest CH_(4)concentration(2.2±0.1 ppm,n=1428)was observed in winter and the lowest(2.0±0.2 ppm,n=1530)in spring.Regarding the daily variation,CH_(4)concentration peaked at 5:00 local time(LT)and reached its lowest level at 14:00 LT,which was attributed to the daily variation of ABLH,lowest in the early morning and highest in the noon.In urban areas,CH_(4)concentrations showed higher levels near restaurants,natural gas stations and sewerage well,with a maximum value of 13.1 ppm,which was caused by CH_(4)emission and natural gas leakage from these places.The annual CH_(4)emission in Shaoxing were estimated to be approximately 69 ton/(km^(2)·year)by the mass balance approach.Compared with other cities in the world,the CH_(4)emission is in higher level which imply some control measures should be conducted to reduce CH_(4)emission in Shaoxing.展开更多
As a major agricultural country, China suffers from severe meteorological drought almost every year.Previous studies have applied a single threshold to identify the onset of drought events, which may cause problems to...As a major agricultural country, China suffers from severe meteorological drought almost every year.Previous studies have applied a single threshold to identify the onset of drought events, which may cause problems to adequately characterize long-term patterns of droughts.This study analyzes meteorological droughts in China based on a set of daily gridded(0.5° 9 0.5°) precipitation data from 1961 to 2014. By using a multi-threshold run theory approach to evaluate the monthly percentage of precipitation anomalies index(Pa), a drought events sequence was identified at each grid cell. The spatiotemporal variations of drought in China were further investigated based on statistics of the frequency, duration,severity, and intensity of all drought events. Analysis of the results show that China has five distinct meteorological drought-prone regions: the Huang-Huai-Hai Plain, Northeast China, Southwest China, South China coastal region,and Northwest China. Seasonal analysis further indicates that there are evident spatial variations in the seasonal contribution to regional drought. But overall, most contribution to annual drought events in China come from the winter. Decadal variation analysis suggests that most of China's water resource regions have undergone an increase in drought frequency, especially in the Liaohe, Haihe, and Yellow River basins, although drought duration and severity clearly have decreased after the 1960 s.展开更多
Guanting Reservoir（GR） is one of the most important water sources for Beijing and neighboring regions.Due to water pollution,it was withdrawn from the system to supply Beijing drinking water;however,after a thorough...Guanting Reservoir（GR） is one of the most important water sources for Beijing and neighboring regions.Due to water pollution,it was withdrawn from the system to supply Beijing drinking water;however,after a thorough treatment process,GR was made a reserve water source since 2007.To develop a comprehensive and quantitative analysis of water yield and purification services in the GR watershed,this study selected two time periods：the period when GR was withdrawn from the system supplying local drinking water and the period that it has been designated a reserve water source.The In VEST model was used to evaluate the quantities of water yields,and total nitrogen and total phosphorus outputs from 1995 to 2010 Additionally,the spatiotemporal variations of water yield services and water quality purification services in the GR watershed were analyzed.The results showed that water yield services in the GR watershed first weakened and then became stronger,but weakened overall during the years 1995 to 2010.Water yield capacity in the basin decreased from 1.89×10^9 m3 in 1995 to 1.43×10^9 m3 in 2010（a drop of 24.0% in total）.Water quality purification services also showed the same tendency.Total nitrogen output decreased from 4028.7 t in 1995 to 3611.4 t in 2010,while total phosphorus decreased from 379.7 t in 1995 to 354.0 t in 2010.Nitrogen and phosphorus purification services were enhanced by 10.4% and 6.8%,respectively.Changes in the climate and land use were the main factors which lead to the changes in the water yield service in the GR watershed.Policies intended to protect water resource have matched the varying trends of water quality purification services during different periods.On one hand,the research results provide a foundation to identify key fields for eco-compensation in the Guanting Reservoir basin.On another hand,the ecosystem service value will increase on the basis of eco-compensation criteria through setting the scenarios of returning farmland to forest and ecological protection.This method directly reflects increases in ecosystem service values that have occurred since measures to protect the ecological environment have been implemented.This method is more persuasive and feasible than using eco-compensation criteria based on regional ecosystem service values determined by land use/coverage type.It can provide a new way to assess eco-compensation in the Guanting Reservoir basin and other regions.展开更多
Gross primary productivity (GPP) of vegetation is a critical indicator of ecosystem growth and carbon sequestration. The spatiotemporal variation characteristics of land vegetation GPP trends in a specific region of A...Gross primary productivity (GPP) of vegetation is a critical indicator of ecosystem growth and carbon sequestration. The spatiotemporal variation characteristics of land vegetation GPP trends in a specific region of Asia from 2001 to 2020 were analyzed by Sen and MK trend analysis methods in this study .Moreover , a GPP change attribution model was established to explore the driving influences of factors such as Leaf Area Index (LAI), Land Surface Temperature (LST), Vapor Pressure Deficit (VPD), Soil Moisture, Solar Radiation and Wind Speed on GPP. The results indicate that summer GPP values are significantly higher than those in other months, accounting for 60.8% of the annual total GPP;spring and autumn contribute 18.91% and 13.04%, respectively. In winter, due to vegetation being nearly dormant, the contribution is minimal at 7.19%. Spatially, GPP shows a decreasing trend from southeast to northwest. LAI primarily drives the spatial and seasonal variations of regional GPP, while VPD, surface temperature, solar radiation, and soil moisture have varying impacts on GPP across different dimensions. Additionally, wind speed exhibits a minor contribution to GPP across different dimensions.展开更多
Sediment components and their fluxes of Cores MD12-3428(water depth: 903 m), MD12-3433(water depth: 2125 m),and MD12-3434(water depth: 2995 m), obtained along a transect on the continental slope of the northern South ...Sediment components and their fluxes of Cores MD12-3428(water depth: 903 m), MD12-3433(water depth: 2125 m),and MD12-3434(water depth: 2995 m), obtained along a transect on the continental slope of the northern South China Sea, have been conducted to reveal the spatiotemporal variations and the controlling factors of the sediment components and of their fluxes.Results show that deep-sea sediments in the northern South China Sea are composed mainly of terrigenous(59–89%) and carbonate(6–38%) particles, with minor components of opal(1.6–9.4%) and organic matter(0.7–1.9%). Fluxes of terrigenous and carbonate particles reach up to 2.4–21.8 and 0.4–6.5 g cm–2 kyr–1, respectively, values that are one to two orders of magnitude higher than the fluxes of opal and organic matter. Temporal variations of the percentages and fluxes of deep-sea sediment components have displayed clear glacial-interglacial cyclicity since the last glaciation. Terrigenous, opal, and organic matter percentages and their fluxes increas clearly during marine isotope stage 2, while carbonate percentages and fluxes show an opposite variation pattern or are characterized by an unremarkable increase. This implies that deep-sea carbonate in the South China Sea is affected by the dilution of terrigenous inputs during the sea-level lowstand. With increasing water depth along the transect, the terrigenous percentage increases but with largely decreased fluxes. Both the percentage and flux of carbonate decrease, while the percentages and fluxes of opal and organic matter display much more complicated variational features. The spatiotemporal variations of deep-sea sediment components and of their fluxes since the last glaciation in the northern South China Sea are strongly controlled by sea-level fluctuations. Simultaneously, terrigenous supply associated with monsoonal rainfall, marine primary productivity,and the dilution effect between terrigenous and biogenic particles, also play interconnected roles in the sediment accumulation processes.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42027804,41775026,and 41075012)。
文摘Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and reanalysis data(MERRA-2)from March 2007 to February 2015(eight years).The horizontal distribution reveals lower cirrus fraction values in the northern SCS and higher values in the southern region,with minima observed in March and April and maxima sequentially occurring in August(northern SCS,NSCS),September(middle SCS,MSCS),and December(southern SCS,SSCS).Vertically,the cirrus fraction peaks in summer and reaches its lowest levels in spring.Opaque cirrus dominates during summer in the NSCS and MSCS,comprising 53.6%and 55.9%,respectively,while the SSCS exhibits a higher frequency of opaque cirrus relative to other cloud types.Subvisible cirrus clouds have the lowest frequency year-round,whereas thin cirrus is most prominent in winter in the NSCS(46.3%)and in spring in the MSCS(45.3%).A case study from September 2021 further explores the influence of ice crystal habits on brightness temperature(BT)over the SCS.Simulations utilizing five ice crystal shapes from the ARTS DDA(Atmospheric Radiative Transfer Simulator Discrete Dipole Approximation)database and the RTTOV 12.4 radiative transfer model reveal that the 8-column-aggregate shape best represents BT in the NSCS and SSCS,while the large-block-aggregate shape performs better in the SSCS.
基金the financial support provided by the National Natural Science Foundation of China[Grant No.72373138 and 71973131]Major Project of National Social Science Foundation of China[Grant No.19VHQ002].
文摘The promotion of energy efficiency(EE)helps address energy constraints and promote environmental sustainability.This study comprehensively explores the spatiotemporal variations,influencing factors,and configuration promotion paths of EE in 284 Chinese cities during 2003‒2019 using the global super-efficiency minimum distance to strong efficient frontier(G-S-MinDS),exploratory spatial data analysis(ESDA),multiscale geographically weighted regression(MGWR),and fuzzy set qualitative comparative analysis(fsQCA)methods.The findings are:①China’s cities have an annual average EE of 0.658 with a growth rate of 0.53%,showing considerable promotion potential.②Industrial structure optimization,population agglomeration,economic development,and increased green coverage contribute positively,while government intervention and openness hinder China’s urban EE.③Four configurational promotion paths for enhancing China’s urban EE are identified,where among those paths population density is a core condition,while government intervention is not.This study provides valuable insights into substantially improving urban EE,emphasizing the need for targeted policies to address energy and environmental crises in China.
基金Supported by the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2023JJ10053)the National Natural Science Foundation of China(No.42276205)。
文摘The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of ISWs.The spatiotemporal variations of the dynamic parameters of the ISWs in the northern South China Sea(SCS)were studied based on the reanalysis of long-term temperature and salinity datasets.The results for spectrum analysis show that there are definite geographical differences for the periodic variation of the parameters:in shallow water,all parameters vary with a wave period of one year,while in deep water wave components of the parameters at other frequencies exist.Using wavelet analysis,the wavelet power spectral densities in deep water exhibited an inter-annual variation pattern.For example,the wave component of the dispersion coefficient with a wave period of about half a year reached its power peak once every two years.Based on previous work,this inter-annual variation pattern was deduced to be caused by dynamic processes.In further work on the regulatory mechanisms,empirical orthogonal function(EOF)decomposition was performed.It was found that the modes of the dispersion coefficient have different geographical distributions,explaining the reason why the wave components in different frequencies appeared in different locations.The numerical simulation results confirm that the variations in the parameters of the ISWs derived from the eKdV equation could affect the waveforms significantly because of changes in the polarity of the ISWs.Therefore,the periodic variations of the dynamic parameters are related to the geographical location because of dynamic processes operating.
基金This research was supported by the National Natural Science Foundation of China(41961029)the Gansu Construction Science and Technology Soft Science Project of China(JK2022-16).
文摘Rapid industrialization and urbanization have led to the most serious habitat degradation in China,especially in the loess hilly area of the Yellow River Basin,where the ecological environment is relatively fragile.The contradiction between economic development and ecological environment protection has aroused widespread concern.In this study,we used the habitat quality of Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST-HQ)model at different scales to evaluate the dynamic evolution characteristics of habitat quality in Lanzhou City,Gansu Province of China.The spatiotemporal variations of habitat quality were analyzed by spatial autocorrelation.A Geographical Detector(Geodetector)model was used to explore the driving factors that influencing the spatial differentiation of habitat quality,including natural factors,socio-economic factors,and ecological protection factors.The results showed that the habitat quality index of Lanzhou City decreased from 0.4638 to 0.4548 during 2000-2018.The areas with reduced the habitat quality index were mainly located in the Yellow River Basin and Qinwangchuan Basin,where are the main urban areas and the new economic development areas,respectively.The spatial distribution of habitat quality presented a trend of high in the surrounding areas and low in the middle,and showed a significant positive spatial autocorrelation.With the increase of study scale,the spatial distribution of habitat quality changed from concentrated to dispersed.The spatial differentiation of habitat quality in the study area was the result of multiple factors.Among them,topographic relief and slope were the key factors.The synergistic enhancement among these driving factors intensified the spatial differentiation of habitat quality.The findings of this study can provide a scientific basis for land resources utilization and ecosystem restoration in the arid and semi-arid land.
基金Supported by the Public Science and Technology Research Funds Projects of Ocean(No.201205009)
文摘The process of habitat degradation varies in habitat type and driving force which shows certain spatial and temporal heterogeneity on regional scales. In the present study, a new diagnostic model for enclosed bay habitat degradation was established, with which the spatial and temporal variation patterns of habitat degradation during 1991–2012 in Sansha Bay, Fujian, China was investigated. The results show that anthropogenic disturbance is the major controlling factor for the habitat degradation in large temporal heterogeneity in the bay. On the other hand, the habitat degradation experienced signifi cant spatial variations among six sub-bays. Under the joint action of temporal and spatial heterogeneity, the degradation trend in growing scale shows a more signifi cant correlation with the distribution of local leading industries along shorelines. Therefore, we quantifi ed the main characters of habitat degradation in Sansha Bay, and have understood the relationship between the status of habitats spatio-temporal variation value and the main controlling factor leading to the changes. However, a defi ciency of this research is the lack of or inaccessible to the detailed data, which shall be better solved in the future study for accessing more data from more sources.
基金supported by the Global Change Research Program of China (No. 2010CB951402)the Natural Science Foundation of China (Nos. 91025013, 91325202)+1 种基金the State Key Laboratory of Frozen Soil Engineering (No. SKLFSE-ZY-06), CAS, Chinathe Major Research Plan of the Natural Science Foundation of China (No. 2013CBA01802)
文摘Investigation on spatiotemporal variations of maximum seasonal freeze depth （MSFD） over the Heihe River Basin is of great importance for systematic understanding of regional climate and environmental change, ecological-hydrological processes, water resources assessment, construction and resource development. Based on soil and air temperatures at the meteorological stations of the China Meteorological Administration （CMA） over the Heihe River Basin, MSFDs time series are structured into a composite time series over the 1960-2007 period. Evaluating the averaged MSFD time series for 1960 2007 reveals a statistically significant trend of 4.0 cm/decade or a net change of-19.2 cm for the 48-year period over the basin. The MSFD had significantly negative correlation with mean annual air temperature （MAAT）, winter air temperature, mean annual ground surface temperature （MAGST）, degree days of thawing for the air （DDTa） as well as for the surface （DDTs）, and degree days of freezing for the surface （DDFs）. While there was significantly positive correlation between DDF,. and MSFD time series, MSFD was deeper and changed greatly in the Heihe River source area. It was shallower in the east-central basin and gradually deepened in other sections of the basin. The MSFD distribution pattern in 2003-2005 is consistent with that of averaged degree days of freezing for air （DDFa） in 1960-2007. However, the maximum of MSFD may not be accurate, because there is no long term observation data in the deep seasonally frozen ground regions near the lower boundary of permafrost. With increasing elevation, averaged DDFa increased at a rate of 51.6 ℃-day/100m, therefore, the MSFG and the date reaching MSFG became deeper and later, respectively.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2016YFC0502203)the National Science Funds for Creative Research Groups of China(Grant No.51421006)the Key Program of the National Natural Science Foundation of China(Grant No.91647206).
文摘River hydrogeochemistry offers necessary guidance for effective water environmental management.However,the influence of cascade reservoirs on river hydrogeochemistry remains unknown.In this study,the Jinsha River,the headwaters of the Yangtze River of China,was selected to investigate the spatiotemporal variations of hydrogeochemistry after the construction of six cascade reservoirs.Major ions,total dissolved solids,electrical conductivity,and pH values of sampled water in the upper natural reaches and lower reservoir-regulated reaches were analyzed in both flood and dry seasons.The results of Piper diagram and Gibbs plots showed that the hydrogeochemistry of the Jinsha River was naturally controlled by both evaporation-crystallization and carbonate weathering processes,but it was also artificially affected by reservoirs.The impoundment of cascade reservoirs affected the hydrodynamic condition of the river.The river flow in the flood season was reduced by approximately 24.5%,altering the proportions of water sources and leading to notable hydrogeochemical alterations in reservoir-regulated reaches.Conversely,river hydrogeochemistry generally remained unchanged in the dry season,owing to the insignificant effect of cascade reservoirs on river flow.In contrast to what has been observed in previous studies of individual reservoirs,the cumulative influence of cascade reservoirs on the Jinsha River flow regime did not cause abrupt hydrogeochemical changes between the upstream and downstream areas of each reservoir.Moreover,the water quality assessments revealed that the impoundment of cascade reservoirs improved downstream irrigational water quality,with lower Naþratio values in the flood season.This study provides the earliest evaluation of cascade reservoir influence on the hydrogeochemistry of the Jinsha River.The findings of this study can be used as a reference for scientific guidelines for future environmental management of cascade reservoirs in large rivers.
基金This study was supported by the Science and Technology Basic Work Special(No 2014FY120700).
文摘Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species.In this study,we evaluated changes in microbial communities in soil samples from C.fargesii forests.The phospholipid fatty acid(PLFA)biomarker method was used to obtain bacteria,fungi,actinomycetes,gram-positive bacteria(G?),gram-negative bacteria(G-),aerobic bacteria,and anaerobic bacteria to investigate spatiotemporal changes in microbial communities during the growing season.The results show that soil microorganisms were mainly concentrated in the upper 20-cm layer,demonstrating an obvious surface aggregation(P<0.05).Large amounts of litter and heavy rainfall during the early growing season resulted in the highest PLFA contents for various microorganisms,whereas relatively low and stable levels were observed during other times.The dominant species during each period were bacteria.G+ or aerobic bacteria were the main bacterial populations,providing insights into the overall trends of soil bacterial PLFA contents.Due to the relative accumulation of refractory substances during the later stages of litter decomposition,the effects of fungi increased significantly.Overall,our findings demonstrate that the main factors influencing microbial communities were litter,rainfall,and soil field capacity.
基金Under the auspices of National Natural Science Foundation of China(No.41901219,41671430,41801326)Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0301)。
文摘Spatiotemporal variations of anthropogenic heat flux(AHF)is reported to be associated with global warming.However,confined to the low spatial resolution of energy consumption statistical data,details of AHF was not well descripted.To obtain high spatial resolution data of AHF,Defense Meteorological Satellite Program/Operational Linescan System(DMSP/OLS)nighttime light time-series product and Moderate Resolution Imaging Spectroradiometer(MODIS)satellite monthly normalized difference vegetation index(NDVI)product were applied to construct the human settlement index.Based on the spatial regression relationship between human settlement index and energy consumption data.A 1-km resolution dataset of AHF of 12 selected cities in the eastern China was obtained.Ordinary least-squares(OLS)model was applied to detect the mechanism of spatial patterns of AHF.Results showed that industrial emission in selected cities of the eastern China was accountable for 63%of the total emission.AHF emission in megacities,such as Tianjin,Jinan,Qingdao,and Hangzhou,was most significant.AHF increasing speed in most areas in the chosen cities was quite low.High growth or extremely high growth of AHF were located in central downtown areas.In Beijing,Shanghai,Guangzhou,Jinan,Hangzhou,Changzhou,Zhaoqing,and Jiangmen,a single kernel of AHF was observed.Potential influencing factors showed that precipitation,temperature,elevation,normalized different vegetation index,gross domestic product,and urbanization level were positive with AHF.Overall,this investigation implied that urbanization level and economic development level might dominate the increasing of AHF and the spatial heterogeneousness of AHF.Higher urbanization level or economic development level resulted in high increasing speeds of AHF.These findings provide a novel way to reconstruct of AHF and scientific supports for energy management strategy development.
基金The National Natural Science Foundation of China under contract Nos 41976068 and 41576061。
文摘Mangroves can not only provide multiple ecosystem service functions,but are also efficient carbon producers,capturers,and sinks.The estimation of the organic carbon accumulation rate(OCAR)in mangrove sediments is fundamental for elucidating the role of mangroves in the global carbon budget.In particular,understanding the past changes in the OCAR in mangrove sediments is vital for predicting the future role of mangroves in the rapidly changing environment.In this study,three dated sediment cores from interior and fringe of mangroves in the Yingluo Bay,China,were used to reconstruct the spatiotemporal variations of the calculated OCAR since 1900 in this area.The increasing OCAR in the mangrove interior was attributed to mangrove flourishment induced by climate change characterized by the rising temperature.However,in the mangrove fringe,the strengthening hydrodynamic conditions under the sea level rise were responsible for the decreasing OCAR,particularly after the1940 s.Furthermore,the duration of inundation by seawater was the primary factors controlling the spatial variability of the OCAR from the mangrove fringe to interior,while the strengthened hydrodynamic conditions after the 1940 s broke this original pattern.
基金The National Key Research and Development Program of China under contract No.2016YFC0502904the Public Science and Technology Research Funds Projects of Oceans under contract No.201305030。
文摘In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)were conducted in two core sites,i.e.,Huangcuo(HC)and Nanxian-Shibaxian(NX),in the Xiamen Amphioxus Nature Reserve in China.A total of 155 species of macrofauna were recorded,therein,polychaetes were dominant in terms of species number and density.Significant spatiotemporal variations of macrofaunal communities were observed.The density of polychaetes and the biomass of molluscs in the HC site were higher than those in the NX site.Macrofauna were more diverse and abundant in the cold seasons(winter and spring)than that in the warm seasons(summer and autumn).The annual variations of macrofaunal communities may be attributed to the changes in sediment texture among the three years of the survey.The variations in macrofaunal communities were mainly related to the proportion of polychaetes within the community.In addition,the density of amphioxus(include Branchiostoma japonicum and B.belcheri)was negatively correlated to that of polychaetes,bivalves,and crustaceans.Amphioxus was less likely to be found in the sediments with higher silt and clay content.Five biotic indices including Margaref’s richness index(d),Peilou’s evenness index(J′),Shannon-Wiener diversity index(H′),AMBI and M-AMBI were calculated in the present study.AMBI seems suitable in assessing benthic health at the"Amphioxus Sand"habitat,and a potential risk of ecological health in Xiamen Amphioxus Nature Reserve should be aware.
文摘Benzene,toluene,ethylbenzene,and xylene(BTEX)pollution poses a serious threat to public health and the environment because of its respiratory and neurological effects,carcinogenic properties,and adverse effects on air quality.BTEX exposure is a matter of grave concern in India owing to the growing vehicular and development activities,necessitating the assessment of atmospheric concentrations and their spatial variation.This paper presents a comprehensive assessment of ambient concentrations and spatiotemporal variations of BTEX in India.The study investigates the correlation of BTEX with other criteria pollutants andmeteorological parameters,aiming to identify interrelationships and diagnostic indicators for the source characterization of BTEX emissions.Additionally,the paper categorizes various regions in India according to the Air Quality Index(AQI)based on BTEX pollution levels.The results reveal that the northern zone of India exhibits the highest levels of BTEX pollution compared to central,eastern,and western regions.In contrast,the southern zone experiences the least pollution with BTEX.Seasonal analysis indicates that winter and postmonsoon periods,characterized by lower temperatures,are associated with higher BTEX levels due to the accumulation of localized emissions.When comparing the different zones in India,high traffic emissions and localized activities,such as solvent use and solvent evaporation,are found to be the primary sources of BTEX.The findings of the current study aid in source characterization and identification,and better understanding of the region’s air quality problems,which helps in the development of focused BTEX pollution reduction and control strategies.
基金Supported by the Natural Science Foundation of Fujian Province(No.2022J05278)the Marine and Fishery Development Special Fund of Xiamen(No.23YYST064QCB36)。
文摘Coastal ecosystems are plagued by high levels of microplastic pollution.Conducting baseline surveys is crucial to comprehend the distribution and influencing factors of this pollution.The present study investigates the spatiotemporal variation and diversity of microplastic on the coastal beaches in Xiamen City,China,considering the combined effects of seasons,human activities,and physicochemical properties of sediments.It is detected that the abundance of microplastics in Xiamen beaches was 0.271±0.01 items/g.The abundance of microplastics in dry season was significantly higher than in rainy season.In terms of spatial variation,the beaches that attracted a larger number of tourists exhibited significantly higher microplastic abundance.The temporal pattern of microplastic distribution on different beaches varied greatly due to region-specific human activities(e.g.,mangrove restoration project)and sedimentary properties(e.g.,bulk density).When the assemblage of microplastics in the coastal area was viewed as a biological community,the Shannon-Wiener index and Pielou's index were higher in rainy season and in the beaches with high intensity of tourist activities,which suggests that the human activities and the surface runoff may contribute to the diversity of microplastics on coastal beaches.Future investigations are encouraged to combine controlled experiments and long-term monitoring at multiple scales to elucidate the underlying mechanisms and factors associated with microplastic pollution in coastal zone.
基金supported by the funding provided by the State Key Laboratory of Hydraulics and Mountain River Engineering(SKHL2210)National Natural Science Foundation of China(42171304)+1 种基金the Sichuan Science and Technology Program(2023YFS0380)Natural Science Foundation of Jiangsu Province of China(BK20242018)。
文摘The Yellow River Basin in Sichuan Province(YRS)is undergoing severe soil erosion and exacerbated ecological vulnerability,which collectively pose formidable challenges for regional water conservation(WC)and sustainable development.While effectively enhancing WC necessitates a comprehensive understanding of its driving factors and corresponding intervention strategies,existing studies have largely neglected the spatiotemporal heterogeneity of both natural and socio-economic drivers.Therefore,this study explored the spatiotemporal heterogeneity of WC drivers in YRS using multi-scale geographically weighted regression(MGWR)and geographically and temporally weighted regression(GTWR)models from an eco-hydrological perspective.We discovered that downstream regions,which are more developed,achieved significantly better WC than upstream regions.The results also demonstrated that the influence of temperature and wind speed is consistently dominant and temporally stable due to climate stability,while the influence of vegetation shifted from negative to positive around 2010,likely indicating greater benefits from understory vegetation.Economic growth positively impacted WC in upstream regions but had a negative effect in the more developed downstream regions.These findings highlight the importance of targeted water conservation strategies,including locally appropriate revegetation,optimization of agricultural and economic structures,and the establishment of eco-compensation mechanisms for ecological conservation and sustainable development.
基金The National Natural Science Foundation of China under contract Nos 42406259,42175172,and 41975134the Science Foundation for Youths of Hunan Province(Category C)under contract No.2025JJ60240.
文摘As the Arctic undergoes rapid warming and sea ice continues to decline,Ocean-to-Ice Heat Flux(OIHF)plays a crucial role in regulating sea ice dynamics.This study investigates the seasonal variations in ocean-to-ice heat flux in north of the Fram Strait using the regional Arctic Ocean/sea ice reanalysis product from 1991 to 2020.The analysis reveals that the OIHF exhibits significant seasonal variability,with a pronounced peak during winter in north of the Fram Strait,driven by inflows of Atlantic water.Warm Atlantic water intrusion begins in October,reaches its peak in January and February,and results in a delayed increase in OIHF,with maximum flux observed 2−3 months later.These results highlight the significant role of Atlantic water inflows in influencing Arctic sea ice dynamics and emphasize the need for further investigation into the coupled ocean-atmosphere processes that govern seasonal fluctuations in OIHF.
基金supported by the National Natural Science Foundation of China(No.42327806)the National Key R&D Program of China(No.2022YFC3703500)+4 种基金Zhejiang Province“Lingyan”Research and Development Project(No.2022C03073)Zhejiang Provincial Natural Science Foundation of China(No.LQ23B070009)China Postdoctoral Science Foundation(No.2023M743763)Zhejiang Provincial Postdoctoral Research Excellence Funding Project(No.ZJ2023144)Shaoxing Science and Technology Plan Project(No.2022B41006).
文摘Methane(CH_(4))is the second greenhouse gas and has a profound impact on global climate change due to its high global warming potential and concentration.By 2022,the CH_(4)concentration was approximately 1.9 ppm,which was 264%of the pre-industrial level.The spatiotemporal distribution of CH_(4)was investigated by a portable CH_(4)detector on an unmanned aerial vehicle and electric bicycles in Shaoxing,a city situated in the Yangtze River Delta,China.The vertical distribution revealed CH_(4)concentration generally decreased slowly with height.However,the inversion condition and low atmospheric boundary layer height(ABLH)leaded to the enhancement of CH_(4)with height.The highest CH_(4)concentration(2.2±0.1 ppm,n=1428)was observed in winter and the lowest(2.0±0.2 ppm,n=1530)in spring.Regarding the daily variation,CH_(4)concentration peaked at 5:00 local time(LT)and reached its lowest level at 14:00 LT,which was attributed to the daily variation of ABLH,lowest in the early morning and highest in the noon.In urban areas,CH_(4)concentrations showed higher levels near restaurants,natural gas stations and sewerage well,with a maximum value of 13.1 ppm,which was caused by CH_(4)emission and natural gas leakage from these places.The annual CH_(4)emission in Shaoxing were estimated to be approximately 69 ton/(km^(2)·year)by the mass balance approach.Compared with other cities in the world,the CH_(4)emission is in higher level which imply some control measures should be conducted to reduce CH_(4)emission in Shaoxing.
基金provided by the National Basic Research Program of China (2012CB955403)the National Natural Science Foundation of China (41425002)the National Youth Top-notch Talent Support Program in China
文摘As a major agricultural country, China suffers from severe meteorological drought almost every year.Previous studies have applied a single threshold to identify the onset of drought events, which may cause problems to adequately characterize long-term patterns of droughts.This study analyzes meteorological droughts in China based on a set of daily gridded(0.5° 9 0.5°) precipitation data from 1961 to 2014. By using a multi-threshold run theory approach to evaluate the monthly percentage of precipitation anomalies index(Pa), a drought events sequence was identified at each grid cell. The spatiotemporal variations of drought in China were further investigated based on statistics of the frequency, duration,severity, and intensity of all drought events. Analysis of the results show that China has five distinct meteorological drought-prone regions: the Huang-Huai-Hai Plain, Northeast China, Southwest China, South China coastal region,and Northwest China. Seasonal analysis further indicates that there are evident spatial variations in the seasonal contribution to regional drought. But overall, most contribution to annual drought events in China come from the winter. Decadal variation analysis suggests that most of China's water resource regions have undergone an increase in drought frequency, especially in the Liaohe, Haihe, and Yellow River basins, although drought duration and severity clearly have decreased after the 1960 s.
基金National Natural Science Foundation of China(51379084)National Key R&D Plan(2016YFC0503405)
文摘Guanting Reservoir（GR） is one of the most important water sources for Beijing and neighboring regions.Due to water pollution,it was withdrawn from the system to supply Beijing drinking water;however,after a thorough treatment process,GR was made a reserve water source since 2007.To develop a comprehensive and quantitative analysis of water yield and purification services in the GR watershed,this study selected two time periods：the period when GR was withdrawn from the system supplying local drinking water and the period that it has been designated a reserve water source.The In VEST model was used to evaluate the quantities of water yields,and total nitrogen and total phosphorus outputs from 1995 to 2010 Additionally,the spatiotemporal variations of water yield services and water quality purification services in the GR watershed were analyzed.The results showed that water yield services in the GR watershed first weakened and then became stronger,but weakened overall during the years 1995 to 2010.Water yield capacity in the basin decreased from 1.89×10^9 m3 in 1995 to 1.43×10^9 m3 in 2010（a drop of 24.0% in total）.Water quality purification services also showed the same tendency.Total nitrogen output decreased from 4028.7 t in 1995 to 3611.4 t in 2010,while total phosphorus decreased from 379.7 t in 1995 to 354.0 t in 2010.Nitrogen and phosphorus purification services were enhanced by 10.4% and 6.8%,respectively.Changes in the climate and land use were the main factors which lead to the changes in the water yield service in the GR watershed.Policies intended to protect water resource have matched the varying trends of water quality purification services during different periods.On one hand,the research results provide a foundation to identify key fields for eco-compensation in the Guanting Reservoir basin.On another hand,the ecosystem service value will increase on the basis of eco-compensation criteria through setting the scenarios of returning farmland to forest and ecological protection.This method directly reflects increases in ecosystem service values that have occurred since measures to protect the ecological environment have been implemented.This method is more persuasive and feasible than using eco-compensation criteria based on regional ecosystem service values determined by land use/coverage type.It can provide a new way to assess eco-compensation in the Guanting Reservoir basin and other regions.
文摘Gross primary productivity (GPP) of vegetation is a critical indicator of ecosystem growth and carbon sequestration. The spatiotemporal variation characteristics of land vegetation GPP trends in a specific region of Asia from 2001 to 2020 were analyzed by Sen and MK trend analysis methods in this study .Moreover , a GPP change attribution model was established to explore the driving influences of factors such as Leaf Area Index (LAI), Land Surface Temperature (LST), Vapor Pressure Deficit (VPD), Soil Moisture, Solar Radiation and Wind Speed on GPP. The results indicate that summer GPP values are significantly higher than those in other months, accounting for 60.8% of the annual total GPP;spring and autumn contribute 18.91% and 13.04%, respectively. In winter, due to vegetation being nearly dormant, the contribution is minimal at 7.19%. Spatially, GPP shows a decreasing trend from southeast to northwest. LAI primarily drives the spatial and seasonal variations of regional GPP, while VPD, surface temperature, solar radiation, and soil moisture have varying impacts on GPP across different dimensions. Additionally, wind speed exhibits a minor contribution to GPP across different dimensions.
基金supported by the National Natural Science Foundation of China (Grant Nos. 91528304, 41530964, 91428310 & 41525020)
文摘Sediment components and their fluxes of Cores MD12-3428(water depth: 903 m), MD12-3433(water depth: 2125 m),and MD12-3434(water depth: 2995 m), obtained along a transect on the continental slope of the northern South China Sea, have been conducted to reveal the spatiotemporal variations and the controlling factors of the sediment components and of their fluxes.Results show that deep-sea sediments in the northern South China Sea are composed mainly of terrigenous(59–89%) and carbonate(6–38%) particles, with minor components of opal(1.6–9.4%) and organic matter(0.7–1.9%). Fluxes of terrigenous and carbonate particles reach up to 2.4–21.8 and 0.4–6.5 g cm–2 kyr–1, respectively, values that are one to two orders of magnitude higher than the fluxes of opal and organic matter. Temporal variations of the percentages and fluxes of deep-sea sediment components have displayed clear glacial-interglacial cyclicity since the last glaciation. Terrigenous, opal, and organic matter percentages and their fluxes increas clearly during marine isotope stage 2, while carbonate percentages and fluxes show an opposite variation pattern or are characterized by an unremarkable increase. This implies that deep-sea carbonate in the South China Sea is affected by the dilution of terrigenous inputs during the sea-level lowstand. With increasing water depth along the transect, the terrigenous percentage increases but with largely decreased fluxes. Both the percentage and flux of carbonate decrease, while the percentages and fluxes of opal and organic matter display much more complicated variational features. The spatiotemporal variations of deep-sea sediment components and of their fluxes since the last glaciation in the northern South China Sea are strongly controlled by sea-level fluctuations. Simultaneously, terrigenous supply associated with monsoonal rainfall, marine primary productivity,and the dilution effect between terrigenous and biogenic particles, also play interconnected roles in the sediment accumulation processes.
