Halocarbons play a vital role in ozone depletion and global warming,and are regulated by the Montreal Protocol(MP)and its amendments.China has been identified as an important contributor to the halocarbon emissions,bu...Halocarbons play a vital role in ozone depletion and global warming,and are regulated by the Montreal Protocol(MP)and its amendments.China has been identified as an important contributor to the halocarbon emissions,but the regional sources of halocarbons in China are not yet well comprehended.To investigate the characteristics,emissions,and source profiles,this study conducted a field campaign in Xiamen,a coastal city in southeastern China.Higher enhancements were found in the unregulated halocarbons(CH_(3)Cl,CH_(2)Cl_(2),CHCl_(3))than in the MP eliminated species(CCl_(4),CH_(3)Br)and theMP controlled species(HCFCs,HFCs).Many of the measured halocarbons varied seasonally and regionally,depending on the anthropogenic sources and atmospheric transport.Backward trajectory analysis showed that the air masses from inland were polluted over Shandong,Hebei,and northern Fujian in the cold season,while the air masses fromthe sea in the warm season were clean.Different air masses in two seasons were associated with the halocarbon patterns in the study area.Industrial activities,especially solvent usage,were the primary sources of halocarbons.The emission hot spots in Fujian Province were concentrated in Sanming,Fuzhou,and Xiamen,and the unregulated halocarbons made the largest contribution.This study provides an insight for a deep understanding of the characteristics and potential sources of halocarbons,and for strengthened management of halocarbons in China.展开更多
Marine heatwaves(MHWs)in the East China Sea(ECS),especially those occurring on the ocean bottom(referred to as bottom marine heatwaves,BMHWs),can significantly affect regional ecosystems.However,our understanding of t...Marine heatwaves(MHWs)in the East China Sea(ECS),especially those occurring on the ocean bottom(referred to as bottom marine heatwaves,BMHWs),can significantly affect regional ecosystems.However,our understanding of the seasonal variations in the MHWs in the ECS remains limited.This study investigates the characteristics of MHWs in the ECS in summer and winter using high-resolution oceanic reanalysis.Our analyses reveal distinct spatial patterns of BMHWs in these seasons.During summer,the Taiwan Warm Current plays a crucial role in transporting warm water northward,potentially leading to intense BMHWs on the central ECS shelf.These BMHW events usually occur independently of surface warming due to strong stratification in summer.Conversely,winter BMHWs are more prevalent in coastal regions under the influence of coastal currents and typically feature consistent warming from surface to bottom with a deepened mixed layer.These findings inform the coherent vertical structure and driving mechanisms of MHWs in the ECS,which are essential for predicting and managing these extreme events in the future.展开更多
The distributions and seasonal variations of total dissolved inorganic arsenic （TDIAs, [TDIAs] = [As^5＋]＋[As^3＋]） and arsenite （As3.） in the Yellow Sea and East China Sea are presented hero based on the observa...The distributions and seasonal variations of total dissolved inorganic arsenic （TDIAs, [TDIAs] = [As^5＋]＋[As^3＋]） and arsenite （As3.） in the Yellow Sea and East China Sea are presented hero based on the observations of 9 cruises carried out in 2000 - 2003. The study area covers a broad range of hydrographic and chemical properties. The emphasis is put on a southeast transect from Changjiang Estuary to the Ryukyu Islands （i.e. PN section） in the East China Sea to discuss the impact of terrestdal input on the marginal seas of China. Arsenic species （TDlAs and arsenite） are determined by selective hydride generation - atomic fluorescence spectrometry （HG-AFS）. TDIAs concentrations were high in the coastal area of Changjiang Estuary and decreased slightly towards the shelf region. High concentratiOns of TDIAs were also existed in the near bottom layer of shelf edge of the East China Sea which indicated another source of arsenic from the incursion of Kuroshio Waters. The seasonal variations of TDIAs in the study area depend on the hydrographic stages of Changjiang and the incursion intensity of Kuroshio Waters. Arsenite showed opposite distributions with TDIAs, with higher concentrations appeared at the surface layer of shelf region, which was positive correlated with the chlorophyll a. Biological conversion of arsenate into arsenite was hypothesized for the observed distribution pattern and its seasonal variations. The stoichoimetric ratios of As to P were estimated to be about 2×10^3 at PN Section in summer. The concentrations of dissolved arsenic in the Yellow Sea and East China Sea were comparable with other areas in the world.展开更多
Objective To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. Methods Samples of particulate matters （PM2,5）, PM10, and total suspended p...Objective To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. Methods Samples of particulate matters （PM2,5）, PM10, and total suspended particle （TSP） aerosols were collected simultaneously in Beijing from July 2001 to April 2003. The aerosol was chemically characterized by measuring 23 elements and 18 water-soluble ions by inductively coupled plasma-atomic emission spectroscopy （ICP-AES） and ion chromatography （IC）, respectively. Results The samples were divided into four categories： spring non-dust, spring dust, summer dust, and winter dust. TSP, PM10, and PM2.5 were most abundant in the spring dust, and the least in summer dust. The average mass ratios of PM〉10, PM2,5-10, and PM2.5 to TSP confirmed that in the spring dust both the large coarse （PM〉10） and fine particles （PM2.5） contributed significantly in summer PM2.5, PM2,5-10, and PM〉10 contributed similar fractions to TSP, and in winter much PM2.5. The seasonal variation characteristics of the elements and ions were used to divide them into four groups： crustal, pollutant, mixed, and secondary. The highest levels of crustal elements, such as AI, Fe, and Ca, were found in the dust season, the highest levels of pollutant elements and ions, such as As, F, and Cl^-, were observed in winter, and the highest levels of secondary ions （SO4^2-, NO3^-, and NH4^＋） were seen both in summer and in winter. The mixed group （Eu, Ni, and Cu） showed the characteristics of both crustal and pollutant elements. The mineral aerosol from outside Beijiug contributed more than that from the local part in all the reasons but summer, estimated using a newly developed element tracer technique.展开更多
The seasonal variations of the Asian monsoon were explored by applying the atmospheric general circulation model R42L9 that was developed recently at the State Key Laboratory of Numerical Modeling for At...The seasonal variations of the Asian monsoon were explored by applying the atmospheric general circulation model R42L9 that was developed recently at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG/IAP/CAS). The 20-yr (1979–1998) simulation was done using the prescribed 20-yr monthly SST and sea-ice data as required by Atmospheric Model Intercomparison Project (AMIP) II in the model. The monthly precipitation and monsoon circulations were analyzed and compared with the observations to validate the model’s performance in simulating the climatological mean and seasonal variations of the Asian monsoon. The results show that the model can capture the main features of the spatial distribution and the temporal evolution of precipitation in the Indian and East Asian monsoon areas. The model also reproduced the basic patterns of monsoon circulation. However, some biases exist in this model. The simulation of the heating over the Tibetan Plateau in summer was too strong. The overestimated heating caused a stronger East Asian monsoon and a weaker Indian monsoon than the observations. In the circulation ?elds, the South Asia high was stronger and located over the Tibetan Plateau. The western Paci?c subtropical high was extended westward, which is in accordance with the observational results when the heating over the Tibetan Plateau is stronger. Consequently, the simulated rainfall around this area and in northwest China was heavier than in observations, but in the Indian monsoon area and west Paci?c the rainfall was somewhat de?cient.展开更多
In this study, the diurnal and seasonal variations of CO2 fluxes in a subtropical mixed evergreen forest in Ningxiang of Hunan Province, part of the East Asian monsoon region, were quantified for the first time. The f...In this study, the diurnal and seasonal variations of CO2 fluxes in a subtropical mixed evergreen forest in Ningxiang of Hunan Province, part of the East Asian monsoon region, were quantified for the first time. The fluxes were based on eddy covariance measurements from a newly initiated flux tower. The relationship between the CO2 fluxes and climate factors was also analyzed. The results showed that the target ecosystem appeared to be a clear carbon sink in 2013, with integrated net ecosystem CO2exchange（NEE）, ecosystem respiration（RE）, and gross ecosystem productivity（GEP） of-428.8, 1534.8 and1963.6 g C m^-2yr^-1, respectively. The net carbon uptake（i.e. the-NEE）, RE and GEP showed obvious seasonal variability,and were lower in winter and under drought conditions and higher in the growing season. The minimum NEE occurred on12 June（-7.4 g C m^-2d^-1）, due mainly to strong radiation, adequate moisture, and moderate temperature; while a very low net CO2 uptake occurred in August（9 g C m^-2month^-1）, attributable to extreme summer drought. In addition, the NEE and GEP showed obvious diurnal variability that changed with the seasons. In winter, solar radiation and temperature were the main controlling factors for GEP, while the soil water content and vapor pressure deficit were the controlling factors in summer. Furthermore, the daytime NEE was mainly limited by the water-stress effect under dry and warm atmospheric conditions, rather than by the direct temperature-stress effect.展开更多
Soil water is the key factor that restricts the restoration of the local ecological systems in the Loess Plateau of China.Studying the effects of vegetation types on soil water and its seasonal variation helps to unde...Soil water is the key factor that restricts the restoration of the local ecological systems in the Loess Plateau of China.Studying the effects of vegetation types on soil water and its seasonal variation helps to understand hydrological characteristics and provides insights into the sustainable restoration of vegetation.Therefore,the Caijiachuan watershed was chosen as the research object to investigate the water status of a 0-10 m soil layer under different vegetation types including Pinus tabulaeformis,Robinia pseudoacacia,Platycladus orientalis,apple orchard,natural forestland,farmland and grassland.By comparing the difference between soil water of different land use types and that of grassland during the same period,the seasonal changes of soil water status of different types were judged.The results show that(1)in the 0-10 m soil layer,the largest value of soil water content was in the0.3-0.4 m layer,and the lowest was in the 5.6-5.8 m layer.The depths at which the vegetation cover influenced the soil water were up to 10 m;(2)among summer,fall and spring,the soil water storage wasthe highest in the fall.In addition,the lowest value of relative accumulation was in the fall,which was the period in which the soil water recovered;(3)the soil water in the 0-10 m layer was in a relatively deficient state in the artificial forestlands,apple orchards and native forestlands,while the relative accumulation was in the farmland.In addition,the relative deep soil layers(8-10 m)had more serious deficits in the areas in which P.tabulaeformis,R.pseudoacacia and the apple orchard grew;(4)during the study period,the farmland in the summer had the largest relative accumulation(182.71 mm),and the land under R.pseudoacacia in the fall had the lowest relative deficit(512.20 mm).In the Loess Plateau,vegetation cover will affect the change of deep soil moisture and artificial forest will cause soil water loss in different degrees.展开更多
The seasonal variations of several main water masses in the southern Yellow Sea (SYS) and East China Sea (ECS) in 2011 were analyzed using the in-situ data collected on four cruises.There was something special in the ...The seasonal variations of several main water masses in the southern Yellow Sea (SYS) and East China Sea (ECS) in 2011 were analyzed using the in-situ data collected on four cruises.There was something special in the observations for the Yellow Sea Warm Current (YSWC) ,the Yellow Sea Cold Water Mass (YSCWM) and the Changjiang Diluted Water (CDW) during that year.The YSWC was confirmed to be a seasonal current and its source was closely associated with the Kuroshio onshore intrusion and the northerly wind.It was also found that the YSCWM in the summer of 2011 occupied a more extensive area in comparison with the climatologically-mean case due to the abnormally powerful wind prevailing in the winter of 2010 and decaying gradually thereafter.Resulting from the reduced Changjiang River discharge,the CDW spreading toward the Cheju Island in the summer of 2011 was weaker than the long-term mean and was confined to flow southward in the other seasons.The other water masses seemed normal without noticeable anomalies in 2011.The Yellow Sea Coastal Current (YSCC) water,driven by the northerly wind,flowed southeastward as a whole except for its northeastward surface layer in summer.The Taiwan Warm Current (TWC) was the strongest in summer and the weakest in winter in its northward movement.The Kuroshio water with an enhanced onshore intrusion in autumn was stable in hydrographic features apart from the seasonal variation of its surface layer.展开更多
Size-segregated ambient particulate matter(PM) samples were collected seasonally in suburban Nanjing of east China from 2016 to 2017 and chemically speciated. In both fine(< 2.1μm, PM2.1) and coarse(> 2.1 μm, ...Size-segregated ambient particulate matter(PM) samples were collected seasonally in suburban Nanjing of east China from 2016 to 2017 and chemically speciated. In both fine(< 2.1μm, PM2.1) and coarse(> 2.1 μm, PM>2.1) PM, organic carbon(OC) accounted for the highest fractions(26.9% ± 10.9% and 23.1% ± 9.35%) of all measured species, and NO3-lead in average concentrations of water-soluble inorganic ions(WSIIs). The size distributions of measured components were parameterized using geometric mean diameter(GMD). GMD values of NO_(3)^(-), Cl^(-), OC, and PM for the whole size range varied from < 2.1 μm in winter to > 2.1μm in warm seasons, which was due to the fact that the size distributions of semi-volatile components(e.g., NH4NO3, NH4Cl, and OC) had a dependency on the ambient temperature.Unlike OC, elemental carbon(EC), and elements, NH_(4)^(+), NO_(3)^(-), and SO_(4)^(2-)exhibited an increase trend in GMD values with relative humidity, indicating that the hygroscopic growth might also play a role in driving seasonal changes of PM size distributions. Positive matrix factorization was performed using compositional data of fine and coarse particles, respectively. The secondary formation of inorganic salts contributing to the majority(> 70%) of fine PM and 20.2% ± 19.9% of speciated coarse PM. The remaining coarse PM content was attributed to a variety of dust sources. Considering that coarse and fine PM had comparable mass concentrations, more attention should be paid to local dust emissions in future air quality plans.展开更多
This study was performed at three eutrophic rivers in Southeast China aiming to determine the magnitude and patterns of dissolved N2O concentrations and fluxes over a seasonal （in 2009） and diurnal （24 h） temporal...This study was performed at three eutrophic rivers in Southeast China aiming to determine the magnitude and patterns of dissolved N2O concentrations and fluxes over a seasonal （in 2009） and diurnal （24 h） temporal scale.The results showed that N2O concentrations varied from 0.28 to 0.38 （mean 0.32±0.04）,0.29 to 0.46 （mean 0.37±0.07）,and 2.07 to 3.47 （mean 2.84±0.63） μg N-N2O L-1 in the Fengle,Hangbu and Nanfei rivers,respectively,in the diurnal study performed during the summer of 2008.The study found that mean N2O concentration and estimated N2O flux （67.89 ± 6.71 μg N-N2O m-2 h-1） measured from the Nanfei River with serious urban wastewater pollution was significantly higher than those from the Fengle and the Hangbu Rivers with agricultural runoff.In addition,the seasonal study during June and December of 2009 also showed that the mean N2O concentration （10.59±14.67 μg N-N2O L-1） and flux （236.87±449.74 μg N-N2O m-2 h-1） observed from the Nanfei River were significantly higher than those from the other two rivers.Our study demonstrated both N2O concentrations and fluxes exhibited seasonal and diurnal fluctuations.Over three consecutive days during the summer of 2008,N2O accumulation rates varied within the range of 3.91-7.21,2.76-15.71,and 3.23-30.03 μg N-N2O m-2 h-1 for the Fengle,Hangbu and Nanfei Rivers,respectively,and exponentially decreased with time.展开更多
Based on sediment and discharge flux data for the Yellow River, realistic forcing fields and bathymetry of the Bohai Sea, a suspended sediment transport module is driven by a wave-current coupled model to research sea...Based on sediment and discharge flux data for the Yellow River, realistic forcing fields and bathymetry of the Bohai Sea, a suspended sediment transport module is driven by a wave-current coupled model to research seasonal variations and mechanisms of sus- pended load transport to the Bohai Sea. It could be concluded that surface sediment concentration indicates a distinct spatial distribution characteristic that varies seasonally in the Bohai Sea. Sediment concentration is rather high near the Yellow River estuary, seasonal variations of which are controlled by quantity of sediment from the YeUow River, suspended sediment concentration reaches its maximum during summer and fall. Furthermore, sediment concentration decreases rapidly in other seas far from the Yellow River estuary and maintains a very low level in the center of the Bohai Sea, and is dominated by seasonal variations of climatology wind field in the Bohai Sea. Only a small amount of sediments imported from the Yellow River are delivered northwestward to the southern coast of the Bohai Bay. Majority of sediments are transported southeastward to the Laizhou Bay, where sediments are con- tinuously delivered into the center of the Bohai Sea in a northeastward direction, and part of them are transported eastward alongshore through the Bohai Strait. 69% of sediments from the Yellow River are deposited near the river delta, 31% conveyed seaward, within which, 4% exported to the northern Yellow Sea through the Bohai Strait. Wind wave is the most essential contributor to seasonal variations of sediment concentration in the Bohai Sea, and the contribution of tidal currents is also significant in shallow waters when wind speed is low.展开更多
In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model...In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model was used to study the seasonal variations of vertical profiles of chlorophyll-a(Chl-a) in the SCS. Three parameters(i.e., SCM layer(SCML) depth, thickness, and intensity) were defined to characterize the vertical distribution of Chl-a in SCML and were obtained by fitting the vertical profile of Chl-a in the subsurface layer using a Gaussian function. The seasonal variations of SCMs are reproduced reasonably well compared to the observations. The annual averages of SCML depth, thickness, and intensity are 75 ± 10 m, 31 ± 6.7 m, and 0.37 ± 0.11 mg m-3, respectively. A thick, close to surface SCML together with a higher intensity occurs during the northeastern monsoon. Both the SCML thickness and intensity are sensitive to the changes of surface wind speed in winter and summer, but the surface wind speed exerts a minor influence on the SCML depth; for example, double strengthening of the southwestern monsoon in summer can lead to the thickening of SCML by 46%, the intensity decreasing by 30%, and the shoaling by 6%. This is because part of nutrients are pumped from the upper nutricline to the surface mixed layer by strong vertical mixing. Increasing initial nutrient concentrations by two times will increase the intensity of SCML by over 80% in winter and spring. The sensitivity analysis indicates that light attenuation is critical to the three parameters of SCM. Decreasing background light attenuation by 20% extends the euphotic zone, makes SCML deeper(~20%) and thicker(12% – 41%), and increases the intensity by over 16%. Overall, the depth of SCML is mainly controlled by light attenuation, and the SCML thickness and intensity are closely associated with wind and initial nitrate concentration in the SCS.展开更多
Princeton Ocean Model (POM) is employed to investigate the Taiwan Warm Current (TWC) and its seasonal variations. Results show that the TWC exhibits pronounced seasonal variations in its sources,strength and flow patt...Princeton Ocean Model (POM) is employed to investigate the Taiwan Warm Current (TWC) and its seasonal variations. Results show that the TWC exhibits pronounced seasonal variations in its sources,strength and flow patterns. In summer, the TWC flows northeast in straight way and reaches around 32°N; it comes mainly from the Taiwan Strait, while its lower part is from the shelf-intrusion of the Kuroshio subsurface water (KSSW). In winter, coming mainly from the shelf-intrusion of the Kuroshio northeast of Taiwan, the TWC flows northward in a winding way and reaches up around 30°N. The Kuroshio intrusion also has distinct seasonal patterns. The shelf-intrusion of KSSW by upwelling is almost the same in four seasons with a little difference in strength; it is a persistent source of the TWC. However, Kuroshio surface water (KSW) can not intrude onto the shelf in summer, while in winter the intrusion of KSW always occurs. Additional experiments were conducted to examine effects of winds and transport through the Taiwan Strait on the TWC. In winter, northerly winds enhance the shelf-intrusion of the Kuroshio and spread northward, but hamper the northward inflow from the Taiwan Strait. In summer, the effect of the winds is confined in the surface layer, and less obvious than that of winter. Transport through the Taiwan Strait influences the TWC significantly. With the Taiwan Strait closed in the simulation, the TWC would be dramatically weakened.展开更多
Developed regions of the world represent a major atmospheric methane(CH_4) source,but these regional emissions remain poorly constrained.The Yangtze River Delta(YRD) region of China is densely populated(about 16% of C...Developed regions of the world represent a major atmospheric methane(CH_4) source,but these regional emissions remain poorly constrained.The Yangtze River Delta(YRD) region of China is densely populated(about 16% of China's total population) and consists of large anthropogenic and natural CH_4 sources.Here,atmospheric CH_4 concentrations measured at a 70-m tall tower in the YRD are combined with a scale factor Bayesian inverse(SFBI) modeling approach to constrain seasonal variations in CH_4 emissions.Results indicate that in 2018 agricultural soils(AGS,rice production) were the main driver of seasonal variability in atmospheric CH_4 concentration.There was an underestimation of emissions from AGS in the a priori inventories(EDGAR—Emissions Database for Global Atmospheric Research v432 or v50),especially during the growing seasons.Posteriori CH_4 emissions from AGS accounted for 39%(4.58 Tg,EDGAR v432) to 47%(5.21 Tg,EDGAR v50) of the total CH_4 emissions.The posteriori natural emissions(including wetlands and water bodies) were1.21 Tg and 1.06 Tg,accounting for 10.1%(EDGAR v432) and 9.5%(EDGAR v50) of total emissions in the YRD in2018.Results show that the dominant factor for seasonal variations in atmospheric concentration in the YRD was AGS,followed by natural sources.In summer,AGS contributed 42%(EDGAR v432) to 64%(EDGAR v50) of the CH_4 concentration enhancement while natural sources only contributed about 10%(EDGAR v50) to 15%(EDGAR v432).In addition,the newer version of the EDGAR product(EDGAR v50) provided more reasonable seasonal distribution of CH_4 emissions from rice cultivation than the old version(EDGAR v432).展开更多
Estuarine wetland is the transitional interface linking terrestrial with marine ecosystems,and wetland microbes are crucial to the biogeochemical cycles of nutrients.The soil samples were collected in four seasons(spr...Estuarine wetland is the transitional interface linking terrestrial with marine ecosystems,and wetland microbes are crucial to the biogeochemical cycles of nutrients.The soil samples were collected in four seasons(spring,S1;summer,S2;autumn,S3;and winter,S4)from Suaeda wetland of Shuangtaizi River estuary,Northeast China,and the variations of bacterial community were evaluated by high-throughput sequencing.Soil properties presented a significant seasonal change,including p H,carbon(C)and total nitrogen(TN),and the microbial diversity,richness and structure also differed with seasons.Canonical correspondence analysis(CCA)and Mantel tests implied that soil p H,C and TN were the key factors structuring the microbial community.Gillisia(belonging to Bacteroidetes)and Woeseia(affiliating with Gammaproteobacteria)were the two primary components in the rhizosphere soils,displaying opposite variations with seasons.Based on PICRUSt(Phylogenetic Investigation of Communities by Reconstruction of Unobserved States)prediction,the xenobiotics biodegradation related genes exhibited a seasonal decline,while the majority of biomarker genes involved in nitrogen cycle showed an ascending trend.These findings could advance the understanding of rhizosphere microbiota of Suaeda in estuarine wetland.展开更多
This study aimed to discuss the energy budget of Elliot's pheasant Syrmaticus ellioti in different seasons, with life and health, good growth and normal digestion of Elliot's pheasant as the tested objects, Th...This study aimed to discuss the energy budget of Elliot's pheasant Syrmaticus ellioti in different seasons, with life and health, good growth and normal digestion of Elliot's pheasant as the tested objects, The energy budget of Elliot's pheasant was measured by daily collection of the trial pheasants' excrement in the biological garden of Guangxi Normal University from March 2011 to February 2012. The results showed that the gross energy consumption, metabolic energy and excrement energy varied by season, increasing as temperature decreased. There was significant difference in gross energy consumption, metabolic energy, excrement energy between adults and nonages. There was also a trend that food digestibility of pheasants increases as temperature increases. In the same season, the food digestibility of adults was better than that of nonages. Throughout spring, summer, autumn and winter, the metabolic energy of 4-year adults were 305.77±13.40 kJ/d, 263.67±11.89 kJ/d, 357.23±25.49 kJ/d and 403.12±24.91 kJ/d, respectively, and the nonages were 284.86±17.22 kJ/d, 284. 66±15.16 kJ/d, 402. 26±31.46 kJ/d and 420. 30±31.98 kJ/d, respectively. The minimum metabolic energies were 247.65±21.81 g, 265.86±26.53 g, respectively for each group, detected between 4-year adults and 1-year nonages. Further study is needed to determine whether 29.6 C is the optimal temperature for the Elliot's pheasant.展开更多
Data on aerosol optical thickness(AOT) and single scattering albedo(SSA) derived from Moderate Resolution Imaging Spectrometer(MODIS) and Ozone Monitoring Instrument(OMI) measurements,respectively,are used jointly to ...Data on aerosol optical thickness(AOT) and single scattering albedo(SSA) derived from Moderate Resolution Imaging Spectrometer(MODIS) and Ozone Monitoring Instrument(OMI) measurements,respectively,are used jointly to examine the seasonal variations of aerosols over East Asia.The seasonal signals of the total AOT are well defined and nearly similar over the land and over the ocean.These findings indicate a natural cycle of aerosols that originate primarily from natural emissions. In contrast,the small-sized aerosols represented by the fine-mode AOT,which are primarily generated over the land by human activities,do not have evident seasonalscale fluctuations.A persistent maximum of aerosol loadings centered over the Sichuan basin is associated with considerable amounts of fine-mode aerosols throughout the year.Most regions exhibit a general spring maximum. During the summer,however,the aerosol loadings are the most marked over north central China.This occurrence may result from anthropogenic fine particles,such as sulfate and nitrate.Four typical regions were selected to perform a covariation analysis of the monthly gridded AOT and SSA.Over southwestern and southeastern China,if the aerosol loadings are small to moderate they are composed primarily of the highly absorptive aerosols. However,more substantial aerosol loadings probably represent less-absorptive aerosols.The opposite covariation pattern occurring over the coastal-adjacent oceans suggests that the polluted oceanic atmosphere is closely correlated with the windward terrestrial aerosols.North central China is strongly affected by dust aerosols that show moderate absorption.This finding may explain the lower variability in the SSA that accompanies increasing aerosol loadings in this region.展开更多
Using a net surface heat flux （Qnet） product obtained from the objectively analyzed air-sea fluxes （OAFlux） project and the international satellite cloud climatology project （ISCCP）, and temperature from the sim...Using a net surface heat flux （Qnet） product obtained from the objectively analyzed air-sea fluxes （OAFlux） project and the international satellite cloud climatology project （ISCCP）, and temperature from the simple ocean data assimilation （SODA）, the seasonal variations of the air-sea heat fluxes in the northwestern Pa cific marginal seas （NPMS） and their roles in sea surface temperature （SST） seasonality are studied. The seasonal variations of Qnet, which is generally determined by the seasonal cycle of latent heat flux （LH）, are in response to the advection-induced changes of SST over the Kuroshio and its extension. Two dynamic regimes are identified in the NPMS： one is the area along the Kuroshio and its extension, and the other is the area outside the Kuroshio. The oceanic thermal advection dominates the variations of SST and hence the sea-air humidity plays a primary role and explains the maximum heat losing along the Kuroshio. The heat transported by the Kuroshio leads to a longer period of heat losing over the Kuroshio and its Extension. Positive anomaly of heat content corresponds with the maximum heat loss along the Kuroshio. The oceanic advection controls the variations of heat content and hence the surface heat flux. This study will help us understand the mechanism controlling variations of the coupled ocean-atmosphere system in the NPMS. In the Kuroshio region, the ocean current controls the ocean temperature along the main stream of the Ku roshio, and at the same time, forces the air-sea fluxes.展开更多
To study seasonal and intraseasonal variations of the Taiwan Warm Current (TWC) in detail,Rotated Empirical Orthogonal Function (REOF) and Extended Associate Pattern Analysis (EAPA) are jointly adopted with daily sea ...To study seasonal and intraseasonal variations of the Taiwan Warm Current (TWC) in detail,Rotated Empirical Orthogonal Function (REOF) and Extended Associate Pattern Analysis (EAPA) are jointly adopted with daily sea surface salinity (SSS), sea surface temperature (SST) and sea surface height (SSH)datasets covering 1126 days from American Navy Experimental Real-Time East Asian Seas Ocean Nowcast System in the present paper. Results show that the first and second REOFs of SST in the southern East China Sea(SECS) account for 50,8% and 39.8% of the total variance. The surface TWC contains persistent (multi-year mean), seasonal and intraseasonal components. The persistent one mainly inosculates with the Kuroshio but the seasonal and intraseasonal ones are usually active only on the continental shelf. Its persistent component is produced by inertial flow of the Kuroshio, however its seasonal and intraseasonal ones seems coming from seasonal and intraseasonal oscillations of monsoon force. The seasonal one reaches its maximum in late summer,lasting about four months and the intraseasonal one takes place at any seasons, lasting more than 40 days.展开更多
Water samples were collected in the coastal area of the Changjiang Estuary on four cruises from August 2002 to May 2003. The seasonal variations of dissolved inorganic arsenic （DIAs） distributions were analyzed. The...Water samples were collected in the coastal area of the Changjiang Estuary on four cruises from August 2002 to May 2003. The seasonal variations of dissolved inorganic arsenic （DIAs） distributions were analyzed. The results showed that the distributions of DIAs were mainly influenced by Water （KSSW）. The concentration of the total dissolved the terrestrial input and the intrusion of the Kuroshio Subsurface inorganic arsenic （TDIAs） decreased consecutively from winter to summer, while it increased in autumn. The distributions of TDIAs showed some relationships with salinity and suspended particulate matter （SPM）. The relationships between DIAs speciation （including arsenite [ As（ Ⅲ ） ] and arsenate [ As（ Ⅴ ） ]）, biological activity and the availabilities of the phosphate were investigated in the study area for the cruise August 2002. The ratio of As （Ⅲ）/TDIAs increased with the decrease of phosphate concentrations. In the bottom water, the As（ Ⅲ ）/TDIAs ratio decreased with the increasing of N/P. The concentration of TDIAs decreased 28.7% approximately after the occurrence of harmful algal blooms （HAB） because of the uptake of arsenate by algae. Further study is needed about the arsenic source/sink relationships in their vertical or horizontal profiles and the uptake mechanism during the occurrence of harmful algal blooms.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42030707,72394404)the International Partnership Program of the Chinese Academy of Sciences(No.121311KYSB20190029)the Fundamental Research Fund for the Central Universities(Nos.20720210083,20720210082).
文摘Halocarbons play a vital role in ozone depletion and global warming,and are regulated by the Montreal Protocol(MP)and its amendments.China has been identified as an important contributor to the halocarbon emissions,but the regional sources of halocarbons in China are not yet well comprehended.To investigate the characteristics,emissions,and source profiles,this study conducted a field campaign in Xiamen,a coastal city in southeastern China.Higher enhancements were found in the unregulated halocarbons(CH_(3)Cl,CH_(2)Cl_(2),CHCl_(3))than in the MP eliminated species(CCl_(4),CH_(3)Br)and theMP controlled species(HCFCs,HFCs).Many of the measured halocarbons varied seasonally and regionally,depending on the anthropogenic sources and atmospheric transport.Backward trajectory analysis showed that the air masses from inland were polluted over Shandong,Hebei,and northern Fujian in the cold season,while the air masses fromthe sea in the warm season were clean.Different air masses in two seasons were associated with the halocarbon patterns in the study area.Industrial activities,especially solvent usage,were the primary sources of halocarbons.The emission hot spots in Fujian Province were concentrated in Sanming,Fuzhou,and Xiamen,and the unregulated halocarbons made the largest contribution.This study provides an insight for a deep understanding of the characteristics and potential sources of halocarbons,and for strengthened management of halocarbons in China.
基金The National Natural Science Foundation of China under contract No.42030410the Laoshan Laboratory under contract Nos LSKJ202202404 and LSKJ202202403+2 种基金the Startup Foundation for Introducing Talent of Nanjing University of Information Science and TechnologyJiangsu Innovation Research Group under contract No.JSSCTD202346Jiangsu Funding Program for Excellent Postdoctoral Talent under contract No.2023ZB690。
文摘Marine heatwaves(MHWs)in the East China Sea(ECS),especially those occurring on the ocean bottom(referred to as bottom marine heatwaves,BMHWs),can significantly affect regional ecosystems.However,our understanding of the seasonal variations in the MHWs in the ECS remains limited.This study investigates the characteristics of MHWs in the ECS in summer and winter using high-resolution oceanic reanalysis.Our analyses reveal distinct spatial patterns of BMHWs in these seasons.During summer,the Taiwan Warm Current plays a crucial role in transporting warm water northward,potentially leading to intense BMHWs on the central ECS shelf.These BMHW events usually occur independently of surface warming due to strong stratification in summer.Conversely,winter BMHWs are more prevalent in coastal regions under the influence of coastal currents and typically feature consistent warming from surface to bottom with a deepened mixed layer.These findings inform the coherent vertical structure and driving mechanisms of MHWs in the ECS,which are essential for predicting and managing these extreme events in the future.
基金funded by National Science Foundation of China (No. 40606028)National Basic Research Programs of China (No. 2006CB400601and 2001CB409703)
文摘The distributions and seasonal variations of total dissolved inorganic arsenic （TDIAs, [TDIAs] = [As^5＋]＋[As^3＋]） and arsenite （As3.） in the Yellow Sea and East China Sea are presented hero based on the observations of 9 cruises carried out in 2000 - 2003. The study area covers a broad range of hydrographic and chemical properties. The emphasis is put on a southeast transect from Changjiang Estuary to the Ryukyu Islands （i.e. PN section） in the East China Sea to discuss the impact of terrestdal input on the marginal seas of China. Arsenic species （TDlAs and arsenite） are determined by selective hydride generation - atomic fluorescence spectrometry （HG-AFS）. TDIAs concentrations were high in the coastal area of Changjiang Estuary and decreased slightly towards the shelf region. High concentratiOns of TDIAs were also existed in the near bottom layer of shelf edge of the East China Sea which indicated another source of arsenic from the incursion of Kuroshio Waters. The seasonal variations of TDIAs in the study area depend on the hydrographic stages of Changjiang and the incursion intensity of Kuroshio Waters. Arsenite showed opposite distributions with TDIAs, with higher concentrations appeared at the surface layer of shelf region, which was positive correlated with the chlorophyll a. Biological conversion of arsenate into arsenite was hypothesized for the observed distribution pattern and its seasonal variations. The stoichoimetric ratios of As to P were estimated to be about 2×10^3 at PN Section in summer. The concentrations of dissolved arsenic in the Yellow Sea and East China Sea were comparable with other areas in the world.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29837190, 30230310, 20077004, and 20477004),and Beijing Natural Science Foundation (Grant No. 8991002 and 8041003).
文摘Objective To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. Methods Samples of particulate matters （PM2,5）, PM10, and total suspended particle （TSP） aerosols were collected simultaneously in Beijing from July 2001 to April 2003. The aerosol was chemically characterized by measuring 23 elements and 18 water-soluble ions by inductively coupled plasma-atomic emission spectroscopy （ICP-AES） and ion chromatography （IC）, respectively. Results The samples were divided into four categories： spring non-dust, spring dust, summer dust, and winter dust. TSP, PM10, and PM2.5 were most abundant in the spring dust, and the least in summer dust. The average mass ratios of PM〉10, PM2,5-10, and PM2.5 to TSP confirmed that in the spring dust both the large coarse （PM〉10） and fine particles （PM2.5） contributed significantly in summer PM2.5, PM2,5-10, and PM〉10 contributed similar fractions to TSP, and in winter much PM2.5. The seasonal variation characteristics of the elements and ions were used to divide them into four groups： crustal, pollutant, mixed, and secondary. The highest levels of crustal elements, such as AI, Fe, and Ca, were found in the dust season, the highest levels of pollutant elements and ions, such as As, F, and Cl^-, were observed in winter, and the highest levels of secondary ions （SO4^2-, NO3^-, and NH4^＋） were seen both in summer and in winter. The mixed group （Eu, Ni, and Cu） showed the characteristics of both crustal and pollutant elements. The mineral aerosol from outside Beijiug contributed more than that from the local part in all the reasons but summer, estimated using a newly developed element tracer technique.
文摘The seasonal variations of the Asian monsoon were explored by applying the atmospheric general circulation model R42L9 that was developed recently at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG/IAP/CAS). The 20-yr (1979–1998) simulation was done using the prescribed 20-yr monthly SST and sea-ice data as required by Atmospheric Model Intercomparison Project (AMIP) II in the model. The monthly precipitation and monsoon circulations were analyzed and compared with the observations to validate the model’s performance in simulating the climatological mean and seasonal variations of the Asian monsoon. The results show that the model can capture the main features of the spatial distribution and the temporal evolution of precipitation in the Indian and East Asian monsoon areas. The model also reproduced the basic patterns of monsoon circulation. However, some biases exist in this model. The simulation of the heating over the Tibetan Plateau in summer was too strong. The overestimated heating caused a stronger East Asian monsoon and a weaker Indian monsoon than the observations. In the circulation ?elds, the South Asia high was stronger and located over the Tibetan Plateau. The western Paci?c subtropical high was extended westward, which is in accordance with the observational results when the heating over the Tibetan Plateau is stronger. Consequently, the simulated rainfall around this area and in northwest China was heavier than in observations, but in the Indian monsoon area and west Paci?c the rainfall was somewhat de?cient.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41305066 and 91125016)the Special Funds for Public Welfare of China (Grant No. GYHY201306045)
文摘In this study, the diurnal and seasonal variations of CO2 fluxes in a subtropical mixed evergreen forest in Ningxiang of Hunan Province, part of the East Asian monsoon region, were quantified for the first time. The fluxes were based on eddy covariance measurements from a newly initiated flux tower. The relationship between the CO2 fluxes and climate factors was also analyzed. The results showed that the target ecosystem appeared to be a clear carbon sink in 2013, with integrated net ecosystem CO2exchange（NEE）, ecosystem respiration（RE）, and gross ecosystem productivity（GEP） of-428.8, 1534.8 and1963.6 g C m^-2yr^-1, respectively. The net carbon uptake（i.e. the-NEE）, RE and GEP showed obvious seasonal variability,and were lower in winter and under drought conditions and higher in the growing season. The minimum NEE occurred on12 June（-7.4 g C m^-2d^-1）, due mainly to strong radiation, adequate moisture, and moderate temperature; while a very low net CO2 uptake occurred in August（9 g C m^-2month^-1）, attributable to extreme summer drought. In addition, the NEE and GEP showed obvious diurnal variability that changed with the seasons. In winter, solar radiation and temperature were the main controlling factors for GEP, while the soil water content and vapor pressure deficit were the controlling factors in summer. Furthermore, the daytime NEE was mainly limited by the water-stress effect under dry and warm atmospheric conditions, rather than by the direct temperature-stress effect.
基金funded by the National Key Research and Development Program of China(2016YFC0501704)the Major Science and Technology Program for Water Pollution Control and Treatment(2017ZX07102-001)。
文摘Soil water is the key factor that restricts the restoration of the local ecological systems in the Loess Plateau of China.Studying the effects of vegetation types on soil water and its seasonal variation helps to understand hydrological characteristics and provides insights into the sustainable restoration of vegetation.Therefore,the Caijiachuan watershed was chosen as the research object to investigate the water status of a 0-10 m soil layer under different vegetation types including Pinus tabulaeformis,Robinia pseudoacacia,Platycladus orientalis,apple orchard,natural forestland,farmland and grassland.By comparing the difference between soil water of different land use types and that of grassland during the same period,the seasonal changes of soil water status of different types were judged.The results show that(1)in the 0-10 m soil layer,the largest value of soil water content was in the0.3-0.4 m layer,and the lowest was in the 5.6-5.8 m layer.The depths at which the vegetation cover influenced the soil water were up to 10 m;(2)among summer,fall and spring,the soil water storage wasthe highest in the fall.In addition,the lowest value of relative accumulation was in the fall,which was the period in which the soil water recovered;(3)the soil water in the 0-10 m layer was in a relatively deficient state in the artificial forestlands,apple orchards and native forestlands,while the relative accumulation was in the farmland.In addition,the relative deep soil layers(8-10 m)had more serious deficits in the areas in which P.tabulaeformis,R.pseudoacacia and the apple orchard grew;(4)during the study period,the farmland in the summer had the largest relative accumulation(182.71 mm),and the land under R.pseudoacacia in the fall had the lowest relative deficit(512.20 mm).In the Loess Plateau,vegetation cover will affect the change of deep soil moisture and artificial forest will cause soil water loss in different degrees.
基金supported by National Basic Research Program of China(973 Program,2010CB428904)
文摘The seasonal variations of several main water masses in the southern Yellow Sea (SYS) and East China Sea (ECS) in 2011 were analyzed using the in-situ data collected on four cruises.There was something special in the observations for the Yellow Sea Warm Current (YSWC) ,the Yellow Sea Cold Water Mass (YSCWM) and the Changjiang Diluted Water (CDW) during that year.The YSWC was confirmed to be a seasonal current and its source was closely associated with the Kuroshio onshore intrusion and the northerly wind.It was also found that the YSCWM in the summer of 2011 occupied a more extensive area in comparison with the climatologically-mean case due to the abnormally powerful wind prevailing in the winter of 2010 and decaying gradually thereafter.Resulting from the reduced Changjiang River discharge,the CDW spreading toward the Cheju Island in the summer of 2011 was weaker than the long-term mean and was confined to flow southward in the other seasons.The other water masses seemed normal without noticeable anomalies in 2011.The Yellow Sea Coastal Current (YSCC) water,driven by the northerly wind,flowed southeastward as a whole except for its northeastward surface layer in summer.The Taiwan Warm Current (TWC) was the strongest in summer and the weakest in winter in its northward movement.The Kuroshio water with an enhanced onshore intrusion in autumn was stable in hydrographic features apart from the seasonal variation of its surface layer.
基金supported by the National Key Research and Development Program of China (No. 2016YFC0208504)the National Natural Science Foundation of China (Nos. 42177211, 41701551)。
文摘Size-segregated ambient particulate matter(PM) samples were collected seasonally in suburban Nanjing of east China from 2016 to 2017 and chemically speciated. In both fine(< 2.1μm, PM2.1) and coarse(> 2.1 μm, PM>2.1) PM, organic carbon(OC) accounted for the highest fractions(26.9% ± 10.9% and 23.1% ± 9.35%) of all measured species, and NO3-lead in average concentrations of water-soluble inorganic ions(WSIIs). The size distributions of measured components were parameterized using geometric mean diameter(GMD). GMD values of NO_(3)^(-), Cl^(-), OC, and PM for the whole size range varied from < 2.1 μm in winter to > 2.1μm in warm seasons, which was due to the fact that the size distributions of semi-volatile components(e.g., NH4NO3, NH4Cl, and OC) had a dependency on the ambient temperature.Unlike OC, elemental carbon(EC), and elements, NH_(4)^(+), NO_(3)^(-), and SO_(4)^(2-)exhibited an increase trend in GMD values with relative humidity, indicating that the hygroscopic growth might also play a role in driving seasonal changes of PM size distributions. Positive matrix factorization was performed using compositional data of fine and coarse particles, respectively. The secondary formation of inorganic salts contributing to the majority(> 70%) of fine PM and 20.2% ± 19.9% of speciated coarse PM. The remaining coarse PM content was attributed to a variety of dust sources. Considering that coarse and fine PM had comparable mass concentrations, more attention should be paid to local dust emissions in future air quality plans.
基金National Natural Science Foundation of China, No.20777073 Acknowledgements The authors would like to thank Sun Pu of Anhui Hydrological Bureau for the help of sampling in the field.
文摘This study was performed at three eutrophic rivers in Southeast China aiming to determine the magnitude and patterns of dissolved N2O concentrations and fluxes over a seasonal （in 2009） and diurnal （24 h） temporal scale.The results showed that N2O concentrations varied from 0.28 to 0.38 （mean 0.32±0.04）,0.29 to 0.46 （mean 0.37±0.07）,and 2.07 to 3.47 （mean 2.84±0.63） μg N-N2O L-1 in the Fengle,Hangbu and Nanfei rivers,respectively,in the diurnal study performed during the summer of 2008.The study found that mean N2O concentration and estimated N2O flux （67.89 ± 6.71 μg N-N2O m-2 h-1） measured from the Nanfei River with serious urban wastewater pollution was significantly higher than those from the Fengle and the Hangbu Rivers with agricultural runoff.In addition,the seasonal study during June and December of 2009 also showed that the mean N2O concentration （10.59±14.67 μg N-N2O L-1） and flux （236.87±449.74 μg N-N2O m-2 h-1） observed from the Nanfei River were significantly higher than those from the other two rivers.Our study demonstrated both N2O concentrations and fluxes exhibited seasonal and diurnal fluctuations.Over three consecutive days during the summer of 2008,N2O accumulation rates varied within the range of 3.91-7.21,2.76-15.71,and 3.23-30.03 μg N-N2O m-2 h-1 for the Fengle,Hangbu and Nanfei Rivers,respectively,and exponentially decreased with time.
基金National Natural Science Foundation of China, No.40771030 No.40571020
文摘Based on sediment and discharge flux data for the Yellow River, realistic forcing fields and bathymetry of the Bohai Sea, a suspended sediment transport module is driven by a wave-current coupled model to research seasonal variations and mechanisms of sus- pended load transport to the Bohai Sea. It could be concluded that surface sediment concentration indicates a distinct spatial distribution characteristic that varies seasonally in the Bohai Sea. Sediment concentration is rather high near the Yellow River estuary, seasonal variations of which are controlled by quantity of sediment from the YeUow River, suspended sediment concentration reaches its maximum during summer and fall. Furthermore, sediment concentration decreases rapidly in other seas far from the Yellow River estuary and maintains a very low level in the center of the Bohai Sea, and is dominated by seasonal variations of climatology wind field in the Bohai Sea. Only a small amount of sediments imported from the Yellow River are delivered northwestward to the southern coast of the Bohai Bay. Majority of sediments are transported southeastward to the Laizhou Bay, where sediments are con- tinuously delivered into the center of the Bohai Sea in a northeastward direction, and part of them are transported eastward alongshore through the Bohai Strait. 69% of sediments from the Yellow River are deposited near the river delta, 31% conveyed seaward, within which, 4% exported to the northern Yellow Sea through the Bohai Strait. Wind wave is the most essential contributor to seasonal variations of sediment concentration in the Bohai Sea, and the contribution of tidal currents is also significant in shallow waters when wind speed is low.
基金supported by the National Natural Science Foundation of China (Nos. 41106007, 41210008)the China Postdoctoral Science Foundation (No. 2013M 541958)the International Cooperation Project of China (No. 2010DFA91350)
文摘In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model was used to study the seasonal variations of vertical profiles of chlorophyll-a(Chl-a) in the SCS. Three parameters(i.e., SCM layer(SCML) depth, thickness, and intensity) were defined to characterize the vertical distribution of Chl-a in SCML and were obtained by fitting the vertical profile of Chl-a in the subsurface layer using a Gaussian function. The seasonal variations of SCMs are reproduced reasonably well compared to the observations. The annual averages of SCML depth, thickness, and intensity are 75 ± 10 m, 31 ± 6.7 m, and 0.37 ± 0.11 mg m-3, respectively. A thick, close to surface SCML together with a higher intensity occurs during the northeastern monsoon. Both the SCML thickness and intensity are sensitive to the changes of surface wind speed in winter and summer, but the surface wind speed exerts a minor influence on the SCML depth; for example, double strengthening of the southwestern monsoon in summer can lead to the thickening of SCML by 46%, the intensity decreasing by 30%, and the shoaling by 6%. This is because part of nutrients are pumped from the upper nutricline to the surface mixed layer by strong vertical mixing. Increasing initial nutrient concentrations by two times will increase the intensity of SCML by over 80% in winter and spring. The sensitivity analysis indicates that light attenuation is critical to the three parameters of SCM. Decreasing background light attenuation by 20% extends the euphotic zone, makes SCML deeper(~20%) and thicker(12% – 41%), and increases the intensity by over 16%. Overall, the depth of SCML is mainly controlled by light attenuation, and the SCML thickness and intensity are closely associated with wind and initial nitrate concentration in the SCS.
文摘Princeton Ocean Model (POM) is employed to investigate the Taiwan Warm Current (TWC) and its seasonal variations. Results show that the TWC exhibits pronounced seasonal variations in its sources,strength and flow patterns. In summer, the TWC flows northeast in straight way and reaches around 32°N; it comes mainly from the Taiwan Strait, while its lower part is from the shelf-intrusion of the Kuroshio subsurface water (KSSW). In winter, coming mainly from the shelf-intrusion of the Kuroshio northeast of Taiwan, the TWC flows northward in a winding way and reaches up around 30°N. The Kuroshio intrusion also has distinct seasonal patterns. The shelf-intrusion of KSSW by upwelling is almost the same in four seasons with a little difference in strength; it is a persistent source of the TWC. However, Kuroshio surface water (KSW) can not intrude onto the shelf in summer, while in winter the intrusion of KSW always occurs. Additional experiments were conducted to examine effects of winds and transport through the Taiwan Strait on the TWC. In winter, northerly winds enhance the shelf-intrusion of the Kuroshio and spread northward, but hamper the northward inflow from the Taiwan Strait. In summer, the effect of the winds is confined in the surface layer, and less obvious than that of winter. Transport through the Taiwan Strait influences the TWC significantly. With the Taiwan Strait closed in the simulation, the TWC would be dramatically weakened.
基金supported by the National Key R&D Program of China (Grant Nos.2020YFA0607501 and 2019YFA0607202 to WX)the Natural Science Foundation of Jiangsu Province (Grant No.BK20200802 to CH)the Key Laboratory of Meteorology and Ecological Environment of Hebei Province (Grant No.Z201901H to WX)。
文摘Developed regions of the world represent a major atmospheric methane(CH_4) source,but these regional emissions remain poorly constrained.The Yangtze River Delta(YRD) region of China is densely populated(about 16% of China's total population) and consists of large anthropogenic and natural CH_4 sources.Here,atmospheric CH_4 concentrations measured at a 70-m tall tower in the YRD are combined with a scale factor Bayesian inverse(SFBI) modeling approach to constrain seasonal variations in CH_4 emissions.Results indicate that in 2018 agricultural soils(AGS,rice production) were the main driver of seasonal variability in atmospheric CH_4 concentration.There was an underestimation of emissions from AGS in the a priori inventories(EDGAR—Emissions Database for Global Atmospheric Research v432 or v50),especially during the growing seasons.Posteriori CH_4 emissions from AGS accounted for 39%(4.58 Tg,EDGAR v432) to 47%(5.21 Tg,EDGAR v50) of the total CH_4 emissions.The posteriori natural emissions(including wetlands and water bodies) were1.21 Tg and 1.06 Tg,accounting for 10.1%(EDGAR v432) and 9.5%(EDGAR v50) of total emissions in the YRD in2018.Results show that the dominant factor for seasonal variations in atmospheric concentration in the YRD was AGS,followed by natural sources.In summer,AGS contributed 42%(EDGAR v432) to 64%(EDGAR v50) of the CH_4 concentration enhancement while natural sources only contributed about 10%(EDGAR v50) to 15%(EDGAR v432).In addition,the newer version of the EDGAR product(EDGAR v50) provided more reasonable seasonal distribution of CH_4 emissions from rice cultivation than the old version(EDGAR v432).
基金supported by the National Natural Science Foundation of China(Nos.31970107,51508068)the Fundamental Research Funds for the Central Universities(No.DUT19JC17)support from the Undergraduate Innovation and En-trepreneurship Training Program in Dalian University of Technology。
文摘Estuarine wetland is the transitional interface linking terrestrial with marine ecosystems,and wetland microbes are crucial to the biogeochemical cycles of nutrients.The soil samples were collected in four seasons(spring,S1;summer,S2;autumn,S3;and winter,S4)from Suaeda wetland of Shuangtaizi River estuary,Northeast China,and the variations of bacterial community were evaluated by high-throughput sequencing.Soil properties presented a significant seasonal change,including p H,carbon(C)and total nitrogen(TN),and the microbial diversity,richness and structure also differed with seasons.Canonical correspondence analysis(CCA)and Mantel tests implied that soil p H,C and TN were the key factors structuring the microbial community.Gillisia(belonging to Bacteroidetes)and Woeseia(affiliating with Gammaproteobacteria)were the two primary components in the rhizosphere soils,displaying opposite variations with seasons.Based on PICRUSt(Phylogenetic Investigation of Communities by Reconstruction of Unobserved States)prediction,the xenobiotics biodegradation related genes exhibited a seasonal decline,while the majority of biomarker genes involved in nitrogen cycle showed an ascending trend.These findings could advance the understanding of rhizosphere microbiota of Suaeda in estuarine wetland.
基金National Natural Science Foundation of China(31160426 30560023)the Projects of Science and Technology Office of Hunan (2011FJ3071)
文摘This study aimed to discuss the energy budget of Elliot's pheasant Syrmaticus ellioti in different seasons, with life and health, good growth and normal digestion of Elliot's pheasant as the tested objects, The energy budget of Elliot's pheasant was measured by daily collection of the trial pheasants' excrement in the biological garden of Guangxi Normal University from March 2011 to February 2012. The results showed that the gross energy consumption, metabolic energy and excrement energy varied by season, increasing as temperature decreased. There was significant difference in gross energy consumption, metabolic energy, excrement energy between adults and nonages. There was also a trend that food digestibility of pheasants increases as temperature increases. In the same season, the food digestibility of adults was better than that of nonages. Throughout spring, summer, autumn and winter, the metabolic energy of 4-year adults were 305.77±13.40 kJ/d, 263.67±11.89 kJ/d, 357.23±25.49 kJ/d and 403.12±24.91 kJ/d, respectively, and the nonages were 284.86±17.22 kJ/d, 284. 66±15.16 kJ/d, 402. 26±31.46 kJ/d and 420. 30±31.98 kJ/d, respectively. The minimum metabolic energies were 247.65±21.81 g, 265.86±26.53 g, respectively for each group, detected between 4-year adults and 1-year nonages. Further study is needed to determine whether 29.6 C is the optimal temperature for the Elliot's pheasant.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q11-03)
文摘Data on aerosol optical thickness(AOT) and single scattering albedo(SSA) derived from Moderate Resolution Imaging Spectrometer(MODIS) and Ozone Monitoring Instrument(OMI) measurements,respectively,are used jointly to examine the seasonal variations of aerosols over East Asia.The seasonal signals of the total AOT are well defined and nearly similar over the land and over the ocean.These findings indicate a natural cycle of aerosols that originate primarily from natural emissions. In contrast,the small-sized aerosols represented by the fine-mode AOT,which are primarily generated over the land by human activities,do not have evident seasonalscale fluctuations.A persistent maximum of aerosol loadings centered over the Sichuan basin is associated with considerable amounts of fine-mode aerosols throughout the year.Most regions exhibit a general spring maximum. During the summer,however,the aerosol loadings are the most marked over north central China.This occurrence may result from anthropogenic fine particles,such as sulfate and nitrate.Four typical regions were selected to perform a covariation analysis of the monthly gridded AOT and SSA.Over southwestern and southeastern China,if the aerosol loadings are small to moderate they are composed primarily of the highly absorptive aerosols. However,more substantial aerosol loadings probably represent less-absorptive aerosols.The opposite covariation pattern occurring over the coastal-adjacent oceans suggests that the polluted oceanic atmosphere is closely correlated with the windward terrestrial aerosols.North central China is strongly affected by dust aerosols that show moderate absorption.This finding may explain the lower variability in the SSA that accompanies increasing aerosol loadings in this region.
基金The National Natural Science Foundation of China under contract Nos 41221063 and 41222037the China’s National Basic Re-search Priorities Programmer under contract No.2013CB956202+3 种基金the Project of Global Change and Air-Sea interaction under contract No.GASI-03-01-01-02the National Special Research Fund for Non-Profit Marine Sector under contract No.201205018the State Oceanic Administration Marine Science Foundation for Youth under contract No.2012204the Open Research Program of the Key Laboratory of Ocean Circulation and Wave,Institute of Oceanology,Chinese Academy of Sciences,under contract Nos KLOCAW1201 and KLOCAW1102
文摘Using a net surface heat flux （Qnet） product obtained from the objectively analyzed air-sea fluxes （OAFlux） project and the international satellite cloud climatology project （ISCCP）, and temperature from the simple ocean data assimilation （SODA）, the seasonal variations of the air-sea heat fluxes in the northwestern Pa cific marginal seas （NPMS） and their roles in sea surface temperature （SST） seasonality are studied. The seasonal variations of Qnet, which is generally determined by the seasonal cycle of latent heat flux （LH）, are in response to the advection-induced changes of SST over the Kuroshio and its extension. Two dynamic regimes are identified in the NPMS： one is the area along the Kuroshio and its extension, and the other is the area outside the Kuroshio. The oceanic thermal advection dominates the variations of SST and hence the sea-air humidity plays a primary role and explains the maximum heat losing along the Kuroshio. The heat transported by the Kuroshio leads to a longer period of heat losing over the Kuroshio and its Extension. Positive anomaly of heat content corresponds with the maximum heat loss along the Kuroshio. The oceanic advection controls the variations of heat content and hence the surface heat flux. This study will help us understand the mechanism controlling variations of the coupled ocean-atmosphere system in the NPMS. In the Kuroshio region, the ocean current controls the ocean temperature along the main stream of the Ku roshio, and at the same time, forces the air-sea fluxes.
基金Supported by the National Basic Research Program (No. G1999043803), Hi-Tetch Research and Development Program of China (No. 2001AA633060) and the grant of Institute of Oceanology, Chinese Academy of Sciences (No.L370221117).
文摘To study seasonal and intraseasonal variations of the Taiwan Warm Current (TWC) in detail,Rotated Empirical Orthogonal Function (REOF) and Extended Associate Pattern Analysis (EAPA) are jointly adopted with daily sea surface salinity (SSS), sea surface temperature (SST) and sea surface height (SSH)datasets covering 1126 days from American Navy Experimental Real-Time East Asian Seas Ocean Nowcast System in the present paper. Results show that the first and second REOFs of SST in the southern East China Sea(SECS) account for 50,8% and 39.8% of the total variance. The surface TWC contains persistent (multi-year mean), seasonal and intraseasonal components. The persistent one mainly inosculates with the Kuroshio but the seasonal and intraseasonal ones are usually active only on the continental shelf. Its persistent component is produced by inertial flow of the Kuroshio, however its seasonal and intraseasonal ones seems coming from seasonal and intraseasonal oscillations of monsoon force. The seasonal one reaches its maximum in late summer,lasting about four months and the intraseasonal one takes place at any seasons, lasting more than 40 days.
基金This research was supported by the National Basic Research Program of China （Nos. 2001CB409703 and G1999043705） the National Natural Science Foundation of China （Nos. 40036010 and 40206017）.
文摘Water samples were collected in the coastal area of the Changjiang Estuary on four cruises from August 2002 to May 2003. The seasonal variations of dissolved inorganic arsenic （DIAs） distributions were analyzed. The results showed that the distributions of DIAs were mainly influenced by Water （KSSW）. The concentration of the total dissolved the terrestrial input and the intrusion of the Kuroshio Subsurface inorganic arsenic （TDIAs） decreased consecutively from winter to summer, while it increased in autumn. The distributions of TDIAs showed some relationships with salinity and suspended particulate matter （SPM）. The relationships between DIAs speciation （including arsenite [ As（ Ⅲ ） ] and arsenate [ As（ Ⅴ ） ]）, biological activity and the availabilities of the phosphate were investigated in the study area for the cruise August 2002. The ratio of As （Ⅲ）/TDIAs increased with the decrease of phosphate concentrations. In the bottom water, the As（ Ⅲ ）/TDIAs ratio decreased with the increasing of N/P. The concentration of TDIAs decreased 28.7% approximately after the occurrence of harmful algal blooms （HAB） because of the uptake of arsenate by algae. Further study is needed about the arsenic source/sink relationships in their vertical or horizontal profiles and the uptake mechanism during the occurrence of harmful algal blooms.
