Characteristics Variation of Atmospheric CO_(2)and CH_(4)in Yongxing Island,South China Sea

Using the observation data in Yongxing Island,South China Sea(SCS)from December 2013 to November 2018,the multiple time scales variation of atmospheric CO_(2)and CH_(4)were analyzed to understand their temporal variation characteristics and controlling factors.The regional-averaged background mole fractions of CO_(2)and CH_(4)both show a single-period sinusoidal variation with a lower value at noon and a higher value in the wee hours.In the seasonal scale,they exhibited a significant seasonal difference with higher values in winter and lower values in summer.In the annual scale,CO_(2)and CH_(4)both show an increasing trend,with an annual growth rate of approximately 3.2 ppm and 12 ppb,respectively.The annual growth rate at this site was higher than the global average.The change in atmospheric CO_(2)and CH_(4)in Yongxing Island was probably caused by the higher emission of the surrounding areas and the airflows driven by monsoon.Hopefully,the long-term and high-resolution greenhouse gases(GHGs)dataset will aid relevent researchers and decision-makers in performing more in-depth studies for GHG sources in order to derive effective strategies.

Background levels of OCPs,PCBs,and PAHs in soils from the eastern Pamirs,China,an alpine region influenced by westerly atmospheric transport

Long-range atmospheric transport(LRAT)plays a crucial role in the occurrence of persis-tent organic pollutants(POPs)in remote regions.When studying the LRAT of POPs on the Tibetan Plateau,westerly-controlled regions have received insufficient attention compared with regions influenced by the Indian monsoon or air flow from East Asia.We investigated the residual levels of POPs in soils from the eastern Pamirs and used air backward trajectory analysis to elucidate the influence of potential source regions via LRAT.Organochlorine pes-ticides(OCPs,mainly comprising DDTs,HCHs,and HCB),polychlorinated biphenyls(PCBs,mainly comprising penta-and hexa-CBs),and polycyclic aromatic hydrocarbons(PAHs,mainly comprising three-and four-ring)were detected at low concentrations of 40-1000,<MDL-88,and 2100-34,000 pg/g,respectively.We elucidated three major geographical dis-tribution patterns of POPs,which were influenced by(1)the distribution of total organic carbon and black carbon in soil,(2)historical use of pesticides in the Tarim Basin,and(3)continuous emissions.Central Asia and the Tarim Basin were major potential source regions of POPs reaching the eastern Pamirs via LRAT.Historical use of technical HCH or lindane and technical DDT in potential source regions may contribute to the accumulation of HCHs and DDTs in the eastern Pamirs,respectively.Local sources seem to play a more important role in the occurrence of PAHs in the study area.By being under the control of less contaminated westerly air flow,the eastern Pamirs are more pristine than the core of the Tibetan Plateau where the Indian and East Asia monsoons deliver contaminants from highly industrialized areas in East China and India.

Long-range atmospheric transport and alpine condensation of short-chain chlorinated paraffins on the southeastern Tibetan Plateau

Pristine alpine regions are ideal regions for investigating the long-range atmospheric transport and cold trapping effects of short chain chlorinated paraffins(SCCPs).The concentrations and alpine condensation of SCCPs were investigated in lichen samples collected from the southeastern Tibetan Plateau.The concentrations of SCCPs ranged from 3098 to 6999 ng/g lipid weight(lw)and appeared to have an increasing trend with altitude.For congeners,C10 dominated among all the congener groups.The different environmental behavior for different congener groups was closely related to their octanol-air partition coefficient(Koa).C10 congeners showed an increasing trend with altitude,whereas C13 congeners were negatively correlated with altitude.Volumetric bioconcentration factors(BCF)of SCCPs reached 8.71 in lichens,which were higher than other semivolatile organic compounds(SVOCs)such as organochlorine pesticides(OCPs),polybrominated diphenyl ethers(PBDEs),polychlorinated biphenyls(PCBs),and hexabromocyclododecane(HBCD).These results suggested that SCCPs were prone to accumulate in the lichen from the air and provided evidence for the role of lichens as a suitable atmospheric indicator in the Tibetan Plateau.

The Effect of Mesoscale Flows on Regional Atmospheric Transport in a Complex Terrain

Model results simulated over a complex terrain under a synoptically calm condition, using a three-dimensional (3-D) regional-scale meteorological acid deposition model (RMADM), show that thermally induced mesoscale circulations (MCs): sea-and land-breeze circulations and up- and down-slope flow circulations play a fundamental role in determining how the pollutants being dispersed . Analysis showed that under synoptically calm condition, the role played by the MC would dilute the smoke released during the early stage of the emission; the accumulation, however, would become important if the synoptically calm condition lasts long. Since the structure and intensity of the MCs depend on geography and topographical allocation, land surface coverage, incoming solar radiation intensity and so on, it makes the estimates of source-reception relationship and long-range atmospheric dispersion more difficulty. It concluded that it is impossible for a pollution model to correctly simulate smokes transport using only the synoptic station data, since the mesoscale information can not be resolved from these datasets.

Pathways of meridional atmospheric moisture transport in the central Arctic

Atmospheric moisture transport plays an important role in latent heat release and hydrologic interactions in the Arctic.In recent years,with the rapid decline in sea ice,this transport has changed.Here,we calculated the vertically integrated atmospheric moisture meridional transport(AMTv)from two global reanalysis datasets,from1979–2015,and found moisture pathways into the central Arctic.Four stable pathways showed an occurrence frequency greater than 70%,and these pathways exhibited a perennial seasonal pattern in the atmosphere above the Laptev Sea Pathway(LSP),Canadian Arctic Archipelago Pathway(CAAP),both sides of the Greenland plateau.Another seasonal pathway appeared above the east of the Chukchi Sea(CSP)during the melting/freezing months(March to September).Through these pathways,AMTv contributed a total moisture exchange of60%–80%—averaged over a 75°N circle—and focused on the low troposphere.Transports across the LSP,CSP and CAAP pathways likely create an enclosed moisture route.Meridional moisture fluxes are intensified in the Pacific sector of Arctic(PSA),especially during melting/freezing months.AMTv interannual variabilities are illustrated mainly in the Laptev Sea and the east Greenland pathway.Results indicate that accompanying a tendency for a stronger Beaufort Sea High in this sea level pressure field,AMTv through PSA pathways,switched from output to input,and approximately 960 km^3 of equivalent liquid water was transferred into the central Arctic during each decade.The detrended AMTv increment is highly correlated with the rapid decline of old ice areas(correlation coefficient is–0.78)for their synchronous fluctuations in the 1980 s and the last decade.

The impact of concurrent variation of atmospheric meridional heat transport in western Baffen Bay and eastern Greenland on summer Arctic sea ice

Based on the climatological reanalysis data of the European Center for Medium-Range Weather Forecasts and the Arctic sea ice data of the National Snow and Ice Data Center, the relationship between the Arctic sea ice area(SIA)and the interannual variation of atmospheric meridional heat transport(AMHT) was analyzed. The results show that the atmospheric meridional heat transported by transient eddy(TAMHT) dominates the June AMHT in midhigh latitudes of the Northern Hemisphere, while the western Baffin Bay(B) and the eastern Greenland(G) are two gates for TAMHT entering the Arctic. TAMHT in the western Baffin Bay(B-TAMHT) and eastern Greenland(G-TAMHT) has a concurrent variation of reverse phase, which is closely related to the summer Arctic SIA.Possible mechanism is that the three Arctic atmospheric circulation patterns(AD, AO and NAO) in June can cause the concurrent variation of TAMHT in the B and G regions. This concurrent variation helps to maintain AD anomaly in summer through wave action and changes the polar air temperature, thus affecting the summer Arctic SIA. Calling the heat entering the Arctic as warm transport and the heat leaving Arctic as cold transport, then the results are classified into three situations based on B-TAMHT and G-TAMHT: warm B corresponding to cold G(WC), cold B corresponding to warm G(CW), cold B corresponding to cold G(CC), while warm B corresponding to warm G is virtually non-existent. During the WC situation, the SIA in the Pacific Arctic sediments and Kara Sea decreases;during the CW situation, the SIA in the Laptev Sea and Kara Sea decreases;during the CC situation, the SIA in the Kara Sea, Laptev Sea and southern Beaufort Sea increases.

Using Longwave Infrared Hyperspectral Imaging for a Quantitative Atmospheric Tracer Monitoring in Outdoor Environments

Quantitative real-time retrieval of concentration-lengths (CL) through gaseous plumes is an important tool for environmental monitoring, enabling remote monitoring of emissions from industrial facilities and risk assessment in scenarios of toxic gas releases. The adoption of LWIR (Long Wave InfraRed) hyperspectral imaging as a leading technique for remote gas plume detection paved the way for an introduction of a precise CL estimation and two-dimensional (2D) mapping. A novel methodology for evaluating and characterizing the performance of a retrieval algorithm is presented. The algorithm utilizes state-of-the-art retrieved hyperspectral 2D mapping and is applied on a series of localized atmospheric tracer gas (SF6) releases in monitored environmental conditions. The retrieved CL distributions are compared to a numeric atmospheric T&D (Transport and Diffusion) model. Satisfactory agreement between retrieved and simulated CL prediction is manifested, and the uncertainty involved is quantified. Possible sources for the remained discrepancies between retrieved and simulated CL values are characterized, and methods to minimize them are discussed.

Spatial and seasonal patterns of atmospheric nitrogen deposition in North China

As one of the regions with intensive agriculture and rapid economic development in China,North China also has a high nitrogen(N)deposition.This study characterized the spatial pattern of N deposition in North China,combining the tropospheric columns from satellite measurements and the simulated profiles from an atmospheric chemistry transport model.The total N deposition fluxes ranged from 16.3 to 106.5 kg N ha−1 yr−1,with an average of 54.5±17.2 kg N ha−1 yr−1.The high values were concentrated in urban and farmland areas,while low values were found in forests and grasslands with less human activities.Of the total N deposition,36%was deposited via precipitation,12%was deposited through dry particulate deposition,and the remaining 52%was comprised of dry gaseous deposition.For the seasonal variation of dry deposition,gaseous HNO3 and particulate NO3−were higher in winter and autumn,but lower in spring and summer.In contrast,gaseous NH3 and particulate NH4+were higher in spring and summer,but lower in winter and autumn.This is possibly caused by the seasonal differences in emission intensity between NOx and NH3 emission sources.The gaseous NO2 deposition did not show strong seasonal variation.The wet deposition was mainly affected by precipitation,with high values in summer and low values in winter.This research provides an objective spatial perspective and insight into the total N deposition in North China.

Role of Extratropical Cyclones in the Recently Observed Increase in Poleward Moisture Transport into the Arctic Ocean

Poleward atmospheric moisture transport(AMT) into the Arctic Ocean can change atmospheric moisture or water vapor content and cause cloud formation and redistribution, which may change downward longwave radiation and, in turn, surface energy budgets, air temperatures, and sea-ice production and melt. In this study, we found a consistently enhanced poleward AMT across 60?N since 1959 based on the NCAR–NCEP reanalysis. Regional analysis demonstrates that the poleward AMT predominantly occurs over the North Atlantic and North Pacific regions, contributing about 57% and 32%, respectively, to the total transport. To improve our understanding of the driving force for this enhanced poleward AMT, we explored the role that extratropical cyclone activity may play. Climatologically, about 207 extratropical cyclones move across 60?N into the Arctic Ocean each year, among which about 66(32% of the total) and 47(23%) originate from the North Atlantic and North Pacific Ocean, respectively. When analyzing the linear trends of the time series constructed by using a 20-year running window, we found a positive correlation of 0.70 between poleward yearly AMT and the integrated cyclone activity index(measurement of cyclone intensity, number, and duration). This shows the consistent multidecadal changes between these two parameters and may suggest cyclone activity plays a driving role in the enhanced poleward AMT. Furthermore, a composite analysis indicates that intensification and poleward extension of the Icelandic low and accompanying strengthened cyclone activity play an important role in enhancing poleward AMT over the North Atlantic region.

The Role of Ocean Dynamics in the Cross-equatorial Energy Transport under a Thermal Forcing in the Southern Ocean

Under external heating forcing in the Southern Ocean,climate models project anomalous northward atmosphere heat transport(AHT)across the equator,accompanied by a southward shift of the intertropical convergence zone(ITCZ).Comparison between a fully coupled and a slab ocean model shows that the inclusion of active ocean dynamics tends to partition the cross-equatorial energy transport and significantly reduce the ITCZ shift response by a factor of 10,a finding which supports previous studies.To understand how ocean dynamics damps the ITCZ’s response to an imposed thermal heating in the Southern Ocean,we examine the ocean heat transport(OHT)and ocean circulation responses in a set of fully coupled experiments.Results show that both the Indo-Pacific and the Atlantic contribute to transport energy across the equator mainly through its Eulerian-mean component.However,different from previous studies that linked the changes in OHT to the changes in the wind-driven subtropical cells or the Atlantic meridional overturning circulation(AMOC),our results show that the cross-equatorial OHT anomaly is due to a broad clockwise overturning circulation anomaly below the subtropical cells(approximately bounded by the 5°C to 20°C isotherms and 50°S to 10°N).Further elimination of the wind-driven component,conducted by prescribing the climatological wind stress in the Southern Ocean heat perturbation experiments,leads to little change in OHT,suggesting that the OHT response is predominantly thermohaline-driven by air-sea thermal interactions.

Study of atmospheric CO2 and CH4 at Longfengshan WMO/GAW regional station： The variations, trends, influence of local sources/sinks, and transport

Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.

Seasonal variation and sources of atmospheric polycyclic aromatic hydrocarbons in a background site on the Tibetan Plateau

The study of atmospheric polycyclic aromatic hydrocarbons(PAHs) in northeastern Tibetan Plateau with fragile ecological environment and complex atmospheric circulation system is blank. To understand the characteristics and sources of persistent organic pollutants in the atmosphere of the northeastern Tibetan Plateau, we monitored levels in the central Qilian Mountain. From 2016 to 2017, we collected 45-pair(particle + gas) samples using active air samplers to investigate the sources, transport paths, and their influencing factors.Sources of PAHs were analysed with a source diagnostic model, and atmospheric transport paths were calculated. The concentration range for Σ15PAHs was 439–4666 pg/m^(3), and the average was 2015 pg/m^(3). The PAHs in central Qilian Mountain are mainly low molecular weight(LMW) PAHs. Winter concentrations of PAHs were higher than those in summer. The transport of PAHs is mainly affected by westerlies, and there are seasonal differences. Source analysis showed that PAHs mainly came from coal and biomass combustion and vehicle emissions, with seasonal differences. This study clarifies the concentration and seasonal variation of PAHs in the northern Tibetan Plateau, which is conducive to understanding the atmospheric transport process and fate of pollutants. The background site of Qilian Mountains located in the Silk Road economic belt has the value and significance of longterm observation of pollutants.

Spatial variability of chemical tracers in surface snow along the traverse route from the coast to 1000 km inland at east Dronning Maud Land, Antarctica

We measured the spatial variability of Cl -, Na +, SO 2- 4, NO - 3 and 7Be concentrations in snow cover along the traverse route from S16 to Dome Fuji station in east Dronning Maud Land, Antarctica. The concentrations of Cl - and Na + at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200 1000 km inland, the concentrations of Na + were nearly constant. On the other hand, the concentrations of Cl - increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl - and Na + decreased and the Cl -/Na + ratio and the nssCl -/Cl - ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl - other than sea salt exists in the inland plateau of Antarctica. The concentrations of SO 2- 4, NO - 3 and 7Be in snow were relatively high in the coastal region and the inland plateau region compared with those in the katabatic wind region.

A new implementation of FLEXPART with Enviro-HIRLAM meteorological input,and a case study during a heavy air pollution event

We integrated Enviro-HIRLAM(Environment-High Resolution Limited Area Model)meteorological output into FLEXPART(FLEXible PARTicle dispersion model).A FLEXPART simulation requires meteorological input from a numerical weather prediction(NWP)model.The publicly available version of FLEXPART can utilize either ECMWF(European Centre for Medium-range Weather Forecasts)Integrated Forecast System(IFS)forecast or reanalysis NWP data,or NCEP(U.S.National Center for Environmental Prediction)Global Forecast System(GFS)forecast or reanalysis NWP data.The primary benefits of using Enviro-HIRLAM are that it runs at a higher resolution and accounts for aerosol effects in meteorological fields.We compared backward trajectories gener-ated with FLEXPART using Enviro-HIRLAM(both with and without aerosol effects)to trajectories generated using NCEP GFS and ECMWF IFS meteorological inputs,for a case study of a heavy haze event which occurred in Beijing,China in November 2018.We found that results from FLEXPART were considerably different when using different meteorological inputs.When aerosol effects were included in the NWP,there was a small but noticeable differ-ence in calculated trajectories.Moreover,when looking at potential emission sensitivity instead of simply expressing trajectories as lines,additional information,which may have been missed when looking only at trajectories as lines,can be inferred.

Halomethoxybenzenes in air of the Nordic region

Halomethoxybenzenes(HMBs)are a group of compounds with natural and anthropogenic origins.Here we extend a 2002e2015 survey of bromoanisoles(BAs)in the air and precipitation at Rå€o on the Swedish west coast and Pallas in Subarctic Finland.New BAs data are reported for 2018 and 2019 and chlorinated HMBs are included for these and some previous years:drosophilin A methyl ether(DAME:1,2,4,5-tetrachloro-3,6-dimethoxybenzene),tetrachloroveratrole(TeCV:1,2,3,4-tetrachloro-5,6-dimethoxybenzene),and pentachloroanisole(PeCA).The order of abundance of HMBs at Råo was SBAs>DAME>TeCV>PeCA,whereas at Pallas the order of abundance was DAME>SBAs>TeCA>PeCA.The lower abundance of BAs at Pallas reflects its inland location,away from direct marine influence.Clausius-Clapeyron(CC)plots of log partial pressure(Pair)/Pa versus 1/T suggested distant transport at both sites for PeCA and local exchange for DAME and TeCV.BAs were dominated by distant transport at Pallas and by both local and distant sources at Rå€o.Relationships between air and precipitation concentrations were examined by scavenging ratios,SR=(ng m^(-3))precip/(ng m^(-3))air.SRs were higher at Pallas than Rå€o due to greater Henry's law partitioning of gaseous compounds into precipitation at colder temperatures.DAME is produced by terrestrial fungi.We screened 19 fungal species from Swedish forests and found seven of them contained 0.01e3.8 mg DAME per kg fresh weight.We suggest that the volatilization of DAME from fungi and forest litter containing fungal mycelia may contribute to atmospheric levels at both sites.

Organochlorine Pesticides(OCPs) in Soils Along the Eastern Slope of the Tibetan Plateau

Soil samples collected from several sites along an altitudinal transect on the eastern slope of the Tibetan Plateau were analyzed for hexachlorobenzenes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs).The results showed that HCHs and DDTs were found in the soil samples from the remote high altitude areas away from source regions,which confirmed the long-range atmospheric transport phenomenon of these organochlorine pesticides(OCPs) insecticides.The OCP concentrations in the soils had a significant negative correlation with altitude;they showed a trend to increase with decreasing altitude,but the increase was not continuous,being interrupted at some moderate-altitude sites on the transect.The distances from the source region,landforms,soil properties,and physical-chemical properties of OCPs were more important than total organic carbon content to the distribution of OCPs in soils disturbed by human activities.An analysis of the compositions of HCH isomers and DDTs revealed predominantly low ratios of α-HCH to γ-HCH,ranging from 0.06 to 4.79,which suggested current lindane inputs.On the other hand,low p,p-DDT/p,p-DDE and o,p-DDT/p,p-DDT ratios were observed,indicating mainly aged historical DDT residues in the study area.

Inequality in historical transboundary anthropogenic PM_(2.5) health impacts

Atmospheric transport of fine particulate matter(PM_(2.5)),the leading environmental risk factor for public health,is estimated to exert substantial transboundary effects at present.During the past several decades,human-produced pollutant emissions have undergone drastic and regionally distinctive changes,yet it remains unclear about the resulting global transboundary health impacts.Here we show that between 1950 and 2014,global anthropogenic PM_(2.5)has led to 185.7 million premature deaths cumulatively,including about 14%from transboundary pollution.Among four country groups at different affluence levels,on a basis of per capita contribution to transboundary mortality,a richer region tends to exert severer cumulative health externality,with the poorest bearing the worst net externality after contrasting import and export of pollution mortality.The temporal changes in transboundary mortality and cross-regional inequality are substantial.Effort to reduce PM_(2.5)-related transboundary mortality should seek international collaborative strategies that account for historical responsibility and inequality.

Simulation and Validation of the Aerosol Optical Thickness over China in 2006

The Model of Atmospheric Transport and Chemistry （MATCH） developed by the US National Center for Atmospheric Research （NCAR） was used to calculate the aerosol optical thickness （AOT） over China in 2006, with emission source data of the Intercontinental Chemical Transport Experiment Phase B （INTEX-B） and NCEP/NCAR reanalysis data as inputs. The simulation results of AOT were then validated with obser- vational data from the Moderate Resolution Imaging Spectroradiometer （MODIS）, Chinese Sun Hazemeter Network （CSHNET）, Aerosol Robotics Network （AERONET）, and China Aerosol Remote Sensing Network （CARSNET） at more than 30 stations over China. The comparison results indicated that the high values of AOT in the areas such as the Sichuan basin and East and South China and the low values of AOT over the Tibetan Plateau and Northwest and Northeast China were reasonably simulated by the MATCH. This model tended to underestimate the AOT values in high-aerosol-loading areas but overestimate the AOT val- ues in less polluted areas because there are still large uncertainties in the expression of emission sources, the description of the optical properties of aerosols, the treatment of cloud and precipitation, and the selection of grid resolution. The modeling results were consistent with the CSHNET, CARSNET, AERONET, and MODIS data in most parts of China, and the correlation coefficient of the monthly mean AOT between the model and the observation was 0.79 with CSHNET data at 23 stations, 0.51 with MODIS data, and 0.88 with data at 3 CARSNET stations and 2 other stations. All of them passed the significance test with c 〈 0.0001. The results demonstrated that the MATCH has the ability to simulate the characteristics of the AOT distribution and its seasonal variation over China.