scholarly journals GNAQPMS-Hg v1.0, a global nested atmospheric mercury transport model: model description, evaluation and application to trans-boundary transport of Chinese anthropogenic emissions

2015 ◽  
Vol 8 (9) ◽  
pp. 2857-2876 ◽  
Author(s):  
H. S. Chen ◽  
Z. F. Wang ◽  
J. Li ◽  
X. Tang ◽  
B. Z. Ge ◽  
...  
Keyword(s):  
North America ◽  
East Asia ◽  
Aqueous Phase ◽  
Wet Deposition ◽  
Transport Model ◽  
Atmospheric Mercury ◽  
Model Description ◽  
Anthropogenic Emissions ◽  
Comparison Results ◽  
Western Asia

Abstract. Atmospheric mercury (Hg) is a toxic pollutant and can be transported over the whole globe due to its long lifetime in the atmosphere. For the purpose of assessing Hg hemispheric transport and better characterizing regional Hg pollution, a global nested atmospheric Hg transport model (GNAQPMS-Hg – Global Nested Air Quality Prediction Modeling System for Hg) has been developed. In GNAQPMS-Hg, the gas- and aqueous-phase Hg chemistry representing the transformation among three forms of Hg: elemental mercury (Hg(0)), divalent mercury (Hg(II)), and primary particulate mercury (Hg(P)) are calculated. A detailed description of the model, including mercury emissions, gas- and aqueous-phase chemistry, and dry and wet deposition is given in this study. Worldwide observations including extensive data in China have been collected for model evaluation. Comparison results show that the model reasonably simulates the global mercury budget and the spatiotemporal variation of surface mercury concentrations and deposition. Overall, model predictions of annual total gaseous mercury (TGM) and wet deposition agree with observations within a factor of 2, and within a factor of 5 for oxidized mercury and dry deposition. The model performs significantly better in North America and Europe than in East Asia. This can probably be attributed to the large uncertainties in emission inventories, coarse model resolution and to the inconsistency between the simulation and observation periods in East Asia. Compared to the global simulation, the nested simulation shows improved skill at capturing the high spatial variability of surface Hg concentrations and deposition over East Asia. In particular, the root mean square error (RMSE) of simulated Hg wet deposition over East Asia is reduced by 24 % in the nested simulation. Model sensitivity studies indicate that Chinese primary anthropogenic emissions account for 30 and 62 % of surface mercury concentrations and deposition over China, respectively. Along the rim of the western Pacific, the contributions from Chinese sources are 11 and 15.2 % over the Korean Peninsula, 10.4 and 8.2 % over Southeast Asia, and 5.7 and 5.9 % over Japan. But for North America, Europe and western Asia, the contributions from China are all below 5 %.

scholarly journals GNAQPMS-Hg v1.0, a global nested atmospheric mercury transport model: model description, evaluation and application to trans-boundary transport of Chinese anthropogenic emissions

2014 ◽  
Vol 7 (5) ◽  
pp. 6949-6996
Author(s):  
H. S. Chen ◽  
Z. F. Wang ◽  
J. Li ◽  
X. Tang ◽  
B. Z. Ge ◽  
...  
Keyword(s):  
North America ◽  
East Asia ◽  
Aqueous Phase ◽  
Wet Deposition ◽  
Transport Model ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Model Description ◽  
Anthropogenic Emissions ◽  
Comparison Results

Abstract. Atmospheric mercury (Hg) is a toxic pollutant and can be transported over the whole globe due to its long lifetime in the atmosphere. For the purpose of assessing Hg hemispheric transport and better characterizing regional Hg pollution, a global nested atmospheric Hg transport model (GNAQPMS-Hg) has been developed. In GNAQPMS-Hg, the gas and aqueous phase Hg chemistry representing the transformation among three forms of Hg: elemental mercury (Hg(0)), divalent mercury (Hg(II)), and primary particulate mercury (Hg(P)) are calculated. A detailed description of the model, including mercury emissions, gas and aqueous phase chemistry, and dry and wet deposition is given in this study. Worldwide observations including extensive data in China have been collected for model evaluation. Comparison results show that the model reasonably simulates the global mercury budget and the spatial–temporal variation of surface mercury concentrations and deposition. Overall, model predictions of annual total gaseous mercury (TGM) and wet deposition agree with observations within a factor of two, and within a factor of five for oxidized mercury and dry deposition. The model performs significantly better in North America and Europe than in East Asia. This can probably be attributed to the large uncertainties in emission inventories, coarse model resolution and to the inconsistency between the simulation and observation periods in East Asia. Compared to the global simulation, the nested simulation shows improved skill at capturing the high spatial variability of Hg concentrations and deposition over East Asia. In particular, the root mean square error (RMSE) of simulated Hg wet deposition over East Asia is reduced by 24% in the nested simulation. Model sensitivity studies indicate that Chinese primary anthropogenic emissions account for 30 and 62% of surface mercury concentrations and deposition over China, respectively. Along the rim of the western Pacific, the contributions from Chinese sources are 11 and 15.2% over the Korean Peninsula, 10.4 and 8.2% over Southeast Asia, and 5.7 and 5.9% over Japan. But for North America, Europe and West Asia, the contributions from China are all below 5%.

scholarly journals Intercontinental transport and deposition patterns of atmospheric mercury from anthropogenic emissions

2014 ◽  
Vol 14 (18) ◽  
pp. 10163-10176 ◽  
Author(s):  
L. Chen ◽  
H. H. Wang ◽  
J. F. Liu ◽  
Y. D. Tong ◽  
L. B. Ou ◽  
...  
Keyword(s):  
North America ◽  
Southeast Asia ◽  
East Asia ◽  
Transport Model ◽  
Indian Subcontinent ◽  
Atmospheric Mercury ◽  
Anthropogenic Emissions ◽  
Mercury Deposition ◽  
Mercury Emissions ◽  
Source Receptor Relationships

Abstract. Global policies that regulate anthropogenic mercury emissions to the environment require quantitative and comprehensive source–receptor relationships for mercury emissions, transport and deposition among major continental regions. In this study, we use the GEOS-Chem global chemical transport model to establish source–receptor relationships among 11 major continental regions worldwide. Source–receptor relationships for surface mercury concentrations (SMC) show that some regions (e.g., East Asia, the Indian subcontinent, and Europe) should be responsible for their local surface Hg(II) and Hg(P) concentrations due to near-field transport and deposition contributions from their local anthropogenic emissions (up to 64 and 71% for Hg(II) and Hg(P), respectively, over East Asia). We define the region of primary influence (RPI) and the region of secondary influence (RSI) to establish intercontinental influence patterns. Results indicate that East Asia is the SMC RPI for almost all other regions, while Europe, Russia, and the Indian subcontinent also make some contributions to SMC over some receptor regions because they are dominant RSI source regions. Source–receptor relationships for mercury deposition show that approximately 16 and 17% of dry and wet deposition, respectively, over North America originate from East Asia, indicating that transpacific transport of East Asian emissions is the major foreign source of mercury deposition in North America. Europe, Southeast Asia, and the Indian subcontinent are also important mercury deposition sources for some receptor regions because they are the dominant RSIs. We also quantify seasonal variation on mercury deposition contributions over other regions from East Asia. Results show that mercury deposition (including dry and wet) contributions from East Asia over the Northern Hemisphere receptor regions (e.g., North America, Europe, Russia, the Middle East, and Middle Asia) vary seasonally, with the maximum values in summer and minimum values in winter. The opposite seasonal pattern occurs on mercury dry deposition contributions over Southeast Asia and the Indian subcontinent.

scholarly journals Nested-grid simulation of mercury over North America

2012 ◽  
Vol 12 (1) ◽  
pp. 2603-2646 ◽  
Author(s):  
Y. Zhang ◽  
L. Jaeglé ◽  
A. van Donkelaar ◽  
R. V. Martin ◽  
C. D. Holmes ◽  
...  
Keyword(s):  
North America ◽  
Wet Deposition ◽  
Transport Model ◽  
Atmospheric Mercury ◽  
Anthropogenic Emissions ◽  
Spatial And Temporal Variability ◽  
Deposition Flux ◽  
Nested Model ◽  
The Us ◽  
Nested Grid

Abstract. We have developed a new high-resolution (1/2° latitude by 2/3° longitude) nested-grid mercury (Hg) simulation over North America employing the GEOS-Chem global chemical transport model. Emissions, chemistry, deposition, and meteorology are self-consistent between the global and nested domains. Compared to the global model (4° latitude by 5° longitude), the nested model shows improved skill at capturing the high spatial and temporal variability of Hg wet deposition over North America observed by the Mercury Deposition Network (MDN) in 2008–2009. The nested simulation resolves features such as land/ocean contrast and higher deposition due to orographic precipitation, and predicts more efficient convective rain scavenging of Hg over the southeast United States. However, the nested model overestimates Hg wet deposition over the Ohio River Valley region (ORV) by 27%. We modify anthropogenic emission speciation profiles in the US EPA National Emission Inventory (NEI) to account for the rapid in-plume reduction of reactive to elemental Hg (IPR simulation). This leads to a decrease in the model bias to +3% over the ORV region. Over the contiguous US, the correlation coefficient (r) between MDN observations and our IPR simulation increases from 0.63 to 0.78. The IPR nested simulation generally reproduces the seasonal cycle in surface concentrations of speciated Hg from the Atmospheric Mercury Network (AMNet) and Canadian Atmospheric Mercury Network (CAMNet). In the IPR simulation, annual mean reactive gaseous and particulate-bound Hg are within 80% and 10% of observations, respectively. In contrast, the simulation with unmodified anthropogenic Hg speciation profiles overestimates these observations by factors of 2 to 4. The nested model shows improved skill at capturing the horizontal variability of Hg observed over California during the ARCTAS aircraft campaign. We find that North American anthropogenic emissions account for 10–22% of Hg wet deposition flux over the US, depending on the anthropogenic emissions speciation profile assumed. The percent contribution can be as high as 60% near large point emission sources in ORV. The contribution for the dry deposition is 13–20%.

scholarly journals Nested-grid simulation of mercury over North America

2012 ◽  
Vol 12 (14) ◽  
pp. 6095-6111 ◽  
Author(s):  
Y. Zhang ◽  
L. Jaeglé ◽  
A. van Donkelaar ◽  
R. V. Martin ◽  
C. D. Holmes ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
Wet Deposition ◽  
Atmospheric Mercury ◽  
Point Sources ◽  
Anthropogenic Emissions ◽  
Spatial And Temporal Variability ◽  
Nested Model ◽  
The Us ◽  
Nested Grid

Abstract. We have developed a new nested-grid mercury (Hg) simulation over North America with a 1/2° latitude by 2/3° longitude horizontal resolution employing the GEOS-Chem global chemical transport model. Emissions, chemistry, deposition, and meteorology are self-consistent between the global and nested domains. Compared to the global model (4° latitude by 5° longitude), the nested model shows improved skill at capturing the high spatial and temporal variability of Hg wet deposition over North America observed by the Mercury Deposition Network (MDN) in 2008–2009. The nested simulation resolves features such as higher deposition due to orographic precipitation, land/ocean contrast and and predicts more efficient convective rain scavenging of Hg over the southeast United States. However, the nested model overestimates Hg wet deposition over the Ohio River Valley region (ORV) by 27%. We modify anthropogenic emission speciation profiles in the US EPA National Emission Inventory (NEI) to account for the rapid in-plume reduction of reactive to elemental Hg (IPR simulation). This leads to a decrease in the model bias to −2.3% over the ORV region. Over the contiguous US, the correlation coefficient (r) between MDN observations and our IPR simulation increases from 0.60 to 0.78. The IPR nested simulation generally reproduces the seasonal cycle in surface concentrations of speciated Hg from the Atmospheric Mercury Network (AMNet) and Canadian Atmospheric Mercury Network (CAMNet). In the IPR simulation, annual mean gaseous and particulate-bound Hg(II) are within 140% and 11% of observations, respectively. In contrast, the simulation with unmodified anthropogenic Hg speciation profiles overestimates these observations by factors of 4 and 2 for gaseous and particulate-bound Hg(II), respectively. The nested model shows improved skill at capturing the horizontal variability of Hg observed over California during the ARCTAS aircraft campaign. The nested model suggests that North American anthropogenic emissions account for 10–22% of Hg wet deposition flux over the US, depending on the anthropogenic emissions speciation profile assumed. The modeled percent contribution can be as high as 60% near large point sources in ORV. Our results indicate that the North American anthropogenic contribution to dry deposition is 13–20%.

scholarly journals Intercontinental transport and deposition patterns of atmospheric mercury from anthropogenic emissions

2013 ◽  
Vol 13 (9) ◽  
pp. 25185-25218 ◽  
Author(s):  
L. Chen ◽  
H.-H. Wang ◽  
J.-F. Liu ◽  
W. Zhang ◽  
D. Hu ◽  
...  
Keyword(s):  
North America ◽  
Southeast Asia ◽  
East Asia ◽  
Indian Subcontinent ◽  
Seasonal Pattern ◽  
Atmospheric Mercury ◽  
Anthropogenic Emissions ◽  
Mercury Deposition ◽  
Mercury Emissions ◽  
Source Receptor Relationships

Abstract. Global policies that regulate anthropogenic mercury emissions to the environment require quantitative and comprehensive source–receptor relationships for mercury emissions, transport and deposition among major continental regions. In this study, we use the GEOS-Chem model to establish source–receptor relationships among eleven major continental regions worldwide. Source–receptor relationships for surface mercury concentrations (SMC) show that some regions (e.g. East Asia, the Indian subcontinent and Europe) should be responsible for their local surface Hg(II) and Hg(P) concentrations because of near-field transport and deposition contributions from their local anthropogenic emissions (up to 64% and 71% for Hg(II) and Hg(P), respectively, over East Asia). We define region of primary influence (RPI) and region of secondary influence (RSI) to establish intercontinental influence patterns. Results indicate that East Asia is SMC RPI for almost all other regions, while Europe, Russia and the Indian subcontinent also make some contributions to SMC over some receptor regions because they are dominant RSI source regions. Source–receptor relationships for mercury deposition show that approximately 16% and 17% of dry and wet deposition, respectively, over North America originate from East Asia, indicating that trans-pacific transport of East Asian emissions is the major foreign source of mercury deposition in North America. Europe, Southeast Asia and the Indian subcontinent are also important mercury deposition sources for some receptor regions because they are dominant RSI. We also quantify seasonal variation on mercury deposition contributions over other regions from East Asia. Results show that mercury deposition (including dry and wet) contributions from East Asia over the Northern Hemisphere receptor regions (e.g. North America, Europe, Russia, Middle East and Middle Asia) vary seasonally, with the maximum values in summer and minimum values in winter. The opposite seasonal pattern occurs on mercury dry deposition contributions over Southeast Asia and the Indian subcontinent.

scholarly journals Multi-model study of HTAP II on sulphur and nitrogen deposition

2018 ◽  
Author(s):  
Jiani Tan ◽  
Joshua S. Fu ◽  
Frank Dentener ◽  
Jian Sun ◽  
Louisa Emmons ◽  
...  
Keyword(s):  
North America ◽  
East Asia ◽  
South Asia ◽  
Wet Deposition ◽  
Task Force ◽  
East Asian ◽  
Control Policy ◽  
N Deposition ◽  
Eastern United States ◽  
S Deposition

Abstract. This study uses multi-model ensemble results of 11 models from the 2nd phase of Task Force Hemispheric Transport of Air Pollution (HTAP II) to calculate the global sulfur (S) and nitrogen (N) deposition in 2010. Modelled wet deposition is evaluated with observation networks in North America, Europe and Asia. The modelled results agree well with observations, with 76–83 % of stations having predicted within ±50 % of observations. The results underestimate SO42−, NO3− and NH4+ wet depositions in some European and East Asian stations, but overestimate NO3− wet deposition in Eastern United States. Inter-comparison with previous projects (PhotoComp, ACCMIP and HTAP I) shows HTPA II has considerably improved the estimation of deposition at European and East Asian stations. Modelled dry deposition is generally higher than the “inferential” data calculated by observed concentration and modelled velocity in North America, but the inferential data has high uncertainty, too. The global S deposition is 84 Tg(S) in 2010, with 49 % of the deposits on continental regions and 51 % on ocean (19 % on coastal). The global N deposition consists of 59 Tg(N) oxidized nitrogen (NOy) deposition and 64 Tg(N) reduced nitrogen (NHx) deposition in 2010. 65 % of N is deposited on the continental regions and 35 % is on ocean (15 % on coastal). The estimated outflow of pollution from land to ocean is about 4 Tg(S) for S deposition and 18 Tg(N) for N deposition. Compared our results to the results in 2001 from HTAP I, we find that the global distributions of S and N depositions have changed considerably during the last 10 years. The global S deposition decreases 2 Tg(S) (3 %) from 2001 to 2010, with significant decreases in Europe (5 Tg(S) and 55 %), North America (3 Tg(S) and 29 %) and Russia (2 Tg(S) and 26 %), and increases in South Asia (2 Tg(S) and 42 %) and the Middle East (1 Tg(S) and 44% ). The global N deposition increases by 7 Tg(N) (6 %), mainly contributed by South Asia (5 Tg(N) and 39 %), East Asia (4 Tg(N) and 21 %) and Southeast Asia (2 Tg(N) and 21 %). The NHx deposition is increased with no control policy on NH3 emission in North America. On the other hand, NOy deposition starts to dominate in East Asia (especially China) due to boosted NOx emission in recent years.

scholarly journals Evaluation of global EMEP MSC-W (rv4.34) WRF (v3.9.1.1) model surface concentrations and wet deposition of reactive N and S with measurements

2021 ◽  
Vol 14 (11) ◽  
pp. 7021-7046
Author(s):  
Yao Ge ◽  
Mathew R. Heal ◽  
David S. Stevenson ◽  
Peter Wind ◽  
Massimo Vieno
Keyword(s):  
North America ◽  
Southeast Asia ◽  
East Asia ◽  
Atmospheric Chemistry ◽  
Wet Deposition ◽  
Global Analysis ◽  
Monitoring Networks ◽  
Model Framework ◽  
Annual Total ◽  
Model Measurement

Abstract. Atmospheric pollution has many profound effects on human health, ecosystems, and the climate. Of concern are high concentrations and deposition of reactive nitrogen (Nr) species, especially of reduced N (gaseous NH3, particulate NH4+). Atmospheric chemistry and transport models (ACTMs) are crucial to understanding sources and impacts of Nr chemistry and its potential mitigation. Here we undertake the first evaluation of the global version of the EMEP MSC-W ACTM driven by WRF meteorology (1∘×1∘ resolution), with a focus on surface concentrations and wet deposition of N and S species relevant to investigation of atmospheric Nr and secondary inorganic aerosol (SIA). The model–measurement comparison is conducted both spatially and temporally, covering 10 monitoring networks worldwide. Model simulations for 2010 compared use of both HTAP and ECLIPSEE (ECLIPSE annual total with EDGAR monthly profile) emissions inventories; those for 2015 used ECLIPSEE only. Simulations of primary pollutants are somewhat sensitive to the choice of inventory in places where regional differences in primary emissions between the two inventories are apparent (e.g. China) but are much less sensitive for secondary components. For example, the difference in modelled global annual mean surface NH3 concentration using the two 2010 inventories is 18 % (HTAP: 0.26 µg m−3; ECLIPSEE: 0.31 µg m−3) but is only 3.5 % for NH4+ (HTAP: 0.316 µg m−3; ECLIPSEE: 0.305 µg m−3). Comparisons of 2010 and 2015 surface concentrations between the model and measurements demonstrate that the model captures the overall spatial and seasonal variations well for the major inorganic pollutants NH3, NO2, SO2, HNO3, NH4+, NO3-, and SO42- and their wet deposition in East Asia, Southeast Asia, Europe, and North America. The model shows better correlations with annual average measurements for networks in Southeast Asia (mean R for seven species: R7‾=0.73), Europe (R7‾=0.67), and North America (R7‾=0.63) than in East Asia (R5‾=0.35) (data for 2015), which suggests potential issues with the measurements in the latter network. Temporally, both model and measurements agree on higher NH3 concentrations in spring and summer and lower concentrations in winter. The model slightly underestimates annual total precipitation measurements (by 13 %–45 %) but agrees well with the spatial variations in precipitation in all four world regions (0.65–0.94 R range). High correlations between measured and modelled NH4+ precipitation concentrations are also observed in all regions except East Asia. For annual total wet deposition of reduced N, the greatest consistency is in North America (0.75–0.82 R range), followed by Southeast Asia (R=0.68) and Europe (R=0.61). Model–measurement bias varies between species in different networks; for example, bias for NH4+ and NO3- is largest in Europe and North America and smallest in East Asia and Southeast Asia. The greater uniformity in spatial correlations than in biases suggests that the major driver of model–measurement discrepancies (aside from differing spatial representativeness and uncertainties and biases in measurements) are shortcomings in absolute emissions rather than in modelling the atmospheric processes. The comprehensive evaluations presented in this study support the application of this model framework for global analysis of current and potential future budgets and deposition of Nr and SIA.

scholarly journals Overview of mercury dry deposition, litterfall, and throughfall studies

2016 ◽  
Author(s):  
L. Paige Wright ◽  
Leiming Zhang ◽  
Frank J. Marsik
Keyword(s):  
North America ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Current Knowledge ◽  
Measurement Methods ◽  
Anthropogenic Emissions ◽  
Transport Models ◽  
Modelling Method ◽  
Chemical Transport Models ◽  
Or Modelling

Abstract. The current knowledge concerning mercury dry deposition is reviewed, including dry deposition algorithms used in chemical transport models (CTMs) and at monitoring sites and related deposition calculations, measurement methods and studies for quantifying dry deposition of gaseous oxidized mercury (GOM) and particulate bound mercury (PBM), and measurement studies of litterfall and throughfall mercury. Measured median GOM plus PBM dry deposition in Asia (10.7 μg m−2 yr−1) almost double that in North America (6.1 μg m−2 yr−1) due to the higher anthropogenic emissions in Asia. Measured median litterfall and throughfall mercury are 22.3 and 56.5 μg m−2 yr−1, respectively, in Asia, 12.8 and 16.3 μg m−2 yr−1 in Europe, and 11.9 and 7.0 μg m−2 yr−1 in North America. The much higher litterfall mercury than GOM plus PBM dry deposition suggests the important contribution of gaseous elemental mercy (GEM) to mercury dry deposition to vegetated canopies. Over all the regions, including the Amazon, dry deposition, estimated as the sum of litterfall and throughfall minus open-field wet deposition, is more dominant than wet deposition for Hg deposition. Regardless of the measurement or modelling method used, a factor of two or larger uncertainties in GOM plus PBM dry deposition need to be kept in mind when using these numbers for mercury impact studies.

scholarly journals Source attribution of Arctic black carbon constrained by aircraft and surface measurements

2017 ◽  
Vol 17 (19) ◽  
pp. 11971-11989 ◽  
Author(s):  
Jun-Wei Xu ◽  
Randall V. Martin ◽  
Andrew Morrow ◽  
Sangeeta Sharma ◽  
Lin Huang ◽  
...  
Keyword(s):  
North America ◽  
Biomass Burning ◽  
Western Siberia ◽  
Transport Model ◽  
Chemical Transport ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
Chemical Transport Model ◽  
Northern Asia ◽  
Airborne Measurements

Abstract. Black carbon (BC) contributes to Arctic warming, yet sources of Arctic BC and their geographic contributions remain uncertain. We interpret a series of recent airborne (NETCARE 2015; PAMARCMiP 2009 and 2011 campaigns) and ground-based measurements (at Alert, Barrow and Ny-Ålesund) from multiple methods (thermal, laser incandescence and light absorption) with the GEOS-Chem global chemical transport model and its adjoint to attribute the sources of Arctic BC. This is the first comparison with a chemical transport model of refractory BC (rBC) measurements at Alert. The springtime airborne measurements performed by the NETCARE campaign in 2015 and the PAMARCMiP campaigns in 2009 and 2011 offer BC vertical profiles extending to above 6 km across the Arctic and include profiles above Arctic ground monitoring stations. Our simulations with the addition of seasonally varying domestic heating and of gas flaring emissions are consistent with ground-based measurements of BC concentrations at Alert and Barrow in winter and spring (rRMSE  < 13 %) and with airborne measurements of the BC vertical profile across the Arctic (rRMSE  = 17 %) except for an underestimation in the middle troposphere (500–700 hPa).Sensitivity simulations suggest that anthropogenic emissions in eastern and southern Asia have the largest effect on the Arctic BC column burden both in spring (56 %) and annually (37 %), with the largest contribution in the middle troposphere (400–700 hPa). Anthropogenic emissions from northern Asia contribute considerable BC (27 % in spring and 43 % annually) to the lower troposphere (below 900 hPa). Biomass burning contributes 20 % to the Arctic BC column annually.At the Arctic surface, anthropogenic emissions from northern Asia (40–45 %) and eastern and southern Asia (20–40 %) are the largest BC contributors in winter and spring, followed by Europe (16–36 %). Biomass burning from North America is the most important contributor to all stations in summer, especially at Barrow.Our adjoint simulations indicate pronounced spatial heterogeneity in the contribution of emissions to the Arctic BC column concentrations, with noteworthy contributions from emissions in eastern China (15 %) and western Siberia (6.5 %). Although uncertain, gas flaring emissions from oilfields in western Siberia could have a striking impact (13 %) on Arctic BC loadings in January, comparable to the total influence of continental Europe and North America (6.5 % each in January). Emissions from as far as the Indo-Gangetic Plain could have a substantial influence (6.3 % annually) on Arctic BC as well.

scholarly journals Composite study of aerosol export events from East Asia and North America

2012 ◽  
Vol 12 (8) ◽  
pp. 21977-22022 ◽  
Author(s):  
Y. Luan ◽  
L. Jaeglé
Keyword(s):  
Boundary Layer ◽  
North America ◽  
East Asia ◽  
Transport Model ◽  
Lower Troposphere ◽  
Temporal Variations ◽  
The Arctic ◽  
Chemical Transport Model ◽  
Mean Values ◽  
Warm Conveyor Belts

Abstract. We use satellite observations of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectrometer (MODIS) together with the GEOS-Chem global chemical transport model to contrast export of aerosols from East Asia and North America during 2004–2010. The GEOS-Chem model reproduces the spatial distribution and temporal variations of Asian aerosol outflow generally well, although a low bias (−30%) is found in the model fine mode AOD. We use the model to identify 244 aerosol pollution export events from E. Asia and 251 export events from N. America over our 7-yr study period. When these events are composited by season, we find that the AOD in the outflow is enhanced by 50–100% relative to seasonal mean values. The composite Asian plume splits into one branch going poleward towards the Arctic, with the other crossing the Pacific in 6–8 days. A fraction of the aerosols is trapped in the subtropical Pacific High. The N. American plume travels to the northeast Atlantic, reaching Europe after 4–5 days. Part of the composite plume turns anticyclonically in the Azores High, where it slowly decays. Both the Asian and N. American export events are favored by a dipole structure in sea-level pressure anomalies, associated with mid-latitude cyclone activity over the respective source regions. The observed AOD in the E. Asian outflow exhibits stronger seasonality, with a spring maximum, than the N. American outflow, with a weak summer maximum. The large spring AOD in the Asian outflow is the result of enhanced sulfate and dust aerosol concentrations, but is also due to a larger export efficiency of sulfate and SO2 from the Asian boundary layer relative to the N. American boundary layer. While the N. American sulfate outflow is mostly found in the lower troposphere (1–3 km altitude), the Asian sulfate outflow occurs at higher altitudes (2–6 km). In the Asian outflow 42–59% of the sulfate column is present above 2 km altitude, with only 24–35% in the N. American outflow. We link this to the factor of 2–5 lower precipitation in the warm conveyor belts (WCB) of midlatitude cyclones over E. Asia compared to N. America. This relative lack of precipitation makes Asian WCB very efficient for injecting aerosols in the middle troposphere.

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