scholarly journals Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling

2019 ◽  
Vol 5 (2) ◽  
pp. eaau8052 ◽  
Author(s):  
P. Winiger ◽  
T. E. Barrett ◽  
R. J. Sheesley ◽  
L. Huang ◽  
S. Sharma ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Transport Model ◽  
The Arctic ◽  
Emission Inventories ◽  
Source Contributions ◽  
Model Predictions ◽  
The Impact ◽  
Good Agreement

Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 ± 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.

scholarly journals Sources of Springtime Surface Black Carbon in the Arctic: An Adjoint Analysis

2017 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Daven K. Henze ◽  
Hsien-Liang Tseng ◽  
Cenlin He
Keyword(s):  
Natural Gas ◽  
Black Carbon ◽  
Biomass Burning ◽  
Transport Model ◽  
Lower Troposphere ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
Anthropogenic Source ◽  
Gas Flaring ◽  
Arctic Front

Abstract. We quantify source contributions to springtime (April 2008) surface black carbon (BC) in the Arctic by interpreting surface observations of BC at five receptor sites (Denali, Barrow, Alert, Zeppelin, and Summit) using a global chemical transport model (GEOS-Chem) and its adjoint. Contributions to BC at Barrow, Alert, and Zeppelin are dominated by Asian anthropogenic sources (40–43 %) before April 18 and by Siberian open biomass burning emissions (29–41 %) afterward. In contrast, Summit, a mostly free tropospheric site, has predominantly an Asian anthropogenic source contribution (24–68 %, with an average of 45 %). We compute the adjoint sensitivity of BC concentrations at the five sites during a pollution episode (April 20–25) to global emissions from March 1 to April 25. The associated contributions are the combined results of these sensitivities and BC emissions. Local and regional anthropogenic sources in Alaska are the largest anthropogenic sources of BC at Denali (63 %), and natural gas flaring emissions in the Western Extreme North of Russia (WENR) are the largest anthropogenic sources of BC at Zeppelin (26 %) and Alert (13 %). We find that long-range transport of emissions from Beijing-Tianjin-Hebei (also known as Jing-Jin-Ji), the biggest urbanized region in Northern China, contribute significantly (~ 10 %) to surface BC across the Arctic. On average it takes ~ 12 days for Asian anthropogenic emissions and Siberian biomass burning emissions to reach Arctic lower troposphere, supporting earlier studies. Natural gas flaring emissions from the WENR reach Zeppelin in about a week. We find that episodic, direct transport events dominate BC at Denali (87 %), a site outside the Arctic front, a strong transport barrier. The relative contribution of direct transport to surface BC within the Arctic front is much smaller (~ 50 % at Barrow and Zeppelin and ~ 10 % at Alert). The large contributions from Asian anthropogenic sources are predominately in the form of ‘chronic’ pollution (~ 40 % at Barrow and 65 % at Alert and 57 % at Zeppelin) on 1–2 month timescales. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic. Both finer temporal resolution of biomass burning emissions and accounting for the Wegener-Bergeron-Findeisen (WBF) process in wet scavenging improve the source attribution estimates.

scholarly journals Tagged tracer simulations of black carbon in the Arctic: Transport, source contributions, and budget

2017 ◽  
Author(s):  
Kohei Ikeda ◽  
Hiroshi Tanimoto ◽  
Takafumi Sugita ◽  
Hideharu Akiyoshi ◽  
Yugo Kanaya ◽  
...  
Keyword(s):  
East Asia ◽  
Black Carbon ◽  
Long Range ◽  
Biomass Burning ◽  
East Asian ◽  
The Arctic ◽  
Long Range Transport ◽  
Middle Troposphere ◽  
Source Contributions ◽  
Range Transport

Abstract. We implemented a tagged tracer method of black carbon (BC) into a global chemistry-transport model GEOS-Chem, examined the pathways and efficiency of long-range transport from a variety of anthropogenic and biomass burning emission sources to the Arctic, and quantified the source contributions of individual emissions. Firstly, we evaluated the simulated BC by comparing it with observations at the Arctic sites and found that the simulated seasonal variations were improved by implementing an aging parameterization and reducing the wet scavenging rate by ice clouds. For tagging BC, we added BC tracers distinguished by source types (anthropogenic and biomass burning) and regions; the global domain was divided into 16 and 27 regions for anthropogenic and biomass burning emissions, respectively. Our simulations showed that BC emitted from Europe and Russia was transported to the Arctic mainly in the lower troposphere during winter and spring. In particular, BC transported from Russia was widely spread over the Arctic in winter and spring, leading to a dominant contribution of 62 % to the Arctic BC near the surface as the annual mean. In contrast, BC emitted from East Asia was found to be transported in the middle troposphere into the Arctic mainly over the Okhotsk Sea and East Siberia during winter and spring. We identified an important window area, which allowed a strong incoming of East Asian BC to the Arctic (130°–180° E and 3–8 km altitude at 66° N). The model demonstrated that the contribution from East Asia to the Arctic had a maximum at about 5 km altitude due to uplifting during the long-range transport in early spring. The efficiency of BC transport from East Asia to the Arctic was smaller than that from other large source regions such as Europe, Russia and North America. However, the East Asian contribution was most important for BC in the middle troposphere (41 %) and BC burden over the Arctic (27 %) because of the large emissions from this region. These results suggested that the main sources of the Arctic BC differed with altitude. The contribution of all the anthropogenic sources to Arctic BC concentrations near the surface was dominant (90 %) on an annual basis. The contributions of biomass burning in boreal regions (Siberia, Alaska and Canada) to the annual total BC deposition onto the Arctic were estimated to be 12–15 %, which became the maximum during summer.

scholarly journals Aircraft observations of enhancement and depletion of black carbon mass in the springtime Arctic

2010 ◽  
Vol 10 (6) ◽  
pp. 15167-15196
Author(s):  
J. R. Spackman ◽  
R. S. Gao ◽  
W. D. Neff ◽  
J. P. Schwarz ◽  
L. A. Watts ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Black Carbon ◽  
Biomass Burning ◽  
Boundary Layer Transition ◽  
Arctic Climate ◽  
The Arctic ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Air Mass ◽  
The Impact

Abstract. Understanding the processes controlling black carbon (BC) in the Arctic is crucial for evaluating the impact of anthropogenic and natural sources of BC on Arctic climate. Vertical profiles of BC mass were observed from the surface to near 7-km altitude in April 2008 using a Single-Particle Soot Photometer (SP2) during flights on the NOAA WP-3D research aircraft from Fairbanks, Alaska. These measurements were conducted during the NOAA-sponsored Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project as part of POLARCAT, an International Polar Year (IPY) activity. In the free troposphere, the Arctic air mass was influenced by long-range transport from biomass-burning and anthropogenic source regions at lower latitudes especially during the latter part of the campaign. Maximum average BC mass loadings of 150 ng kg−1 were observed near 5.5-km altitude in the aged Arctic air mass. In biomass-burning plumes, BC was enhanced from near the top of the Arctic boundary layer (ABL) to 5.5 km compared to the aged Arctic air mass. At the bottom of some of the profiles, positive vertical gradients in BC were observed in the vicinity of open leads in the sea-ice. BC mass loadings increased by about a factor of two across the boundary layer transition in the ABL in these cases while carbon monoxide (CO) remained constant, evidence for depletion of BC in the ABL. BC mass loadings were positively correlated with O3 in ozone depletion events (ODEs) for all the observations in the ABL suggesting that BC was removed by dry deposition of BC on the snow or ice because molecular bromine, Br2, which photolyzes and catalytically destroys O3, is thought to be released near the open leads in regions of ice formation. We estimate the deposition flux of BC mass to the snow using a box model constrained by the vertical profiles of BC in the ABL. The open leads may increase vertical mixing in the ABL and entrainment of pollution from the free troposphere possibly enhancing the deposition of BC to the snow.

scholarly journals Sources of springtime surface black carbon in the Arctic: an adjoint analysis for April 2008

2017 ◽  
Vol 17 (15) ◽  
pp. 9697-9716 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Daven K. Henze ◽  
Hsien-Liang Tseng ◽  
Cenlin He
Keyword(s):  
Natural Gas ◽  
Black Carbon ◽  
Biomass Burning ◽  
Transport Model ◽  
Lower Troposphere ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
Anthropogenic Source ◽  
Chemical Transport Model ◽  
Gas Flaring

Abstract. We quantify source contributions to springtime (April 2008) surface black carbon (BC) in the Arctic by interpreting surface observations of BC at five receptor sites (Denali, Barrow, Alert, Zeppelin, and Summit) using a global chemical transport model (GEOS-Chem) and its adjoint. Contributions to BC at Barrow, Alert, and Zeppelin are dominated by Asian anthropogenic sources (40–43 %) before 18 April and by Siberian open biomass burning emissions (29–41 %) afterward. In contrast, Summit, a mostly free tropospheric site, has predominantly an Asian anthropogenic source contribution (24–68 %, with an average of 45 %). We compute the adjoint sensitivity of BC concentrations at the five sites during a pollution episode (20–25 April) to global emissions from 1 March to 25 April. The associated contributions are the combined results of these sensitivities and BC emissions. Local and regional anthropogenic sources in Alaska are the largest anthropogenic sources of BC at Denali (63 % of total anthropogenic contributions), and natural gas flaring emissions in the western extreme north of Russia (WENR) are the largest anthropogenic sources of BC at Zeppelin (26 %) and Alert (13 %). We find that long-range transport of emissions from Beijing–Tianjin–Hebei (also known as Jing–Jin–Ji), the biggest urbanized region in northern China, contribute significantly (∼ 10 %) to surface BC across the Arctic. On average, it takes ∼ 12 days for Asian anthropogenic emissions and Siberian biomass burning emissions to reach the Arctic lower troposphere, supporting earlier studies. Natural gas flaring emissions from the WENR reach Zeppelin in about a week. We find that episodic transport events dominate BC at Denali (87 %), a site outside the Arctic front, which is a strong transport barrier. The relative contribution of these events to surface BC within the polar dome is much smaller (∼ 50 % at Barrow and Zeppelin and ∼ 10 % at Alert). The large contributions from Asian anthropogenic sources are predominately in the form of chronic pollution (∼ 40 % at Barrow, 65 % at Alert, and 57 % at Zeppelin) on about a 1-month timescale. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic.

Uncertainties in biomass burning emission estimates and their impact on air pollution model predictions over Africa

2021 ◽  
Author(s):  
Idir Bouarar ◽  
Angelika Heil ◽  
Adrien Deroubaix ◽  
Auke Visser ◽  
Folkert Boersma ◽  
...  
Keyword(s):  
Air Pollution ◽  
Biomass Burning ◽  
Model Simulation ◽  
Tropospheric Chemistry ◽  
Sensor Data ◽  
Burned Area ◽  
Emission Inventories ◽  
Model Predictions ◽  
The Impact ◽  
Air Pollution Model

<p>Africa is the biggest continental source of biomass burning (BB) emissions. The large fluxes of chemical pollutants and aerosol emitted during intense BB events can strongly alter tropospheric chemistry and cloud dynamics and can result in widespread air pollution. Available BB emission inventories differ in terms of satellite sensor data and assumptions and methodologies used to estimate emission fluxes, and show substantial differences in emission totals and spatial and temporal patterns. The omission of small fires (<100 ha) by most satellite products is one key factor on the accuracy of the emission inventories.</p><p>The ESA Fire_CCI project has released the first burned area product for Africa from 20 m Sentinel satellite information (FireCCISFD11). Here we present new BB emission estimates for Africa based on FireCCISFD11. By resolving small fires, this inventory (Fire_CCI) yields 60 to 110% higher burning rates in 2016 than the MODIS-based products such as GFED4s, GFED4, MCD64A1 Collection 6, FireCCI51 and FINN. We perform WRF-Chem model simulation with three BB emission inventories (FINN, GFED4s and Fire_CCI) for summer 2016 corresponding with the DACCIWA aircraft campaign, which took place in June-July 2016 over Africa. We investigate the impact of uncertainties in BB emission estimates on air pollution model predictions using measurements of chemical species and aerosols from DACCIWA, NO2 and CO data from OMI and MOPITT satellites, respectively, and ground-based AOD observations from the Aeronet network. We furthermore assess the ability of the model in terms of the representation of transport of BB air masses and of the representation of chemical composition in such plumes.</p>

scholarly journals Space-based retrieval of NO<sub>2</sub> over biomass burning regions: quantifying and reducing uncertainties

2014 ◽  
Vol 7 (10) ◽  
pp. 3431-3444 ◽  
Author(s):  
N. Bousserez
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Shape Factor ◽  
Transport Model ◽  
Sensitivity Analyses ◽  
The Arctic ◽  
Ozone Monitoring Instrument ◽  
Aerosol Optical Properties ◽  
Atmospheric Scattering ◽  
The Impact

Abstract. The accuracy of space-based nitrogen dioxide (NO2) retrievals from solar backscatter radiances critically depends on a priori knowledge of the vertical profiles of NO2 and aerosol optical properties. This information is used to calculate an air mass factor (AMF), which accounts for atmospheric scattering and is used to convert the measured line-of-sight "slant" columns into vertical columns. In this study we investigate the impact of biomass burning emissions on the AMF in order to quantify NO2 retrieval errors in the Ozone Monitoring Instrument (OMI) products over these sources. Sensitivity analyses are conducted using the Linearized Discrete Ordinate Radiative Transfer (LIDORT) model. The NO2 and aerosol profiles are obtained from a 3-D chemistry-transport model (GEOS-Chem), which uses the Fire Locating and Monitoring of Burning Emissions (FLAMBE) daily biomass burning emission inventory. Aircraft in situ data collected during two field campaigns, the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) and the Dust and Biomass-burning Experiment (DABEX), are used to evaluate the modeled aerosol optical properties and NO2 profiles over Canadian boreal fires and West African savanna fires, respectively. Over both domains, the effect of biomass burning emissions on the AMF through the modified NO2 shape factor can be as high as −60%. A sensitivity analysis also revealed that the effect of aerosol and shape factor perturbations on the AMF is very sensitive to surface reflectance and clouds. As an illustration, the aerosol correction can range from −20 to +100% for different surface reflectances, while the shape factor correction varies from −70 to −20%. Although previous studies have shown that in clear-sky conditions the effect of aerosols on the AMF was in part implicitly accounted for by the modified cloud parameters, here it is suggested that when clouds are present above a surface layer of scattering aerosols, an explicit aerosol correction would be beneficial to the NO2 retrieval. Finally, a new method that uses slant column information to correct for shape-factor-related AMF error over NOx emission sources is proposed, with possible application to near-real-time OMI retrievals.

scholarly journals Aircraft observations of enhancement and depletion of black carbon mass in the springtime Arctic

2010 ◽  
Vol 10 (19) ◽  
pp. 9667-9680 ◽  
Author(s):  
J. R. Spackman ◽  
R. S. Gao ◽  
W. D. Neff ◽  
J. P. Schwarz ◽  
L. A. Watts ◽  
...  
Keyword(s):  
Sea Ice ◽  
Black Carbon ◽  
Biomass Burning ◽  
Dry Deposition ◽  
Arctic Climate ◽  
The Arctic ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Air Mass ◽  
The Impact

Abstract. Understanding the processes controlling black carbon (BC) in the Arctic is crucial for evaluating the impact of anthropogenic and natural sources of BC on Arctic climate. Vertical profiles of BC mass loadings were observed from the surface to near 7-km altitude in April 2008 using a Single-Particle Soot Photometer (SP2) during flights on the NOAA WP-3D research aircraft from Fairbanks, Alaska. These measurements were conducted during the NOAA-sponsored Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project. In the free troposphere, the Arctic air mass was influenced by long-range transport from biomass-burning and anthropogenic source regions at lower latitudes especially during the latter part of the campaign. Average BC mass mixing ratios peaked at about 150 ng BC (kg dry air )−1 near 5.5 km altitude in the aged Arctic air mass and 250 ng kg−1 at 4.5 km in biomass-burning influenced air. BC mass loadings were enhanced by up to a factor of 5 in biomass-burning influenced air compared to the aged Arctic air mass. At the bottom of some of the profiles, positive vertical gradients in BC were observed over the sea-ice. The vertical profiles generally occurred in the vicinity of open leads in the sea-ice. In the aged Arctic air mass, BC mass loadings more than doubled with increasing altitude within the ABL and across the boundary layer transition while carbon monoxide (CO) remained constant. This is evidence for depletion of BC mass in the ABL. BC mass loadings were positively correlated with O3 in ozone depletion events (ODEs) for all the observations in the ABL. Since bromine catalytically destroys ozone in the ABL after being released as molecular bromine in regions of new sea-ice formation at the surface, the BC–O3 correlation suggests that BC particles were removed by a surface process such as dry deposition. We develop a box model to estimate the dry deposition flux of BC mass to the snow constrained by the vertical profiles of BC mass in the ABL. Open leads in the sea-ice may increase vertical mixing and entrainment of pollution from the free troposphere possibly enhancing the deposition of BC aerosol to the snow.

scholarly journals Fossil fuel combustion and biomass burning sources of global black carbon from GEOS-Chem simulation and carbon isotope measurements

2019 ◽  
Vol 19 (17) ◽  
pp. 11545-11557 ◽  
Author(s):  
Ling Qi ◽  
Shuxiao Wang
Keyword(s):  
Black Carbon ◽  
Carbon Isotope ◽  
Biomass Burning ◽  
Fossil Fuel ◽  
Transport Model ◽  
Fuel Combustion ◽  
The Arctic ◽  
Fossil Fuel Combustion ◽  
The Antarctic ◽  
Isotope Measurements

Abstract. We identify sources (fossil fuel combustion versus biomass burning) of black carbon (BC) in the atmosphere and in deposition using a global 3-D chemical transport model GEOS-Chem. We validate the simulated sources against carbon isotope measurements of BC around the globe and find that the model reproduces mean biomass burning contribution (fbb; %) in various regions within a factor of 2 (except in Europe, where fbb is underestimated by 63 %). GEOS-Chem shows that contribution from biomass burning in the Northern Hemisphere (fbb: 35±14 %) is much less than that in the Southern Hemisphere (50±11 %). The largest atmospheric fbb is in Africa (64±20 %). Comparable contributions from biomass burning and fossil fuel combustion are found in southern (S) Asia (53±10 %), southeastern (SE) Asia (53±11 %), S America (47±14 %), the S Pacific (47±7 %), Australia (53±14 %) and the Antarctic (51±2 %). fbb is relatively small in eastern Asia (40±13 %), Siberia (35±8 %), the Arctic (33±6 %), Canada (31±7 %), the US (25±4 %) and Europe (19±7 %). Both observations and model results suggest that atmospheric fbb is higher in summer (59 %–78 %, varying with sub-regions) than in winter (28 %–32 %) in the Arctic, while it is higher in winter (42 %–58 %) and lower in summer (16 %–42 %) over the Himalayan–Tibetan Plateau. The seasonal variations of Atmosphericfbb are relatively flat in North America, Europe and Asia. We conducted four experiments to investigate the uncertainties associated with biofuel emissions, hygroscopicity of BC in fresh emissions, the aging rate and size-resolved wet scavenging. We find that doubling biofuel emissions for domestic heating north of 45∘ N increases fbb values in Europe in winter by ∼30 %, reducing the discrepancy between observed and modeled atmospheric fbb from −63 % to −54 %. The remaining large negative discrepancy between model and observations suggests that the biofuel emissions are probably still underestimated at high latitudes. Increasing the fraction of thickly coated hydrophilic BC from 20 % to 70 % in fresh biomass burning plumes increases the fraction of hydrophilic BC in biomass burning plumes by 0 %–20 % (varying with seasons and regions) and thereby reduces atmospheric fbb by up to 11 %. Faster aging (4 h e-folding time versus 1.15 d e-folding time) of BC in biomass burning plumes reduces atmospheric fbb by 7 % (1 %–14 %, varying with seasons and regions), with the largest reduction in remote regions, such as the Arctic, the Antarctic and the S Pacific. Using size-resolved scavenging accelerates scavenging of BC particles in both fossil fuel and biomass burning plumes, with a faster scavenging of BC in fossil fuel plumes. Thus, atmospheric fbb increases in most regions by 1 %–14 %. Overall, atmospheric fbb is determined mainly by fbb in emissions and, to a lesser extent, by atmospheric processes, such as aging and scavenging. This confirms the assumption that fbb in local emissions determines atmospheric fbb in previous studies, which compared measured atmospheric fbb directly with local fbb in bottom-up emission inventories.

scholarly journals Parameterization of black carbon aging in the OsloCTM2 and implications for regional transport to the Arctic

2011 ◽  
Vol 11 (12) ◽  
pp. 32499-32534 ◽  
Author(s):  
M. T. Lund ◽  
T. Berntsen
Keyword(s):  
Black Carbon ◽  
High Latitude ◽  
Transport Model ◽  
Seasonal Pattern ◽  
Particle Interaction ◽  
Model Performance ◽  
High Arctic ◽  
The Arctic ◽  
The Impact ◽  
Snow And Ice

Abstract. A critical parameter for the atmospheric lifetime of black carbon (BC) aerosols, and hence for the range over which the particles can be transported, is the aging time, i.e. the time before the aerosols become available for removal by wet deposition. This study compares two different parameterizations of BC aging in the chemistry transport model OsloCTM2: (i) a bulk parameterization (BULK) where aging is represented by a constant transfer to hydrophilic mode and (ii) a microphysical module (M7) where aging occurs through particle interaction and where the particle size distribution is accounted for. We investigate the effect of including microphysics on the distribution of BC globally and in the Arctic. We also focus on the impact on estimated contributions to Arctic BC from selected emission source regions. With more detailed microphysics (M7) there are regional and seasonal variations in aging. The aging is slower during high-latitude winter, when the production of sulfate is lower, than in lower latitudes and during summer. High-latitude concentrations of BC are significantly increased during winter compared to BULK. Furthermore, M7 improves the model performance at high Arctic surface stations, especially the accumulation of BC during winter. A proper representation of vertical BC load is important because the climate effects of the aerosols depend on their altitude in the atmosphere. Comparisons with measured vertical profiles indicate that the model generally overestimates the BC load, particularly at higher altitudes, and this overestimation is exacerbated with M7 compared to BULK. Both parameterizations show that north of 65° N emissions in Europe contribute most to atmospheric BC concentration and to BC in snow and ice. M7 leads to a pronounced seasonal pattern in contributions and contributions from Europe and Russia increase strongly during winter compared to BULK. There is generally a small increase in the amount of BC in snow and ice with M7 compared to BULK, but concentrations are still underestimated relative to measurements.

scholarly journals Fossil fuel combustion and biomass burning sources of global black carbon

2019 ◽  
Author(s):  
Ling Qi ◽  
Shuxiao Wang
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Fossil Fuel ◽  
Transport Model ◽  
The Arctic ◽  
Fossil Fuel Combustion ◽  
Chemical Transport Model ◽  
Fresh Biomass ◽  
The Us ◽  
The Antarctic

Abstract. We identify sources (fossil fuel versus biomass burning) of black carbon (BC) in the atmosphere and in deposition using a global 3D chemical transport model GEOS-Chem. We validate the simulated sources against carbon isotope measurements of BC around the globe and find that the model reproduces biomass burning contribution (fbb, %) in various regions within a factor of 2. GEOS-Chem shows that contribution from biomass burning in the Northern Hemisphere (fbb: 34 %) is much less than that in the Southern Hemisphere (52 %). Specifically, we find comparable contribution from biomass burning and fossil fuel in South Asia, S. America, S. Pacific, Australia and the Antarctic. fbb is the largest in Africa (64 %), followed by that in East Asia (40 %), Siberia (35 %), the Arctic (33 %), Canada (31 %), the US (25 %), and Europe (19 %). fbb is higher in summer (59–78 %) than in winter (28–32 %) in the Arctic, while it is higher in winter (42–58 %) and lower in summer (16–42 %) over the Himalayan–Tibetan plateau. The seasonal variations of fbb are relatively flat in North America, Europe, and Asia. We find that double biofuel emissions for domestic heating during cold seasons northern than 45° N increases fbb values in the Arctic and Europe in winter by ~ 30 %, resulting in a ~ 20 % reduction of discrepancies of fbb in the two regions. The remaining large negative discrepancies (Europe: 41 %; Arctic: 46 %) suggest that the biofuel emissions are probably still underestimated at high latitudes. Increasing fraction of thickly coated hydrophilic BC from 20 % to 70 % in fresh biomass burning plumes increases the fraction of hydrophilic BC in biomass burning plumes by 0–20 % (vary with seasons and regions), and thereby reduces atmospheric fbb by up to 11 %. Faster aging (4 hour e-folding time versus 1.15 days of e-folding time) of BC in biomass burning plumes reduces atmospheric fbb by 7 % (1–14 %), with the largest reduction in remote regions, such as the Arctic, the Antarctic and S. Pacific. Using size resolved scavenging accelerates scavenging of BC particles in both fossil fuel and biomass burning plumes, with a larger increase of the former. Thus, atmospheric fbb increases in most regions by 1–14 %. Overall, atmospheric fbb is determined by fbb in emissions mainly and by atmospheric processes, such as aging and scavenging, to a less extent.

Sign in / Sign up

Export Citation Format

Share Document