scholarly journals Size-dependent wet removal of black carbon in Canadian biomass burning plumes

2014 ◽  
Vol 14 (13) ◽  
pp. 19469-19513 ◽  
Author(s):  
J. W. Taylor ◽  
J. D. Allan ◽  
G. Allen ◽  
H. Coe ◽  
P. I. Williams ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Vertical Gradient ◽  
Radiative Energy ◽  
Dominant Mechanism ◽  
Calculated Mass ◽  
Nucleation Scavenging ◽  
Opposing Effects ◽  
Wet Removal

Abstract. Wet deposition is the dominant mechanism for removing black carbon (BC) from the atmosphere, and is key in determining its atmospheric lifetime, vertical gradient and global transport. Despite the importance of BC in the climate system, especially in terms of its ability to modulate the radiative energy budget, there are few quantitative case studies of wet removal in ambient environments. We present a case study of BC wet removal by examining aerosol size distributions and BC coating properties sampled in three Canadian boreal biomass burning plumes, one of which passed through a precipitating cloud. In this plume, the largest and most coated BC particles were found to be preferentially removed, suggesting that nucleation scavenging was the likely dominant mechanism. Calculated mass absorption coefficient (MAC) in the plumes showed no significant variation, as the shifts to smaller BC cores and thinner coatings had opposing effects. Similarly, calculated single-scatter albedo (SSA) showed little variation, as a large number of non-BC particles were also present in the precipitation-affected plume. The remaining BC cores were smaller than those observed in previous studies of BC in post-precipitation outflow over Asia, possibly due to the thick coatings associated with the biomass burning particles. This study provides important constraints to model parameterisations of BC wet removal in biomass burning regions, which will help to reduce uncertainty in radiative forcing calculations.

scholarly journals Size-dependent wet removal of black carbon in Canadian biomass burning plumes

2014 ◽  
Vol 14 (24) ◽  
pp. 13755-13771 ◽  
Author(s):  
J. W. Taylor ◽  
J. D. Allan ◽  
G. Allen ◽  
H. Coe ◽  
P. I. Williams ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Vertical Gradient ◽  
Single Scattering ◽  
Radiative Energy ◽  
Dominant Mechanism ◽  
Nucleation Scavenging ◽  
Biomass Burning Particles ◽  
Wet Removal

Abstract. Wet deposition is the dominant mechanism for removing black carbon (BC) from the atmosphere and is key in determining its atmospheric lifetime, vertical gradient and global transport. Despite the importance of BC in the climate system, especially in terms of its ability to modulate the radiative energy budget, there are few quantitative case studies of wet removal in ambient environments. We present a case study of BC wet removal by examining aerosol size distributions and BC coating properties sampled in three Canadian boreal biomass burning plumes, one of which passed through a precipitating cloud. This depleted the majority of the plume's BC mass, and the largest and most coated BC-containing particles were found to be preferentially removed, suggesting that nucleation scavenging was likely the dominant mechanism. Calculated single-scattering albedo (SSA) showed little variation, as a large number of non-BC particles were also present in the precipitation-affected plume. The remaining BC cores were smaller than those observed in previous studies of BC in post-precipitation outflow over Asia, possibly due to the thick coating by hydrophilic compounds associated with the Canadian biomass burning particles. This study provides measurements of BC size, mixing state and removal efficiency to constrain model parameterisations of BC wet removal in biomass burning regions, which will help to reduce uncertainty in radiative forcing calculations.

scholarly journals Wet removal of black carbon in Asian outflow: Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign

2012 ◽  
Vol 117 (D3) ◽  
pp. n/a-n/a ◽  
Author(s):  
N. Oshima ◽  
Y. Kondo ◽  
N. Moteki ◽  
N. Takegawa ◽  
M. Koike ◽  
...  
Keyword(s):  
East Asia ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Aerosol Radiative Forcing ◽  
Aerosol Radiative ◽  
Wet Removal

scholarly journals Influence of cloud microphysical processes on black carbon wet removal, global distributions, and radiative forcing

2018 ◽  
Author(s):  
Jiayu Xu ◽  
Jiachen Zhang ◽  
Junfeng Liu ◽  
Kan Yi ◽  
Songlin Xiang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Wet Deposition ◽  
Radiative Forcing ◽  
Cloud Water ◽  
Ice Nucleation ◽  
Cloud Microphysical Processes ◽  
Vertical Distributions ◽  
Microphysical Processes ◽  
Aerosol Activation ◽  
Wet Removal

Abstract. Parameterizations that impact wet removal of black carbon remain uncertain in global climate models. In this study, we enhance the default wet deposition scheme for BC in the Community Earth System Model (CESM) to (a) add relevant physical processes that were not resolved in the default model, and (b) facilitate understanding of the relative importance of various cloud processes on BC distributions. We find that the enhanced scheme greatly improves model performance against HIPPO observations relative to the default scheme. We find that convection scavenging, aerosol activation, ice nucleation, evaporation of rain/snow, and below cloud scavenging dominate wet deposition of BC. BC conversion rates for processes related to in-cloud water/ice conversion (i.e., riming, the Bergeron processes, and evaporation of cloud water sedimentation) are relatively smaller, but have large seasonal variations. We also conduct sensitivity simulations that turn off each cloud process one at a time to quantify the influence of cloud processes on BC distributions and radiative forcing. Convective scavenging is found to most significantly influence BC concentrations at mid-altitudes over the tropics and even globally. In addition, BC is sensitive to all cloud processes over the Northern Hemisphere at high latitudes. As for BC vertical distributions, convective scavenging has a dominant influence. Aerosol activation mainly increases the fraction of column BC below 5 km whereas ice nucleation decreases that above 10 km. During wintertime, the Bergeron process also significantly increases BC concentrations at lower altitudes over the Arctic. Our simulation yields a global BC burden of 85 Gg; corresponding direct radiative forcing (DRF) of BC estimated using the Parallel Offline Radiative Transfer (PORT) is 0.13 W m−2, much lower than previous studies. The range of DRF derived from sensitivity simulations is large, 0.09–0.33 W m−2, corresponding to BC burdens varying from 73 Gg to 151 Gg. Due to differences in BC vertical distributions among each sensitivity simulation, fractional changes in DRF (relative to the baseline simulation) are always higher than fractional changes in BC burdens; this occurs because relocating BC in the vertical influences the radiative forcing per BC mass. Our results highlight the influences of cloud microphysical processes on BC concentrations and radiative forcing.

scholarly journals Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

2016 ◽  
Vol 9 (12) ◽  
pp. 6117-6137 ◽  
Author(s):  
Adam T. Ahern ◽  
Ramachandran Subramanian ◽  
Georges Saliba ◽  
Eric M. Lipsky ◽  
Neil M. Donahue ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Particle Mass ◽  
Laser Vaporization ◽  
Mass Spectrometers ◽  
Ir Laser ◽  
Biomass Burning Particles

Abstract. Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IR vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.

scholarly journals Influence of cloud microphysical processes on black carbon wet removal, global distributions, and radiative forcing

2019 ◽  
Vol 19 (3) ◽  
pp. 1587-1603 ◽  
Author(s):  
Jiayu Xu ◽  
Jiachen Zhang ◽  
Junfeng Liu ◽  
Kan Yi ◽  
Songlin Xiang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Wet Deposition ◽  
Radiative Forcing ◽  
Cloud Water ◽  
Ice Nucleation ◽  
The Arctic ◽  
Cloud Microphysical Processes ◽  
Vertical Distributions ◽  
Microphysical Processes ◽  
Wet Removal

Abstract. Parameterizations that impact wet removal of black carbon (BC) remain uncertain in global climate models. In this study, we enhance the default wet deposition scheme for BC in the Community Earth System Model (CESM) to (a) add relevant physical processes that were not resolved in the default model and (b) facilitate understanding of the relative importance of various cloud processes on BC distributions. We find that the enhanced scheme greatly improves model performance against HIPPO observations relative to the default scheme. We find that convection scavenging, aerosol activation, ice nucleation, evaporation of rain or snow, and below-cloud scavenging dominate wet deposition of BC. BC conversion rates for processes related to in-cloud water–ice conversion (i.e., riming, the Bergeron process, and evaporation of cloud water sedimentation) are relatively smaller, but have large seasonal variations. We also conduct sensitivity simulations that turn off each cloud process one at a time to quantify the influence of cloud processes on BC distributions and radiative forcing. Convective scavenging is found to have the largest impact on BC concentrations at mid-altitudes over the tropics and even globally. In addition, BC is sensitive to all cloud processes over the Northern Hemisphere at high latitudes. As for BC vertical distributions, convective scavenging greatly influences BC fractions at different altitudes. Suppressing BC droplet activation in clouds mainly decreases the fraction of column BC below 5 km, whereas suppressing BC ice nucleation increases that above 10 km. During wintertime, the Bergeron process also significantly increases BC concentrations at lower altitudes over the Arctic. Our simulation yields a global BC burden of 85 Gg; corresponding direct radiative forcing (DRF) of BC estimated using the Parallel Offline Radiative Transfer (PORT) is 0.13 W m−2, much lower than previous studies. The range of DRF derived from sensitivity simulations is large, 0.09–0.33 W m−2, corresponding to BC burdens varying from 73 to 151 Gg. Due to differences in BC vertical distributions among each sensitivity simulation, fractional changes in DRF (relative to the baseline simulation) are always higher than fractional changes in BC burdens; this occurs because relocating BC in the vertical influences the radiative forcing per BC mass. Our results highlight the influences of cloud microphysical processes on BC concentrations and radiative forcing.

scholarly journals Cross-polar transport and scavenging of Siberian aerosols containing black carbon during the 2012 ACCESS summer campaign

2017 ◽  
Vol 17 (18) ◽  
pp. 10969-10995 ◽  
Author(s):  
Jean-Christophe Raut ◽  
Louis Marelle ◽  
Jerome D. Fast ◽  
Jennie L. Thomas ◽  
Bernadett Weinzierl ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Large Scale ◽  
Arctic Region ◽  
Anthropogenic Sources ◽  
The Arctic ◽  
Convective Precipitation ◽  
Svalbard Archipelago ◽  
Wet Removal ◽  
The Arctic Region

Abstract. During the ACCESS airborne campaign in July 2012, extensive boreal forest fires resulted in significant aerosol transport to the Arctic. A 10-day episode combining intense biomass burning over Siberia and low-pressure systems over the Arctic Ocean resulted in efficient transport of plumes containing black carbon (BC) towards the Arctic, mostly in the upper troposphere (6–8 km). A combination of in situ observations (DLR Falcon aircraft), satellite analysis and WRF-Chem simulations is used to understand the vertical and horizontal transport mechanisms of BC with a focus on the role of wet removal. Between the northwestern Norwegian coast and the Svalbard archipelago, the Falcon aircraft sampled plumes with enhanced CO concentrations up to 200 ppbv and BC mixing ratios up to 25 ng kg−1. During transport to the Arctic region, a large fraction of BC particles are scavenged by two wet deposition processes, namely wet removal by large-scale precipitation and removal in wet convective updrafts, with both processes contributing almost equally to the total accumulated deposition of BC. Our results underline that applying a finer horizontal resolution (40 instead of 100 km) improves the model performance, as it significantly reduces the overestimation of BC levels observed at a coarser resolution in the mid-troposphere. According to the simulations at 40 km, the transport efficiency of BC (TEBC) in biomass burning plumes was larger (60 %), because it was impacted by small accumulated precipitation along trajectory (1 mm). In contrast TEBC was small (< 30 %) and accumulated precipitation amounts were larger (5–10 mm) in plumes influenced by urban anthropogenic sources and flaring activities in northern Russia, resulting in transport to lower altitudes. TEBC due to large-scale precipitation is responsible for a sharp meridional gradient in the distribution of BC concentrations. Wet removal in cumulus clouds is the cause of modeled vertical gradient of TEBC, especially in the mid-latitudes, reflecting the distribution of convective precipitation, but is dominated in the Arctic region by the large-scale wet removal associated with the formation of stratocumulus clouds in the planetary boundary layer (PBL) that produce frequent drizzle.

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