Black carbon over a central Himalayan Glacier (Satopanth): Pathways and direct radiative impacts

Abstract. Fires and the aerosols that they emit impact air quality, health, and climate, but the abundance and properties of carbonaceous aerosol (both black carbon and organic carbon) from biomass burning (BB) remain uncertain and poorly constrained. We aim to explore the uncertainties associated with fire emissions and their air quality and radiative impacts from underlying dry matter consumed and emissions factors. To investigate this, we compare model simulations from a global chemical transport model, GEOS-Chem, driven by a variety of fire emission inventories with surface and airborne observations of black carbon (BC) and organic aerosol (OA) concentrations and satellite-derived aerosol optical depth (AOD). We focus on two fire-detection-based and/or burned-area-based (FD-BA) inventories using burned area and active fire counts, respectively, i.e., the Global Fire Emissions Database version 4 (GFED4s) with small fires and the Fire INventory from NCAR version 1.5 (FINN1.5), and two fire radiative power (FRP)-based approaches, i.e., the Quick Fire Emission Dataset version 2.4 (QFED2.4) and the Global Fire Assimilation System version 1.2 (GFAS1.2). We show that, across the inventories, emissions of BB aerosol (BBA) differ by a factor of 4 to 7 over North America and that dry matter differences, not emissions factors, drive this spread. We find that simulations driven by QFED2.4 generally overestimate BC and, to a lesser extent, OA concentrations observations from two fire-influenced aircraft campaigns in North America (ARCTAS and DC3) and from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, while simulations driven by FINN1.5 substantially underestimate concentrations. The GFED4s and GFAS1.2-driven simulations provide the best agreement with OA and BC mass concentrations at the surface (IMPROVE), BC observed aloft (DC3 and ARCTAS), and AOD observed by MODIS over North America. We also show that a sensitivity simulation including an enhanced source of secondary organic aerosol (SOA) from fires, based on the NOAA Fire Lab 2016 experiments, produces substantial additional OA; however, the spread in the primary emissions estimates implies that this magnitude of SOA can be neither confirmed nor ruled out when comparing the simulations against the observations explored here. Given the substantial uncertainty in fire emissions, as represented by these four emission inventories, we find a sizeable range in 2012 annual BBA PM2.5 population-weighted exposure over Canada and the contiguous US (0.5 to 1.6 µg m−3). We also show that the range in the estimated global direct radiative effect of carbonaceous aerosol from fires (−0.11 to −0.048 W m−2) is large and comparable to the direct radiative forcing of OA (−0.09 W m−2) estimated in the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). Our analysis suggests that fire emissions uncertainty challenges our ability to accurately characterize the impact of smoke on air quality and climate.

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Estimating radiative impacts of black carbon associated with mixing state in the lower atmosphere over the northern North China Plain

Chemosphere ◽

10.1016/j.chemosphere.2020.126455 ◽

2020 ◽

Vol 252 ◽

pp. 126455 ◽

Cited By ~ 2

Author(s):

Kang Hu ◽

Delong Zhao ◽

Dantong Liu ◽

Shuo Ding ◽

Ping Tian ◽

...

Keyword(s):

Black Carbon ◽

North China Plain ◽

North China ◽

Lower Atmosphere ◽

Mixing State ◽

Radiative Impacts

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Black carbon fractal morphology and short-wave radiative impact: a modelling study

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-23103-2011 ◽

2011 ◽

Vol 11 (8) ◽

pp. 23103-23137

Author(s):

M. Kahnert ◽

A. Devasthale

Keyword(s):

Optical Properties ◽

Fractal Dimension ◽

Black Carbon ◽

Radiative Forcing ◽

Homogeneous Sphere ◽

Radiative Impacts ◽

Radiative Impact ◽

Sphere Approximation ◽

Carbon Aerosols ◽

Black Carbon Aerosols

Abstract. We investigate the impact of the morphological properties of freshly emitted black carbon aerosols on optical properties and on radiative forcing. To this end, we model the optical properties of fractal black carbon aggregates by use of numerically exact solutions to Maxwell's equations within a spectral range from the UVC to the mid-IR. The results are coupled to radiative transfer computations, in which we consider six realistic case studies representing different atmospheric pollution conditions and surface albedos. The spectrally integrated radiative impacts of black carbon are compared for two different fractal morphologies, which brace the range of recently reported experimental observations of black carbon fractal structures. We also gauge our results by performing corresponding calculations based on the homogeneous sphere approximation, which is commonly employed in climate models. We find that at top of atmosphere the aggregate models yield radiative impacts that can be as much as 2 times higher than those based on the homogeneous sphere approximation. An aggregate model with a low fractal dimension can predict a radiative impact that is higher than that obtained with a high fractal dimension by a factor ranging between 1.1–1.6. Although the lower end of this scale seems like a rather small effect, a closer analysis reveals that the single scattering optical properties of more compact and more lacy aggregates differ considerably. In radiative flux computations there can be a partial cancellation due to the opposing effects of differences in the optical cross sections and asymmetry parameters. However, this cancellation effect can strongly depend on atmospheric conditions and is therefore quite unpredictable. We conclude that the fractal morphology of black carbon aerosols and their fractal parameters can have a profound impact on their radiative forcing effect, and that the use of the homogeneous sphere model introduces unacceptably high biases in radiative impact studies. We emphasise that there are other potentially important morphological features that have not been addressed in the present study, such as sintering and coating of freshly emitted black carbon by films of organic material.

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Global Radiative Impacts of Black Carbon Acting as Ice Nucleating Particles

Geophysical Research Letters ◽

10.1029/2020gl089056 ◽

2020 ◽

Vol 47 (20) ◽

Author(s):

Zachary McGraw ◽

Trude Storelvmo ◽

Bjørn Hallvard Samset ◽

Camilla Weum Stjern

Keyword(s):

Black Carbon ◽

Radiative Impacts

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Global radiative effects of solid fuel cookstove aerosol emissions

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-5219-2018 ◽

2018 ◽

Vol 18 (8) ◽

pp. 5219-5233 ◽

Cited By ~ 5

Author(s):

Yaoxian Huang ◽

Nadine Unger ◽

Trude Storelvmo ◽

Kandice Harper ◽

Yiqi Zheng ◽

...

Keyword(s):

Black Carbon ◽

Solid Fuel ◽

Surface Albedo ◽

Mixed Phase ◽

Radiative Effects ◽

Ice Clouds ◽

Ice Cloud ◽

Radiative Impacts ◽

Standard Deviations ◽

Aerosol Emissions

Abstract. We apply the NCAR CAM5-Chem global aerosol-climate model to quantify the net global radiative effects of black and organic carbon aerosols from global and Indian solid fuel cookstove emissions for the year 2010. Our assessment accounts for the direct radiative effects, changes to cloud albedo and lifetime (aerosol indirect effect, AIE), impacts on clouds via the vertical temperature profile (semi-direct effect, SDE) and changes in the surface albedo of snow and ice (surface albedo effect). In addition, we provide the first estimate of household solid fuel black carbon emission effects on ice clouds. Anthropogenic emissions are from the IIASA GAINS ECLIPSE V5a inventory. A global dataset of black carbon (BC) and organic aerosol (OA) measurements from surface sites and aerosol optical depth (AOD) from AERONET is used to evaluate the model skill. Compared with observations, the model successfully reproduces the spatial patterns of atmospheric BC and OA concentrations, and agrees with measurements to within a factor of 2. Globally, the simulated AOD agrees well with observations, with a normalized mean bias close to zero. However, the model tends to underestimate AOD over India and China by ∼  19 ± 4 % but overestimate it over Africa by ∼  25 ± 11 % (± represents modeled temporal standard deviations for n = 5 run years). Without BC serving as ice nuclei (IN), global and Indian solid fuel cookstove aerosol emissions have net global cooling radiative effects of −141 ± 4 mW m−2 and −12 ± 4 mW m−2, respectively (± represents modeled temporal standard deviations for n = 5 run years). The net radiative impacts are dominated by the AIE and SDE mechanisms, which originate from enhanced cloud condensation nuclei concentrations for the formation of liquid and mixed-phase clouds, and a suppression of convective transport of water vapor from the lower troposphere to the upper troposphere/lower stratosphere that in turn leads to reduced ice cloud formation. When BC is allowed to behave as a source of IN, the net global radiative impacts of the global and Indian solid fuel cookstove emissions range from −275 to +154 mW m−2 and −33 to +24 mW m−2, with globally averaged values of −59 ± 215 and 0.3 ± 29 mW m−2, respectively. Here, the uncertainty range is based on sensitivity simulations that alter the maximum freezing efficiency of BC across a plausible range: 0.01, 0.05 and 0.1. BC–ice cloud interactions lead to substantial increases in high cloud (<  500 hPa) fractions. Thus, the net sign of the impacts of carbonaceous aerosols from solid fuel cookstoves on global climate (warming or cooling) remains ambiguous until improved constraints on BC interactions with mixed-phase and ice clouds are available.

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Measurements and modelling of the impacts of light absorbing impurities during two contrasted snow seasons at Col du Lautaret

10.5194/egusphere-egu2020-3633 ◽

2020 ◽

Author(s):

Marie Dumont ◽

Francois Tuzet ◽

Ghislain Picard ◽

Maxim Lamare ◽

Didier Voisin ◽

...

Keyword(s):

Optical Properties ◽

Black Carbon ◽

Elemental Carbon ◽

Meteorological Conditions ◽

Climate Feedbacks ◽

Seasonal Snow ◽

Chemical Measurements ◽

Radiative Impacts ◽

The Alps ◽

Snow Model

<p>Light absorbing impurities (LAP) in snow, such as dust or black carbon, trigger potent snow-climate feedbacks. However, detailed measurements of the evolution of LAPs in seasonal snow are scarce, especially in the Alps. Here, we conducted detailed measurements of LAP in snow, snow physical and optical properties in the French Alps at a high altitude site. The dataset includes chemical measurements of mineral dust and black carbon (precisely elemental carbon and refractory black carbon), as well as spectral albedo measurements. The analysis of this dataset reveals strong discrepancies between elemental carbon and refractory black carbon measured concentrations, making it challenging to link the content of LAP to their radiative impacts. Using the dataset, the ensemble version of the Crocus snow model is evaluated and used to estimate the impacts of light-absorbing particles on snow cover evolution. Their impact on snowmelt turns out to be extremely sensitive to both meteorological conditions and uncertainties of the snow model, with a median shortening of 10 days for both snow seasons.</p>

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Black carbon fractal morphology and short-wave radiative impact: a modelling study

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-11745-2011 ◽

2011 ◽

Vol 11 (22) ◽

pp. 11745-11759 ◽

Cited By ~ 57

Author(s):

M. Kahnert ◽

A. Devasthale

Keyword(s):

Optical Properties ◽

Fractal Dimension ◽

Black Carbon ◽

Radiative Forcing ◽

Homogeneous Sphere ◽

Radiative Impacts ◽

Radiative Impact ◽

Sphere Approximation ◽

Carbon Aerosols ◽

Black Carbon Aerosols

Abstract. We investigate the impact of the morphological properties of freshly emitted black carbon aerosols on optical properties and on radiative forcing. To this end, we model the optical properties of fractal black carbon aggregates by use of numerically exact solutions to Maxwell's equations within a spectral range from the UVC to the mid-IR. The results are coupled to radiative transfer computations, in which we consider six realistic case studies representing different atmospheric pollution conditions and surface albedos. The spectrally integrated radiative impacts of black carbon are compared for two different fractal morphologies, which brace the range of recently reported experimental observations of black carbon fractal structures. We also gauge our results by performing corresponding calculations based on the homogeneous sphere approximation, which is commonly employed in climate models. We find that at top of atmosphere the aggregate models yield radiative impacts that can be as much as 2 times higher than those based on the homogeneous sphere approximation. An aggregate model with a low fractal dimension can predict a radiative impact that is higher than that obtained with a high fractal dimension by a factor ranging between 1.1–1.6. Although the lower end of this scale seems like a rather small effect, a closer analysis reveals that the single scattering optical properties of more compact and more lacy aggregates differ considerably. In radiative flux computations there can be a partial cancellation due to the opposing effects of different error sources. However, this cancellation effect can strongly depend on atmospheric conditions and is therefore quite unpredictable. We conclude that the fractal morphology of black carbon aerosols and their fractal parameters can have a profound impact on their radiative forcing effect, and that the use of the homogeneous sphere model introduces unacceptably high biases in radiative impact studies. We emphasise that there are other potentially important morphological features that have not been addressed in the present study, such as sintering and coating of freshly emitted black carbon by films of organic material. Finally, we found that the spectral variation of the absorption cross section of black carbon significantly deviates from a simple 1/λ scaling law. We therefore discourage the use of single-wavelength absorption measurements in conjunction with a 1/λ scaling relation in broadband radiative forcing simulations of black carbon.

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How emissions uncertainty influences the distribution and radiative impacts of smoke from fires in North America

10.5194/acp-2019-589 ◽

2019 ◽

Author(s):

Therese S. Carter ◽

Colette L. Heald ◽

Jose L. Jimenez ◽

Pedro Campuzano-Jost ◽

Yutaka Kondo ◽

...

Keyword(s):

Air Quality ◽

North America ◽

Black Carbon ◽

Dry Matter ◽

Organic Aerosol ◽

Carbonaceous Aerosol ◽

Burned Area ◽

Emission Inventories ◽

Fire Emissions ◽

Radiative Impacts

Abstract. Fires and the aerosols that they emit impact air quality, health, and climate, but the abundance and properties of carbonaceous aerosol (both black carbon and organic carbon) from biomass burning (BB) remain uncertain and poorly constrained. We aim to quantify the uncertainties associated with fire emissions and their air quality and radiative impacts from underlying dry matter consumed and emissions factors. To explore this, we compare model simulations from a global chemical transport model, GEOS-Chem, driven by a variety of fire emission inventories with surface and airborne observations of black carbon (BC) and organic aerosol (OA) concentrations and satellite-derived aerosol optical depth (AOD). We focus on two fire detection/burned area-based (FD/BA) inventories using burned area and active fire counts, respectively: the Global Fire Emissions Database version 4 (GFED4s) with small fires and the Fire INventory from NCAR version 1.5 (FINN1.5) and two fire radiative power (FRP)-based approaches: the Quick Fire Emission Dataset version 2.4 (QFED2.4) and the Global Fire Assimilation System version 1.2 (GFAS1.2). We show that, across the inventories, emissions of BB aerosol (BBA) differ by a factor of 4 to 7 over North America and that dry matter differences, not emissions factors, drive this spread. We find that simulations driven by QFED2.4 generally overestimate BC and, to a lesser extent, OA concentrations observations from two fire-influenced aircraft campaigns in North America (ARCTAS and DC3) and from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, while simulations driven by FINN1.5 substantially underestimate concentrations. The GFED4s and GFAS1.2-driven simulations provide the best agreement with OA and BC mass concentrations at the surface (IMPROVE), BC observed aloft (DC3 and ARCTAS), and AOD observed by MODIS over North America. We also show that a sensitivity simulation including an enhanced source of secondary organic aerosol (SOA) from fires based on the NOAA Fire Lab 2016 experiments produces substantial additional OA; however, the spread in the primary emissions estimates implies that this magnitude of SOA cannot be either confirmed or ruled out when comparing the simulations against the observations explored here. Given the substantial uncertainty in fire emissions, as represented by these four emission inventories, we find a sizeable range in BBA population-weighted exposure over Canada and the contiguous United States (0.5 to 1.6 µg m−3). We also show that the range in the estimated global direct radiative effect of carbonaceous aerosol from fires (−0.11 to −0.048 W m−2) is large and comparable to the direct radiative forcing of OA (−0.09 W m−2) estimated in AR5. Our analysis suggests that fire emissions uncertainty challenges our ability to accurately characterize the impact of smoke on air quality and climate.

Download Full-text