Modelling optical properties of atmospheric black carbon aerosols

Kahnert, Michael; Kanngießer, Franz

doi:10.1016/j.jqsrt.2020.106849

Cited by 60 publications

(49 citation statements)

References 190 publications

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“…The coating shapes in individual BC particles have rarely been considered in previous studies (Fierce et al., 2020; Kahnert & Kanngieβer, 2020; Liu et al., 2012; Wu et al., 2018; Zhang et al., 2018). For example, Zhang et al.…”

Section: Resultsmentioning

confidence: 99%

Constructing Shapes and Mixing Structures of Black Carbon Particles With Applications to Optical Calculations

et al. 2021

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Black carbon (BC), emitted by incomplete combustion of biomass and fossil fuels, can strongly absorb sunlight in the atmosphere (Bond & Bergstrom, 2006). BC can transform electromagnetic energy into thermal energy and heat the atmosphere (Buseck et al., 2014) and is one of the most important aerosol components affecting radiative forcing in the atmosphere (Jacobson, 2001). Moreover, BC can indirectly affect the climate through influencing the albedo and lifetime of clouds, snow, and ice (Flanner et al., 2007;Koch & Del Genio, 2010;Menon et al., 2010). Understanding the optical properties of BC is necessary to estimate its

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Section: Resultsmentioning

confidence: 99%

Constructing Shapes and Mixing Structures of Black Carbon Particles With Applications to Optical Calculations

et al. 2021

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“…Light absorbing carbon or eBC mass concentrations based on the refractory black carbon mass can be obtained from the reported absorption coefficients, applying a Mass Absorption Cross section (MAC) value (6.95 m 2 g −1 ) derived at the same measurement site for the reported wavelength (Zanatta et al., 2018), while there is further work on the variability of an MAC (Ohata et al., 2021). The b abs reported here is the measured response of arctic light absorbing aerosol (Liu et al., 2020) with the absorption due not only to the associated elemental carbon content of the aerosol but also due to the occasional brown carbon content often present in biomass burning aerosol and the complex microphysical processes leading to absorption enhancement observed for a core‐shell aerosol mixing state (Kahnert & Kanngießer, 2020). It is therefore a direct metric relevant to radiative transfer modeling rather than directly representing the initial light absorbing carbon mass (Bond et al., 2013).…”

Section: Measurements Modeling and Statistical Analysesmentioning

confidence: 99%

Large Circulation Patterns Strongly Modulate Long‐Term Variability of Arctic Black Carbon Levels and Areas of Origin

Stathopoulos

Evangeliou

Stohl

et al. 2021

Geophysical Research Letters

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Black Carbon (BC) aerosol is a major climate forcer in the Arctic. Here, we present 15 years (2001–2015) of surface observations of the aerosol absorption coefficient babs (corresponding to Equivalent BC), obtained at the Zeppelin Observatory, Ny Ålesund, Svalbard, coupled with backward transport modeling with Flexpart in order to calculate the Potential Source Contribution Function (PSCF) for BC. The observed long‐term variability superimposed on a strong annual cycle is studied as a function of large‐scale circulation patterns represented by monthly index values for the North Atlantic Oscillation (NAO) and the Scandinavian pattern (SCAN). We find a 35% increase of babs values at Zeppelin during the SCAN− phase in the winter half‐year compared to the SCAN+ phase but no significant difference in babs values between the NAO index phases. Both NAO and SCAN induce significant regional variability on the areas of origin of babs, mainly Siberia, Europe, and North America.

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“…Negligible enhancements ( E abs ~ 1) have been reported in BBA originating from forest fires in North America, even when substantial coatings were present (Cappa et al, 2012; Healy et al, 2015), whereas E abs values up to 1.6 have been observed in the Amazonia region (Lack et al, 2012; Liu et al, 2017). Several hypotheses have been put forward to explain this variability: (1) A restructuring of rBC‐containing particles from fractal morphologies towards a compact core could counteract the lensing effect (Kahnert & Kanngießer, 2020; Shingler et al, 2016); (2) rBC‐containing particles are not entirely coated but instead exhibit an aggregate structure with non‐rBC material (Liu & Mishchenko, 2007), thus leading to overall little change in absorption by rBC‐containing particles when internally mixed (Wu et al, 2018); (3) BBA absorption enhancement is partly attributed to the presence of light‐absorbing organic aerosols termed brown carbon (BrC) (Brown et al, 2018; Chylek et al, 2019); (4) accounting for mixing‐state diversity within the rBC‐containing particle population (i.e., the distribution of coating material across the ensemble of rBC‐containing particles), as has been done by Fierce et al (2016) and Liu et al (2017), is necessary to accurately quantify the average absorption. In part because of the paucity of comprehensive ambient measurements of rBC mixing state in BBA plumes, the mechanisms responsible for the large variation of E abs remain elusive.…”

Section: Introductionmentioning

confidence: 99%

Unexpected Biomass Burning Aerosol Absorption Enhancement Explained by Black Carbon Mixing State

Denjean

Brito

Libois

et al. 2020

Geophysical Research Letters

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Direct and semi-direct radiative effects of biomass burning aerosols (BBA) from southern and central African fires are still widely debated, in particular because climate models have been unsuccessful in reproducing the low single scattering albedo in BBA over the eastern Atlantic Ocean. Using state-of-the-art airborne in situ measurements and Mie scattering simulations, we demonstrate that low single scattering albedo in well-aged BBA plumes over southern West Africa results from the presence of strongly absorbing refractory black carbon (rBC), whereas the brown carbon contribution to the BBA absorption is negligible. Coatings enhance light absorption by rBC-containing particles by up to 210%. Our results show that accounting for the diversity in black carbon mixing state by combining internal and external configurations is needed to accurately estimate the optical properties and henceforth the shortwave direct radiative effect and heating rate of BBA over southern West Africa. Plain Language Summary Extensive seasonal fires over southern and central Africa result in the transport of massive amounts of biomass burning aerosols over huge areas of the eastern Atlantic Ocean. Recent field observations highlight that biomass burning aerosols transported from the coast of southern Africa to the far north over southern West Africa were characterized by low single scattering albedo. This finding is of paramount interest, because radiative heating within the absorbing aerosol layer is hypothesized to affect the low cloud deck over this specific region and may ultimately influence the large-scale circulation. However, debate remains about the causes of the low single scattering albedo by biomass burning aerosols, causing ambiguous parameterizations of their optical properties in climate models. Here we present simultaneous airborne measurements of the composition and optical properties of biomass burning aerosols transported over southern West Africa. We show that black carbon particles dominated the light absorption by biomass burning aerosols at mid-visible wavelengths. Our findings indicate that the black carbon mixing state plays a significant role in the aerosol optical properties and may be an important modulator to be considered in climate models for simulating direct and semi-direct radiative effects of biomass burning aerosol over southern West Africa.

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Modelling optical properties of atmospheric black carbon aerosols

Cited by 60 publications

References 190 publications

Constructing Shapes and Mixing Structures of Black Carbon Particles With Applications to Optical Calculations

Constructing Shapes and Mixing Structures of Black Carbon Particles With Applications to Optical Calculations

Large Circulation Patterns Strongly Modulate Long‐Term Variability of Arctic Black Carbon Levels and Areas of Origin

Unexpected Biomass Burning Aerosol Absorption Enhancement Explained by Black Carbon Mixing State

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