scholarly journals Brown carbon: a significant atmospheric absorber of solar radiation?

2013 ◽  
Vol 13 (17) ◽  
pp. 8607-8621 ◽  
Author(s):  
Y. Feng ◽  
V. Ramanathan ◽  
V. R. Kotamarthi
Keyword(s):  
Organic Carbon ◽  
Solar Radiation ◽  
Black Carbon ◽  
Organic Aerosols ◽  
Transfer Model ◽  
Anthropogenic Aerosols ◽  
Brown Carbon ◽  
Enhanced Absorption ◽  
Aerosol Absorption ◽  
Carbon Aerosols

Abstract. Several recent observational studies have shown organic carbon aerosols to be a significant source of absorption of solar radiation. The absorbing part of organic aerosols is referred to as "brown" carbon (BrC). Using a global chemical transport model and a radiative transfer model, we estimate for the first time the enhanced absorption of solar radiation due to BrC in a global model. The simulated wavelength dependence of aerosol absorption, as measured by the absorption Ångström exponent (AAE), increases from 0.9 for non-absorbing organic carbon to 1.2 (1.0) for strongly (moderately) absorbing BrC. The calculated AAE for the strongly absorbing BrC agrees with AERONET spectral observations at 440–870 nm over most regions but overpredicts for the biomass burning-dominated South America and southern Africa, in which the inclusion of moderately absorbing BrC has better agreement. The resulting aerosol absorption optical depth increases by 18% (3%) at 550 nm and 56% (38%) at 380 nm for strongly (moderately) absorbing BrC. The global simulations suggest that the strongly absorbing BrC contributes up to +0.25 W m−2 or 19% of the absorption by anthropogenic aerosols, while 72% is attributed to black carbon, and 9% is due to sulfate and non-absorbing organic aerosols coated on black carbon. Like black carbon, the absorption of BrC (moderately to strongly) inserts a warming effect at the top of the atmosphere (TOA) (0.04 to 0.11 W m−2), while the effect at the surface is a reduction (−0.06 to −0.14 W m−2). Inclusion of the strongly absorption of BrC in our model causes the direct radiative forcing (global mean) of organic carbon aerosols at the TOA to change from cooling (−0.08 W m−2) to warming (+0.025 W m−2). Over source regions and above clouds, the absorption of BrC is higher and thus can play an important role in photochemistry and the hydrologic cycle.

scholarly journals Brown carbon: a significant atmospheric absorber of solar radiation?

2013 ◽  
Vol 13 (1) ◽  
pp. 2795-2833 ◽  
Author(s):  
Y. Feng ◽  
V. Ramanathan ◽  
V. R. Kotamarthi
Keyword(s):  
Solar Radiation ◽  
Black Carbon ◽  
Transport Model ◽  
Organic Aerosols ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Anthropogenic Aerosols ◽  
Brown Carbon ◽  
Enhanced Absorption ◽  
Aerosol Absorption

Abstract. Several recent observational studies have shown organic carbon aerosols to be a significant source of absorption of solar radiation. The absorbing part of organic aerosols is referred to as brown carbon. Comparisons with observations indicate that model-simulated aerosol absorption is under-estimated in global models, one of the reasons being the neglect of brown carbon. Using a global chemical transport model coupled with a radiative transfer model, we estimate for the first time the enhanced absorption of solar radiation due to "brown" carbon (BrC) in a global model. When BrC is included, the simulated wavelength dependence of aerosol absorption, as measured by the Angstrom exponent increases from 0.9 to 1.2 and thus agrees better with AERONET spectral observations at 440–870 nm. The resulting absorbing aerosol optical depth increases by 3–18% at 550 nm and up to 56% at 350 nm. The global simulations suggest that BrC contributes up to +0.25 W m−2 or 19% of the absorption by anthropogenic aerosols, of which 72% is attributed to black carbon, and 9% is due to sulfate and non-absorbing organic aerosols coated on black carbon. Like black carbon, the overall forcing of BrC at the top of the atmosphere (TOA) is a warming effect (+0.11 W m−2), while the effect at the surface is a reduction or dimming (−0.14 W m−2). Because of the inclusion of BrC in our model, the direct radiative effect of organic carbonaceous aerosols changes from cooling (−0.08 W m−2) to warming (+0.025 W m−2) at the TOA, on a global mean basis. Over source regions and above clouds, the absorption of BrC is more significant and thus can play an important role in photochemistry and the hydrologic cycle.

Atmospheric Brown Clouds

2016 ◽  
Author(s):  
Sumit Sharma ◽  
Liliana Nunez ◽  
Veerabhadran Ramanathan
Keyword(s):  
Indian Ocean ◽  
Organic Carbon ◽  
Solar Radiation ◽  
Black Carbon ◽  
Scale Effects ◽  
United Nations Environment Programme ◽  
Monsoon Circulation ◽  
Anthropogenic Aerosols ◽  
Brown Carbon ◽  
The Indian Ocean

Atmospheric brown clouds (ABCs) are widespread pollution clouds that can at times span an entire continent or an ocean basin. ABCs extend vertically from the ground upward to as high as 3 km, and they consist of both aerosols and gases. ABCs consist of anthropogenic aerosols such as sulfates, nitrates, organics, and black carbon and natural dust aerosols. Gaseous pollutants that contribute to the formation of ABCs are NOx (nitrogen oxides), SOx (sulfur oxides), VOCs (volatile organic compounds), CO (carbon monoxide), CH4 (methane), and O3 (ozone). The brownish color of the cloud (which is visible when looking at the horizon) is due to absorption of solar radiation at short wavelengths (green, blue, and UV) by organic and black carbon aerosols as well as by NOx. While the local nature of ABCs around polluted cities has been known since the early 1900s, the widespread transoceanic and transcontinental nature of ABCs as well as their large-scale effects on climate, hydrological cycle, and agriculture were discovered inadvertently by The Indian Ocean Experiment (INDOEX), an international experiment conducted in the 1990s over the Indian Ocean. A major discovery of INDOEX was that ABCs caused drastic dimming at the surface. The magnitude of the dimming was as large as 10–20% (based on a monthly average) over vast areas of land and ocean regions. The dimming was shown to be accompanied by significant atmospheric absorption of solar radiation by black and brown carbon (a form of organic carbon). Black and brown carbon, ozone and methane contribute as much as 40% to anthropogenic radiative forcing. The dimming by sulfates, nitrates, and carbonaceous (black and organic carbon) species has been shown to disrupt and weaken the monsoon circulation over southern Asia. In addition, the ozone in ABCs leads to a significant decrease in agriculture yields (by as much as 20–40%) in the polluted regions. Most significantly, the aerosols (in ABCs) near the ground lead to about 4 million premature mortalities every year. Technological and regulatory measures are available to mitigate most of the pollution resulting from ABCs. The importance of ABCs to global environmental problems led the United Nations Environment Programme (UNEP) to form the international ABC program. This ABC program subsequently led to the identification of short-lived climate pollutants as potent mitigation agents of climate change, and in recognition, UNEP formed the Climate and Clean Air Coalition to deal with these pollutants.

scholarly journals A new algorithm for brown and black carbon identification and organic carbon detection in fine atmospheric aerosols by a multi-wavelength Aethalometer

2012 ◽  
Vol 5 (1) ◽  
pp. 1003-1027 ◽  
Author(s):  
F. Esposito ◽  
M. R. Calvello ◽  
E. Gueguen ◽  
G. Pavese
Keyword(s):  
Organic Carbon ◽  
Absorption Coefficient ◽  
Black Carbon ◽  
Atmospheric Aerosols ◽  
Light Attenuation ◽  
Wavelength Dependence ◽  
Carbonaceous Aerosol ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Novel Approach

Abstract. A novel approach for the analysis of aerosol absorption coefficient measurements is presented. A 7-wavelenghts aethalometer has been employed to identify brown carbon (BrC) and black carbon (BC) and to detect organic carbon (OC) in fine atmospheric aerosols (PM2.5). The Magee Aethalometer estimates the BC content in atmospheric particulate by measuring the light attenuation in the aerosols accumulated on a quartz filter, at the standard wavelength λ = 0.88 μm. The known Magee algorithm is based on the hypothesis of a mass absorption coefficient inversely proportional to the wavelength. The new algorithm has been developed and applied to the whole spectral range; it verifies the spectral absorption behavior and, thus, it distinguishes between black and brown carbon. Moreover, it allows also to correct the absorption estimation at the UV wavelength commonly used to qualitatively detect the presence of mixed hydrocarbons. The algorithm has been applied to data collected in Agri Valley, located in Southern Italy, where torched crude oil undergoes a pre-treatment process. The Magee Aethalometer has been set to measure Aerosol absorption coefficients τaer (λ, t) every 5 min. Wavelength dependence of τaer (λ, t) has been analyzed by a best-fit technique and, excluding UV-wavelengths, both the absorption Angstrom coefficient α and the BC (or BrC) concentration have been determined. Finally, daily histograms of α provide information on optical properties of carbonaceous aerosol, while the extrapolation at UV-wavelengths gives information on the presence of semivolatile organic carbon (OC) particles.

scholarly journals Seasonal and diurnal variations of black carbon and organic carbon aerosols in Bangkok

2011 ◽  
Vol 116 (D15) ◽  
Author(s):  
L. K. Sahu ◽  
Y. Kondo ◽  
Y. Miyazaki ◽  
Prapat Pongkiatkul ◽  
N. T. Kim Oanh
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Diurnal Variations ◽  
Seasonal And Diurnal Variations ◽  
Carbon Aerosols

scholarly journals Production of particulate brown carbon during atmospheric aging of residential wood-burning emissions

2018 ◽  
Vol 18 (24) ◽  
pp. 17843-17861 ◽  
Author(s):  
Nivedita K. Kumar ◽  
Joel C. Corbin ◽  
Emily A. Bruns ◽  
Dario Massabó ◽  
Jay G. Slowik ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Wavelength Dependence ◽  
Organic Aerosol ◽  
Geometric Standard Deviation ◽  
Wood Combustion ◽  
Brown Carbon ◽  
Atmospheric Aging ◽  
Aerosol Absorption ◽  
Uv Visible

Abstract. We investigate the optical properties of light-absorbing organic carbon (brown carbon) from domestic wood combustion as a function of simulated atmospheric aging. At shorter wavelengths (370–470 nm), light absorption by brown carbon from primary organic aerosol (POA) and secondary organic aerosol (SOA) formed during aging was around 10 % and 20 %, respectively, of the total aerosol absorption (brown carbon plus black carbon). The mass absorption cross section (MAC) determined for black carbon (BC, 13.7 m2 g−1 at 370 nm, with geometric standard deviation GSD =1.1) was consistent with that recommended by Bond et al. (2006). The corresponding MAC of POA (5.5 m2 g−1; GSD =1.2) was higher than that of SOA (2.4 m2 g−1; GSD =1.3) at 370 nm. However, SOA presents a substantial mass fraction, with a measured average SOA ∕ POA mass ratio after aging of ∼5 and therefore contributes significantly to the overall light absorption, highlighting the importance of wood-combustion SOA as a source of atmospheric brown carbon. The wavelength dependence of POA and SOA light absorption between 370 and 660 nm is well described with absorption Ångström exponents of 4.6 and 5.6, respectively. UV-visible absorbance measurements of water and methanol-extracted OA were also performed, showing that the majority of the light-absorbing OA is water insoluble even after aging.

scholarly journals A global modeling study on carbonaceous aerosol microphysical characteristics and radiative effects

2010 ◽  
Vol 10 (15) ◽  
pp. 7439-7456 ◽  
Author(s):  
S. E. Bauer ◽  
S. Menon ◽  
D. Koch ◽  
T. C. Bond ◽  
K. Tsigaridis
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Radiative Flux ◽  
Radiative Effects ◽  
Carbonaceous Particle ◽  
Flux Change ◽  
Aerosol Effects ◽  
The Impact ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

Abstract. Recently, attention has been drawn towards black carbon aerosols as a short-term climate warming mitigation candidate. However the global and regional impacts of the direct, indirect and semi-direct aerosol effects are highly uncertain, due to the complex nature of aerosol evolution and the way that mixed, aged aerosols interact with clouds and radiation. A detailed aerosol microphysical scheme, MATRIX, embedded within the GISS climate model is used in this study to present a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative effects. Our best estimate for net direct and indirect aerosol radiative flux change between 1750 and 2000 is −0.56 W/m2. However, the direct and indirect aerosol effects are quite sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative flux change can vary between −0.32 to −0.75 W/m2 depending on these carbonaceous particle properties at emission. Taking into account internally mixed black carbon particles let us simulate correct aerosol absorption. Absorption of black carbon aerosols is amplified by sulfate and nitrate coatings and, even more strongly, by organic coatings. Black carbon mitigation scenarios generally showed reduced radiative fluxeswhen sources with a large proportion of black carbon, such as diesel, are reduced; however reducing sources with a larger organic carbon component as well, such as bio-fuels, does not necessarily lead to a reduction in positive radiative flux.

scholarly journals The direct effect of aerosols on solar radiation based on satellite observations, reanalysis datasets, and spectral aerosol optical properties from Global Aerosol Data Set (GADS)

2007 ◽  
Vol 7 (1) ◽  
pp. 753-783 ◽  
Author(s):  
N. Hatzianastassiou ◽  
C. Matsoukas ◽  
E. Drakakis ◽  
P. W. Stackhouse ◽  
P. Koepke ◽  
...  
Keyword(s):  
Optical Properties ◽  
Solar Radiation ◽  
Hydrological Cycle ◽  
Regional Scale ◽  
Local Scale ◽  
Transfer Model ◽  
Surface Cooling ◽  
Anthropogenic Aerosols ◽  
Aerosol Optical Properties ◽  
Data Set

Abstract. A global estimate of the seasonal direct radiative effect (DRE) of natural plus anthropogenic aerosols on solar radiation under all-sky conditions is obtained by combining satellite measurements and reanalysis data with a spectral radiative transfer model. The estimates are obtained with detailed spectral model computations separating the ultraviolet (UV), visible and near-infrared wavelengths. The global distribution of spectral aerosol optical properties was taken from the Global Aerosol Data Set (GADS) whereas data for clouds, water vapour, ozone, carbon dioxide, methane and surface albedo were taken from various satellite and reanalysis datasets. Using these aerosol properties and other related variables, we generate climatological (for the 12-year period 1984–1995) monthly mean aerosol DREs. The global annual mean DRE on the outgoing SW radiation at the top of atmosphere (TOA, ΔFTOA) is 1.62 Wm−2 (with a range of –10 to 15 Wm−2, positive values corresponding to planetary cooling), the effect on the atmospheric absorption of SW radiation (ΔFatmab) is 1.6 Wm−2 (values up to 35 Wm−2, corresponding to atmospheric warming), and the effect on the surface downward and absorbed SW radiation (Δ Fsurf, and ΔFsurfnet, respectively) is –3.93 and –3.22 Wm−2 (values up to –45 and –35 Wm−2, respectively, corresponding to surface cooling.) According to our results, aerosols decrease/increase the planetary albedo by –3 to 13% at the local scale, whereas on planetary scale the result is an increase of 1.5%. Aerosols can warm locally the atmosphere by up to 0.98 K day−1, whereas they can cool the Earth's surface by up to –2.9 K day−1. Both these effects, which can significantly modify atmospheric dynamics and the hydrological cycle, can produce significant planetary cooling on a regional scale, although planetary warming can arise over highly reflecting surfaces. The aerosol DRE at the Earth's surface compared to TOA can be up to 15 times larger at the local scale. The largest aerosol DRE takes place in the northern hemisphere both at the surface and the atmosphere, arising mainly at ultraviolet and visible wavelengths.

scholarly journals Aerosol light absorption and the role of extremely low volatility organic compounds

2020 ◽  
Vol 20 (19) ◽  
pp. 11625-11637
Author(s):  
Antonios Tasoglou ◽  
Evangelos Louvaris ◽  
Kalliopi Florou ◽  
Aikaterini Liangou ◽  
Eleni Karnezi ◽  
...  
Keyword(s):  
Black Carbon ◽  
Organic Compounds ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Scanning Mobility Particle Sizer ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Aerosol Mass ◽  
Particle Sizer

Abstract. A month-long set of summertime measurements in a remote area in the Mediterranean is used to quantify aerosol absorption and the role of black and brown carbon. The suite of instruments included a high-resolution aerosol mass spectrometer (HR-ToF-AMS) and a scanning mobility particle sizer (SMPS), both coupled to a thermodenuder and an Aethalometer, a photoacoustic extinctiometer (PAX405), and a single particle soot photometer (SP2). The average refractory black carbon (rBC) concentration during the campaign was 0.14 µg m−3, representing 3 % of the fine aerosol mass. The measured light absorption was two or more times higher than that of fresh black carbon (BC). Mie theory indicated that the absorption enhancement due to the coating of BC cores by nonrefractory material could explain only part of this absorption enhancement. The role of brown carbon (BrC) and other non-BC light-absorbing material was then investigated. A good correlation (R2=0.76) between the unexplained absorption and the concentration of extremely low volatility organic compounds (ELVOCs) mass was found.

scholarly journals Aerosol light absorption and the role of extremely low volatility organic compounds

2020 ◽  
Author(s):  
Antonios Tasoglou ◽  
Evangelos Louvaris ◽  
Kalliopi Florou ◽  
Aikaterini Liangou ◽  
Eleni Karnezi ◽  
...  
Keyword(s):  
Black Carbon ◽  
Organic Compounds ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Scanning Mobility Particle Sizer ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Aerosol Mass ◽  
Particle Sizer

Abstract. A month-long set of summertime measurements in a remote area in the Mediterranean is used to quantify aerosol absorption and the role of black and brown carbon. The suite of instruments included a high-resolution Aerosol Mass Spectrometer (HR-ToF-AMS), and a Scanning Mobility Particle Sizer (SMPS) both coupled to a thermodenuder and an aethalometer, a photoacoustic extinctiometer (PAX405), a Multi-Angle Absorption Photometer (MAAP), and a Single Particle Soot Photometer (SP2). The average refractory black carbon (rBC) concentration during the campaign was 0.14 μg m−3, representing 3 % of the fine aerosol mass. The measured light absorption was two or more times higher than that of fresh black carbon (BC). Mie theory indicated that the absorption enhancement due to the coating of BC cores by non-refractory material could explain only part of this absorption enhancement. The role of brown carbon (BrC) and other non-BC light-absorbing material was then investigated. A good correlation (R2 = 0.65) between the unexplained absorption and the concentration of extremely low volatility organic compounds (ELVOCs) mass was found.

scholarly journals Optical and hygroscopic properties of black carbon influenced by particle microphysics at the top of the anthropogenically polluted boundary layer

2021 ◽  
Vol 21 (2) ◽  
pp. 681-694
Author(s):  
Shuo Ding ◽  
Dantong Liu ◽  
Kang Hu ◽  
Delong Zhao ◽  
Ping Tian ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Solar Radiation ◽  
Black Carbon ◽  
Mass Fraction ◽  
Single Scattering ◽  
Daily Basis ◽  
Absorption Capacity ◽  
Pollution Level ◽  
Enhanced Absorption ◽  
Hygroscopic Properties

Abstract. Aerosols at the top of the planetary boundary layer (PBL) could modify its atmospheric dynamics by redistributing the solar radiation and start to be activated to form low-level cloud at this layer. Black carbon (BC), as an aerosol component efficiently absorbing solar radiation, can introduce heating and positive radiative effects at this sensitive layer, especially in the polluted PBL over the continent. This study presents continuous measurements of detailed BC properties at a mountain site located at the top of the polluted PBL over the North China Plain, during seasons (3 and 4 weeks of data during winter and summer, respectively) with contrasting emission structure and meteorology. The pollution level was persistently influenced by local surface anthropogenic emission on a daily basis through daytime convective mixing, but the concentration was also enhanced or diluted depending on air mass direction, defined as a neutral, polluted and diluted PBL, respectively. Winter was observed to have a higher BC mass fraction (4 %–8 %) than summer (2 %–7 %). By resolving the detailed particle size-resolved mixing state of BC in optical and hygroscopic models, we found an enhanced BC mass absorption cross section (MACBC) for the polluted PBL (up to 13 m2 g−1 at λ = 550 nm), which was 5 % higher during summer than winter due to a smaller BC core size. The higher BC mass fraction in winter corresponded to a lower single-scattering albedo by 0.03–0.09 than summer, especially the lowest for the diluted winter PBL (0.86 ± 0.02). The water supersaturation (SS) required to activate half the number of BC decreased from 0.21 % ± 0.08 % to 0.1 % ± 0.03 % for the winter diluted and polluted PBL and from 0.22 % ± 0.06 % to 0.17 % ± 0.05 % for summer. Notably, at the top of the anthropogenically polluted PBL in both seasons, the enlarged BC with enhanced absorption capacity could also be efficiently droplet activated; e.g. winter (summer) BC with an MAC of 9.84 ± 1.2 (10.7 ± 1) m2 g−1 could be half activated at SS = 0.13 % ± 0.06 % (0.18 % ± 0.05 %). This BC at the top of the PBL can more directly interact with the free troposphere and be transported to a wider region, exerting important direct and indirect radiative impacts.

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