Optical closure experiments for biomass smoke aerosols

Mack, Laura; Levin, Ezra J. T.; Kreidenweis, Sonia M.; Obrist, Daniel; Moosmüller, Hans; Lewis, K.; Arnott, W. P.; McMeeking, G. R.; Sullivan, A. P.; Wold, Cyle; Hao, Wei Min; Collett, Jeffrey L.; Malm, William C.

doi:10.5194/acpd-10-7469-2010

Cited by 3 publications

(3 citation statements)

References 32 publications

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“…Average density is either assumed or calculated from measured chemical composition mass fractions. 22,23 Volume distributions are inferred from the measured size distributions (assuming spherical particles). Mass concentrations are determined gravimetrically, 14,[19][20][21]25 using an aerosol mass spectrometer 29 or a laser-induced incandescence instrument (elemental carbon only).…”

Section: ■ Introductionmentioning

confidence: 99%

“…This method is highly sensitive to the accuracy of ρ, V and M and any error in data collection or fitting amplifies MAC uncertainty without consideration to inherent particle variability. 19,22,23 Further, MAC values are typically reported at a single wavelength. When multiple wavelengths are available, AAEs are calculated from pairwise fits of the PAS data or from multiwavelength filter attenuation data in conjunction with PAS data to correct for filter biases.…”

Section: ■ Introductionmentioning

confidence: 99%

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Direct In Situ Mass Specific Absorption Spectra of Biomass Burning Particles Generated from Smoldering Hard and Softwoods

Radney

You

Zachariah

et al. 2017

Environ. Sci. Technol.

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Particles from smoldering biomass burning (BB) represent a major source of carbonaceous aerosol in the terrestrial atmosphere. In this study, mass specific absorption spectra of laboratory-generated smoldering wood particles (SWP) from 3 hardwood and 3 softwood species were measured in situ. Absorption data spanning from λ = 500 to 840 nm were collected using a photoacoustic spectrometer coupled to a supercontinuum laser with a tunable wavelength and bandwidth filter. SWP were size- (electrical mobility) and mass-selected prior to optical characterization allowing data to be reported as mass-specific absorption cross sections (MAC). The median measured MAC at λ = 660 nm for smoldering oak particles was 1.1 (0.57/1.8) × 10 m g spanning from 83 femtograms (fg) to 517 fg (500 nm ≤ mobility diameter ≤950 nm), MAC values in parentheses are the 16 and 84 percentiles of the measured data (i.e., 1σ). The collection of all six wood species (Oak, Hickory, Mesquite, Western redcedar, Baldcypress, and Blue spruce) had median MAC values ranging from 1.4 × 10 m g to 7.9 × 10 m g at λ = 550 nm with absorption Ångström exponents (AAE) between 3.5 and 6.2. Oak, Western redcedar, and Blue spruce possessed statistically similar (p > 0.05) spectra while the spectra of Hickory, Mesquite, and Baldcypress were distinct (p < 0.01) as calculated from a point-by-point analysis using the Wilcox rank-sum test.

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Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Direct In Situ Mass Specific Absorption Spectra of Biomass Burning Particles Generated from Smoldering Hard and Softwoods

Radney

You

Zachariah

et al. 2017

Environ. Sci. Technol.

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“…The reason for the greater cooling tendency in DRE with larger particle sizes (either through sub-grid coagulation or larger emissions) is due to the mass scattering and absorption efficiencies (the scattering and absorption cross sections per unit mass). For a refractive index generally representative of biomass burning smoke (1.53 -0.1i; [36]), the diameter of peak mass scattering efficiency is about 400 nm, whereas the mass absorption efficiency is relatively constant across submicron diameters [17]. In Janhäll et al (2010), the average fresh plume has a mass median diameter of 272 nm [32].…”

Section: Ambient Size Distribution Sensitivity To Biomass Burningmentioning

confidence: 99%

Response to Referee 1

Ramnarine¹

2019

Preprint

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Biomass burning is a significant global source of aerosol number and mass. In fresh biomass burning plumes, aerosol coagulation reduces aerosol number and increases the median size of aerosol size distributions, impacting aerosol radiative effects. Near-source biomass burning aerosol coagulation occurs at spatial scales much smaller than the grid boxes of global and many regional models. To date, these models ignore sub-grid coagulation and instantly mix fresh biomass burning emissions into coarse grid boxes. A previous study found that the rate of particle growth by coagulation within an individual smoke plume can be approximated using the aerosol mass emissions rate, initial size distribution median diameter and modal width, plume mixing depth, and wind speed. In this thesis, we use this parameterization of sub-grid coagulation in the GEOS-Chem-TOMAS global aerosol microphysics model to quantify the impacts on global aerosol size distributions, the direct radiative effect, and the cloud-albedo aerosol indirect effect.We find that inclusion of biomass burning sub-grid coagulation reduces the biomass burning impact on the number concentration of particles larger than 80 nm (a proxy for CCN-sized particles) by 37% globally. This CCN reduction causes our estimated global biomass burning cloud-albedo aerosol indirect effect to decrease from -76 to -43 mW m −2 . Further, as sub-grid coagulation moves mass to sizes with more efficient scattering, including it increases our estimated biomass burning all-sky direct effect from -224 to -231 mW m −2 with assumed external mixing and from -188 to -197 mW m −2 with assumed internal mixing with core-shell morphology. However, due to differences in fire and meteorological conditions across regions, the impact of sub-grid coagulation is not globally uniform. We also test the sensitivity of the impact of sub-grid coagula-

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Biomass burning smoke aerosol properties measured during Fire Laboratory at Missoula Experiments (FLAME)

et al. 2010

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[1] During the Fire Laboratory at Missoula Experiments (FLAME), we studied the physical, chemical, and optical properties of biomass burning smoke from the laboratory combustion of various wildland fuels. A good understanding of these properties is important in determining the radiative effects of biomass burning aerosols, with impacts on both local and regional visibility and global climate. We measured aerosol size distributions with two instruments: a differential mobility particle sizer (DMPS) and an optical particle counter (OPC). Volume size distributions from different burns varied from monomodal to multimodal, with geometric mean diameters ranging from 0.20-0.57 mm and geometric standard deviations ranging from 1.68-2.97. By reconciling the differences between the two sizing instruments, we estimated aerosol effective refractive indices with values ranging from 1.41 to 1.61. We reconstructed aerosol chemical composition for each burn using data from filters collected and analyzed with the Interagency Monitoring of Protected Visual Environments (IMPROVE) samplers and protocols. Aerosols were generally comprised of carbon with organic species accounting for the largest mass fraction in most cases. We used composition data to calculate aerosol density, which ranged from 1.22-1.92 g cm −3 , and real and imaginary refractive indices, which had ranges of 1.55-1.80 and 0.01-0.50 respectively. Aerosol physical, chemical, and optical characterizations were combined to calculate dry mass scattering (MSE) and absorption (MAE) efficiencies at 532 nm. These parameters had values between 1.6-5.7 m 2 g −1 and 0.04-0.94 m 2 g −1 .

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Optical closure experiments for biomass smoke aerosols

Cited by 3 publications

References 32 publications

Direct In Situ Mass Specific Absorption Spectra of Biomass Burning Particles Generated from Smoldering Hard and Softwoods

Direct In Situ Mass Specific Absorption Spectra of Biomass Burning Particles Generated from Smoldering Hard and Softwoods

Response to Referee 1

Biomass burning smoke aerosol properties measured during Fire Laboratory at Missoula Experiments (FLAME)

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