Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Liu, Fengshan; Wong, Cecillia; Snelling, David R.; Smallwood, Gregory J.

doi:10.1080/02786826.2013.847525

Cited by 54 publications

(40 citation statements)

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“…For the parameterization of biomass burning fractal-like aerosol particles used here, these requirements are adequately met (Farias et al, 1996). The model assumes negligible interactions between the particles themselves, and several studies have verified that multiple scattering effects are indeed negligible for fractal-like aerosol (Farias et al, 1996;Liu et al, 2013a).…”

mentioning

confidence: 85%

“…Mie theory describes electromagnetic radiation scattering by spherical particles with size parameters (x = π d/λ) of approximately unity, indicating that the diameter of the sphere (d) is on the same length scale as the wavelength of the radiation (λ) (Bohren and Huffman, 1983). Rayleigh-DebyeGans theory has been used extensively to approximate the physical properties of fractal-like aerosol (Chakrabarty et al, 2007;Liu et al, 2013a;Sorensen, 2001). The approximation assumes that fractals are composed of small identical monomers, and requires the following conditions to be fulfilled: | m − 1| 1, where m is the complex refractive index; and 2x p ( m − 1) 1 with x p equal to size parameter of the monomer.…”

mentioning

confidence: 99%

“…Chakrabarty et al (2006) (2006) based on fuel type. The scattering angle-dependent structure factor, which is needed to calculate the RDG phase function, was adopted from Sorensen et al (Liu et al, 2013a;Sorensen et al, 1992;Yang and Köylü, 2005). Details of the phase function calculations based on the RDG model can be found in Liu et al (2013a) and Kandilian et al (2015).…”

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confidence: 99%

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Investigating biomass burning aerosol morphology using a laser imaging nephelometer

et al. 2018

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Abstract. Particle morphology is an important parameter affecting aerosol optical properties that are relevant to climate and air quality, yet it is poorly constrained due to sparse in situ measurements. Biomass burning is a large source of aerosol that generates particles with different morphologies. Quantifying the optical contributions of non-spherical aerosol populations is critical for accurate radiative transfer models, and for correctly interpreting remote sensing data. We deployed a laser imaging nephelometer at the Missoula Fire Sciences Laboratory to sample biomass burning aerosol from controlled fires during the FIREX intensive laboratory study. The laser imaging nephelometer measures the unpolarized scattering phase function of an aerosol ensemble using diode lasers at 375 and 405 nm. Scattered light from the bulk aerosol in the instrument is imaged onto a chargecoupled device (CCD) using a wide-angle field-of-view lens, which allows for measurements at 4-175 • scattering angle with ∼ 0.5 • angular resolution. Along with a suite of other instruments, the laser imaging nephelometer sampled fresh smoke emissions both directly and after removal of volatile components with a thermodenuder at 250 • C. The total integrated aerosol scattering signal agreed with both a cavity ring-down photoacoustic spectrometer system and a traditional integrating nephelometer within instrumental uncertainties. We compare the measured scattering phase functions at 405 nm to theoretical models for spherical (Mie) and fractal (Rayleigh-Debye-Gans) particle morphologies based on the size distribution reported by an optical particle counter.Results from representative fires demonstrate that particle morphology can vary dramatically for different fuel types. In some cases, the measured phase function cannot be described using Mie theory. This study demonstrates the capabilities of the laser imaging nephelometer instrument to provide realtime, in situ information about dominant particle morphology, which is vital for understanding remote sensing data and accurately describing the aerosol population in radiative transfer calculations.

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Investigating biomass burning aerosol morphology using a laser imaging nephelometer

et al. 2018

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“…It is important that the gaseous combustion products in the fire do not scatter the radiation. The radiation scattering by soot aggregates in the infrared range is also negligible (a considerable scattering by soot aggregates can be observed in the visible range only) [10][11][12][13]. As a result, one can observe local regions of small water droplets near the flame axis because of their infrared scattering.…”

Section: Introductionmentioning

confidence: 75%

An infrared scattering by evaporating droplets at the initial stage of a pool fire suppression by water sprays

Dombrovsky

Dembele

Wen

2018

Infrared Physics & Technology

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h i g h l i g h t sAn initial stage of a pool fire suppression is considered. The motion, heating, and evaporation of water droplets are calculated. Focusing of evaporating water droplets in local regions is obtained. A strong infrared scattering by small water droplets is analyzed. The spectral region of a significant infrared scattering is determined. a r t i c l e i n f o b s t r a c tThe computational analysis of downward motion and evaporation of water droplets used to suppress a typical transient pool fire shows local regions of a high volume fraction of relatively small droplets. These droplets are comparable in size with the infrared wavelength in the range of intense flame radiation. The estimated scattering of the radiation by these droplets is considerable throughout the entire spectrum except for a narrow region in the vicinity of the main absorption peak of water where the anomalous refraction takes place. The calculations of infrared radiation field in the model pool fire indicate the strong effect of scattering which can be observed experimentally to validate the fire computational model.

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“…properties of fractal-like aerosol (Chakrabarty et al, 2007;Liu et al, 2013a). The approximation assumes that fractals are composed of small identical monomers, and requires the following conditions to be fulfilled: | − 1| ≪ 1 where m is the complex refractive index; and |2 ( − 1)| ≪ 1 with wavenumber ( = 2 ) and a equal to the monomer radius.…”

Section: Parameterizations Of Phase Functions From Particle Morphologymentioning

confidence: 99%

Investigating biomass burning aerosol morphology using a laser imaging nephelometer

Manfred¹,

Washenfelder²,

Wagner³

et al. 2017

Preprint

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Abstract. Particle morphology is an important parameter affecting aerosol optical properties that are relevant to climate and air quality, yet it is poorly constrained due to sparse in situ measurements. Biomass burning is a large source of aerosol that generates particles with different morphologies. Quantifying the optical contributions of non-spherical aerosol populations is 15 critical for accurate radiative transfer models, and for correctly interpreting remote sensing data. We deployed a laser imaging nephelometer at the Missoula Fire Sciences Laboratory to sample biomass burning aerosol from controlled fires during the FIREX intensive laboratory study. The laser imaging nephelometer measures the unpolarized scattering phase function of an aerosol ensemble using diode lasers at 375 nm and 405 nm. Scattered light from the bulk aerosol in the instrument is imaged onto a CCD using a wide-angle field-of-view lens, which allows for measurements at 4 -175° scattering angle with ~0.5° 20 angular resolution. Along with a suite of other instruments, the laser imaging nephelometer sampled fresh smoke emissions both directly and after removal of volatile components with a thermodenuder at 250°C. The total integrated aerosol scattering signal agreed with both a cavity ring-down photoacoustic spectrometer system and a traditional integrating nephelometer within instrumental uncertainties. We compare the measured scattering phase functions at 405 nm to theoretical models for spherical (Mie) and fractal (Rayleigh-Debye-Gans) particle morphologies based on the size distribution reported by an optical 25 particle counter. Results from representative fires demonstrate that particle morphology can vary dramatically for different fuel types. In some cases, the measured phase function cannot be described using Mie theory. This study demonstrates the capabilities of the laser imaging nephelometer instrument to provide real-time, in situ information about dominant particle morphology, which is vital for understanding remote sensing data and accurately describing the aerosol population in radiative transfer calculations. 30Atmos. Chem. Phys. Discuss., https://doi

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Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Cited by 54 publications

References 51 publications

Investigating biomass burning aerosol morphology using a laser imaging nephelometer

Investigating biomass burning aerosol morphology using a laser imaging nephelometer

An infrared scattering by evaporating droplets at the initial stage of a pool fire suppression by water sprays

Investigating biomass burning aerosol morphology using a laser imaging nephelometer

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