Use of group theory for the description of electromagnetic scattering from molecular systems

Borghese, Ferdinando; Denti, P.; Saija, Rosalba; Toscano, G.; Sindoni, O. I.

doi:10.1364/josaa.1.000183

Cited by 47 publications

(23 citation statements)

References 10 publications

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“…The optical properties of such aggregates can be computed by use of rigorous electromagnetic scattering theory (Borghese et al 1984;Mackowski and Mishchenko 1996;Xu and Gustafson 2001) or by use of approximate methods (Sorensen 2001;Okada et al 2007). Applications of approximate methods have, for example, been presented by Zhao and Ma (2009).…”

Section: Introductionmentioning

confidence: 99%

On the Discrepancy between Modeled and Measured Mass Absorption Cross Sections of Light Absorbing Carbon Aerosols

Kahnert

2010

Aerosol Science and Technology

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Recent modeling studies based on the Rayleigh-Debye-Gans (RDG) approximation have revealed a discrepancy between modeled and measured mass absorption cross sections (MAC) for atmospheric light absorbing carbon (LAC) aerosols. One plausible explanation is that this discrepancy is due to errors introduced by neglecting electromagnetic interactions among monomers in LAC aggregates within the RDG approximation. Here we compute MAC by use of numerically exact solutions to Maxwell's equations and investigate the sensitivity of the results to a variation in the aggregates' physical properties and refractive index. The results do confirm that approximate methods can introduce large errors in the results for the optical properties. However, these errors alone cannot explain the discrepancy between measured and modeled values of MAC. An agreement between observations and theoretical results can only be attained when assuming a fairly high value of the real and imaginary parts of the refractive index along the void-fraction curve and a mass density not exceeding 1.5-1.7 g/cm 3 .

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Section: Introductionmentioning

confidence: 99%

On the Discrepancy between Modeled and Measured Mass Absorption Cross Sections of Light Absorbing Carbon Aerosols

Kahnert

2010

Aerosol Science and Technology

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“…by Zhao and Ma (2009). In parallel, methods based on rigorous electromagnetic scattering theory have been developed (Borghese et al, 1984;Mackowski and Mishchenko, 1996;Xu and Gustafson, 2001) and applied to various case studies. Applications to atmospheric LAC have, e.g., been reported by Liu et al (2008).…”

Section: Introductionmentioning

confidence: 99%

Modelling the optical and radiative properties of freshly emitted light absorbing carbon within an atmospheric chemical transport model

Kahnert

2010

Atmos. Chem. Phys.

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Abstract. Light absorbing carbon (LAC) aerosols have a complex, fractal-like aggregate structure. Their optical and radiative properties are notoriously difficult to model, and approximate methods may introduce large errors both in the interpretation of aerosol remote sensing observations, and in quantifying the direct radiative forcing effect of LAC. In this paper a numerically exact method for solving Maxwell's equations is employed for computing the optical properties of freshly emitted, externally mixed LAC aggregates. The computations are performed at wavelengths of 440 nm and 870 nm, and they cover the entire size range relevant for modelling these kinds of aerosols. The method for solving the electromagnetic scattering and absorption problem for aggregates proves to be sufficiently stable and fast to make accurate multiple-band computations of LAC optical properties feasible. The results from the electromagnetic computations are processed such that they can readily be integrated into a chemical transport model (CTM), which is a prerequisite for constructing robust observation operators for chemical data assimilation of aerosol optical observations. A case study is performed, in which results obtained with the coupled optics/CTM model are employed as input to detailed radiative transfer computations at a polluted European location. It is found that the still popular homogeneous sphere approximation significantly underestimates the radiative forcing at top of atmosphere as compared to the results obtained with the aggregate model. Notably, the LAC forcing effect predicted with the aggregate model is less than that one obtains by assuming a prescribed mass absorption cross section for LAC.

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“…the angular dependence of the forward scattering amplitude can be determined analytically, and our theoretical curves are consistent with such angular dependence. We want Only to stress that according to the parameters reported in fig.2 and fig.3 the convergency of our calculations would require at least LH= 6 . Actually we have to use LM=1O for both cases.…”

Section: Figmentioning

confidence: 96%

“…1. Our extension is effected by describing the particles through the exact Mie amplitudes 5 , 6 and including up to the quadrupole terms for the largest spheres. We tentatively considered also a medium composed of particles with' size parameter up to 1-.0 by including terms up to the 24-poles to ensure the convergency of our calculations.…”

Section: Introductionmentioning

confidence: 99%

The Optical Properties of Aerosols

Borghese¹

1990

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Use of group theory for the description of electromagnetic scattering from molecular systems

Cited by 47 publications

References 10 publications

On the Discrepancy between Modeled and Measured Mass Absorption Cross Sections of Light Absorbing Carbon Aerosols

On the Discrepancy between Modeled and Measured Mass Absorption Cross Sections of Light Absorbing Carbon Aerosols

Modelling the optical and radiative properties of freshly emitted light absorbing carbon within an atmospheric chemical transport model

The Optical Properties of Aerosols

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