Determination of Aerosol Size Distribution from Angular Light-Scattering Signals by Using a SPSO-DE Hybrid Algorithm

The comparison of the angular light-scattering method (ALSM) and the spectral extinction method (SEM) in solving the inverse problem of aerosol size distribution (ASD) are studied. The inverse problem is solved by a SPSO-DE hybrid algorithm, which is based on the stochastic particle swarm optimization (SPSO) algorithm and differential evolution (DE) algorithm. To improve the retrieval accuracy, the sensitivity analysis of measurement signals to characteristic parameters in ASDs is studied; and the corresponding optimal measurement angle selection region for ALSM and optimal measurement wavelength selection region for SEM are proposed, respectively. Results show that more satisfactory convergence properties can be obtained by using the SPSO-DE hybrid algorithm. Moreover, short measurement wavelengths and forward measurement angles are beneficial to obtaining more accurate results. Then, common monomodal and bimodal ASDs are estimated under different random measurement errors by using ALSM and SEM, respectively. Numerical tests show that retrieval results by using ALSM show better convergence accuracy and robustness than those by using SEM, which is attributed to the distribution of the objective function value. As a whole, considering the convergence properties and the independence on prior optical information, the ALSM combined with SPSO-DE hybrid algorithm provides a more effective and reliable technique to obtain the ASDs.

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Optimum Angles for Multi-Angle Elastic Light Scattering Experiments

Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B ◽

10.1115/imece2011-64748 ◽

2011 ◽

Author(s):

D. W. Burr ◽

K. J. Daun ◽

K. A. Thomson ◽

G. J. Smallwood

Keyword(s):

Inverse Problem ◽

Light Scattering ◽

Light Intensity ◽

Size Distribution ◽

Design Of Experiment ◽

Scattered Light ◽

Scattered Light Intensity ◽

Elastic Light Scattering ◽

Optimal Angle ◽

Ill Posed

In multiangle elastic light scattering (MAELS) experiments, the morphology of aerosolized particles is inferred by shining collimated radiation through the aerosol and then measuring the scattered light intensity over a set of angles. In the case of soot-laden aerosols MAELS can be used to recover, among other things, the size distribution of soot aggregates. This involves solving an ill-posed set of equations, however. While previous work focused on regularizing the inverse problem using Bayesian priors, this paper presents a design-of-experiment methodology for identifying the set of measurement angles that minimizes its ill-posedness. The inverse problem produced by the optimal angle set requires less regularization and is less sensitive to noise, compared with two other measurement angle sets commonly used to carry out MAELS experiments.

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Optical Properties of the Urban Aerosol Particles Obtained from Ground Based Measurements and Satellite-Based Modelling Studies

Advances in Meteorology ◽

10.1155/2015/898376 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Genrik Mordas ◽

Nina Prokopciuk ◽

Steigvilė Byčenkienė ◽

Jelena Andriejauskienė ◽

Vidmantas Ulevicius

Keyword(s):

Optical Properties ◽

Light Scattering ◽

Urban Environment ◽

Size Distribution ◽

Number Concentration ◽

Scattering Coefficient ◽

Dust Particles ◽

Aerosol Size Distribution ◽

Air Masses ◽

The Impact

Applications of satellite remote sensing data combined with ground measurements and model simulation were applied to study aerosol optical properties as well as aerosol long-range transport under the impact of large scale circulation in the urban environment in Lithuania (Vilnius). Measurements included the light scattering coefficients at 3 wavelengths (450, 550, and 700 nm) measured with an integrating nephelometer and aerosol particle size distribution (0.5–12 μm) and number concentration (Dpa> 0.5 μm) registered by aerodynamic particle sizer. Particle number concentration and mean light scattering coefficient varied from relatively low values of 6.0 cm−3and 12.8 Mm−1associated with air masses passed over Atlantic Ocean to relatively high value of 119 cm−3and 276 Mm−1associated with South-Western air masses. Analysis shows such increase in the aerosol light scattering coefficient (276 Mm−1) during the 3rd of July 2012 was attributed to a major Sahara dust storm. Aerosol size distribution with pronounced coarse particles dominance was attributed to the presence of dust particles, while resuspended dust within the urban environment was not observed.

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