Optical particle spectrometry—Problems and prospects

Szymanski, Wladyslaw W.; Nagy, Attila; Czitrovszky, A.

doi:10.1016/j.jqsrt.2009.02.024

Cited by 47 publications

(24 citation statements)

References 24 publications

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“…It is required, for example, for closure experiments (consistency checks between different measurement methods involving an aerosol model, e.g., Wiegner et al, 2009;Gasteiger et al, 2011b;Müller et al, 2012;Bell et al, 2013;Ma et al, 2014;Zieger et al, 2014;Düsing et al, 2018), radiative transfer studies (e.g., Otto et al, 2009;Emde et al, 2010), the inversion of remote-sensing measurements (e.g., Dubovik et al, 2006;Gasteiger et al, 2011a;Müller et al, 2016), the inversion of in situ data (e.g., Weinzierl et al, 2009;Szymanski et al, 2009;Kassianov et al, 2014), aerosol layer visibility simulations (e.g., Weinzierl et al, 2012), dynamic aerosol transport models (e.g., Heinold et al, 2007;Balzarini et al, 2015), aerosol characterization (e.g., Gasteiger et al, 2017;Che et al, 2018;Zhuang et al, 2018), and solar energy (e.g., Polo et al, 2016;Kosmopoulos et al, 2017).…”

Section: Applicationsmentioning

confidence: 99%

MOPSMAP v1.0: a versatile tool for the modeling of aerosol optical properties

Gasteiger

Wiegner²

2018

Geosci. Model Dev.

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Abstract. The spatiotemporal distribution and characterization of aerosol particles are usually determined by remotesensing and optical in situ measurements. These measurements are indirect with respect to microphysical properties, and thus inversion techniques are required to determine the aerosol microphysics. Scattering theory provides the link between microphysical and optical properties; it is not only needed for such inversions but also for radiative budget calculations and climate modeling. However, optical modeling can be very time-consuming, in particular if nonspherical particles or complex ensembles are involved.In this paper we present the MOPSMAP package (Modeled optical properties of ensembles of aerosol particles), which is computationally fast for optical modeling even in the case of complex aerosols. The package consists of a data set of pre-calculated optical properties of single aerosol particles, a Fortran program to calculate the properties of userdefined aerosol ensembles, and a user-friendly web interface for online calculations. Spheres, spheroids, and a small set of irregular particle shapes are considered over a wide range of sizes and refractive indices. MOPSMAP provides the fundamental optical properties assuming random particle orientation, including the scattering matrix for the selected wavelengths. Moreover, the output includes tables of frequently used properties such as the single-scattering albedo, the asymmetry parameter, or the lidar ratio. To demonstrate the wide range of possible MOPSMAP applications, a selection of examples is presented, e.g., dealing with hygroscopic growth, mixtures of absorbing and non-absorbing particles, the relevance of the size equivalence in the case of nonspherical particles, and the variability in volcanic ash microphysics.The web interface is designed to be intuitive for expert and nonexpert users. To support users a large set of default settings is available, e.g., several wavelength-dependent refractive indices, climatologically representative size distributions, and a parameterization of hygroscopic growth. Calculations are possible for single wavelengths or user-defined sets (e.g., of specific remote-sensing application). For expert users more options for the microphysics are available. Plots for immediate visualization of the results are shown. The complete output can be downloaded for further applications. All input parameters and results are stored in the user's personal folder so that calculations can easily be reproduced. The web interface is provided at https://mopsmap.net (last access: 9 July 2018) and the Fortran program including the data set is freely available for offline calculations, e.g., when large numbers of different runs for sensitivity studies are to be made.

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Section: Applicationsmentioning

confidence: 99%

MOPSMAP v1.0: a versatile tool for the modeling of aerosol optical properties

Gasteiger

Wiegner²

2018

Geosci. Model Dev.

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“…-Even if quasi-monotonicity between particle size and (discretized) scattering signal amplitude can be established for particles of certain intrinsic properties (e.g., polystyrene latex spheres) by a smart choice of OPC collecting optics (Barnard and Harrison, 1988) and/or bin threshold values, this does not automatically hold for particles of different intrinsic properties (e.g., different refractive index or shape) (Szymanski et al, 2009). …”

Section: Existing Concepts For Size Assignment and Calibration Evaluamentioning

confidence: 99%

“…One reason for this is the measurement principle itself, as particle size is only indirectly inferred from scattered light intensity. This intensity, in general, is a non-monotonic function of particle size and depends also on particle intrinsic properties, such as complex refractive index and shape (Szymanski and Liu, 1986;Szymanski et al, 2009). Especially for particle sizes that are comparable or larger than the wavelength of the incident light, the size dependency of scattered intensity tends to be flat and occasionally ambiguous, so that uncertainties in the particle's intrinsic properties can introduce large sizing uncertainties (Reid et al, 2003;Formenti et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

On the parametrization of optical particle counter response including instrument-induced broadening of size spectra and a self-consistent evaluation of calibration measurements

et al. 2017

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Abstract. Optical particle counters (OPCs) are common tools for the in situ measurement of aerosol particle number size distributions. As the actual quantity measured by OPCs is the intensity of light scattered by individual particles, it is necessary to translate the distribution of detected scattering signals into the desired information, i.e., the distribution of particle sizes. A crucial part in this challenge is the modeling of OPC response and the calibration of the instrumentin other words, establishing the relation between instrumentspecific particle scattering cross-section and measured signal amplitude. To date, existing methods lack a comprehensive parametrization of OPC response, particularly regarding the instrument-induced broadening of signal amplitude distributions. This deficiency can lead to significant size distribution biases. We introduce an advanced OPC response model including a simple parametrization of the broadening effect and a self-consistent way to evaluate calibration measurements using a Markov chain Monte Carlo (MCMC) method. We further outline how to consistently derive particle number size distributions with realistic uncertainty estimates within this new framework. Based on measurements of particle standards for two OPCs, the Grimm model 1.129 (SkyOPC) and the DMT Passive Cavity Aerosol Spectrometer Probe (PCASP), we demonstrate that residuals between measured and modeled response can be substantially reduced when using the new approach instead of existing methods. More importantly, for the investigated set of measurements only the new approach yields results that conform with the true size distributions within the range of model uncertainty. The presented innovations will help improving the accuracy of OPC-derived size distributions and the assessment of their precision.

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“…At this time comprehensive numerical performance test together with the first laboratory measurement results were published (Nagy et al, 2007;Szymanski et al, 2009). A mobile prototype instrument was developed and built to study the method during field measurement campaigns and in order to compare its results with that of other devices.…”

Section: Dual Wavelength Optical Particle Spectrometer -Dwopsmentioning

confidence: 99%

“…This provides sufficient information to obtain unique data about the optical particle size and its complex index of refraction, especially the imaginary part representing the absorptivity (Szymanski et al, 2002;Nagy et al, 2007;Szymanski et al, 2009). The real-time determination of ambient aerosols' absorbing properties may provide information regarding the origin of atmospheric particulate matter.…”

Section: Introductionmentioning

confidence: 99%

Real-Time Determination of Absorptivity of Ambient Particles in Urban Aerosol in Budapest, Hungary

Nagy

Czitrovszky

Kerekes

et al. 2016

Aerosol Air Qual. Res.

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The absorption properties of ambient urban aerosols as well as their size distributions were measured in real-time using a dual wavelength optical particle spectrometer (DWOPS). A photoacoustic spectrometer (PAS) was simultaneously used to directly measure light absorptivity of the particles in question along with an Aethalometer and a commercial optical particle counter (OPC). The sizing performance of the DWOPS was compared with the commercial OPC unit showing very good agreement. The data from DWOPS, PAS and Aethalometer instruments are presented and show the potential of the DWOPS technique for a direct and simple assessment of the absorbing part of the complex refractive index of ambient particles as a function of particle size.

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Optical particle spectrometry—Problems and prospects

Cited by 47 publications

References 24 publications

MOPSMAP v1.0: a versatile tool for the modeling of aerosol optical properties

MOPSMAP v1.0: a versatile tool for the modeling of aerosol optical properties

On the parametrization of optical particle counter response including instrument-induced broadening of size spectra and a self-consistent evaluation of calibration measurements

Real-Time Determination of Absorptivity of Ambient Particles in Urban Aerosol in Budapest, Hungary

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