Angular Illumination and Truncation of Three Different Integrating Nephelometers: Implications for Empirical, Size-Based Corrections

Müller, Thomas; Nowak, Andreas; Wiedensohler, Alfred; Sheridan, Patrick J.; Laborde, M.; Covert, David S.; Marinoni, Angela; Imre, Kornélia; Henzing, Bas; Roger, J. C.; Santos, Sebastiao Martins Dos; Wilhelm, R.; Wang, Yaqiang; Leeuw, G. de

doi:10.1080/02786820902798484

Cited by 79 publications

(83 citation statements)

References 13 publications

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“…The systematic error due to non-idealities is strongly dependent on particle size and is more significant for particles >1 μm in diameter (Müller et al 2009) due to the forward truncation angle cutoff altering measurements of these strongly forward-scattering particles. Sub-micron particles are more prone to errors resulting from non-Lambertian illumination.…”

Section: The Nephelometermentioning

confidence: 99%

“…The correction factor for each channel (C(λ) A&O ) is derived using the equation a(λ)+b(λ)•å scat,uncor (λ) and values in Table 1 for sub-micron particles in A&O. A recent reevaluation of the A&O method produced correction factor estimates that are unchanged from original values (Müller et al 2009). After this, a corrected scattering coefficient is found for each channel.…”

Section: The Nephelometermentioning

confidence: 99%

“…After calibration with reference gases and blanking (see the SI), adjustments for most nephelometers take into account truncation errors, non-ideal angular response, imperfect wavelength response, and aerosol sampling issues (Anderson et al 1996;Müller et al 2009). For backscattering measurements, the shutter does not provide a perfectly sharp separation at 90…”

Section: The Nephelometermentioning

confidence: 99%

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Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

Singh

Fiddler

Smith

et al. 2014

Aerosol Science and Technology

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Despite the substantial improvements in the measurements of aerosol physical and chemical properties and in the direct and indirect radiative effects of aerosols, there is still a need for studying the properties of aerosols under controlled laboratory conditions to develop a mechanistic and quantitative understanding of aerosol formation, chemistry, and dynamics. In this work, we present the factors that affect measurement accuracy and the resulting uncertainties of the extinction-minus-scattering method using a combination of cavity ring-down spectroscopy (CRDS) and integrating nephelometry at a wider range of optical wavelengths than previously attempted. Purely scattering polystyrene latex (PSL) spheres with diameters from 107-303 nm and absorbing polystyrene spheres (APSL) with 390 nm diameter were used to determine the consistency and agreement, within experimental uncertainties, of CRDS and nephelometer values with theoretical calculations derived from Mie theory for non-absorbing spheres. Overall uncertainties for extinction cross-section were largely 10%-11% and dominated by condensation particle counter (CPC) measurement error. Two methods for determining σ ext error are described, and they were found to produce equivalent results. Systematic uncertainties due to particle losses, RD cell geometry (R L ), CPC counting efficiency, ring-down regression fitting, blank drift, optical tweezing, and recapturing of forward scattered light are also investigated. The random error observed in this work for absorbing spheres is comparable to previous reported measurements. For both absorbing and non-absorbing spheres, a statistical framework is developed for including the contributions to random error due to CPC measurement uncertainty, R L , statistical fluctuations in

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Section: The Nephelometermentioning

confidence: 99%

Section: The Nephelometermentioning

confidence: 99%

Section: The Nephelometermentioning

confidence: 99%

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Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

Singh

Fiddler

Smith

et al. 2014

Aerosol Science and Technology

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“…Because illumination functions of integrating nephelometers deviate little from a sine-function (Anderson et al, 1996;, and due to a limited range of angular integration (e.g. Anderson et al, 1996;Moosmüller and Arnott, 2003), integrating nephelometers measure the so called nephelometer total scattering σ neph ts and nephelometer backscattering σ neph bs . In the following, the term angular sensitivity comprises both the non-Lambertian illumination and the angular truncation.…”

Section: Theory Of Integrating Nephelometersmentioning

confidence: 99%

Design and performance of a three-wavelength LED-based total scatter and backscatter integrating nephelometer

Müller

Laborde

Kassell³

et al. 2011

Atmos. Meas. Tech.

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210

203

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Abstract.Integrating nephelometers are instruments that directly measure a value close to the light scattering coefficient of airborne particles. Different models of nephelometers have been used for decades for monitoring and research applications. Now, a series of nephelometers (Ecotech models M9003, Aurora 1000 and Aurora 3000) with newly designed light sources based on light emitting diodes are available. This article reports on the design of these integrating nephelometers and a comparison of the Aurora 3000 to another commercial instrument (TSI model 3563) that uses an incandescent lamp. Both instruments are three-wavelength, total and backscatter integrating nephelometers.We present a characterization of the new light source design of the Aurora 3000 and provide parameterizations for its angular sensitivity functions. These parameterizations facilitate to correct for measurement artefacts using Mie-theory. Furthermore, correction factors are provided as a function of theÅngström exponent. Comparison measurements against the TSI 3563 with laboratory generated white particles and ambient air are also shown and discussed. Both instruments agree well within the calibration uncertainties and detection limit for total scattering with differences less than 5 %. Differences for backscattering are higher by up to 11 %. Highest differences were found for the longest wavelengths, where the signal to noise ratio is lowest. Differences at the blue and green wavelengths are less than 4 % and 3 %, respectively, for both total and backscattering.

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“…Many previous works have been done to correct the truncation error for the TSI 3563 integrating Nephelometer (Anderson and Ogren, 1998;Heintzenberg et al, 2006;Bond et al, 2009;Müller et al, 2009), but little was known for the EcoTech-made instrument used in the present study. However, as mentioned by Müller et al (2009) and also by the manufacturer, the Ecotech's Aurora model nephelometer light source has been updated to produce an angular intensity distribution function that is closer to Lambertian. Besides, the light source has an increased number of LEDs and a shorter axial dimension.…”

Section: Scattering Measurement and Correctionmentioning

confidence: 99%

Aerosol Optical Properties Observed at a Semi-Arid Rural Site in Northeastern China

Zhang

et al. 2012

Aerosol Air Qual. Res.

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Continuous in situ measurements), respectively, in spring 2011. These values are lower than the majority of measurements made in other areas of China. The mean single scattering albedo (ω) was 0.90, greater than values found in some developed areas in China, indicating more scattering or less absorbing aerosols at Tongyu site. Mean values (and standard deviation) of the Ångström exponent of absorption (α ab ) were 1.61 (0.27) and 1.64 (0.28) for spring of 2010 and 2011, respectively, and of the scattering (α sc ) were 1.48 (0.50) and 1.10 (0.50), respectively. The values of α ab were higher than those of pure BC, implying the presence of other light absorbing materials having larger α ab values. The moderate values of α sc indicated that considerable amount of coarse particles presented at Tongyu site. Distinct diurnal variations of aerosol optical properties were observed. ω, α ab and α sc had nearly opposite diurnal variations compared to those of σ ab and σ sc . Dust aerosols from the northwest and anthropogenic aerosols from the south were major sources contributing to the episodic aerosol events and thus, unusual aerosol optical properties, in spring at Tongyu site. High levels of PM 2.5 , if mainly caused by dust particles, do not necessarily introduce high values of σ ab and σ sc .

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Angular Illumination and Truncation of Three Different Integrating Nephelometers: Implications for Empirical, Size-Based Corrections

Cited by 79 publications

References 13 publications

Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

Design and performance of a three-wavelength LED-based total scatter and backscatter integrating nephelometer

Aerosol Optical Properties Observed at a Semi-Arid Rural Site in Northeastern China

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