Parameterization of the Aerosol Upscatter Fraction as Function of the Backscatter Fraction and Their Relationships to the Asymmetry Parameter for Radiative Transfer Calculations

Moosmüller, Hans; Ogren, J. A.

doi:10.3390/atmos8080133

Cited by 31 publications

(22 citation statements)

References 32 publications

(70 reference statements)

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“…This gaseous heating generates a pressure wave, which is detected by a microphone located within the PAS cell. The amplitude of the microphone signal is related to the sample absorption coefficient through calibration (Arnott et al, 1999;Davies et al, 2018;Moosmüller et al, 2009). Much of this analysis relies on accurate PAS absorption measurements and thus we focus here on describing the uncertainty associated with these measurements.…”

Section: Photoacoustic and Cavity Ring-down Spectrometersmentioning

confidence: 99%

Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

et al. 2019

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Biases in absorption coefficients measured using a filter-based absorption photometer (Tricolor Absorption Photometer, or TAP) at wavelengths of 467, 528 and 652 nm are evaluated by comparing to measurements made using photoacoustic spectroscopy (PAS). We report comparisons for ambient sampling covering a range of aerosol types including urban, fresh biomass burning and aged biomass burning. Data are also used to evaluate the performance of three different TAP correction schemes. We found that photoacoustic and filter-based measurements were well correlated, but filter-based measurements generally overestimated absorption by up to 45 %. Biases varied with wavelength and depended on the correction scheme applied. Optimal agreement to PAS data was achieved by processing the filterbased measurements using the recently developed correction scheme of Müller et al. (2014), which consistently reduced biases to 0 %-18 % at all wavelengths. The biases were found to be a function of the ratio of organic aerosol mass to light-absorbing carbon mass, although applying the Müller et al. (2014) correction scheme to filter-based absorption measurements reduced the biases and the strength of this correlation significantly. Filter-based absorption measurement biases led to aerosol single-scattering albedos that were biased low by values in the range 0.00-0.07 and absorption Ångström exponents (AAEs) that were in error by ± (0.03-0.54). The discrepancy between the filter-based and PAS absorption measurements is lower than reported in some earlier studies and points to a strong dependence of filterbased measurement accuracy on aerosol source type.

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Section: Photoacoustic and Cavity Ring-down Spectrometersmentioning

confidence: 99%

Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

et al. 2019

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“…Black carbon (BC) mass concentrations are measured by a multi-angle absorption photometer (MAAP model 5012, Thermo, Inc., Waltham, MA USA) at UCAS and by an Aethalometer (AE33) (Hansen et al, 1984;Drinovec et al, 2015) at PKU and Gucheng. The aerosol σ sca is measured at wavelengths of 450, 525, and 635 nm by an Aurora 3000 nephelometer and the corresponding values are recorded every minute (Müller et al, 2011).…”

Section: Instruments and Datasetsmentioning

confidence: 99%

“…When the σ sca is smaller, the deviations become larger. Some other empirical relationships between b and g (Moosmüller and Ogren, 2017) are also tested. This parameterization scheme almost has the same result as Wiscombe and Grams (1976), which means that the previously established parameterization scheme is not applicable in the NCP…”

Section: Influence Of Rh On Gmentioning

confidence: 99%

Calculating the aerosol asymmetry factor based on measurements from the humidified nephelometer system

Zhao

Kuang

et al. 2018

Atmos. Chem. Phys.

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Abstract. The aerosol asymmetry factor (g) is one of the most important factors for assessing direct aerosol radiative forcing. However, little attention has been paid to the measurement and parameterization of g. In this study, the characteristics of g are studied based on field measurements over the North China Plain (NCP) using the Mie scattering theory. The results show that calculated g values for dry aerosol can vary over a wide range (between 0.54 and 0.67). Furthermore, when ambient relative humidity (RH) reaches 90 %, g is significantly enhanced by a factor of 1.2 due to aerosol hygroscopic growth. For the first time, a novel method of calculating g based on measurements from the humidified nephelometer system is proposed. This method can constrain the uncertainty of g to within 2.56 % for dry aerosol populations and 4.02 % for ambient aerosols, providing that aerosol hygroscopic growth is taken into account. Sensitivity studies show that aerosol hygroscopicity plays a vital role in the accuracy of predicting g.

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“…This can lead to heating or cooling, depending on the ratio of aerosol scattering and extinction coefficients (single scattering albedo, or SSA), the particle scattering asymmetry parameter, and the albedo of the underlying surface [3][4][5][6]. In addition to these direct effects, aerosols can also have indirect effects on the radiation balance by changing the properties of clouds, thus influencing their optical properties and lifetime [7,8].…”

Section: Introductionmentioning

confidence: 99%

Evolution of Multispectral Aerosol Absorption Properties in a Biogenically-Influenced Urban Environment during the CARES Campaign

et al. 2017

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Abstract:We present the evolution of multispectral optical properties through urban aerosols that have aged and interacted with biogenic emissions, resulting in stronger short wavelength absorption and the formation of moderately brown secondary organic aerosols. Ground-based aerosol measurements were made in June 2010 within the Sacramento urban area (site T0) and at a 40-km downwind location (site T1) in the forested Sierra Nevada foothills area. Data on black carbon (BC) and non-refractory aerosol mass and composition were collected at both sites. In addition, photoacoustic (PA) instruments with integrating nephelometers were used to measure spectral absorption and scattering coefficients for wavelengths ranging from 355 to 870 nm. The daytime absorption Ångström exponent (AAE) indicated a modest wavelength-dependent enhancement of absorption at both sites throughout the study. From 22 to 28 June 2010, secondary organic aerosol mass increased significantly at both sites, which was due to increased biogenic emissions coupled with intense photochemical activity and air mass recirculation in the area. During this period, the median BC mass-normalized absorption cross-section (MAC) values for 405 nm and 532 nm at T1 increased by~23% and~35%, respectively, compared with the relatively less aged urban emissions at the T0 site. In contrast, the average MAC values for the 870 nm wavelength were similar for both sites. These results suggest the formation of moderately brown secondary organic aerosols in biogenically-influenced urban air.

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Parameterization of the Aerosol Upscatter Fraction as Function of the Backscatter Fraction and Their Relationships to the Asymmetry Parameter for Radiative Transfer Calculations

Cited by 31 publications

References 32 publications

Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

Calculating the aerosol asymmetry factor based on measurements from the humidified nephelometer system

Evolution of Multispectral Aerosol Absorption Properties in a Biogenically-Influenced Urban Environment during the CARES Campaign

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