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

Zhao, Gang; Zhao, Chunsheng; Kuang, Ye; Bian, Yuxuan; Tao, Jiangchuan; Shen, Chuanyang; Yu, Yingli

doi:10.5194/acp-18-9049-2018

Cited by 30 publications

(21 citation statements)

References 38 publications

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“…a/γ was 0.930/0.329, 0.971/0.372 and 0.988/0.356 for the clean, moderate and heavy pollution period, respectively, according to the study. The RH influence on g was calculated according to Zhao et al (2018), expressed as…”

Section: Aerosol Optical Propertiesmentioning

confidence: 99%

In situ vertical characteristics of optical properties and heating rates of aerosol over Beijing

et al. 2020

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Abstract. Characterizing vertical profiles of aerosol optical properties is important because relying on only the surface or column-integrated measurements cannot unambiguously constrain the radiative impacts of aerosol. This study presents series of vertical profiles of in situ measured multi-wavelength optical properties of aerosols during three pollution events from November to December 2016 over the Beijing region. For all pollution events, the clean periods (CPs) before pollution initialization showed a higher scattering Ångström exponent (SAE) and a smaller asymmetry parameter (g) with relatively uniform vertical structures. The heavy pollution periods (HPs) showed an increased particle size, causing these parameters to vary in the opposite way. During the transition periods (TPs), regional transport of aged aerosols at higher altitudes was found. The Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) matched the in situ measurements within 10 %; however the AERONET absorption optical depth (AAOD) was 10 %–20 % higher than the in situ measurements, and this positive discrepancy increased to 30 % at shorter wavelengths. The absorption of brown carbon (BrC) was identified by the increased-absorption Ångström exponent (AAE), and the heating rate of black carbon (BC) and BrC was estimated by computing the spectral absorption coefficient and actinic flux calculated by a radiative transfer model. BC and BrC had a heating rate of up to 0.18 and 0.05 K h−1 in the planetary boundary layer (PBL), respectively, during the pollution period. The fraction of BrC absorption increased from 12 % to 40 % in the PBL from the CP to the HP. Notably, a higher contribution of BrC heating was found above the PBL under polluted conditions. This study paints a full picture of shortwave heating impacts of carbonaceous aerosols during different stages of pollution events and highlights the increased contribution of BrC absorption especially at higher altitudes during pollution.

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Section: Aerosol Optical Propertiesmentioning

confidence: 99%

In situ vertical characteristics of optical properties and heating rates of aerosol over Beijing

et al. 2020

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“…As for the aerosol g, it decreases from 0.667 to 0.602 with the increment of the aerosol RRI. The ambient g values in the NCP are found within 0.55 and 0.66 (Zhao et al, 2018a). Thus, the variations of the RRI have significant influence on the g. The aerosol optical properties change significantly with the variation of the ambient aerosol RRI.…”

Section: Influence Of Rri Variation On Aerosol Optical Properties Andmentioning

confidence: 88%

“…SSA is defined as the ratio of σ sca to σ ext , which reflects concentration of the absorbing aerosol (Tao et al, 2014) to some extent. The g expresses the distribution of the scattering light intensity in different directions (Zhao et al, 2018a).…”

Section: Calculate Aerosol Optical Properties Using Different Rrimentioning

confidence: 99%

A new parameterization scheme of the real part of the ambient aerosols refractive index

Zhao¹,

Tan²,

Zhao³

et al. 2019

Preprint

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Abstract. The refractive index of ambient aerosols, which directly determines the aerosol optical properties, is widely used in atmospheric models and remote sensing. Traditionally, the real part of the refractive index (RRI) is mainly parameterized by the measurement of ambient aerosol main inorganic components. In this paper, the characteristics of the ambient aerosol RRI are studied based on the field measurement in the East China. Results show that the ambient aerosol RRI varies significantly between 1.36 and 1.56. The direct aerosol radiative forcing is estimated to vary by 40&#8201;% corresponding to the variation of the measured aerosol RRI. We find that the ambient aerosol RRI is highly related with the aerosol effective density (&#961;eff) rather than the main chemical components. However, parameterization schemes of the ambient aerosol RRI by &#961;eff are not available due to the lack of corresponding simultaneous field measurements. For the first time, the size-resolved ambient aerosol RRI and &#961;eff are measured simultaneously by our designed measurement system. A new parameterization scheme of the ambient aerosols RRI using &#961;eff is proposed. The measured and parameterized RRI agree well with the correlation coefficient of 0.76. Knowledge of the ambient aerosol RRI would improve our understanding of the ambient aerosol radiative effects.

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“…A coupled DMA-SP2 system was employed to measure the aerosol RRI from 24 May to 18 June 2018. This system is introduced elsewhere by Zhao et al (2019), and a brief description is presented here. As schematically shown in Fig.…”

Section: Measuring the Rrimentioning

confidence: 99%

“…In this study, the aerosol RRI and size-resolved ρ eff ( ρ eff ) are measured simultaneously during a field measurement conducted in Taizhou in East China. Ambient aerosol RRI is measured by our designed system, which combines a differential mobility analyzer (DMA) and a single-particle soot photometer (SP2) (Zhao et al, 2019). The ρ eff is measured by using a centrifugal particle mass analyzer (CMPA) and a scanning mobility particle sizer (SMPS).…”

Section: Introductionmentioning

confidence: 99%

A new parameterization scheme for the real part of the ambient urban aerosol refractive index

et al. 2019

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Abstract. The refractive index of ambient aerosols, which directly determines the aerosol optical properties, is widely used in atmospheric models and remote sensing. Traditionally, the real part of the refractive index (RRI) is parameterized by the measurement of ambient aerosol main inorganic components. In this paper, the characteristics of the ambient aerosol RRI are studied based on field measurements in East China. The results show that the measured ambient aerosol RRI varies significantly between 1.36 and 1.56. The direct aerosol radiative forcing is estimated to vary by 40 % when the RRI values were varied between 1.36 and 1.56. We find that the ambient aerosol RRI is highly correlated with the aerosol effective density (ρeff) rather than the main chemical components. However, the parameterization of the ambient aerosol RRI by ρeff is not available due to the lack of corresponding simultaneous field measurements. For the first time, the size-resolved ambient aerosol RRI and ρeff are measured simultaneously by our designed measurement system. A new parameterization scheme for the ambient aerosol RRI using ρeff is proposed for urban environments. The measured and parameterized RRI values agree well, with a correlation coefficient of 0.75 and slope of 0.99. Knowledge of the ambient aerosol RRI would improve our understanding of ambient aerosol radiative effects.

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

Cited by 30 publications

References 38 publications

In situ vertical characteristics of optical properties and heating rates of aerosol over Beijing

In situ vertical characteristics of optical properties and heating rates of aerosol over Beijing

A new parameterization scheme of the real part of the ambient aerosols refractive index

A new parameterization scheme for the real part of the ambient urban aerosol refractive index

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