A parameterization for the light scattering enhancement factor with aerosol chemical compositions

Yu, Yingli; Zhao, Chunsheng; Kuang, Ye; Tao, Jiangchuan; Zhao, Gang; Shen, Chuanyang; Xu, Wanyun

doi:10.1016/j.atmosenv.2018.08.016

Cited by 26 publications

(19 citation statements)

References 45 publications

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“…The ambient aerosols absorb or lose water in response to the change of ambient RH and consequently the particle size and refractive index change, altering the aerosol scattering properties ultimately [16]. Compared with dry conditions ( RH ≤ 40%), the averaged SC enhanced by 228.26 Mm −1 on wet days ( RH ≥ 60%), from 189.71 Mm −1 to 441.99 Mm −1 , which indicates the remarkable impact of aerosol hygroscopicity on the extinction for light.…”

Section: Resultsmentioning

confidence: 99%

“…However, these measurements are commonly performed under dry conditions through heating air mass samples. It is necessary to transform the measured dry aerosol optical properties into corresponding values at ambient RH [16]. In order to quantify the relationship between the two aerosol scattering properties, the scattering hygroscopic growth factor, f ( RH ), was established to picture the response of aerosol optical properties to the different ambient RH [17].…”

Section: Introductionmentioning

confidence: 99%

“…In order to quantify the relationship between the two aerosol scattering properties, the scattering hygroscopic growth factor, f ( RH ), was established to picture the response of aerosol optical properties to the different ambient RH [17]. Notably, the value of f ( RH ) presents significant spatial variety [16]. Quantifying f ( RH ) is necessary to estimate the aerosol direct radiative forcing.…”

Section: Introductionmentioning

confidence: 99%

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Roles of Relative Humidity in Aerosol Pollution Aggravation over Central China during Wintertime

Zang

Wang

Zhu

et al. 2019

IJERPH

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Aerosol pollution elicits considerable public concern due to the adverse influence on air quality, climate change, and human health. Outside of emissions, haze formation is closely related to meteorological conditions, especially relative humidity (RH). Partly due to insufficient investigations on the aerosol hygroscopicity, the accuracy of pollution prediction in Central China is limited. In this study, taking Wuhan as a sample city, we investigated the response of aerosol pollution to RH during wintertime based on in-situ measurements. The results show that, aerosol pollution in Wuhan is dominated by PM2.5 (aerodynamic particle size not larger than 2.5 μm) on wet days (RH ≥ 60%), with the averaged mass fraction of 0.62 for PM10. Based on the RH dependence of aerosol light scattering (f (RH)), aerosol hygroscopicity was evaluated and shows the high dependence on the particle size distribution and chemical compositions. f (RH = 80%) in Wuhan was 2.18 (±0.73), which is comparable to that measured in the Pearl River Delta and Yangtze River Delta regions for urban aerosols, and generally greater than values in Beijing. Ammonium (NH4+), sulfate (SO42−), and nitrate (NO3−) were enhanced by approximately 2.5-, 2-, and 1.5-fold respectively under wet conditions, and the ammonia-rich conditions in wintertime efficiently promoted the formation of SO42− and NO3−, especially at high RH. These secondary ions play an important role in aggravating the pollution level and aerosol light scattering. This study has important implications for understanding the roles of RH in aerosol pollution aggravation over Central China, and the fitted equation between f (RH) and RH may be helpful for pollution forecasting in this region.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Roles of Relative Humidity in Aerosol Pollution Aggravation over Central China during Wintertime

Zang

Wang

Zhu

et al. 2019

IJERPH

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“…It is noteworthy that various chemical species contribute differently to visibility degradation (Huang et al, 2014; Kim et al, 2006; Ouimette & Flagan, 1982; Yu et al, 2018). Hand and Malm (2006) analyzed the correlation between aerosol and visibility based on the IMPROVE monitoring network, indicating that sulfate, nitrate, organic matter, light‐absorbing carbon, sand dust, and NO 2 gas are the main chemical components for visibility impairment.…”

Section: Resultsmentioning

confidence: 99%

Increased Aerosol Extinction Efficiency Hinders Visibility Improvement in Eastern China

Liu

Ren

Huang

et al. 2020

Geophysical Research Letters

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Though China has witnessed substantial particular matter pollution mitigation owing to the strict emission control in recent years, the frequency of haze events with low visibility is not improved as much as expected, especially in cold seasons. Here, 6-year wintertime observations, satellite retrievals, a thermodynamic model, and theoretical calculation were integrated to better understand the complex influence of aerosol chemical composition and hygroscopic behaviors on visibility impairment. We found that the proportion of nitrate in aerosol mass concentration increased by approximately 10% from 2013 to 2018. Such a transition in aerosol chemical compositions together with increasing ambient humidity in past years jointly enhanced aerosol extinction efficiency, and the elevated proportion of nitrate played an increasingly critical role after 2017. The increased aerosol extinction efficiency is responsible for the less improved visibility despite large decrease in aerosol mass concentrations in eastern China. Plain Language Summary Atmospheric aerosol degrades regional visibility as a result of light extinction, which is highly linked with aerosol chemical composition and particle size growth in humid environment. Due to a much sharper drop of sulfur emission than nitrogen emission in China, aerosol has become increasingly nitrate-dominant. The transition in aerosol chemical compositions together with increasing ambient humidity in past years may jointly alter aerosol hygroscopic behaviors and enhance aerosol extinction efficiency. In consequence, although substantial mitigation of aerosol pollution has been achieved in recent years, hazy days with low visibility still frequently occur in eastern China.

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“…The second one is the determination of particle hygroscopicity in order to evaluate the ability of particles to participate as CCN. Particle hygroscopicity, which is highly related to chemical composition and the aging/coating effect, is found to cause nonnegligible variations in cloud droplet activation (Hudson, 2007;Zhang et al, 2017). The last is the influence of high relative humidity (RH) near clouds.…”

Section: Introductionmentioning

confidence: 99%

Method to retrieve cloud condensation nuclei number concentrations using lidar measurements

Tan

Zhao

et al. 2019

Atmos. Meas. Tech.

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Abstract. Determination of cloud condensation nuclei (CCN) number concentrations at cloud base is important to constrain aerosol–cloud interactions. A new method to retrieve CCN number concentrations using backscatter and extinction profiles from multiwavelength Raman lidars is proposed. The method implements hygroscopic enhancements of backscatter and extinction with relative humidity to derive dry backscatter and extinction and humidogram parameters. Humidogram parameters, Ångström exponents, and lidar extinction-to-backscatter ratios are then linked to the ratio of CCN number concentration to dry backscatter and extinction coefficient (ARξ). This linkage is established based on the datasets simulated by Mie theory and κ-Köhler theory with in-situ-measured particle size distributions and chemical compositions. CCN number concentration can thus be calculated with ARξ and dry backscatter and extinction. An independent theoretical simulated dataset is used to validate this new method and results show that the retrieved CCN number concentrations at supersaturations of 0.07 %, 0.10 %, and 0.20 % are in good agreement with theoretical calculated values. Sensitivity tests indicate that retrieval error in CCN arises mostly from uncertainties in extinction coefficients and RH profiles. The proposed method improves CCN retrieval from lidar measurements and has great potential in deriving scarce long-term CCN data at cloud base, which benefits aerosol–cloud interaction studies.

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A parameterization for the light scattering enhancement factor with aerosol chemical compositions

Cited by 26 publications

References 45 publications

Roles of Relative Humidity in Aerosol Pollution Aggravation over Central China during Wintertime

Roles of Relative Humidity in Aerosol Pollution Aggravation over Central China during Wintertime

Increased Aerosol Extinction Efficiency Hinders Visibility Improvement in Eastern China

Method to retrieve cloud condensation nuclei number concentrations using lidar measurements

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