A parameterization for the light scattering enhancement factor with aerosol chemical compositions. (October 2018)

• Record Type: Journal Article
• Authors: Yu, Yingli; Zhao, Chunsheng; Kuang, Ye; Tao, Jiangchuan; Zhao, Gang; Shen, Chuanyang; Xu, Wanyun
• Is Part Of: Atmospheric environment. Volume 191(2018)
• Page Start: 370
• Page End: 377
• Publication Date: 2018-10
• Subjects: The light scattering enhancement factor -- Parameterization -- Aerosol hygroscopicity -- Chemical compositions; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.08.016
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: The light scattering enhancement factor f ( RH ), defined as the ratio of the light scattering coefficient ( σ S P ) observed under an elevated relative humidity ( RH ) conditions to that under dry conditions, is a crucial parameter for estimating aerosol direct radiative effects and atmospheric visibility. In this paper, a new f ( RH ) parameterization scheme considering both the influence of aerosol chemical compositions and that of particle number size distribution (PNSD) is proposed based on in situ measurements in the North China Plain. The development of this parameterization scheme includes three steps. First, aerosol hygroscopicity parameter κ is parameterized with aerosol chemical compositions. Then, the ratio between f ( RH ) fitted parameter κ s c a ( f ( R H ) = 1 + κ s c a R H 100 − R H ) and κ is introduced to correlate f ( RH ) with κ . The ratio, influenced mostly by PNSD, is described as a function of scattering Ångström exponent (SAE) because the SAE can represent the predominant size of aerosol particles to some extent. Finally, f ( RH ) cycle is parameterized with κ s c a . Validation results show that a good consistency between the parameterized and measured f ( RH = 80%) is achieved and the correlation coefficient is 0.80. This parameterization scheme between aerosol chemistry and f ( RH ) can be used in chemical transport models for reducing uncertainties in estimations of direct aerosol radiative forcing and air quality assessments. Highlights: A relationship between the f ( RH ) fitted parameter (κsca ) and the aerosol hygroscopicity parameter (κf(RH) ) is found. The ratio of κsca and κf(RH) increases linearly with the increase of the scattering Ångström exponent. A new parameterization of f ( RH ) considering the aerosol chemical compositions is developed.