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Analytic Expression for the Aerosol Mass Efficiencies for Polydispersed Accumulation Mode

Category: Technical Note

Volume: 18 | Issue: 6 | Pages: 1503-1514
DOI: 10.4209/aaqr.2018.02.0067
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Chang H. Jung 1, Junshik Um2, Soo Ya Bae3, Young Jun Yoon4, Seoung Soo Lee5, Ji Yi Lee6, Yong Pyo Kim7

  • 1 Department of Health Management, Kyungin Women’s University, Incheon 21041, Korea
  • 2 Department of Atmospheric and Environmental Sciences, Pusan National University, Busan 46241, Korea
  • 3 Korea Institute of Atmospheric Prediction Systems, Seoul 07071, Korea
  • 4 Korea Polar Research Institute, Incheon, Korea
  • 5 Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20740, USA
  • 6 Department of Environmental Science and Engineering, Ewha Womans University, Seoul 03760, Korea
  • 7 Department of Chemical Engineering and Materials Science, Ewha Womans University, Seoul 03760, Korea

Highlights

Analytical formula for polydispersed aerosol mass efficiencies was developed.
Size ranges of 0.5–2.5 µm in geometric mean diameter were considered.
Fitting curves were generalized for the polydispersed aerosol.
The results showed a comparable agreement with exact solution.


Abstract

Aerosol mass efficiencies for extinction, scattering, and absorption are important parameters to understand aerosol optical properties. Although the mass efficiency is functions of the refractive index and particle size distribution, due to the complexity of the efficiency, mass efficiency parameters are usually regarded as a size independent and assumed to depend mainly on the chemical composition of aerosols. In this study, we calculated the mass efficiencies of polydispersed aerosols based on different aerosol types. An analytical approach to the approximated formula of the mass efficiency of each chemical species was developed and evaluated by fitting the results to those of the Mie theory that calculated the optical properties of chemical species based on the refractive index and size. We used the lognormal size distributions and external mixture approximations that represent the polydispersity of aerosol particles. Size ranges of 0.5–2.5 µm in the geometric mean diameter were considered for five different chemical species. The parameters of fitting curves were generalized for polydispersed aerosols as functions of the geometric mean diameter and the geometric standard deviation. The results of the newly developed analytic approach showed a good agreement with those of the Mie theory. The proposed approach provides an effective means to estimate the mass extinction efficiency of polydispersed multi-component aerosols.

Keywords

Analytical approach Polydisperse aerosol particles Mass scattering efficiency Mass absorption efficiency Mie theory


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