Retrieval of aerosol physical and chemical properties from mid-infrared extinction spectra

A. Y. Zasetsky, M. E. Earle, B. Cosic, R. Schiwon, I. A. Grishin, R. McPhail, R. G. Pancescu, J. Najera, A. F. Khalizov, K. B. Cook, J. J. Sloan

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

We report several results that validate the accuracy of a retrieval method for the determination of a number of aerosol particle properties from their mid infrared (600-6000 cm-1) extinction spectra. These properties include the number density, chemical composition, phase, size distribution, and to some extent, shape. The approach is based on information obtained in laboratory studies of micron-sized particles using the aerosol flow tube (AFT) technique. We report here experiments in which our method is used to measure a variety of aerosols including SiO2 micro-spheres as well as solid NaCl, (NH4)2SO4, ice and liquid water particles. The uncertainties in the retrieved aerosol properties associated with the particle shapes (spheres, spheroids, cylinders, hexagonal and rectangular prisms) as well as the effect of variations in the spectral range were evaluated. To assess the accuracy of the retrieved size distributions and particle shapes, the properties calculated from infrared spectra were compared with corresponding properties determined using alternative methods. We used scanning electron microscopy (SEM) for solid (NH4)2SO4 and NaCl aerosols and direct particle imaging with an optical microscope assembly for liquid water aerosols. On the basis of the validation results, we discuss the boundaries of applicability of the most popular spectral model, single scattering by spherical, homogeneous aerosol particles.

Original languageEnglish (US)
Pages (from-to)294-305
Number of pages12
JournalJournal of Quantitative Spectroscopy and Radiative Transfer
Volume107
Issue number2
DOIs
StatePublished - Sep 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Radiation
  • Atomic and Molecular Physics, and Optics
  • Spectroscopy

Keywords

  • Aerosol
  • Flow-tube
  • Infrared
  • Inversion
  • Size distribution

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