Assessment of aerosol extinction to backscatter ratio measurements made at 694.3 nm in tucson, arizona

J. A. Reagan, M. V. Apte, A. Ben-David, B. M. Herman

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18 Scopus citations


The aerosol extinction-to-backscatter ratio, Sa, is a key parameter in interpreting scattering measurements made with lidar. Whereas solution techniques for solving the lidar equation generally assume some constraining relation for Sa (i.e., such as Sa is constant with range), few measurements of Sa have been made to establish the statistics and properties of this parameter. Measurements of Sa, for a wavelength 694.3 mm, obtained from slant-path lidar observations made in Tucson, Arizona, from May 1979 to June 1982 yielded values of Sa between ∼ 5 and 100 with the majority concentrated between ∼ 10 and 45. The weighted mean (weighted by inverse variances of Sa) of all Sa values and the arithmetic mean of the main grouping of Sa values (10 < Sa < 45) both equaled approximately 25. Interpretation of the Sa measurements in terms of various size distributions and refractive index values representative of atmospheric aerosols indicated the following: 1) Sa values in the 10 to 20 range are indicative of size distributions with significant coarse mode particle concentrations, larger real refractive index values (greater than ∼ 1.50), and zero or nearly zero imaginary refractive index values; 2) Sa values in the 20 to 45 range appear to correspond to size distributions with less significant but still noticeable coarse mode particle concentrations, somewhat lower real refractive index values, and still fairly low imaginary refractive index values (less than ∼ 0.005); and 3) Sa values greater than about 45 indicate even lower real refractive index values (values of ∼ 1.45 andlower) and even larger imaginary refractive index values (values in the 0.005 to 0.01 range).

Original languageEnglish (US)
Pages (from-to)215-226
Number of pages12
JournalAerosol Science and Technology
Issue number3
StatePublished - 1988

ASJC Scopus subject areas

  • Environmental Chemistry
  • Materials Science(all)
  • Pollution


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