A numerical model evaluating the response of a typical integrating nephelometer is described. The model incorporates the actual scattering geometry as well as the effects of a finite light source, detector size, and a nonideal Lambertian diffuser. An angular scattering weighting function is introduced to provide a tractable approach in numerical calculations and easy application. Using established size distribution ensembles associated with a few representative aerosol types, we compare the calculated response of a real nephelometer with that of an ideal, or perfect, nephelometer. The results indicate that, frequently, the nephelometer-produced aerosol-scattering coefficient is of the order of 10–20% too small; but for some naturally occurring aerosols, the difference may be as large as 40–50%. For a multiple-wavelength nephelometer, the response model can be employed to estimate the expected error in the aerosol-scattering coefficients directly from the measurements themselves.
© 1997 Optical Society of America
Original Manuscript: May 28, 1996
Revised Manuscript: September 30, 1996
Published: April 20, 1997
James M. Rosen, Ronald G. Pinnick, and Dennis M. Garvey, "Nephelometer optical response model for the interpretation of atmospheric aerosol measurements," Appl. Opt. 36, 2642-2649 (1997)