## Abstract

A sensitivity study with an inversion scheme that permits one to
retrieve physical parameters of tropospheric particle size
distributions, e.g., effective radius, volume, surface-area, and number
concentrations, as well as the mean complex refractive index from
backscatter and extinction coefficients at multiple wavelengths is
presented. The optical data for the analysis are derived from
Mie-scattering calculations for monomodal and bimodal
logarithmic-normal distributions in the particle size range between
0.01 and 10 µm. The complex refractive index is taken
between 1.33 and 1.8 in the real part and between 0 and 0.1 in the
imaginary part. The choice of these parameters takes account of
properties of optically active atmospheric particles. The
wavelengths were chosen at 355, 400, 532, 710, 800, and 1064 nm for the
backscatter and at 355 and 532 nm for the extinction data, which are
the available wavelengths of the two lidar systems at the Institute for
Tropospheric Research. Cases of erroneous optical data of the order
of as much as 20%, an unknown refractive index, which may also be
wavelength and size dependent, as well as the *a priori*
unknown modality of the particle size distribution were
considered. It is shown that both extinction channels are necessary
for determining the above-mentioned parameters within reasonable
limits, i.e., effective radius, surface-area, and volume concentrations
to an accuracy of ±50%, the real part of the complex refractive index
to ±0.1, and the imaginary part to ±50%. The number
concentration may have errors larger than 50%. The overall
performance of the inversion scheme permits the evaluation of
experimental data on a routine basis.

© 1999 Optical Society of America

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