  In this letter, we exploit the polarization property of light to investigate
the Angstroem exponent describing the wavelength dependence of optical
backscatter between two wavelengths. Where previous interpretation of Angstroem
exponent was that of a particles size indicator, the use of light polarization
makes it possible to investigate the Angstroem exponent dependence on the
particles shape by separately retrieving the backscattering Angstroem exponent
of the spherical and nonspherical particles contained in an atmospheric
particle mixture. As an output, analytical solutions of the Maxwell equations,
Lorenz Mie theory, spheroidal model,can then be applied to investigate the
Angstroem exponent dependence on the particles size and complex refractive
index for each assigned shape. Interestingly, lidar retrieved vertical profiles
of backscattering Angstroem exponents specific to s and ns particles can be
used by the optical community to evaluate a range of involved particles sizes
and complex refractive indices for both particles shapes, spherical and
nonspherical, as we remotely demonstrate on a case study dedicated to a dust
nucleation event.
