  We present an experimental and theoretical study of the angle- and
polarization-dependent light extinction in random arrays of polydisperse
semiconductor nanowires epitaxially grown on substrates. The specular
reflectance is described by averaging the scattering properties of individual
nanowires obtained from Lorenz-Mie theory over the diameter distribution. The
complex effective refractive index describing the propagation and attenuation
of the coherent beam scattered in forward direction is determined in the
independent scattering approximation and used to calculate the angle- and
polarization-dependent reflectance. Our measurements demonstrate the highly
anisotropic scattering in ensembles of aligned nanowires.
