Model for optical forward scattering by nonspherical raindrops
  We describe a numerical model for the interaction of light with large raindrops using realistic nonspherical drop shapes. We apply geometrical optics and a Monte Carlo technique to perform ray traces through the drops. We solve the problem of diffraction independently by approximating the drops with areaequivalent ellipsoids. Scattering patterns are obtained for different polarizations of the incident light. They exhibit varying degrees of asymmetry and depolarization that can be linked to the distortion and thus the size of the drops. The model is extended to give a simplified long-path integration. 
Oliver N. Ross and Stuart G. Bradley