APPLICABILITY OF REGULAR PARTICLE SHAPES IN LIGHT-SCATTERING CALCULATIONS FOR ATMOSPHERIC ICE PARTICLES

We ascertain the usefulness of simple ice particle geometries for mode ling the intensity distribution of light scattering by atmospheric ice particles. To this end, similarities and differences in light scatter ing by axis-equivalent, regular and distorted hexagonal cylindric, ell ipsoidal, and circular cylindric ice particles are reported. All the r esults pertain to particles with sizes much larger than a wavelength a nd are based on a geometrical optics approximation. At a nonabsorbing wavelength of 0.55 mu m, ellipsoids (circular cylinders) have a much ( slightly) larger asymmetry parameter g than regular hexagonal cylinder s. However, our computations show that only random distortion of the c rystal shape leads to a closer agreement with g values as small as 0.7 as derived from some remote-sensing data analysis. This may suggest t hat scattering by regular particle shapes is not necessarily represent ative of real atmospheric ice crystals at nonabsorbing wavelengths. On the other hand, if real ice particles happen to be hexagonal, they ma y be approximated by circular cylinders at absorbing wavelengths. (C) 1996 Optical Society of America