Light Scattering by Ice Crystals

The relative scattering functions between 10° and 150° scattering angle have been measured for microscopic ice crystals grown in a laboratory cold chamber. All measurements were made using unpolarized incident light at 550 nm and an unpolarized detector. Ice crystal size distribution and shape were determined at the temperature at which they were formed. Nephelometer measurements were made at temperatures of −20, −30 and −40C. The predominant crystal shapes at these temperatures were hexagonal plate, hexagonal column and irregular, respectively. No difference was observed among the relative scattering functions of the three crystal shapes except at scattering angles >130°. Comparison of the measured scattering functions with computed values for water droplets indicates greater relative scattering near 90° for ice crystals.