A theoretical framework has been developed for the computation of polarized radiative transfer involving ice crystal clouds to interpret the polarization pattern observed from space. Based on the limited available observations in near infrared window wavelengths, we demonstrate that the reflected linear or full polarization from sunlight can be employed to discriminate between spherical water droplets (water clouds) and nonspherical ice crystals (ice clouds) in the direction of rainbow angles, about 140° from the sun. In the case of ice clouds, we show that information regarding the ice crystal shape and orientation can be inferred from reflected polarization patterns based on a comprehensive theoretical interpretation.