PHASE FUNCTION CALCULATIONS OF SINGLE HEXAGONAL BULLET-LIKE ICE CRYSTALS

The phase functions of single hexagonal bullet-like ice crystals rando mly oriented in space are calculated using the ray tracing method. Com pared with column-like ice crystals, the reflection and refraction (RE F) model results for bullets show an additional peak in scattered inte nsity between the angles of 0 degrees and the 22 degrees halo, due to the effect of the pyramid; the position of this peak is determined by the bullet angle (delta) between the side face and the vertical axis o f the pyramid. The 22 degrees halo and the additional peak are explain ed geometrically, and the simple geometrical calculation predicts addi tional peak positions which are in good agreement with the numerical m odel results. The results also show that, for delta > 55 degrees, the bigger the bullet angle the larger the additional peak, and for some b ullet angles the additional peak is comparable with the 22 degrees hal o. The additional peak and halo positions will shift for different m(r ) (the real part of the complex refractive index). The phase function for bullet-like ice crystals is different from that of column-like ice crystals, particularly in the angle range between 0 degrees and 22 de grees.