Formation Mechanisms of Twelve-branched Snow Crystals

[摘要] During the observation period (one month from 23 December 1987) of low-temperature types of snow crystals at Kautokeino, Norway, 68 twelve-branched snow crystals were collected and photomicrographed. Side views of twelve-branched snow crystals (from the direction perpendicular to the c-axes) were analyzed. The angles φ between branches were measured from the photomicrographs.Most of the twelve-branched snow crystals were composed of two double plates (or six-branched snow crystals). In the histogram of the angle φ, no evidence of the formation of twelve-branched snow crystals by the so-called rotation twinning mechanisms was found. The formation mechanisms of twelve-branched snow crystals are explained by snowflake formations for the most part, although a slight possibility of a formation by another mechanism exists.

[学科分类] 大气科学