To study early processes of snowflake growth, characteristics of aggregation (collision adhesion process) of needle snow crystal were investigated in examining photomicrographs of snowflakes composed of two crystals. Adhesion type was classified into crossed adhesion and point adhesion: when the sizes of two crystals were similar, which means nearly equal fall velocity, crossed adhesion type increased in number; point adhesion type dominated when there was a large diffreance in size, thus fall velocity.
In the case of crossed adhesion type the angle between the c-axis of two crystals was about 90°, while the point adhesion type indicated no distinct feature in the angle.
It is suggested that the crossed adhesion snowflakes were formed mainly by the interaction of flow fields around two crystals and the point adhesion snowflakes were formed by the inertial collision of smaller crystals to larger ones.
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