An ice crystal exhibiting an elaborately branched (dendritic) structure of hexagonal symmetry, with its much larger dimension lying perpendicular to the principal (c axis) of the crystal. (Or plane de
ndrite; sometimes called stellar crystal.) Such crystals usually form by vapor deposition at atmospheric temperatures between about -14 and -18C. In sufficient concentration they readily aggregate to snowflakes by interlocking of their branches.
The bottom layer of the troposphere that is in contact with the surface of the earth. It is often turbulent and is capped by a statically stable layer of air or temperature inversion.