Definition: Clear ice: Smooth compact rime, usually transparent, without a clearly defined shape or form, with a ragged surface, and morphologically resembling glaze.
At and near the ground, clear ice is deposited mainly on the surface of objects exposed to the wind. It is observed particularly in mountainous regions. In the free atmosphere, it occurs chiefly on the parts of aircraft exposed to the relative wind.
Clear ice is formed by the slow freezing of supercooled water and so penetrates the air gaps between the grains of ice before freezing. Clear ice is very adhesive and can only be removed from the objects by breaking or melting. Clear ice is formed in almost all cases with ambient air temperatures between 0 °C and –3 °C.