Characterizing ice particles using two-dimensional reflections of a lidar beam

We report a phenomenon manifesting itself as brief flashes of light on the snow surface near a lidar beam. The flashes are imaged and interpreted as specular reflection patterns from individual ice particles. Such patterns have two-dimensional structure, and are similar to those previously observed in forward scattering. Patterns are easiest to capture from particles with well-defined horizontal facets, such as near-horizontally aligned plates. The patterns and their position can be used to determine properties such as ice particle shape, size, roughness, alignment and altitude. Data obtained at Summit in Greenland shows the presence of regular hexagonal and scalene plates, columns and rounded plates of various sizes, among others.