| Term: | Diamond dust |
| Definition: |
A type of precipitation composed of slowly falling, very small, unbranched crystals of ice which often seem to float in the air; it may fall from a high cloud or from a cloudless sky, it usually occurs under frosty weather conditions (under very low air temperatures). NSIDCCryosphere
A fall of non-branched (snow crystals are branched) ice crystals in the form of needles, columns, or plates. NOAA-NWS An optically and physically thin layer of ground-level cloud composed of small ice crystals that settle slowly. Typically diamond dust forms by the mixing of relatively moist air from aloft into a low-level inversion layer in which the temperature is 40 IHPGlacierMassBalance Diamond dust forms under very low air temperatures in strong, surface-based temperature inversion layers. Either vertical mixing within or radiational longwave cooling of this layer causes the air to become supersaturated with respect to ice, so that small ice crystals form. These mostly unbranched crystals are seemingly floating in the air, slowly falling from an often apparently cloudless sky (AMS, 2000). Columns (ppco) and plates (pppl) are the dominant shapes found in diamonddust (Walden et al., 2003), but stellar dendrites (ppsd) may also be observed. Long-prism columns having a ratio of length to width 5 are defined as 'Shimizu crystals'. IACSSnow GCW |