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 occur
s under frosty weather conditions (under very low air temperatures).
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'.
An intense flash of light that happens a few seconds before and after totality during a solar eclipse. The effect is caused by the last rays of sunlight before totality (or the first rays of sunlight
after totality) shining through valleys on the edge of the Moon.