hoarfrost

Deposit of ice crystals, generally assuming the form of scales, needles, feathers or fans and which forms on objects whose surface is sufficiently cooled, generally by nocturnal radiation, to bring about the sublimation of the water vapour contained in the ambient air.

 

Source:

UNESCO/WMO International Glossary of Hydrology (2nd revised ed., 1992)

Posted on February 19, 2014 .