GC: n

S: Metoffice – http://www.metoffice.gov.uk/learning/frost/types-of-frost (last access: 15 July 2015); Weatherabout – http://weather.about.com/od/h/g/Hoar_frost.htm (last access: 15 July 2015); RMetS – http://onlinelibrary.wiley.com/doi/10.1002/wea.6080570409/pdf (last access: 15 July 2015).

N: 1. hoarfrost (n): c. 1300, hore-forst; see hoar + frost.

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

3. Hoarfrost, deposit of ice crystals on objects exposed to the free air, such as grass blades, tree branches, or leaves. It is formed by direct condensation of water vapour to ice at temperatures below freezing and occurs when air is brought to its frost point by cooling. Hoarfrost is formed by a process analogous to that by which dew is formed on similar objects, except that, in the case of dew, the saturation point of the air mass is above freezing. The occurrence of temperatures below 0° C (32° F) is not enough to guarantee the formation of hoarfrost.

4. Hoarfrost (is) due to nocturnal radiation. Hoarfrost forms during still, clear nights, is small in amount, needlelike in texture, the “needles” approximately perpendicular to the objects on which they occur, and most abundant along the edges.

5. hoarfrost: sometimes confused with “rime.”

S: 1. Etymonline – http://www.etymonline.com/index.php?term=hoarfrost (last access: 15 July 2015). 2. METEOTERM/International Meteorological Vocabulary, WMO – No. 182 (last access: 15 July 2015). 3. EncBrit – http://global.britannica.com/science/hoarfrost (last access: 15 July 2015). 4 & 5. TERMIUM PLUS (last access: 15 July 2015).

GV: 1. hoarfrost. 2. hoar-frost.

S: 1. TERMIUM PLUS (last access: 15 July 2015); EncBrit – http://global.britannica.com/science/hoarfrost (last access: 15 July 2015); MW – http://www.merriam-webster.com/dictionary/hoarfrost (last access: 15 July 2015). 2. TERMIUM PLUS (last access: 15 July 2015).

SYN: white frost

S: TERMIUM PLUS (last access: 15 July 2015)

CR: freezing fog, frost, glaze, hail, hailstone, rime, sleet, small hail.