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White frost

White frost is a solid deposition of ice which forms directly from water vapour contained in air. It forms when there is a relative humidity above 90% and a temperature below -8 °C (18 °F). The developing heat is then transferred to air by convection. White frost grows against the wind direction, since windward arriving air has a higher humidity than leeward air, but the wind must not be very strong in order not to damage the delicately built icy structures. These structures resemble a heavy coating of hoar frost with big and interlocking crystals, usually needle-shaped. This phenomenon occurs quite rarely: it is considered a kind of intermediate stage between hoar frost and rime and it is often confounded with these.

See also

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "White_frost". A list of authors is available in Wikipedia.
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