Hoar frost

from Wikipedia, the free encyclopedia

Hoar frost is a solid precipitate that is formed from supercooled water droplets from light fog or directly from the water vapor contained in the air through resublimation . This requires a very high relative humidity of over 90% and an air temperature of below −8 ° C. The resulting heat is transferred to the surrounding air by convection , so wind increases the formation of hoarfrost. However, the wind must not be too strong either, otherwise it would destroy the sensitive structures.

Especially against the direction of the wind, needle-shaped ice crystals in the form of six-pointed dendrites are created , which can reach a considerable size and bizarre shapes and usually only grow slowly. Hoar frost grows against the wind, as the air arriving on the windward side has a higher degree of humidity than on the leeward side .

Rime arises comparatively rarely and is often confused with frost or rough ice , for which it represents a kind of intermediate stage. Ice flowers are a special form of hoarfrost .

Damage to trees caused by hoar frost is referred to as fragrance break in forestry .

photos

  • Hoar frost in December

  • Hoarfrost crystals

  • Hoar frost formation under the influence of wind

  • Detail of a branch

  • Hoar frost on the banks of the Main

  • Hoar frost on Ilex

  • Hoar frost in Marienheide

  • Hoar frost on blades of grass

  • Hoar frost on a wooden fence

  • Forest in hoar frost

  • Rose with hoarfrost

  • Rose with hoarfrost

  • Hoar frost on the edge of the forest

  • Hoar frost on a branch

  • Hoar frost rain - thawing hoarfrost rains from trees

  • Hoar frost on a soap bubble

literature

  • Tönjes de Vries, Antje Paschmann: Resublimation - the fascinating formation of hoarfrost. In: CHEMKON. 11 (4) 2004, ISSN  0944-5846 , pp. 185-190.
  • Dew, frost and hoar frost. In: Hannelore Dittmar-Ilgen: How the salt gets into the sea water and why there are no more ice flowers: even more physics for the curious. Hirzel-Verlag, Stuttgart 2005, ISBN 3-7776-1315-0 , p. 72.

Web links

Commons : Hoarfrost  album with pictures, videos and audio files

supporting documents

  1. ↑ Joseph Krauß: Basic features of maritime meteorology and oceanography, reprint of the original from 1917 . Salzwasser Verlag, Paderborn 2011, ISBN 978-3-86444-130-1 ( limited preview in the Google book search).