Raureif

Raureif is a German word that translates to "hoarfrost" in English. Hoarfrost is a deposit of ice crystals that forms on objects when their surfaces are at or below freezing point and the surrounding air contains a high amount of moisture. This moisture then undergoes deposition, transforming directly from water vapor into ice crystals without passing through the liquid phase.

The formation of raureif typically occurs during cold, clear nights when radiative cooling causes surfaces to become colder than the dew point of the air. This process is favored in humid conditions and when there is a slight breeze, which helps to bring moist air into contact with the cold surfaces. The resulting ice crystals can take on various intricate forms, resembling delicate feathery structures, needles, or fans, depending on the atmospheric conditions and the properties of the surface they form on.

Raureif is a common sight in temperate regions during winter and is distinct from rime, which forms when supercooled water droplets freeze onto surfaces. While both are forms of ice accretion, raureif forms from water vapor directly, resulting in crystalline structures. It can create a beautiful, albeit temporary, white coating on vegetation, fences, and other outdoor objects, transforming the landscape into a delicate, icy spectacle.