Expect frost in northern Minnesota this morning

Word of the Day – Wednesday, October 19th



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RIME (rime)

A coating of ice

Common clues: Hoarfrost; Frost's frost; Winter coat; Cover with hoarfrost; Icy cover; White coat; Frosty film; Granular coating; Cold coat; December dew

Crossword puzzle frequency: 3 times a year

Frequency in English language: 35514 / 86800

Rime ice is a white ice that forms when the water droplets in fog freeze to the outer surfaces of objects. It is often seen on trees atop mountains and ridges in winter, when low-hanging clouds cause freezing fog. This fog freezes to the windward (wind-facing) side of tree branches, buildings, or any other solid objects.

Rime ice on a tree in Black Forest, Germany

Rime ice is similar in appearance to hoar frost; but whereas rime ice is formed by vapour first condensing to liquid droplets (of fog, mist or cloud) and then attaching to a surface, hoar frost is formed by direct deposition from water vapour to solid ice.

Scientists at meteorologically-extreme places such as Mount Washington in New Hampshire often have to break huge chunks of rime ice off weather equipment, in order to keep anemometers and other measuring instruments operating. This type of ice can spoil lift and have catastrophic effects on airborne aircraft.

Sometimes the rime ice takes on a feathery look, and looks very much like "snow feathers".

Ice storms may consist of either glaze ice or rime ice. Meteorologists classify transparent and homogeneous ice forming on vertical and horizontal surfaces as glaze. Glaze ice resembles ice-cube ice in appearance. Its amorphous, dense structure helps it cling tenaciously to any surface on which it forms. In contrast, if the ice is milky and crystalline, like sugar, it is termed rime. Rime ice is less dense than glaze ice and clings less tenaciously, therefore damage due to rime is generally minor compared to glaze ice.

Rime ice and glaze ice are also the two types of ice that can form on the surfaces of an aircraft, if it flies through a cloud made of supercooled water liquid droplets.

Rime ice is also formed inside of freezers, and on humid days, objects taken out of freezers will form hoar frost on their surfaces.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Rime (frost)"