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, and any other solid object.

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 surface, hoar frost is formed by direct deposition from water vapour to solid ice.

Scientists at meterologically-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.

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 though a cloud made of supercooled water liquid droplets.

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

Tourist Attractions

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A natural scenery in Jilin City of China, called Jilin ice-rimed trees, is one of the Four Natural Wonders in China, along with Guilin scenery, Yunnan stone forest, and Three Gorges on the Yangtze River.

During the coldest period in January or February in Jilin City, the weeping willow trees along the long bank of Songhua river get ice-rimed in the early morning, as if they're wearing beautiful snow clothes. It is a natural result when water vapor rises up from the warm Songhua River to meet the cold −20 °C night air, causing the crystalisation of water vapour on the willows' branches. Unfortunately, it has been more difficult to see this marvellous spectacle in recent years.

water ice

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