© Claudia Hinz
Mount Fichtelberg, Germany
Latitude: 50° 25' 46'' N
Longitude: 12° 57' 15'' E
01 February 2014 0753 (Local Time)
Image P/S code: P.11.4.5.2
Image I.D.: 4710
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Freezing fog occurs at a temperature below 0 °C when supercooled fog droplets freeze on impact with the ground or other objects to deposit rime.
This picture was taken at the weather station on Tai Mo Shan, the highest peak in Hong Kong (China), during a severe winter monsoon and shows the summit shrouded in hill fog as a result of low cloud covering the high ground. With the air temperature having cooled to around -2 °C, the cloud droplets were in a supercooled state and, driven by a strong wind, they froze on impact with vegetation on the ground and with other objects to produce deposits of rime at 2 and 3.
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This picture was taken at the weather station on Tai Mo Shan, the highest peak in Hong Kong (China), during a severe winter monsoon and shows a deposit of rime on vegetation.
Low cloud had previously covered the high ground with freezing hill fog. The temperature on Tai Mo Shan had fallen from 3 °C at midnight to –2 °C during the day. The cloud droplets became supercooled and, driven by a strong wind, they froze on impact with vegetation and with other objects to form the deposits of rime.
Hard rime is formed by the rapid freezing of supercooled water so that the droplets freeze more or less individually, leaving air gaps. It forms mainly with temperatures between –2 °C and –10 °C and mainly on objects exposed to at least a moderate wind. In the windward direction, the deposit may form a thick layer. Hard rime is rather adhesive but can be scratched off the object.
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The photo shows a thick deposit of hard rime on the summit of Mt. Washington (altitude 1 917 m) in New Hampshire, USA. The deposit has built up to a thickness of about 50 to 65 cm on the windward side of the structure. The rime formed through supercooled water droplets freezing on impact; this produced ice composed of grains with some trapped air gaps, rendering the deposit white.
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In this photo, the windward sides of structures on the summit of Mt. Washington (altitude 1 917 m) in New Hampshire, USA are covered in thick deposits of hard rime (seen at 1 and 2). The ice has formed through supercooled cloud droplets rapidly freezing on impact with the structures, such that the drops have frozen more or less individually to grains of ice, leaving air gaps and rendering this type of ice white. In places the rime deposits are about 50 to 65 cm in thickness, extending outwards from the structures on the windward side (seen at 3 and 4); this indicates that the wind was blowing from right to left.
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This photograph shows deposits of hard rime on a 10 m anemometer tower at Great Dun Fell, 847 m above mean sea-level. The deposits on the south-western (windward) sides of the vertical structure have built up to an extrusion of about 30 cm. Most of the deposits, although rather adhesive, could be removed by chipping. The air temperature was -3°C.
A very weak cold front had cleared the station, leaving clear skies in a north-westerly airstream.
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