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Old April 21st 20, 10:42 AM posted to uk.sci.weather
Bernard Burton Bernard Burton is offline
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First recorded activity by Weather-Banter: Jul 2003
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Default Cobblestone cirrus 21Apr20

Correction to image address

There is an excellent example of cobblestone cirrus over France this
morning. This cloud arises due to contamintion of the moist upper layers,
probably by Saharan dust in this case. The dust particles provide a vast
store of condensation nuclei, allowing thick ice cloud to form where it
would otherwise be absent or tenuous. This in turn alters the radiation
balance in the upper troposphere, causing the lapse rate to steepen towards
the dry adiabatic rate, and allowing convection to become widespread in the
upper layers of the cloud, and producing the cobblestone appearance.

http://www.woksat.info/etcacd21m/ful...sg-0900-uk.JPG

http://www.woksat.info/etcacd21m/ful...sg-0600-uk.JPG



--
Bernard Burton
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