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Iridescence
in Florida pileus clouds. Imaged in July '03 by David
LaPuma (site)
using a Leica Televid 77 APO spotting scope.
The inset shows the area of the main image atop a towering
cumulus cloud. Pileus or "mushroom cap" clouds are
formed above cumulus. During the day warm moist air in cumulus
rises and the clouds tower upwards. Sometimes their vertical growth
pushes up a layer of moist air above them. The air layer expands
as it is forced up into lower pressure surroundings and adiabatically
cools. The water vapour in it suddenly condenses forming a misty
veil-like layer of droplets above the cumulus - pileus cloud. Any
cloud formed suddenly has all its droplets of similar size - ideal
for iridescence or a corona.
Image ©2003 David LaPuma |
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