Nacreous Clouds or Polar Stratospheric
These clouds fly
high in the stratosphere at about 15,000
to 25,000m (50,000 to 80,000 feet) and only
form when temperatures fall below about
-78°C (-108°F), to complete the extreme
conditions, the winds are often very high
as well having been recorded at 230kmh (144mph).
Clouds in the stratosphere are very
rare as it is so dry.
At ground level
however things are less dramatic but far
prettier. The colours are an optical effect
and so change with the position of the cloud
as they move by and with the position of
Picture taken 23/08/2009
12.25 - McMurdo Antarctica.