Asperitas Clouds Over New Zealand
Image Credit & Copyright:
Witta Priester
What kind of clouds are these?
Although their cause is presently unknown, such unusual atmospheric structures,
as menacing as they might seem, do not appear to be harbingers of
meteorological doom.
Formally recognized as a distinct
cloud type only last year,
asperitas
clouds can be stunning in appearance,
unusual in occurrence, and are relatively unstudied.
Whereas most low cloud decks are flat bottomed,
asperitas clouds appear to have significant
vertical structure underneath.
Speculation therefore holds that
asperitas clouds might be related to
lenticular clouds that form near mountains,
or mammatus clouds associated with thunderstorms,
or perhaps a foehn --
a type of dry downward wind that flows off mountains.
Clouds from
such a wind
called the
Canterbury arch
stream toward the east coast of New Zealand's
South Island.
The featured image, taken above
Hanmer Springs in
Canterbury,
New Zealand in 2005,
shows great detail partly because sunlight illuminates the undulating
clouds from the side.