John Dann wrote:

On Fri, 25 Sep 2009 08:47:53 +0100, "Will Hand"
wrote:
Put simply - chaos in action!

If I might be permitted a small hobby-horse aside here, I do wish this
word chaos had never become associated with atmospheric modelling. To
my way of thinking, this behaviour is not chaotic at all, it's
sensitive, or super/hyper-sensitive if you will (to the starting
conditions). Chaotic - to me - implies irrational or unknowable, which
is not what's happening here. Once you can define the starting
conditions with sufficient accuracy then the models can indeed run
with a rational outcome and so aren't chaotic.

JGD


I think the word chaos is used because so many of the important processes
taking place in the atmosphere are at scales that are orders of magnitude
smaller than can be resolved by the numerical models, at least the global and
regional models. If it can't be adequately modelled then it does appear chaotic

Norman