On Tue, 10 Aug 2010 14:14:30 +0100
Martin Brown wrote:
On 10/08/2010 10:39, d wrote:
On 10 Aug 2010 08:28:13 GMT
wrote:
While, at the same time, much of the Pacific Ocean has below average SSTs.
Such
large scale SST anomalies must have an influence on broadscale weather
patterns
but what the result of that will be I haven't a clue:-)

I've always found it curious that on the one hand weather and climate
scientists are quite happy to quote the famous chaos theory butterfly effect
whereby a little insect could in theory cause a hurricane the other side of
the planet,

The problem is that chaotic systems are *extremely* sensitive to initial
conditions and so even the tiniest difference can grow exponentially
with time. It makes weather prediction pretty difficult.

If the tiniest differences can grow exponentially then it follows that
huge differences can grow even faster still.

They can make rough predictions about vapour pressure and available
energy above warmer surface water, but it has to be a huge perturbation
before there is any real certainty in the predictions that can be made.
Otherwise it could be swamped by one of those awkward butterflies.

I wasn't really talking about prediction , I was talking about whether
it would effect weather patterns elsewhere from a basic physics point of view.
You can't on one hand make an assertion that some small event has a large
outcome elsewhere yet assert that a large event has a small or zero outcome
elsewhere when talking about the same physical system.

B2003

On Tuesday 10 August 2010 10:39, d scribbled:

On 10 Aug 2010 08:28:13 GMT
"Norman" wrote:
While, at the same time, much of the Pacific Ocean has below average SSTs.
Such large scale SST anomalies must have an influence on broadscale
weather patterns but what the result of that will be I haven't a clue:-)

I've always found it curious that on the one hand weather and climate
scientists are quite happy to quote the famous chaos theory butterfly
effect whereby a little insect could in theory cause a hurricane the other
side of the planet, yet when you press them on whether abnormal
heating/cooling in a large body of water a few thousand miles across could
affect climate elsewhere they start umming and ahhing.


I don't know which scientists were umming and ahhing. Namias, Lamb,
Ratcliffe, et al didn't umm and ahh forty-odd years ago.

The problem that I have with the warm North Atlantic as it is now is that it
is all warm and so there is no real pattern to it. It could be classified as
a warm-pool type but when a warm pool is surrounded by warm water instead of
cold the consequences are unlikely to be typical of the standard pattern.

--
Graham Davis, Bracknell, Berks. E-mail: "newsman", not "newsboy".
"It pays to keep an open mind, but not so open your brains fall out." - Carl
Sagan

On Aug 10, 1:45*pm, wrote:
On Tue, 10 Aug 2010 14:14:30 +0100



Martin Brown wrote:
On 10/08/2010 10:39, wrote:
On 10 Aug 2010 08:28:13 GMT
*wrote:
While, at the same time, much of the Pacific Ocean has below average SSTs.
Such
large scale SST anomalies must have an influence on broadscale weather
patterns
but what the result of that will be I haven't a clue:-)

I've always found it curious that on the one hand weather and climate
scientists are quite happy to quote the famous chaos theory butterfly effect
whereby a little insect could in theory cause a hurricane the other side of
the planet,

The problem is that chaotic systems are *extremely* sensitive to initial
conditions and so even the tiniest difference can grow exponentially
with time. It makes weather prediction pretty difficult.

If the tiniest differences can grow exponentially then it follows that
huge differences can grow even faster still.

They can make rough predictions about vapour pressure and available
energy above warmer surface water, but it has to be a huge perturbation
before there is any real certainty in the predictions that can be made.
Otherwise it could be swamped by one of those awkward butterflies.

I wasn't really talking about prediction , I was talking about whether
it would effect weather patterns elsewhere from a basic physics point of view.
You can't on one hand make an assertion that some small event has a large
outcome elsewhere yet assert that a large event has a small or zero outcome
elsewhere when talking about the same physical system.

B2003

The butterfly effect comes from the Name of a lecture "Does the flap
of a butterfly’s wings in Brazil set off a tornado in Texas?" given by
Edward Lorenz, a meteorologist and a pioneer in chaos Theory. The
flap of wings does not change the world's climate. It only creates a
tornado. Moreover, it is a question not an assertion and wasn't
intended to be taken literally.

A rise in Atlantic SSTs will produce more water vapour and rain, but
where and when that rains falls is in the lap of the gods, or to be
more scientific will be determined by the machinations of Chaos
Theory.

Cheers, Alastair.

On 10/08/2010 14:45, d wrote:
On Tue, 10 Aug 2010 14:14:30 +0100
Martin wrote:
On 10/08/2010 10:39, d wrote:
On 10 Aug 2010 08:28:13 GMT
wrote:
While, at the same time, much of the Pacific Ocean has below average SSTs.
Such
large scale SST anomalies must have an influence on broadscale weather
patterns
but what the result of that will be I haven't a clue:-)

I've always found it curious that on the one hand weather and climate
scientists are quite happy to quote the famous chaos theory butterfly effect
whereby a little insect could in theory cause a hurricane the other side of
the planet,

The problem is that chaotic systems are *extremely* sensitive to initial
conditions and so even the tiniest difference can grow exponentially
with time. It makes weather prediction pretty difficult.

If the tiniest differences can grow exponentially then it follows that
huge differences can grow even faster still.

No it doesn't. In a non-linear chaotic system the tiniest change can
have enormous consequences some time later, and a large change can damp
out. Response is non-linear so a big perturbation doesn't necessarily
grow at all and may even decay. There are many trajectories for the
system that diverge rapidly away from every possible starting point. The
key point is that in a chaotic system nearby points head off on
completely different paths.

They can make rough predictions about vapour pressure and available
energy above warmer surface water, but it has to be a huge perturbation
before there is any real certainty in the predictions that can be made.
Otherwise it could be swamped by one of those awkward butterflies.

I wasn't really talking about prediction , I was talking about whether
it would effect weather patterns elsewhere from a basic physics point of view.

From a basic physics point of view you can make certain predictions
about the amount of water the air travelling over an ocean will pick up
from a given sea surface temperature and wind velocity.

You can't on one hand make an assertion that some small event has a large
outcome elsewhere yet assert that a large event has a small or zero outcome
elsewhere when talking about the same physical system.

But that is the point of chaotic systems is that a tiny change too small
to measure can make an enormous difference to the outcome. A reasonable
explanation of chaos theory without too much maths is on Wiki
http://en.wikipedia.org/wiki/Chaos_theory#Sensitivity_to_initial_conditions

Note in particular the root of the Lorentz paper on predictability and
his butterfly wings phrase which seems to have developed a life of it's
own. And slightly harder with a 1-D toy system x[n+1] = r.x[n](1-x[n])

http://en.wikipedia.org/wiki/Bifurcation_diagram

Regards,
Martin Brown

On Tue, 10 Aug 2010 at 08:56:35, Col wrote
in uk.sci.weather :

Paul Hyett wrote:
On Mon, 9 Aug 2010 at 11:08:46, Graham Easterling
wrote in uk.sci.weather :

I don't recall seeing so much of the north Atlantic with above normal
SSTs.
http://www.ncdc.noaa.gov/oa/climate/...ni-weekly.html

You'd think that'd allow the air to hold more moisture - but very
little of it seems to be finding its way here...

You must have got at least a couple of mm earlier on this
morning, surely?

Just about, but the main body of rain managed to miss here *again*...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)