Øyvind Seland wrote:

In article , Niels
Vestergaard Jensen writes:
Suppose an air parcel of about 10 km size suddenly (magically?!) changed
its density, humidity and temperature, while staying within normal
atmospheric values. (Energy and mass conservation etc. don't apply at the
instant of transformation.) How long would it take till global weather
was completely scrambled from "what would have been" so that it would
have no similarity to the unperturbed system? (Apart from seasonal
variations, large scale climate etc.)

The question can of course not be answered experimentally, but are there
any results from computer simulations pointing towards a timescale? (Just
order of magnitude).


First of all. Such an event would not scramble the global weather,
it would hardly perturb it at all, although you can always
point to the butterfly effect and develop a couple of storms.

Are you talking about large-scale climate here? That's not what I had in
mind. What I'm interested in knowing is how long it'd take till the
pertubation had grown enough to change the timing and strength of
particular fronts appreciably. If the atmosphere really is a chaotic system
(isn't it?) won't a small perturbation grow?

An example: Detonations of atomic bombs in the atmosphere certainly
scrambled the temperature, density and humidity in a more than 10 km
wide sphere, yet there are no indications that it affected
the global weather very much.

Good comparison. No, I don't expect nuke-size events to start global
warming. (If we ever drop that many of them we'll have bigger problems :-/)
I'm looking for them to contribute the initial pertubation. Unfortunately
we can't compare a nuked atmosphere to an unnuked experimentally, so it's
got to be done by computer which is poor, but all we've got. Any ideas
where to find references?

Timescales:
Within the local area a few hundred km: A few hours
Europe: A couple of days.
Northern or Southern temperate regions: A week
Tropic areas: A month.
The hemisphe 2-3 months
Globe: 1-2 years.

That's about the timescales I presumed for the pertubation to grow enough to
scramble fronts. Is that how I'm supposed to read the table?

Thanks for your interest,

Niels