Re: [ferret_users] Ensemble realization analysis

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi -
I would agree; though the variables in the datsets are of type FLOAT, so 
Ferret's use of single precision for variables isn't causing a loss of 
accuracy in this case.

Ansley

On 4/26/2011 9:41 AM, Martin Schmidt wrote:
> Hi Patrick,
>
> I can reproduce your finding. I GUESS, the i/j-average of the 
> difference between both
> the experiments is pretty small, even if there are significant 
> differences in some areas. The average runs over 10^4
> points. The quantities are of the order 200, the difference is less 
> than +/-10.
>
> Hence it may be that you see simply the limited accuracy of ferret.
>
> I do not know nothing about the experiments, but may it be that some 
> procedure has been applied to
> keep the average values fixed?
>
> Greetings,
> Martin
>
>
>
>
> Brockmann Patrick wrote:
> > Hi all,
> >
> > Sorry for the uncompleted previous message.
> >
> > When you analyze ensemble realizations
> > (read 
> > http://cmip-pcmdi.llnl.gov/cmip5/docs/cmip5_data_reference_syntax.pdf
> > Ensemble menber paragraph), you would like to work with
> > a variable over its realizations seen as a nth dimension and then 
> > apply on it power of ferret transformations.
> >
> > Unfortunatelly, there are only 4 dimensions in ferret.
> > But sometimes, you also may have the chance that the variable you 
> > analyze
> > has 3 dimensions and has a XZT shape.
> >
> > I have imagined to use the ZCAT function to concat the XYT variable 
> > over the Z dimension
> > and then get a XYZT variable with the Z dimension representing a 
> > realization dimension.
> >
> > It seems to work since for one time step I can shade a difference but 
> > when I plot
> > a time evolution I get the same plot from the 2 realizations. That is 
> > not correct.
> >
> > Try the attached script if interested.
> >
> > Any share of experience on this topic is welcome. The challenge of 
> > course is not
> > to physically save files.
> >
> > Patrick