frank.koormann at intevation.de
Thu Apr 17 07:05:35 CEST 2008
Am Mittwoch, 16. April 2008 16:51:51 schrieb vincent.gregorio at epfl.ch:
> I have questions about the statistical calculation on great-er. In the
> pre-processing step, i don't understand if is it the mean flow or the
> median flow to enter in the .rna file( i have a lognormal distibution of
> flow values)?
The flow statistics are assumed to be lognormal distributed. The commonly
available descriptive parameters are mean flow and percentiles, hence
GREAT-ER requires the Q_mean and the Q_5.
> What is the q_stdev calculate( does great-er transform the
> lognormal distribution in a normal distribution? )
The upload transforms the descriptive parameters of the lognormal
distribution, since internally it is easier to derive MC-Shots from a
(Mean, StdDev) distribution description.
> and how does great-er
> make monte-carlo simulation (results of concentration are given in
> percentile, but is it for a lognormal or normal distribution?)
GREAT-ER generates series of random numbers depending on the given standard
distribution of a parameter (constant, uniform, normal or lognormal) which
are then transformed into the actual distribution of the parameter.
The results are considered as lognormal distributed (GREAT-ER desktop Manual,
section "Calculate River Csim X")
> is it possible to have more information about that?
Hope this helps.
Frank Koormann | ++49-541-335 08 30 | http://www.intevation.de/
Intevation GmbH, Georgstr. 4, 49074 Osnabrück, DE | AG Osnabrück, HR B 18998
Geschäftsführer: Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
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