[Go-essp-tech] RIP clarification

[charlotte.pascoe at stfc.ac.uk]

Hi Karl and Bryan,
It is important to know how the r<N>i<M>p<L>  indices are to be implemented in CMIP5 so that we can be sure that information about them is captured correctly by the questionnaire.   Here is my understanding, please correct me if I'm wrong!

The scope of the p<L> and i<M> indices are model wide - these indices must mean the same thing across all simulations for a particular model.
The scope of the r<N> indices are experiment wide -  the r index is not required to mean the same thing across all simulations for a particular model, so the r indices can be reused by different experiments.

Here is an example to show what this would mean in practice.
If the meaning  of the r<N> indices were confined to  an experiment
then if you had used r1, r2, and r3 to label the members of an amip ensemble:
tas_day_HADCM3_amip_r1i1p1_197901-200901.nc
tas_day_HADCM3_amip_r2i1p1_197901-200901.nc
tas_day_HADCM3_amip_r3i1p1_197901-200901.nc
you could use r1,r2 and r3 again to label the members of a different experiment, say decadal2000:
tas_day_HADCM3_decadal2000_r1i2p1_200001-201001.nc
tas_day_HADCM3_decadal2000_r2i2p1_200001-201001.nc
tas_day_HADCM3_decadal2000_r3i2p1_200001-201001.nc
rather than having to begin labelling from a new r index, say r4:
tas_day_HADCM3_decadal2000_r4i2p1_200001-201001.nc

Where
p<L> - identify perturbations in physics (from the same base model)
i<M> - identify perturbations in initialisation method
r<N> - identify ensemble members which differ in other characteristics.

Please shout if my interpretation is wrong!

Kind regards,

Charlotte
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Dr Charlotte Pascoe
NCAS British Atmospheric Data Centre
STFC Rutherford Appleton Laboratory
Phone +44 1235 445869; Fax ...5848
e-mail charlotte.pascoe at stfc.ac.uk<mailto:c.l.pascoe at rl.ac.uk>
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