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New Abiotic-HOWTO -> Control Runs

OCMIP Modelers,

The previously proposed Abiotic Control Run generated some controversy.
Opinions have ranged from the Control being vital to it being worthless.
In the new version of the Abiotic HOWTO (Revision 1.16), now available by
the OCMIP web page, I have changed things somewhat. Groups may make from
0 to 3 Control runs (1 each for the Historical, Future, and Pulse

The four rules below will help you determine, which if any of
the Control Runs you need to make, and if not, what you should
do to provide detailed drift information to the analysis center.
These rules are also detailed in the HOWTO (Section 5).

Under what circumstances should I make a control run?

1. If you will make the Pulse run, you MUST also make the equivalent Pulse
   Control run.
2. If you have NOT respected the Equilibrium drift criteria you MUST
   make the Historical Control and Future Control runs. 

3. If you have respected the recommended Equilibrium drift criteria,
   you may skip making the Historical Control and Future
   Control runs. However, I HIGHLY RECOMMEND that you make these
   simulations, if you can afford them, i.e., if they do
   not represent a large proportion of your annual CPU budget. Having
   this output will simplify analysis and eliminate guess work. 
4. If you have respected the Equilibrium drift criteria and choose not to
   submit Historical Control and Future Control output, you MUST still
   provide an indication of the drift of your model. In other words, you
   must use the three *ctrlH* output routines (see Abiotic HOWTO) to
   provide your output for another year. For instance, you could provide
   output from the 0-D, 2-D, and 3-D *ctrlH* routines for the year 1775.
   We would then compute your model drift and treat it as constant.

In any case, all modelers are encouraged to download the new version of
the Abiotic-HOWTO.  Besides major changes related to the Control (in
sections 3, 4, and 5) That document also contains fixes to minor
inconsistencies concerning model output frequency and an updated section
regarding transfer of your model output.

Best regards,


   James Orr                      
   Laboratoire des Sciences du Climat et de l'Environnement
   Unite Mixte de Recherche CEA-CNRS

   LSCE, CEA Saclay                http://www.ipsl.jussieu.fr/~jomce
   Bat. 709 - Orme                 mailto:  orr@cea.fr
   F-91191 Gif-sur-Yvette Cedex    Phone:   (33) (0)1 69 08 77 23
   FRANCE                          Fax:     (33) (0)1 69 08 77 16