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Revised OCMIP Guidelines (B2)



Dear "ocmip-all" members,

I should not have rushed last night to send out my first message to this
list.  I had another look and realize now that it is was less than clear.
Even I had a hard time understanding it!  Thus please accept my apologies
and the modified version below.  Note that only the introductory text has
changed, but not the guidelines (other than a cleaner formatting).
 
=========================================================================
I would now like to encourage full discussion concerning the formulation
of guidelines for OCMIP simulations dealing with phase B2 and beyond.

OCMIP is currently in phase B1, as described in the Report from OCMIP
Workshop I (May 1996).  Phase B2 analysis will not begin until the first
papers from B1 are submitted, probably sometime around January 1997.
However, that is very soon, thus I need your comments now to make the
guidelines final, so that modeling groups can begin simulations (1-3).
Please send your responses by October 15, 1996.

Although these guidelines were given in rudimentary form in the OCMIP
Workshop Report, I have as yet received few comments or suggestions.
On the other hand, Uwe Mikolajewicz provided the outline for runs
described in 3.1(b) and 3.3.  He has even made these runs already, so
unless there are serious objections, I would like to take advantage of
his experience and make similar runs for OCMIP.

Regards, Jim
- -----------------------------------------------------------------------
BEGIN: Tentative Guidelines for OCMIP Phase B2 and Beyond
       (Send suggestions by 15 October 1996)
- ------------------------------------------------------------------------
1. O2 (Phase B2):
- -----------------
* Two simulations (Natural + anthropogenic Perturbation)?
* Gas exchange consistent with CO2 runs (Phase B1)
* Account for N2 (as a ocean tracer)?

2. C-13 (Phase B2): 
- -------------------

* Two simulations (Natural + Suess Effect)
* Gas exchange consistent with previous runs for CO2 (phase B1)
* Consider biological production constant at a value of -22 per mil, 
  relative to TCO2
* fractionation factors?

 
3. Numerical Tracers (Phase B2):
- --------------------------------
3.1 Age Tracer reset to zero at the surface 
    (a) In all and/or part of the Southern Ocean
    (b) Over whole ocean (suggested by Uwe Mikolajewicz)
 
    * Reset to zero at the surface, wherever sea-ice is < 99% 
      (in the area of interest)
    * Aging every time step by ratio dt/1y
    * Result: age in yr

3.2 "Dye" Tracer (conservative, pulse input) also for S. Ocean?

3.3 Other tracers to study century-scale (and shorter) processes

    At the workshop two of the following were mentioned while the third was
    suggested recently by Uwe:

    (a) A short-lived (fictitious) tracer (mean life 20 yr)
    (b) Ar-39 (mean life 388 yr)
    (c) C-14  (mean life 8237 yr)

    * Infinitely rapid gas exchange (To simplify comparison)
      Thus surface concentrations eternally set to zero everywhere
      (except where sea ice cover > 99%.
    * Finite gas exchange for Ar-39 (an additional run) is proposed
      to better compare model results to data.
   
    * Advantages/Results: - mean lives  exhibit ratios of 1:20
                          - can help deduce advection vs. diffusion 

4. CFC's (Phase C):
- ----------------------
* Warner and Weiss Solubility
* Piston Velocity (same as for CO2, but corrected via Schmidt number
  dependence and no chemical enhancement (Wanninkhof, 1992). The analysis
  center will provide this 2-D field (as we have for CO2), along with
  documentation)
* Atmospheric Record (most recently available from Weiss, thanks to N. Gruber
                      for this lead)
- ------------------------------------------------------------------------
END: Tentative Guidelines OCMIP Phase B2 and Beyond
- ------------------------------------------------------------------------