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6. Output Format

Each modeling group must provide their output in the standard OCMIP-2 format. Model output that does not follow these formatting conventions cannot be included for analysis during OCMIP-2. Model groups must use the standard routines that we have developed specifically for writing output in standard form for OCMIP-2.

If this is the first OCMIP-2 simulation you have made, you will need to recuperate the routine write_nc_MaskAreaBathy.f to write out characteristics of your model grid, mask, and bathymetry using the standard OCMIP-2 format. Use of this routine is detailed in the CFC HOWTO (section 5.1).

Otherwise if you have submitted OCMIP-2 model output previously, you will only need to resubmit the output file produced by write_nc_MaskAreaBathy.f under two conditions:

  1. If your model's grid, mask, or bathymetry have changed; or
  2. If you have been notified by the OCMIP-2 analysis center at IPSL that your output file from this subroutine did not pass the routine integrity tests.

6.1 Output routines

Each modeling group must use the output routine listed in the table below to store results in standard OCMIP-2 format for the Helium Output.

Input to this routine is simply your model's output for the concentrations and air-sea fluxes both tracers (He-3 and He-4). All groups will need to call the 1st output routine write_nc_Helium.f, but ONLY once, at the end of model spin-up. You may be able to skip calling the 2nd routine write_nc_Helium_TS.f (see 2nd footnote).

Routine                        Input                    Units       Comments

write_nc_Helium.f            Conc. of He-3            mol/m^3            (*)
                             Conc. of He-4            mol/m^3            (*)
                             Mean Flux of He-3        mol/(m^2*s)        (*)
                             Mean Flux of He-4        mol/(m^2*s)        (*)

write_nc_Helium_TS.f         Potential temperature    degrees C          (*)(+)
                             Salinity                     psu

(*) This is an equilibrium run: All 2- and 3-D fields should be averaged for
     each month over the last year of the simulation.
(+) You only need to submit this output file if the year from the corresponding
    "dynamic" output differs from that from your Abiotic or Biotic runs. 
     If the year is identical (same T and S fields), simply copy the Abiotic 
     or Biotic output file, and rename it (e.g., changing 
     "" -> "").

6.2 Downloading the output routines

The output routines write_nc_Helium.f and write_nc_Helium_TS.f can be transferred to your machine by clicking on their link while holding down the Shift key.

You will also need to transfer the subroutine handle_errors.f to properly deal with errors while you are writing your netCDF files.

6.3 Compiling the output routines

Here is a an example of how you would compile the output routine with the necessary link to the netCDF library:

f77 -c -O -L/usr/local/lib -lnetcdf -I/usr/local/include \

Because we have made this routine F77 compatible, you may need a function len_trim.f (from Fortran 90), which we also provide and which returns the length of a character string (after neglecting trailing blanks).

6.4 Using the output routine

The output routine write out your model results following the naming and output conventions (netCDF, COARDS, GDT) chosen for OCMIP-2. The output filename is constructed automatically the ouput routine from three of the arguments: the tracer name and the standard model code used during OCMIP-2 to identify your group.

For example, after compiling and linking the OCMIP-2 output routine, we add the following code to the IPSL routines to store output in standard OCMIP-2 form

          call write_nc_Helium("IPSL","NGL46_SI",
       &  imt, jmt, kmt,
       &  60*60*24*365, 1200,
       &  Mhe3, Mhe4,
       &  MFhe3, MFhe4)

By line, the arguments include

  1. the OCMIP-2 model code AND your own model version indicator (in GDT 1.2 terminology, these 2 variables refer to the institution and production, respectively);
  2. dimensions;
  3. the number of seconds per year (in your model), and the number of timesteps per year;
  4. the 12 monthly means for the 3-D tracer arrays for He-3 and He-4 (both in mol/m^3); and
  5. the 12 monthly means for the 2-D air-sea flux for He-3 and He-4 (both in mol/(m^2*s)).

When do I call the above Equilibrium output routine? It should be called only once, at the end of the simulation after building monthly arrays (12 members) for both of the 2-D and 3-D spatial fields given as arguments.

6.5 Name of Output file

All arguments of the Helium output routine are input; none are output. Using the arguments given above, the model output file (netCDF) would be (""), which contains the information for analyzing the IPSL results for 1985. This file should be transferred to IPSL. The filename should NOT be changed. At IPSL, files will subsequently be (1) tested for consistency, (2) included in the OCMIP-2 data base, and (3) processed for base analysis.

6.6 Need more details?

See for additional information about the format netCDF and other conventions (COARDS, GDT) chosen for storing OCMIP-2 model output.

If you have other questions, please contact or

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