passive tracers trends

[jpalmier]

Context

Working with the UKMO version of NEMO, i got some difficulties to get the trends working proprely.

• one reason for this is that new trends have been added by UKMO people that are not expected by the final/"outputing" part of trdtrc. the way this final part is written, if an non expected trend arrives here to be written out by XIOS, breaks the model:

        IF( lk_trdtrc .AND. ln_trdtrc( kjn ) ) THEN
           !
           SELECT CASE( ktrd )
           CASE( jptra_xad  )       ;    WRITE (cltra,'("XAD_",4a)')
           CASE( jptra_yad  )       ;    WRITE (cltra,'("YAD_",4a)')
           CASE( jptra_zad  )       ;    WRITE (cltra,'("ZAD_",4a)')
           CASE( jptra_ldf  )       ;    WRITE (cltra,'("LDF_",4a)')
           CASE( jptra_bbl  )       ;    WRITE (cltra,'("BBL_",4a)')
           CASE( jptra_nsr  )       ;    WRITE (cltra,'("FOR_",4a)')
           CASE( jptra_zdf  )       ;    WRITE (cltra,'("ZDF_",4a)')
           CASE( jptra_dmp  )       ;    WRITE (cltra,'("DMP_",4a)')
           CASE( jptra_sms  )       ;    WRITE (cltra,'("SMS_",4a)')
           CASE( jptra_atf  )       ;    WRITE (cltra,'("ATF_",4a)')
           CASE( jptra_radb )       ;    WRITE (cltra,'("RDB_",4a)')
           CASE( jptra_radn )       ;    WRITE (cltra,'("RDN_",4a)')
           END SELECT
                                            cltra = TRIM(cltra)//TRIM(ctrcnm(kjn))
                                            CALL iom_put( cltra,  ptrtrd(:,:,:) )
           !
        END IF
  
  

  For example, the JPTRA_TOTAD case has been added by the UKMO team. with a call to trd_trc(..., jptra_totad,...)
  This call will arrive in the foreseen piece of code, cltra will not be defined, and the iom_put call will fail without variable name to look after.
• A second problem is that these trends still do not take into account the vvl correction from ticket 1877.
• Some trends we might need for CMIP6 are missing from the list above.
• the namtrc_trd namelist is looking for ln_trdmxl_trc_restart and ln_trdmxl_trc_instant when namelist_top_ref has ln_trdmld_trc_restart, ln_trdmld_trc_instant instead.
• the place where namtrc_trd is read in namtrc starts to be problematic as namtrc_dia includes mainly the namelists read if XIOS is not available.
• Finally the trends are not defined in the field_def.xml file.

Analysis

• The output problem, once seen is easy to fix, it needs to move the cltra = TRIM(cltra)//TRIM(ctrcnm(kjn)); CALL iom_put( cltra, ptrtrd(:,:,:) ) sentences inside each CASE.
• I went to talk to George for the vvl problem. the solution is to copy what have been done for the dynamic.
• I am not sure about the full list of trends we want for the passive tracers, but at least we want the JPTRA_SMS and the total trend. Is there a definitive list of the passive tracer trends required for CMIP6 ? in the while i have added all the dynamical trends that were missing in the passive tracers, and have added a iom_use call before iom_put.
• namtrc_dia should be protected under a IF( .NOT. lk_iomput ) test, and move the namtrc_trd namelist reading in the main routine (might be better to move it in a specific trd routine as for the ice with trc_nam_ice)
• the field_def file needs to be completed.

Fix

A NEMO_3.6 branch has been created: nemo_v3_6_STABLE_trdtrc
first changes can be seen here

Still missing:

---

• Some of the trends are still not working on my MEDUSA testing branch. Once corrected, i'll import the changes.
• i am looking for adding the trends vertical inventory through XIOS. It is feasible, i kind of see how, but would be better with an example It would avoid writing tons of 3D fields when we really want 2D.
• Need to be tested from outside MetOffice? branch version. I removed everything from MEDUSA in this branch, but i cannot test it yet. have to check with Andrew how to test this.