lbc_lnk

lbc_lnk is done for all diagnostic variables in LOBSTER, e.g. trcbio.F90:

            CALL lbc_lnk( zw2d(:,:,jl),'T', 1. )

Q: do I need to do this in MY_TRC?

"tra" seems to represent the tracer concentration in the following time step, therefore I need to update tra instead of trn! The words "update the trend" are confusing to me (it seems the time rate of change is represented by tra. rather it should say update tra with the trend (or flux)).

tra, trn, trb for the next time step will be updated by TRP/trcnxt.F90, as well as the OBC and LBC are computed.

Actually, "tra" does represent the time rate of change in tracer concentration. For example PISCES/p4zflx.F90:

            ! compute the trend
            tra(ji,jj,1,jpdic) = tra(ji,jj,1,jpdic) + ( zfld - zflu ) / fse3t(ji,jj,1)

where zfld - zflu represent the flux [mol/m2/s] which is divided by fse3t (vertical scale factor; thickness of first model layer??) [m]. Thus the division gives [mol/m3/s].