5.6. Adding diagnostics

Icepack produces separate ASCII (text) log output for four cells, each with a different initial condition (full ITD, slab ice, ice free, land) designated by the variable n here. Each of the diagnostic files contains the state information for that cell. The procedure for adding diagnostic variables to the output is outlined here.

1. For non-BGC variables, edit icedrv_diagnostics.F90:

   • If the variable is already defined within the code, then add it to a “use” statement in the subroutine runtime_diags.

   • Note that if the variable is not readily accessible through a use statement, then a global variable may need to be defined. This might be in icedrv_state.F90 or icedrv_flux.F90 for example.

   • Additionally, if the variable is a derived quantity, then the variables needed to calculate the new quantity may need to be added to a use statement. For example, see how hiavg and hsavg are computed.

   • If the variable is a scalar, then follow the example of aice or hiavg, copying the write statement to an appropriate place in the output list, and editing as needed. The format “900” is appropriate for most scalars. The following example adds snow melt (melts).

   use icedrv_flux, only: melts
   
   write(nu_diag_out+n-1,900) 'snow melt (m)         = ',melts(n) ! snow melt
   

   • If the variable is an array, then you can compute the mean value (e.g. hiavg) or print the array values (e.g. fiso_evap). This may requires adding the array sizes and a counter for the loop(s). E.g. to print the category ice area, aicen over ncat thickness categories:

   use icedrv_domain_size, only: ncat
   
   use icedrv_state, only: aicen
   
   ! local variables
   
   integer (kind=int_kind) :: &
      n, nc, k
   
   do nc = 1,ncat
      write(nu_diag_out+n-1,901) 'Category ice area =       ',aicen(n,nc),nc ! category ice area
   enddo
   

   • If the variable is a tracer, then in addition to the variable trcr or trcrn, you will need the tracer index (e.g. nt_Tsfc).

   • In some cases, a new format statement might be needed.

2. For BGC variables, edit icedrv_diagnostics_bgc.F90:

   • If the variable is already defined within the code, then add it to a “use” statement in the subroutine hbrine_diags or bgc_diags and follow a similar procedure for state variables as above.

   • Note that the BGC needs to be activated and the particular tracer turned on.

In general, try to format the output statements to line up with the surrounding print messages. This may require a couple of tries to get it to compile and run.