Finish implementation of proper river runoff from JRA55-do

[koldunovn]

We currently use river runoff climatology. We have to implement monthly means from JRA55. Currently we have a version from Qiang, but this require preprocessing step of interpolating the data to the mesh. Ideally we would like to avoid it, and just provide input netCDF files, that are interpolated in the model internally.

[mscheinert]

The implementation of this feature would be highly appreciated since we (Ocean modelling group at GEOMAR) depend somehow on the inter-annual runoff (successfully ran a full cycle with CORE2 mesh already but with climatological runoff).

Since FESOM 2.7 seems to be far in the future, for the meantime, Is the solution by Qiang available somewhere since I do not know them yet or do you have a contact for me?

Since I'm fairly new to FESOM I do not feel like I could really help with the implementation itself but I'd be willing to support it in any which way.

[JanStreffing]

@dsidoren Have there been any updates to river runoff for the standalone model since this issue was opened (4 years ago!)

[patrickscholz]

The only time-dependent runoff forcing is for DAI09 (Dai and Trenbert) and JRA55, but both only interpolated to fesom mesh! @mscheinert which runoff forcing you wanted to use? So a quick and dirty solution would be to interpolate your runoff forcing onto fesom2 mesh vertices over time.

! runoff  
     if(runoff_data_source=='Dai09' .or. runoff_data_source=='JRA55') then
       
       if(update_monthly_flag) then
         if(runoff_climatology) then
           !climatology monthly mean
           i=month
           if (mstep > 1) i=i+1 
           if (i > 12) i=1
           if (mype==0) write(*,*) 'Updating monthly climatology runoff for month ', i 
           filename=trim(nm_runoff_file)
           call read_2ddata_on_grid_NetCDF(filename,'runoff', i, runoff, partit, mesh)

           !kg/m2/s -> m/s
           runoff=runoff/1000.0_WP

         else
           !monthly data
           i=month
           if (mstep > 1) i=i+1 
           if (i > 12) i=1
           if (mype==0) write(*,*) 'Updating monthly runoff for month             ', i 
           filename=trim(nm_runoff_file)//cyearnew//'.nc' 
           call read_2ddata_on_grid_NetCDF(filename,'runoff', i, runoff, partit, mesh)

           !kg/m2/s -> m/s
           runoff=runoff/1000.0_WP

         end if
       end if

     end if