fill values in 2D fields

[vasmue]

I noticed the fill values were changed (which is awesome for the 3D fields that can run into bathymetry at deeper levels), but it has also been changed for 2D fields (I noticed this for a_ice/m_ice).

Was this changed on purpose for the 2D fields? sea ice concentration = 0 is a physically reasonable value, same for sea ice thickness. On the other hand, I see the point in using different values for ice free points depending on whether there has ever been ice at there in the past (0) or there has never been any ice there (NaN/fill_value).

However, for plotting and computations I had to do a small workaround like this in python:

a_ice[:] = a_ice.fillna(0) -> set all NaN values to 0 (to make open ocean show as 0)

then grid the data for plotting and then apply land sea mask (mask_ne from pyfesom2) to get the land values back to NaN

mask = pf.mask_ne(xx, yy)
a_ice_gridded[mask] = np.nan

without the workaround:

with the workaround:

[patrickscholz]

@JanStreffing @koldunovn @suvarchal: should we limit the zero to fill_value augmentation to only the 3d variables?

Could be done by ...

! Add _FillValue attribute for missing/invalid data (CF-compliant)
if (entry%ndim==2) then
    if (entry%accuracy == i_real8) then
        call assert_nf( nf90_put_att(entry%ncid, entry%varID, '_FillValue', NC_FILL_DOUBLE), __LINE__)
    elseif (entry%accuracy == i_real4) then
        call assert_nf( nf90_put_att(entry%ncid, entry%varID, '_FillValue', NC_FILL_FLOAT), __LINE__)
    end
end

and

            !___________________________________________________________________
            ! write double precision output
            if (entry%accuracy == i_real8) then
!$OMP PARALLEL DO DEFAULT(SHARED) PRIVATE(I,J)
                DO J=1, size(entry%local_values_r8,dim=2)
                    DO I=1, size(entry%local_values_r8,dim=1)
                        ! Check if point has valid data (non-zero accumulated value)
                        ! Use small epsilon to account for floating point precision
                        if (abs(entry%local_values_r8(I,J)) < 1.0e-30_real64) then
-->                        if (size(entry%local_values_r8,dim=1)>1 ) ! only do 0-->fill value augment for 3D data
-->                             entry%local_values_r8_copy(I,J) = NC_FILL_DOUBLE  ! No data - set to fill value
-->                        end if   
                        else
                            entry%local_values_r8_copy(I,J) = entry%local_values_r8(I,J) /real(entry%addcounter,real64)  ! compute_means
                        end if
                        entry%local_values_r8(I,J) = 0._real64 ! clean_meanarrays - reset to 0 for next accumulation
                    END DO ! --> DO I=1, size(entry%local_values_r8,dim=1)
                END DO ! --> DO J=1, size(entry%local_values_r8,dim=2)
!$OMP END PARALLEL DO
                
            !___________________________________________________________________
            ! write single precision output
            else if (entry%accuracy == i_real4) then
!$OMP PARALLEL DO DEFAULT(SHARED) PRIVATE(I,J)
                DO J=1, size(entry%local_values_r4,dim=2)
                    DO I=1, size(entry%local_values_r4,dim=1)
                        ! Check if point has valid data (non-zero accumulated value)
                        ! Use small epsilon to account for floating point precision
                        if (abs(entry%local_values_r4(I,J)) < 1.0e-30_real32) then
-->                        if (size(entry%local_values_r8,dim=1)>1 ) ! only do 0-->fill value augment for 3D data
-->                             entry%local_values_r4_copy(I,J) = NC_FILL_FLOAT  ! No data - set to fill value
-->                        end if
                        else
                            entry%local_values_r4_copy(I,J) = entry%local_values_r4(I,J) /real(entry%addcounter,real32)  ! compute_means
                        end if
                        entry%local_values_r4(I,J) = 0._real32 ! clean_meanarrays - reset to 0 for next accumulation
                    END DO ! --> DO I=1, size(entry%local_values_r4,dim=1)
                END DO ! --> DO J=1, size(entry%local_values_r4,dim=2)
!$OMP END PARALLEL DO
            end if ! --> if (entry%accuracy == i_real8) then

[JanStreffing]

Agree, we should keep the 0 for sea ice in the 2D.