reading data source from IC and LBC

[Jili-Dong]

If users encounter the following errors during the initialization:

fv_regional_bc::get_data_source - input source not found in file gfs_data.nc
or
fv_regional_bc::get_lbc_source - input source not found in file gfs_bndy.tile7.000.nc

that means global attribute "source" is missing in IC (gfs_data.nc) or LBC (gfs_bndy.tile7.000.nc). The accepted FV3 source is one of the following:

"FV3GFS GAUSSIAN NEMSIO FILE"
"FV3GFS GAUSSIAN NETCDF FILE"
"FV3GFS GRIB2 FILE" 

Users can use the following NCO command to add source attribute to the related IC and/or LBC:

ncatted -O -a source,global,c,c,'FV3GFS GAUSSIAN NETCDF FILE' gfs_data.nc
or
ncatted -O -a source,global,c,c,'FV3GFS GRIB2 FILE' gfs_bndy.tile7.000.nc

or consider to modify IC/LBC generation code to write out global attribute "source" to IC/LBC as a long term solution.