Dataset problem: Issues with latitude and longitude for tos of BCCs CMIP6 models

[schlunma]

Describe the dataset issue
The names for the 1D grid_latitude and grid_longitude on irregular grids are set to latitude and longitude, causing iris to find duplicate coordinates. Multidimensional latitude and longitude coordinate do not have bounds.

• Data file has been changed by you in any way
• Project (CMIP5/CMIP6/OBS/obs4mips/etc): CMIP6
• Full dataset description (fill out as many as you know, please):
  • dataset: BCC-CSM2-MR, BCC-ESM1
  • experiment: historical
  • mip: Omon
  • grid: gn
  • variable used: tos
• Pointer to existing copy of data on ESGF node (it would be very useful if you could provide a physical fullpath to the file(s) that are causing the problem, e.g. on CEDA Jasmin or DKRZ):
  /mnt/lustre02/work/ik1017/CMIP6/data/CMIP6/CMIP/BCC/BCC-CSM2-MR/historical/r1i1p1f1/Omon/tos/gn/v20181126/tos_Omon_BCC-CSM2-MR_historical_r1i1p1f1_gn_185001-201412.nc
/mnt/lustre02/work/ik1017/CMIP6/data/CMIP6/CMIP/BCC/BCC-ESM1/historical/r1i1p1f1/Omon/tos/gn/v20181129/tos_Omon_BCC-ESM1_historical_r1i1p1f1_gn_185001-201412.nc

ncdump (without global attributes):

netcdf tos_Omon_BCC-CSM2-MR_historical_r1i1p1f1_gn_185001-201412 {
dimensions:
        time = UNLIMITED ; // (1980 currently)
        lat = 232 ;
        lon = 360 ;
        bnds = 2 ;
variables:
        double time(time) ;
                time:bounds = "time_bnds" ;
                time:units = "days since 1850-1-1" ;
                time:calendar = "365_day" ;
                time:axis = "T" ;
                time:long_name = "time" ;
                time:standard_name = "time" ;
        double time_bnds(time, bnds) ;
        double lat(lat) ;
                lat:bounds = "lat_bnds" ;
                lat:units = "degrees_north" ;
                lat:axis = "Y" ;
                lat:long_name = "latitude" ;
                lat:standard_name = "latitude" ;
        double lat_bnds(lat, bnds) ;
        double lon(lon) ;
                lon:bounds = "lon_bnds" ;
                lon:units = "degrees_east" ;
                lon:axis = "X" ;
                lon:long_name = "Longitude" ;
                lon:standard_name = "longitude" ;
        double lon_bnds(lon, bnds) ;
        float latitude(lat, lon) ;
                latitude:standard_name = "latitude" ;
                latitude:long_name = "latitude" ;
                latitude:units = "degrees_north" ;
                latitude:missing_value = 1.e+20f ;
                latitude:_FillValue = 1.e+20f ;
        float longitude(lat, lon) ;
                longitude:standard_name = "longitude" ;
                longitude:long_name = "longitude" ;
                longitude:units = "degrees_east" ;
                longitude:missing_value = 1.e+20f ;
                longitude:_FillValue = 1.e+20f ;
        float tos(time, lat, lon) ;
                tos:standard_name = "sea_surface_temperature" ;
                tos:long_name = "Sea Surface Temperature" ;
                tos:comment = "Temperature of upper boundary of the liquid ocean, including temperatures below sea-ice and floating ice shelves." ;
                tos:units = "degC" ;
                tos:original_name = "tos" ;
                tos:cell_methods = "area: mean where sea time: mean (interval: 30 minutes)" ;
                tos:cell_measures = "area: areacello" ;
                tos:missing_value = 1.e+20f ;
                tos:_FillValue = 1.e+20f ;
                tos:coordinates = "latitude longitude" ;

netcdf tos_Omon_BCC-CSM2-MR_historical_r1i1p1f1_gn_185001-201412 {
dimensions:
        time = UNLIMITED ; // (1980 currently)
        lat = 232 ;
        lon = 360 ;
        bnds = 2 ;
variables:
        double time(time) ;
                time:bounds = "time_bnds" ;
                time:units = "days since 1850-1-1" ;
                time:calendar = "365_day" ;
                time:axis = "T" ;
                time:long_name = "time" ;
                time:standard_name = "time" ;
        double time_bnds(time, bnds) ;
        double lat(lat) ;
                lat:bounds = "lat_bnds" ;
                lat:units = "degrees_north" ;
                lat:axis = "Y" ;
                lat:long_name = "latitude" ;
                lat:standard_name = "latitude" ;
        double lat_bnds(lat, bnds) ;
        double lon(lon) ;
                lon:bounds = "lon_bnds" ;
                lon:units = "degrees_east" ;
                lon:axis = "X" ;
                lon:long_name = "Longitude" ;
                lon:standard_name = "longitude" ;
        double lon_bnds(lon, bnds) ;
        float latitude(lat, lon) ;
                latitude:standard_name = "latitude" ;
                latitude:long_name = "latitude" ;
                latitude:units = "degrees_north" ;
                latitude:missing_value = 1.e+20f ;
                latitude:_FillValue = 1.e+20f ;
        float longitude(lat, lon) ;
                longitude:standard_name = "longitude" ;
                longitude:long_name = "longitude" ;
                longitude:units = "degrees_east" ;
                longitude:missing_value = 1.e+20f ;
                longitude:_FillValue = 1.e+20f ;
        float tos(time, lat, lon) ;
                tos:standard_name = "sea_surface_temperature" ;
                tos:long_name = "Sea Surface Temperature" ;
                tos:comment = "Temperature of upper boundary of the liquid ocean, including temperatures below sea-ice and floating ice shelves." ;
                tos:units = "degC" ;
                tos:original_name = "tos" ;
                tos:cell_methods = "area: mean where sea time: mean (interval: 30 minutes)" ;
                tos:cell_measures = "area: areacello" ;
                tos:missing_value = 1.e+20f ;
                tos:_FillValue = 1.e+20f ;
                tos:coordinates = "latitude longitude" ;

Fix provided in #560.

[zklaus]

The 2d coordinates are compatible with the tri-polar grid that is claimed in the description; the 1d coordinates are not.

I think we should just drop the 1d coordinates and only go off the 2d coordinates.

Essentially duplicate of #303 and #151, already reported upstream in #303.

[schlunma]

Fix for this exists. I am 99% sure that this data will not be fixed on ESGF (we are approaching CMIP7), so I am closing this now.