CDO

ncdump or panoply does not recognize your file.

hi!

netcdf INPUT {
dimensions:
        y = 27 ;
        x = 27 ;
        time_counter = UNLIMITED ; // (12 currently)
variables:
        float lat(y, x) ;
                lat:units = "degrees_east" ;
                lat:valid_min = -86. ;
                lat:valid_max = 90. ;
                lat:long_name = "Latitude" ;
        float lon(y, x) ;
                lon:units = "degrees_east" ;
                lon:valid_min = -180. ;
                lon:valid_max = 180. ;
                lon:long_name = "Longitude" ;
        float runoff(time_counter, y, x) ;
                runoff:units = "Kg/m2/s" ;
                runoff:long_name = "coastal runoff flux (except from antarctica iceshelves) (Dai and Trenberth) + iceberg meltwater flux (Merino I.)" ;
        int time_counter(time_counter) ;

1. lon,lat do not have a standard_name attribute
2. runoff is not connected to these coordinates at all because the coordinates attribute if note set

you can repair the file with

cdo -setattribute,lon@standard_name=longitude,lat@standard_name=latitude,runoff@coordinates="lat lon" INPUT.nc in.nc

• can use another method like bilinear or distance-weighted (please check the docu for more)
• provide the corners as lat_bounds and lon_bounds fields and give these names as the bounds attribute of each coordinate fields (lon and lat), see here for more information about how to handle cell bounds.

cheers
ralf

Hi Ralf,

Thanks so much. I need to use the conservative method rather than the bilnear. So I find another input data (friver_y2013.nc) which has bounds attribute. The variable 'friver' is also not connected to the coordinates. I have repaired this as you suggested with

cdo -setattribute,friver@coordinates="lat lon" friver_y2013.nc in.nc

(The size of in.nc is 1.5 GB, so I can't attach here.)

Then I can use remapcon operator successfully.
cdo remapcon,output.txt in.nc output.nc

However, the variable lat/lon in the output.nc is missing. Could you please kindly tell me how can I solve this?

Cheers,

Yu

output.nc looks ok

 netcdf output {
dimensions:
        time = UNLIMITED ; // (365 currently)
        bnds = 2 ;
        lon = 204 ;
        lat = 244 ;
variables:
        double time(time) ;
                time:standard_name = "time" ;
                time:long_name = "time" ;
                time:bounds = "time_bnds" ;
                time:units = "days since 1900-01-01 00:00:00" ;
                time:calendar = "gregorian" ;
                time:axis = "T" ;
        double time_bnds(time, bnds) ;
        float lon(lon) ;
                lon:standard_name = "longitude" ;
                lon:long_name = "longitude" ;
                lon:units = "degrees_east" ;
                lon:axis = "X" ;
        float lat(lat) ;
                lat:standard_name = "latitude" ;
                lat:long_name = "latitude" ;
                lat:units = "degrees_north" ;
                lat:axis = "Y" ;
        float friver(time, lat, lon) ;
                friver:standard_name = "water_flux_into_sea_water_from_rivers" ;
                friver:long_name = "Water Flux into Sea Water From Rivers" ;
                friver:units = "kg m-2 s-1" ;
                friver:_FillValue = 1.e+20f ;
                friver:missing_value = 1.e+20f ;
                friver:comment = "computed as the river flux of water into the ocean divided by the area of the ocean portion of the grid cell" ;
                friver:cell_methods = "area: mean where sea time: mean" ;
                friver:cell_measures = "area: areacello" ;

cdo -sinfov output.nc

hth
ralf

Hi again,

Yes, the lat and lon are existed in the file. But except for the variable of 'friver', I also need to use the lat and lon for the calculation in the next step. Do you know how to list the lat/lon 'apparent'? Thanks

Yu

Dear YUU YAN!

CDO will not show coordinates in any listing as long as they are correctly linked to the data variable (like friver). you can still check the values with

• % cdo sinfov output.nc
     File format : NetCDF4 classic
      -1 : Institut Source   T Steptype Levels Num    Points Num Dtype : Parameter name
       1 : unknown  MRI      v instant       1   1     49776   1  F32  : friver        
     Grid coordinates :
       1 : lonlat                   : points=49776 (204x244)
                                lon : 117.4347 to 122.5097 by 0.02499998 degrees_east
                                lat : 36.91948 to 42.99448 by 0.025 degrees_north
     Vertical coordinates :
       1 : surface                  : levels=1
     Time coordinate :  365 steps
       RefTime =  1900-01-01 00:00:00  Units = days  Calendar = gregorian  Bounds = true
    YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss
    2013-01-01 12:00:00  2013-01-02 12:00:00  2013-01-03 12:00:00  2013-01-04 12:00:00

• % cdo griddes output.nc       
  #
  # gridID 1
  #
  gridtype  = lonlat
  gridsize  = 49776
  datatype  = float
  xsize     = 204
  ysize     = 244
  xname     = lon
  xlongname = "longitude" 
  xunits    = "degrees_east" 
  yname     = lat
  ylongname = "latitude" 
  yunits    = "degrees_north" 
  xfirst    = 117.4347
  xinc      = 0.02499998
  yfirst    = 36.91948
  yinc      = 0.025

So you will still be able to use lon and lat for later calculations. In case you want to use CDO for the calculations, you might have a look into the expr operators. They allow point-wise calculations written on the command line as simple formulas and you have access to locations, dates, times and so on:

• the official docu
• some examples
• more examples

hth
ralf