CDO

Is the output precision changed?
I don't know a CDO operator which shows the precision of values.
But you can simply test using "cdo -b {precision} copy out.nc out2.nc" to find the precision of out.nc by comparing file sizes between out.nc and out2.nc.
Details about '-b' option are in CDO user guide.

Best regards,
Jonghun

Anatoliy Z wrote:

Hello everybody!
I execute the command cdo mergetime
"cdo mergetime *.nc out.nc "
I combine 47 .nc files with a total size of 1 GB. But the resulting file out.nc is 20 GB or more. What am I doing wrong?
The files are daily data of one month in size.

Thanks in advance
Anatoliy

OK thanks. I tried NCO - everything turned out as I would like. NCO "ate" even files with a non-standard coordinate format, about which the CDO complained.

regards
Anatoliy

Hi Anatoliy,

I guess that your files are not CF convention conform, but without any file it is not possible to help.

@Jonghun: you can use the sinfon operator to see the dtype of a variable.

-Karin

Karin, thanks for the answer. The files were taken here https://cds.climate.copernicus.eu/cdsapp#!/dataset/sis-agrometeorological-indicators?tab=overview.

regards,
Anatoliy

What did you exactly choose (variable etc)?

Snow thickness

2005-2020 year, three months - December, January, February

The input files are netcdf4 compressed files.

cdo sinfon  Snow-Thickness-LWE-Mean_C3S-glob-agric_AgERA5_daily_20050101-20050131_final-v1.0.nc
   File format : NetCDF4 zip
    -1 : Institut Source   T Steptype Levels Num    Points Num Dtype : Parameter name
     1 : unknown  unknown  v instant       1   1   6483600   1  F32z : Snow_Thickness_LWE_Mean
   Grid coordinates :
     1 : lonlat                   : points=6483600 (3600x1801)
                              lon : -180 to 179.9 by 0.1 degrees_east  circular
                              lat : 90 to -90 by -0.1 degrees_north
   Vertical coordinates :
     1 : surface                  : levels=1
   Time coordinate :  31 steps
     RefTime =  1900-01-01 00:00:00  Units = days  Calendar = proleptic_gregorian
  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss
  2005-01-01 00:00:00  2005-01-02 00:00:00  2005-01-03 00:00:00  2005-01-04 00:00:00
  2005-01-05 00:00:00  2005-01-06 00:00:00  2005-01-07 00:00:00  2005-01-08 00:00:00
  2005-01-09 00:00:00  2005-01-10 00:00:00  2005-01-11 00:00:00  2005-01-12 00:00:00
  2005-01-13 00:00:00  2005-01-14 00:00:00  2005-01-15 00:00:00  2005-01-16 00:00:00
  2005-01-17 00:00:00  2005-01-18 00:00:00  2005-01-19 00:00:00  2005-01-20 00:00:00
  2005-01-21 00:00:00  2005-01-22 00:00:00  2005-01-23 00:00:00  2005-01-24 00:00:00
  2005-01-25 00:00:00  2005-01-26 00:00:00  2005-01-27 00:00:00  2005-01-28 00:00:00
  2005-01-29 00:00:00  2005-01-30 00:00:00  2005-01-31 00:00:00

When the files are read, they are uncompressed and saved as uncompressed data when merged.

You can reduce the size of the merged file using the '-z' option with compression level 1-9,
but this will take some time.

cdo -O -z zip_9 -mergetime Snow-Thickness-LWE-Mean_C3S-glob-agric_AgERA5_daily_*.nc outfile.nc

Ok, thank you very much.

regards
Anatoliy