CDO

Hi Leo,

This limit is defined in the source file src/process.c line:

#define  MAX_STREAM      64

You can change this number and recompile the code.
We have no use case where a higher number of streams is needed, could you add an example command? This would help to optimize CDO.

Cheers, Uwe

Hi Uwe,

I work with a global climate model (CESM) that generates a single monthly history NetCDF containing all variables. Given a certain period of interest and a set of variables, I wrote a script (attached) that extracts the variables from the different monthly files and concatenate them together, thus creating a timeseries for each variable. With CDO I can do this using temporary files for each month/var combination, or using the chaining capability as the script has now. With the current setup I can do no more than 5 consecutive years (5*12 = 60 files).

Thanks, Leo

Hi Leo,

Thanks for your script!
If I understand it correctly then you are using the following CDO command:

cdo cat -selvar,varname file1 -selvar,varname file2 ... -selvar,varname filen result

You can replace this command line by:

cdo select,name=varname file1 file2 ... filen result
or with wildcards:
cdo select,name=varname file* result

Cheers, Uwe

Hi Uwe,

thanks for your reply! This seems to work great for most cases.

One minor annoyance left though. Whenever I try including the first year of the CESM simulation, CDO complains about input streams having different number of variables per timestep. This is because CESM does not write variables that are constant in time (just in the first time step). For the remainder of the simulation, these global attributes are written:

:Time_constant_3Dvars_filename = "./tr_eraimod_5_cap.clm2.h0.2001-01.nc" ;
   :Time_constant_3Dvars = "ZSOI:DZSOI:WATSAT:SUCSAT:BSW:HKSAT:ZLAKE:DZLAKE" ;

I guess this trick is CESM-specific, as CDO SELECT does not account for it. In my previous setup this was not an issue however, as I did the selection before the concatenation. Would be great to hear your thoughts on this.

Cheers, Leo

Hi Leo,

thats right this feature is missing in CDO select. I will add it in the next release!

Cheers, Uwe

Awesome, thanks for that.

Leo