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cdo mergetime: behavior when values overlap

Added by Jed Kaplan over 6 years ago

Reading the documentation, it is not clear to me what 

cdo mergetime infile1 infile2 outfile
does when merging datasets that overlap in time. Does it:

  1. Return the average of the values between the two files in the overlapping period?
  2. Choose data from one file or the other?
  3. Paste the two files together, reproducing the overlapping period?

I would prefer if CDO did option (1) above, but it would be good to know what actually is going on.

Many thanks,

Jed


Replies (6)

RE: cdo mergetime: behavior when values overlap - Added by Jed Kaplan over 6 years ago

Running some tests, it looks like CDO actually does option(3), reproducing the period that overlaps in time. I would be grateful if anyone could propose a method using CDO that would give me what I want, a merge of two files, with the period overlapping in time being the average between the files.

Many thanks again,

Jed

RE: cdo mergetime: behavior when values overlap - Added by Ralf Mueller over 6 years ago

Hi Jed!

in order to average the overlapping time, you have to select these timesteps (possible operators: select,seltimestep) and do the averaging manually (add, divc,2). The oneline could look like this

cdo -divc,2 -add -select,mon=3/4 <ifile1> -select,mon=3/4 <ifile2> <ofile>

hth
ralf

RE: cdo mergetime: behavior when values overlap - Added by Shafiqah M over 6 years ago

Hi, I am having the same situation as Jed. I had tried to run the command that you suggested "cdo -divc,2 -add -select,mon=3/4 <ifile1> -select,mon=3/4 <ifile2> <ofile>", but the operator responded "Too many mainstream and the operator need 1 input and 1 output streams."

Can you help me to solve this?

RE: cdo mergetime: behavior when values overlap - Added by Ralf Mueller over 6 years ago

Shafiqah M wrote:

Hi, I am having the same situation as Jed. I had tried to run the command that you suggested "cdo -divc,2 -add -select,mon=3/4 <ifile1> -select,mon=3/4 <ifile2> <ofile>", but the operator responded "Too many mainstream and the operator need 1 input and 1 output streams."

Can you help me to solve this?

not without

  • your input files
  • the precise call, you are using

RE: cdo mergetime: behavior when values overlap - Added by Shafiqah M over 6 years ago

The data are hourly temperature data. The command that I used is

cdo -divc,5 -add -select,timestep=1/201624 file1.nc -select,timestep=1/201621 file2.nc -select,timestep=1/201621 file3.nc -select,timestep=1/201623 file4.nc -select,timestep=1/201623 file5.nc kb.nc

Thank you.

RE: cdo mergetime: behavior when values overlap - Added by Ralf Mueller over 6 years ago

I don't see an obvious bug in the command line, but, as I said, without the actual files I cannot know whats going on.

-ralf

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