Time axis manipulations

Added by Kevin Havener almost 5 years ago

Trying to set a time axis from absolute to relative; calendar begins 1800-01-01, data begins 1891-01-01 and time value is first day of the month.
I used: cdo settunits,days -settaxis,1800-01-01,00:00:00,1month precip_climo.nc test1.nc
The metadata says the calendar starts in 1800-01-01, but the first values of the time axis are 0, 31, 59, ...; not 33237, 33268, 33296, ... as I expected.
How do I account for the offset between the calendar start and the data start?

Replies (7)

RE: Time axis manipulations - Added by Ralf Mueller almost 5 years ago

hi!

cdo -r

with any operator. docu is available with

cdo -h

hth
ralf

RE: Time axis manipulations - Added by Kevin Havener almost 5 years ago

Well, I also tried: cdo -r -f nc copy,settaxis,1800-01-01,00:00:00,1day precip_climo.nc test1.nc with the same result.
Sadly, the documentation doesn't help much because I am unable to ask the right question of it. I've been searching it for a couple of days now to try to understand what's going on, but there is some fundamental concept I must be missing. I a also unable to ask Google the right question, either.

RE: Time axis manipulations - Added by Ralf Mueller almost 5 years ago

cdo -r -f nc copy,settaxis,1800-01-01,00:00:00,1day precip_climo.nc test1.nc

is worng. copy and settaxis are two operators. the correct for only switching to a relative axis is

cdo -r -f nc -copy precip_climo.nc test1.nc

If you want to set the dates, intervals and units with relative axis you use

cdo -r-f nc -settaxis,1800-01-01,00:00:00,1day precip_climo.nc test1.nc

you might upload the input file for further help

RE: Time axis manipulations - Added by Uwe Schulzweida almost 5 years ago

You have to combine settaxis with setreftime:

cdo setreftime,1800-01-01,00:00:00,days -settaxis,1891-01-01,00:00:00,1month infile outfile

RE: Time axis manipulations - Added by Kevin Havener almost 5 years ago

Well that was even worse, it just numbers the months from 1 to 1537. I am uploading the first year of the file. Even zipped it was too large to send the whole thing.

precip_climo_test.nc (2.97 MB) precip_climo_test.nc

First year of GPCC monthly precip climatology

RE: Time axis manipulations - Added by Kevin Havener almost 5 years ago

I guess our conversation crossed paths. That syntax worked. Couldn't figure out the relationship between setreftime and settaxis. Thank you for clearing that up.

RE: Time axis manipulations - Added by Ralf Mueller almost 5 years ago

I used Uwe's call and upload the data:

        double time(time) ;
                time:standard_name = "time" ;
                time:units = "days since 1800-1-1 00:00:00" ;
                time:calendar = "proleptic_gregorian" ;
                time:axis = "T" ;

 time = 33237, 33268, 33296, 33327, 33357, 33388, 33418, 33449, 33480, 33510, 
    33541, 33571 ;

I used cdo-1.9.6

newRefTime_precip_climo_test.nc (2.97 MB) newRefTime_precip_climo_test.nc

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