Several tasks relating to manipulating netCDF files and dates/times within them are noted here.
- Converting the units and values of the
Setting the time ‘axis’
I have a netcdf file that contains a time variable. The values in the variable’s data array represent
time units since
date time string. Some model output and data formats use
months since as the unit, which strictly speaking is non-standard and not CF compliant. (The integer values in the time variable array simply count increasing months, for example.)
Instead, I would like these to be represented as
days since. So the integer values for time should now represent months.
I also want the month value to be reperesented at the mid-point of the month (The 15th), so I have chained in the
-settaxis command as well.
cdo settunits,days -settaxis,2001-01-15,00:00,1month INFILE.nc NEW_OUTFILE.nc
settunits will change the
time:units value as well, if it is in standard CF format.
It is useful to check the output is correct using
cdo showdate or
2001-01-15 2001-02-15 2001-03-15 2001-04-15 2001-05-15....