Re: To change the time variable attributes in merged netCDF file

From: Bridget Thrasher <bthrasher_at_nyahnyahspammersnyahnyah>
Date: Thu Apr 12 2012 - 11:02:49 MDT

Are you sure the timestamps in the original files are correct? I would
worry about changing the time attribute since they may in fact be correct.
Does the data at i=1260 match the data in the original file for time
185101?

If you used this command "ncrcat -O m1850-2005.nc m1850-2005.nc
m1850-2100.nc" to create a new file, then what you did was concatenate the
1850-2005 file to itself and renamed it m1850-2100.nc, which is incorrect
and would possibly explain your timestamps below. Though it looks like
maybe the m1850-2005.nc file actually contains data starting in 1851? Check
your original files and check the syntax for ncrcat....

-Bridget

On Thu, Apr 12, 2012 at 9:42 AM, Noel Aloysius <noel.aloysius@gmail.com>wrote:

> Hi Dennis,
>
> Thanks for the reply.
>
> I followed as per you reply. When I print the time output, after 200512
> time starts from 185101 as shown below. How can I modify the time
> attribute to correct this.
>
> (1256) 200509
> (1257) 200510
> (1258) 200511
> (1259) 200512
> (1260) 185101
> (1261) 185102
> (1262) 185103
> (1263) 185104
> (1264) 185105
>
> Thanks,
> Noel
>
> On 04/11/2012 06:57 PM, Dennis Shea wrote:
> >
> > Not sure why you want to change the begin time. It does not matter.
> > It is arbitrary
> > If the combined file created by ncrcat
> > is m1850-2100.nc
> >
> > %> ncrcat -O m1850-2005.nc m1850-2005.nc m1850-2100.nc
> >
> > then
> >
> > %> ncks -d time,612,, m1850-2100.nc m1901-2100.nc
> >
> > I think the 612 is correct for 190101
> >
> >
> > Using NCL interactively:
> >
> > ncl <return>
> >
> > f = addfile("m1901-2100.nc", "r")
> > time = f->time
> > yyyymm = cd_calendar(time, -1)
> >
> > print(time+" "+yyyymm)
> >
> > You should see the 1st time as 190101
> >
> > On 4/11/12 4:28 PM, Noel Aloysius wrote:
> >> Hi NCL-talk,
> >>
> >> I used NCO operator 'ncrcat' to merge two monthly timeseries files
> >> ("1850-2005" + "2006-2100") and, then, created a subset for the period
> >> 1901-2100 monthly values. The resultant netCDF file has the time
> >> attributes set to begin on 1850-01.
> >>
> >> To change the time attribute, I tried to create a new file and transfer
> >> all the data to that. I am able to define and create all the attributes
> >> but when I tried to write the data values (precipitiation values in this
> >> case) I get error that says
> >>
> >> "fatal:Variable (pr) is undefined"
> >>
> >> I have attached the script. I appreciate your help to resolve this
> >> issue.
> >>
> >> Thanks,
> >> Noel
> >>
> >>
> >>
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-- 
Bridget Thrasher, PhD
Independent Contractor, Research Scientist

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Received on Thu Apr 12 11:03:00 2012

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