defining new array - repost

Wed Apr 27 17:39:07 EDT 2005

Hi Arindam,
Thanks a lot for tyhe advice. If only I overcome problems with installing
NCO I  should be fine.
Mariusz

On Wed, 27 Apr 2005, Arindam Chakraborty wrote:

> hi Mariusz,
>         to my knowledge, redefinition of time dimension is not
> possible currently in grads (may be dtype netcdf will provide this
> opportunity in the future). Therefore, you may have to (if feasible)
> write down the data to plain binary file, create 2 descriptor files
> and do the subtraction (all these can be done from a single gs file
> itself). However, if you decide to write to an intermediate file, you
> can do the subtraction directly at the time of writing and the
> procedure described in the previous mail is not required.
>
> Alternatively, you can use netcdf operator (NCO). If the dimension
> name for time is 'time' in your netcdf file, the commands may look
> like this:
>
> # extract the 1st hr data starting from 1st day to last-but-one day
> % ncks -F -d time,1,697,24 inputfile.nc outputfile1.nc
>
> # extract the 1st hr data starting from 2nd day to last day
> % ncks -F -d time,25,721,24 inputfile.nc outputfile2.nc
>
> # subtraction
> % ncdiff outputfile2.nc outputfile1.nc daily.nc
>
> Use the -v varname option if you have many variables in one file.
>
> Hope this helps,
> ----------------------------
>  ARINDAM CHAKRABORTY
>  Department of Meteorology
>  Florida State University
>  Tallahassee, FL-32306, USA
>  Tel: +001-850-6443524 (Off)
>       +001-850-5758550 (Res)
>  Fax: +001-850-6449642
> ____________________________
>
> On Wed, 27 Apr 2005, Mariusz Pagowski wrote:
>
> > Thanks Arindam for response.
> >
> > However, the trick with assigning additional dimension
> > to the variable won't work - because I read a netcdf file
> > and z dimension is not defined. I still cannot find a way
> > how to declare/assign values to a daily array in a time loop
> > going over hours  e.g.
> >
> > nreacs=721
> > incrt=24
> > tt=0
> > while(tt <= nrecs-incrt)
> > tt=tt+incrt
> > 'd rainncacc(t='%tt%')-rainncacc(t='%tt-incrt%')'
> > endwhile
> >
> > displays fine but I need to assign values
> >
> > rainncacc(t='%tt%')-rainncacc(t='%tt-incrt%') to an array
> >
> > for further manipulation. Any expression of sort
> > rainncacc(t='%tt%')-rainncacc(t='%tt-incrt%') gets an error
> > message that: Function not found: rainncacc
> >
> > Thanks a lot,
> > Mariusz
> >
> >
> > On Wed, 27 Apr 2005, Arindam Chakraborty wrote:
> >
> > > hi Mariusz,
> > >         the trick is to introduce an additional dimension to the
> > > hourly rainfall data. And the assumption is that the variable
> > > has a free dimension (may be level in this case) and you have only
> > > one variable in this file (this later assumption may not be required if
> > > some other tricks are applied). Well, assuming these you may
> > > try applying the followings:
> > >
> > > View your time series as two dimensional. The z-dimension is hrs
> > > and t-dimension is days. Means, if you have 100 days (2400 time
> > > points in total), you need to write the control file as
> > > ....
> > > zdef 24 linear 1 1
> > > tdef 100 linear 1jan1998 1dy
> > > vars 1
> > > var 24 99 rainfall
> > > endvars
> > >
> > > This is the control file which points to the actual time series of
> > > your data. The next trick is to write another control file which will
> > > point to the same data file but with a shifted time coordinate. This
> > > is to make the subtraction sitting at the same time coordinate. This
> > > 2nd control file will read
> > > ....
> > > zdef 24 linear 1 1
> > > tdef 100 linear 31dec1997 1dy * starts 1 day early
> > > vars 1
> > > var 24 99 rainfall
> > > endvars
> > >
> > > Notice the shift here. The actual rainfall of 1jan98 will be viewed by
> > > the 2nd file as for 31dec97. And actual rainfall of 2jan98 will be
> > > viewed as for 1jan98, and so on. Now we can make the subtraction.
> > >
> > > 'open 1st_file.ctl' * 'actual'
> > > 'open 2nd_file.ctl' * dummy
> > > 'set horizontal dimensions'
> > > 'set t 1 99'
> > > 'set z 1' * z = 1 is the 1st hour
> > > 'd var.2 - var'
> > >
> > >
> > > Hope this works out.
> > > ----------------------------
> > >  ARINDAM CHAKRABORTY
> > >  Department of Meteorology
> > >  Florida State University
> > >  Tallahassee, FL-32306, USA
> > >  Tel: +001-850-6443524 (Off)
> > >       +001-850-5758550 (Res)
> > >  Fax: +001-850-6449642
> > > ____________________________
> > >
> > > On Wed, 27 Apr 2005, Mariusz Pagowski wrote:
> > >
> > > > Hello,
> > > > Sorry for the respost - I forgot to name the subject in the
> > > > header of my previous mail.
> > > >
> > > > In Grads I read a file with model hourly accumulated precipitation
> > > > and store data in "hourly"   array.
> > > > I want to convert hourly accumulated to daily totals. and later process
> > > > it further. In fortran it would  look like that:
> > > >
> > > > real daily  :: (nx,ny,30)
> > > > real hourly :: (nx,ny,721)
> > > >
> > > > daily(1)=hourly(25)-hourly(1)
> > > > ....
> > > > daily(30)=hourly(721)-hourly(697)
> > > >
> > > > After different tries with a define I ran out of ideas
> > > > how to declare a daily array and assign daily precip as above
> > > > in the fortran code.
> > > >
> > > > I would very much appreciate help.
> > > > Thanks,
> > > > Mariusz
> > > >
> > > > ___
> > > >
> > > > Mariusz Pagowski
> > > > NOAA Research-Forecast Systems Laboratory*,
> > > > 325 Broadway FSL/FS1, Boulder, CO 80305-3328
> > > > Tel: (303)497-6443, Fax: (303)497-7262
> > > > e-mail: Mariusz.Pagowski at noaa.gov
> > > >
> > > > *In collaboration with
> > > > Cooperative Institute for Research in the Atmosphere (CIRA),
> > > > Colorado State University
> > > > __________________________________________________________________
> > > >
> > >
> >
> > ___
> >
> > Mariusz Pagowski
> > NOAA Research-Forecast Systems Laboratory*,
> > 325 Broadway FSL/FS1, Boulder, CO 80305-3328
> > Tel: (303)497-6443, Fax: (303)497-7262
> > e-mail: Mariusz.Pagowski at noaa.gov
> >
> > *In collaboration with
> > Cooperative Institute for Research in the Atmosphere (CIRA),
> > Colorado State University
> > __________________________________________________________________
> >
>

___

Mariusz Pagowski
NOAA Research-Forecast Systems Laboratory*,
325 Broadway FSL/FS1, Boulder, CO 80305-3328
Tel: (303)497-6443, Fax: (303)497-7262
e-mail: Mariusz.Pagowski at noaa.gov

*In collaboration with
Cooperative Institute for Research in the Atmosphere (CIRA),
Colorado State University
__________________________________________________________________