[ncl-talk] Time dimension in output to NetCDF

[Dennis Shea]

I don't know GrADS and how it handles 'time'

===
My speculation is that
      prc&time = (/ yyyymm /)
is the source of the problem.
 Likely, GrADS expects 'time' to have units like
'seconds/minutes/hours/days since ...."

I would eliminate the above line .....ALso, not sure why you are
'promoting' the float variable to a double.

GrADS questions should be sent to the GrADS support group.
=======================

  diri   = "./"
  fili   = "precip.mon.total.v7.nc"
  f      = addfile(diri+fili, "r")

  prc    = flt2dble(f->precip(:,{12:33},{30:60}))
  pmsg   = prc at _FillValue      ; convenience

;===============================================================
;write to nc file
;================================================================


prc    = flt2dble(f->precip(:,{12:33},{30:60}))   ; <<< ??why are you
promoting to double?

====

Actually, the netCDF Operators could be used

%> ncks --d lat,12.0,33.0 -d lon,30.0,60.0 -O precip.mon.total.v7.nc
<http://precip.mon.total.v7.nc>prc_3mon.nc

On Thu, Nov 30, 2017 at 2:17 AM, Dr. Muhammad Afzaal <afzaalkarori at gmail.com
> wrote:

> in continuation to my previous email, following is the defined variable
> summary
>
> Variable: prcp
> Type: double
> Total Size: 27336960 bytes
>             3417120 values
> Number of Dimensions: 3
> Dimensions and sizes:   [time | 1356] x [lat | 42] x [lon | 60]
> Coordinates:
>             time: [190101..201312]
>             lat: [12.25..32.75]
>             lon: [30.25..59.75]
> Number Of Attributes: 3
>   units :       (mm)
>   long_name :
>   _FillValue :  -9.969209968386869e+36
>
> Please read the second last line of my code as ncdf->prcp = prcp
>
> Thanks
>
> *Dr. MUHAMMAD AFZAAL KARORI*
> Pakistan Meteorological Department
> Sector H-8/2, Pitras Bukhari Road,
> Islamabad - 44000
> Pakistan
>
>
>
> On Thu, Nov 30, 2017 at 12:06 PM, Dr. Muhammad Afzaal <
> afzaalkarori at gmail.com> wrote:
>
>> Dear NCL users
>>
>> I am using NCL 6.4.0 on ubuntu. I need to write a variable to netcdf
>> file. I did it successfully using Method 1 given on ncl homepage. I have
>> little problem that when I open nc file in grads, the time is not
>> realistic. I mean its like;
>>
>> Time values set: 2320:6:25:0 2320:6:25:0
>>
>> while the variable has the time from 190101 to 201312
>>
>> Can someone please help me how can add time dim as that attached with the
>> define variable? My code is given below
>>
>> ;====================================================
>> begin
>>
>>   diri   = "./"
>>   fili   = "precip.mon.total.v7.nc"
>>   f      = addfile(diri+fili, "r")
>>
>>   prc    = flt2dble(f->precip(:,{12:33},{30:60}))
>>   pmsg   = prc at _FillValue      ; convenience
>>
>> ;*********************************
>> ; plot parameters
>> ;*********************************
>>   dimprc = dimsizes(prc)
>>   ntim   = dimprc(0)
>>   nlat   = dimprc(1)
>>   mlon   = dimprc(2)
>>
>>   tim  = f->time
>>   utc_date = cd_calendar(tim, 0)
>>   year    = tointeger(utc_date(:,0))
>>   yrStrt  = year(0)
>>   yrLast  = year(ntim-1)
>>   nyear   = yrLast-yrStrt+1
>> ;print(year + " " + yrStrt + " "+ yrLast +" "+ nyear)
>>   yyyymm  = yyyymm_time(yrStrt, yrLast, "integer")
>>
>>   yrfrac  = (/ yyyymm_to_yyyyfrac(yyyymm, 0.0) /)
>>   prc&time = (/ yyyymm /)
>>
>> ;===============================================================
>> ;write to nc file
>> ;================================================================
>>
>>     system("/bin/rm -f prc_3mon.nc") ;remove any pre-existing file
>>     ncdf = addfile("prc_3mon.nc" ,"c") ; open output netCDF file
>>
>> ;===============================================================
>> ; create global attributes of the file (optional)
>> ;================================================================
>>        fAtt               = True        ; assign file attributes
>>        fAtt at title         = "GPCC Rainfall"
>>        fAtt at source_file   = "precip.mon.total.v7.nc"
>>        fAtt at Conventions   = "None"
>>        fAtt at creation_date = systemfunc ("date")
>>        fileattdef( ncdf, fAtt )           ; copy file attributes
>>
>> ;===============================================================
>> ; make time an UNLIMITED dimension;recommended for most applications
>> ;===============================================================
>>
>>        filedimdef(ncdf,"time",-1,True)
>>
>> ;===============================================================
>> ; output variables directly; NCL will call appropriate functions
>> ; to write the meta data associated with each variable
>> ;===============================================================
>>        ncdf->spi  = spi                          ; 3D
>> end
>>
>>
>> Regards
>> *Dr. MUHAMMAD AFZAAL KARORI*
>> Pakistan Meteorological Department
>> Sector H-8/2, Pitras Bukhari Road,
>> Islamabad - 44000
>> Pakistan
>>
>>
>>
>
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