[ncl-talk] Reading variable from large NetCDF file

[Vollaro, David]

Hi,

I am having a bit of trouble reading a variable from a large  NetCDF4 file
that I have created using an NCL example as a guide. I have a
4D variable sAvg(time,lev,lat,lon) which was calc by the program. I dimensioned
the output file to have time=unlimited.  Then I defined a output var
u(1,lev,lat,lon).  I then write out a 3D var to output for each time.

The  output file has dimensions as follows:

dimensions:
        time = UNLIMITED ; // (366 currently)
        lev = 29 ;
        lat = 256 ;
        lon = 512 ;
variables:
       float v(time, lev, lat, lon) ;

Here is a snippet of the program that created the file:
==============================================================================
...
  setfileoption("nc","Format","NetCDF4")
  ncdf_out = addfile(ncout ,"c")              ;create output NC file
  setfileoption(ncdf_out,"DefineMode",True)

;   date  processing loop  (tim,lat,lon)
  iout=0
  sname = 'v'
 do i = tim0,tim1,tim_inc
   print (i+" "+TIME(i))
   S = sfile_nc->$sname$(i,lev0:lev1,:,:)       ; read in 3D dataset for 1time
   if (i.eq.tim0.and.ny.eq.0) then
    sNew = new ( (/nyears,ntimes_out,nlev_out,jlat,ilon/), typeof(S) )
   end if
   sNew(ny,iout,:,:,:)=S(:,:,:)
   iout=iout+1
  end do

  ntimes_out1 = 1
  sAvg = new ( (/ntimes_out,nlev_out,jlat,ilon/), typeof(S) )
  u = new ( (/ntimes_out1,nlev_out,jlat,ilon/), typeof(S) )
  stmp = new ( (/nlev_out,jlat,ilon/), typeof(S) )
  sAvg = dim_avg_n(sNew,0)        ;avgs over all years(0th dim)


    dimNames = (/"time", "lev", "lat", "lon"/)
    dimSizes = (/ ntimes_out1,nlev_out,jlat,ilon/)
    dimUnlim = (/ True, False, False,False/)
    filedimdef(ncdf_out,dimNames,dimSizes,dimUnlim)
    filevardef(ncdf_out, sname  ,typeof(S),dimNames)
    filevarattdef(ncdf_out,sname,S)                 ; assign  array atts

  print("Outputting to Netcdf.....")
; output time based vars one at a time since time=unlimited
   do iout = 0,ntimes_out-1
    stmp = (/sAvg(iout,:,:,:)/)
    ncdf_out->$sname$(iout,:,:,:) =(/stmp/)
   end do
==============================================================================
end snippet


Here is a snippet of the program that reads the large NetCDF file
==============================================================================

begin
   filename = "/jm13/djv/CCLIMO+v_1989-1989_512x256.nc"
   ufile_nc = addfile(filename,"r")
    vars = getfilevarnames(ufile_nc)
    print(vars)

  sys_cmd = "ncdump -h "+filename
  system(sys_cmd)

  do i= 160,181
  V=ufile_nc->v(i,6:22,:,:)
  print(V(2,10,10))
 end do
end
==============================================================================
end snippet

When I try to read from this file I get the following error:
fatal:Subscript out of range, error in subscript #0

The program seems to read in the data OK, despite this fatal error.
If I read in the entire array at once I do not get this error:
ie   V=ufile_nc->v

Any ideas on why I am getting this seemingly fatal error?

Thanks


Dave Vollaro


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