[gradsusr] Fortran to Read in GrADS Binary File

Tue Jul 5 11:44:04 EDT 2016

Lydia,

Try this:

do t=1,days
      read(17,REC=irec) tmax
      read(17,REC=irec+1) tmin
      read(17,REC=irec+2) prcp
      read(17,REC=irec+3) srad
      write(18,REC=irec) tmin
      write(18,REC=irec+1) tmin
      write(18,REC=irec+2) prcp
      write(18,REC=irec+3) srad
      irec=irec+4
enddo

Here is some code from a Fortran 90 subroutine I use that works OK:

!
!  IEEE array for writing out the GrADS data
!
real(kind=4), dimension(nx,ny) :: grads_data
!
!  record number for writing out the GrADS data
!
integer :: irec
integer :: k,iv,n

       close(iu)	
       open(iu,file=TRIM(ieee_file),form="unformatted",access="direct", &
            recl=nx*ny*4,status="unknown")

       print *,'Write GrADS ieee data to Unit: ',iu

       irec = 1		! initialize
       do n = 1,nt
         do iv = 1,nv
           do k = 1,nz
	    grads_data(:,:) = dd(:,:,k,iv,n)
             write(iu,rec=irec) grads_data	
             irec = irec + 1		! increment for next write-out record
           enddo
         enddo
       enddo
       close(iu)	

If there still is a problem, sometimes the record length is not "4". 
 From a stackoverflow post, try using the "inquire" function: 
http://stackoverflow.com/questions/9013616/fortran-i-o-specifying-large-record-sizes

Hope this helps,
Chuck

On 07/05/2016 09:57 AM, Lydia Rill wrote:
> Hi all,
>
> I am a new grads user and I have never worked with binary files before.
> I have a large binary file I created in grads (code shown below). I want
> to split up the binary file by latitude and longitude degree into
> smaller binary files. While this is possible in GrADS, it is too slow
> for my needs, so I am trying to do it in Fortran 90.
>
> However, I am having problems reading the GrADS binary file in Fortran.
> It gives me the missing value for each of my variables at every time
> step and every location.
>
> The binary file contains NLDAS 2 forcing data, with 464 x steps, 224 y
> steps, and 13688 daily time steps for 4 variables (only 1 Z level). It
> is a large file at 22GB, and I can successfully display the variables in
> GrADS from this binary file. This binary file was created from data in
> Grib files.
>
> I have tried many various ways of reading in the binary data, using x
> and y loops, or time loops, or looping through the 4 variables, but
> nothing has been successful.
>
> I am working on a Mac (El Capitan).
>
> Here is the GrADS script I used to create the binary file:
>
> functionmain(args)
>
> counthr=subwrd(args,1)
>
> 'reinit'
>
> 'open /Volumes/WebData/NLDAS2/ProcessingFiles/24hours.ctl'
>
> 'set undef 9.999e20'
>
> 'set gxout fwrite'
>
> 'set fwrite -ap /Volumes/WebData/NLDAS2/DailyNLDAS/daily.bin'
>
>
> 'set t 1'
>
> t1=1+4
>
> t1p=1+5
>
> while(t1<=counthr+5-23)
>
> t2=t1+23
>
> t2p=t1p+23
>
> 'd (max(TMP2m,t='t1',t='t2')-273.15)'
>
> 'd (min(TMP2m,t='t1',t='t2')-273.15)'
>
> 'd sum(APCPsfc,t='t1p',t='t2p')'
>
> 'd (ave(DSWRFsfc,t='t1',t='t2')*24*3600/1000000)'
>
> t1=t1+24
>
> t1p=t1p+24
>
> endwhile
>
> 'quit'
>
>
> Here is the Fortran script to read the binary file
>
> ProgramReadbin
>
> implicitnone
>
> integer irec,i,j,t,days
>
> real tmin(464,224),tmax(464,224),prcp(464,224),srad(464,224)
>
> OPEN(17,file='/Volumes/WebData/NLDAS2/DailyNLDAS/daily.bin',&
>
> &STATUS='Old',FORM='UNFORMATTED',ACCESS='DIRECT',RECL=464*224*4)
>
>
> OPEN(18,file='/Volumes/WebData/NLDAS2/DailyNLDAS/testdaily.bin',&
>
> &STATUS='UNKNOWN',FORM='UNFORMATTED',ACCESS='DIRECT',RECL=464*224*4)
>
> days=10
>
> irec=1
>
> do t=1,days
>
>      read(17,REC=irec) ((tmax(i,j),i=1,8),j=1,8)
>
>      read(17,REC=irec+1) ((tmin(i,j),i=1,8),j=1,8)
>
>      read(17,REC=irec+2) ((prcp(i,j),i=1,8),j=1,8)
>
>      read(17,REC=irec+3) ((srad(i,j),i=1,8),j=1,8)
>
>      write(18,REC=irec) ((tmin(i,j),i=1,8),j=1,8)
>
>      write(18,REC=irec+1) ((tmin(i,j),i=1,8),j=1,8)
>
>      write(18,REC=irec+2) ((prcp(i,j),i=1,8),j=1,8)
>
>      write(18,REC=irec+3) ((srad(i,j),i=1,8),j=1,8)
>
>      irec=irec+4
>
> enddo
>
> end program
>
>
> The corresponding control file is:
>
> set ^testdaily.bin
>
> undef 9.999E+20
>
> title Daily NLDAS2 Data for00Z through 23Z
>
> xdef 8linear -124.93750.125
>
> ydef 8linear 25.06250.125
>
> tdef 10linear 00Z02Jan1979 1dy
>
> zdef 1linear 11
>
> vars 4
>
> TMAX 012,105,2**maximum temperature at 2m above surface [C]
>
> TMIN 011,105,2**minimum temperature at 2m above surface [C]
>
> PRCP 061,1,0**total precipitation backward accumulated [kg/m^2ormm]
>
> SRAD 0204,1,0**total surface downward shortwave radiation flux [mJ/m^2]
>
> ENDVARS
>
>
>
> Thanks,
>
> Lydia
>
> --
> Lydia D. Rill
> M.S., Michigan State University 2016
> B.S., Valparaiso University 2014
> (224) 406-5130
> Lydia.D.Rill at gmail.com <mailto:Lydia.D.Rill at gmail.com>
>
>
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>

-- 

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

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