The following Fortran 77 program opens a file and reads vorticity and divergence spectral fields in GRIB format; it then calls INTUVP2 to create spectral U and V fields. Because of the preliminary call to INTOUT, the U and V fields are subsequently interpolated to grid-point fields with resolution 3deg by 3deg without the need for a separate call to INTF. The function INTIN is not used here because the input fields are in GRIB format and are self-defining.
Subroutines PBOPEN, PBCLOSE, PBGRIB and PBWRITE handle pure binary input and output files.
C C Copyright 2015 ECMWF. C C This software is licensed under the terms of the Apache Licence C Version 2.0 which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. C C Unless required by applicable law or agreed to in writing, software C distributed under the License is distributed on an "AS IS" BASIS, C WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. C C In applying this licence, ECMWF does not waive the privileges and immunities C granted to it by virtue of its status as an intergovernmental organisation C nor does it submit to any jurisdiction. C PROGRAM SAMPLE4 C IMPLICIT NONE INTEGER INTV REAL REALV CHARACTER*20 CHARV DIMENSION INTV(4), REALV(4), CHARV(4) C INTEGER JPGRIB, JPBYTES C PARAMETER (JPGRIB = 7000000) C C Set JPBYTES = 8 on a 64-bit machine. PARAMETER (JPBYTES = 4) C INTEGER IVOGRIB (JPGRIB), IDVGRIB (JPGRIB) INTEGER IUGRIB (JPGRIB), IVGRIB (JPGRIB) C INTEGER IUNIT1, IUNIT2, IREC, INLENG, IERR, IRET,J,NARGS C C Externals INTEGER INTOUT, INTUVP2, IARGC LOGICAL ISSAME C CHARACTER*128 INFILE, OUTFILE, CARG(4) C ********************************************************************** C C Pick up file names from command line. C NARGS = IARGC() IF( NARGS.LT.4 ) THEN print*,'Usage: interpolation_example2 -i infile -o outfile' STOP END IF DO 101 J=1,NARGS CALL GETARG(J,CARG(J)) 101 CONTINUE DO 102 J=1,NARGS,2 IF(CARG(J).EQ.'-i') THEN INFILE=CARG(J+1) ELSEIF(CARG(J).EQ.'-o') THEN OUTFILE=CARG(J+1) ELSE print*,'Usage: interpolation_example2 -i infile -o outfile' STOP END IF 102 CONTINUE C ********************************************************************** C Set output grid interval REALV(1) = 3.0 REALV(2) = 3.0 IRET = INTOUT('grid',INTV,REALV,CHARV) IF ( IRET .NE. 0 ) THEN STOP 'grid setting INTOUT failed.' ENDIF C C Open input and output files. CALL PBOPEN(IUNIT1, INFILE, 'r', IERR) IF ( IERR .NE. 0 ) STOP ' PBOPEN failed' CALL PBOPEN(IUNIT2, OUTFILE, 'w', IERR) IF ( IERR .NE. 0 ) STOP ' PBOPEN failed' C C Read vorticity. CALL PBGRIB(IUNIT1, IVOGRIB, JPGRIB * JPBYTES, IREC, IERR) IF ( IERR .EQ. -1 ) GOTO 900 IF ( IERR .NE. 0 ) STOP ' PBGRIB failed for vorticity' C C Read divergence. CALL PBGRIB(IUNIT1, IDVGRIB, JPGRIB * JPBYTES, IREC, IERR) IF ( IERR .EQ. -1 ) GOTO 900 IF ( IERR .NE. 0 ) STOP ' PBGRIB failed for divergence' C C Create U and V WRITE(*,*) ' Create U and V.' INLENG = JPGRIB IRET = INTUVP2(IVOGRIB, IDVGRIB, JPGRIB, IUGRIB, IVGRIB, INLENG) IF ( IRET .NE. 0 ) THEN WRITE(*,*) ' INTUVP failed.' STOP ENDIF C C Write the new U and V products to file IF ( INLENG .GT. 0 ) THEN CALL PBWRITE(IUNIT2, IUGRIB, INLENG*JPBYTES, IERR) IF ( IERR .LT. (INLENG*JPBYTES) ) STOP ' PBWRITE failed' CALL PBWRITE(IUNIT2, IVGRIB, INLENG*JPBYTES, IERR) IF ( IERR .LT. (INLENG*JPBYTES) ) STOP ' PBWRITE failed' ENDIF C C Closedown 900 CONTINUE C C Close input and output files. CALL PBCLOSE(IUNIT1, IERR) CALL PBCLOSE(IUNIT2, IERR) C STOP END