SPTRUNM

The SPTRUNM routine spectrally truncates scalar fields
            on a global cylindrical grid, returning the fields
            to a Mercator grid.
            The wave-space can be either Triangular or Rhomboidal.
            The grid-space can be either an equally-spaced grid
            (with or without pole points) or a Gaussian grid.
            The grid fields may have general indexing.
            The transforms are all multiprocessed.
            Transform several fields at a time to improve vectorization.
            Subprogram can be called from a multiprocessing environment.
 
USAGE:    CALL SPTRUNM(IROMB,MAXWV,IDRTI,IMAXI,JMAXI,KMAX,MI,MJ,
                       IPRIME,ISKIPI,JSKIPI,KSKIPI,KGSKIP,
                       NISKIP,NJSKIP,JCPU,RLAT1,RLON1,DLAT,DLON,
                       GRIDI,GM)

   Input arguments:
      IROMB    - INTEGER SPECTRAL DOMAIN SHAPE
                 (0 FOR TRIANGULAR, 1 FOR RHOMBOIDAL)
      MAXWV    - INTEGER SPECTRAL TRUNCATION
      IDRTI    - INTEGER INPUT GRID IDENTIFIER
                 (IDRTI=4 FOR GAUSSIAN GRID,
                  IDRTI=0 FOR EQUALLY-SPACED GRID INCLUDING POLES,
                  IDRTI=256 FOR EQUALLY-SPACED GRID EXCLUDING POLES)
      IMAXI    - INTEGER EVEN NUMBER OF INPUT LONGITUDES.
      JMAXI    - INTEGER NUMBER OF INPUT LATITUDES.
      KMAX     - INTEGER NUMBER OF FIELDS TO TRANSFORM.
      MI       - INTEGER NUMBER OF POINTS IN THE FASTER ZONAL DIRECTION
      MJ       - INTEGER NUMBER OF POINTS IN THE SLOWER MERID DIRECTION
      IPRIME   - INTEGER INPUT LONGITUDE INDEX FOR THE PRIME MERIDIAN.
                 (DEFAULTS TO 1 IF IPRIME=0)
                 (OUTPUT LONGITUDE INDEX FOR PRIME MERIDIAN ASSUMED 1.)
      ISKIPI   - INTEGER SKIP NUMBER BETWEEN INPUT LONGITUDES
                 (DEFAULTS TO 1 IF ISKIPI=0)
      JSKIPI   - INTEGER SKIP NUMBER BETWEEN INPUT LATITUDES FROM SOUTH
                 (DEFAULTS TO -IMAXI IF JSKIPI=0)
      KSKIPI   - INTEGER SKIP NUMBER BETWEEN INPUT GRID FIELDS
                 (DEFAULTS TO IMAXI*JMAXI IF KSKIPI=0)
      KGSKIP   - INTEGER SKIP NUMBER BETWEEN GRID FIELDS
                 (DEFAULTS TO NPS*NPS IF KGSKIP=0)
      NISKIP   - INTEGER SKIP NUMBER BETWEEN GRID I-POINTS
                 (DEFAULTS TO 1 IF NISKIP=0)
      NJSKIP   - INTEGER SKIP NUMBER BETWEEN GRID J-POINTS
                 (DEFAULTS TO NPS IF NJSKIP=0)
      JCPU     - INTEGER NUMBER OF CPUS OVER WHICH TO MULTIPROCESS
                 (DEFAULTS TO ENVIRONMENT NCPUS IF JCPU=0)
      RLAT1    - REAL LATITUDE OF THE FIRST GRID POINT IN DEGREES
      RLON1    - REAL LONGITUDE OF THE FIRST GRID POINT IN DEGREES
      DLAT     - REAL LATITUDE INCREMENT IN DEGREES SUCH THAT
                 D(PHI)/D(J)=DLAT*COS(PHI) WHERE J IS MERIDIONAL INDEX.
                 DLAT IS NEGATIVE FOR GRIDS INDEXED SOUTHWARD.
                 (IN TERMS OF GRID INCREMENT DY VALID AT LATITUDE RLATI,
                 THE LATITUDE INCREMENT DLAT IS DETERMINED AS
                 DLAT=DPR*DY/(RERTH*COS(RLATI/DPR))
                 WHERE DPR=180/PI AND RERTH IS EARTH'S RADIUS)
      DLON     - REAL LONGITUDE INCREMENT IN DEGREES SUCH THAT
                 D(LAMBDA)/D(I)=DLON WHERE I IS ZONAL INDEX.
                 DLON IS NEGATIVE FOR GRIDS INDEXED WESTWARD.
      GRIDI    - REAL (*) INPUT GRID FIELDS

   Output arguments:
      GM       - REAL (*) MERCATOR FIELDS
 
REMARKS:
        MINIMUM GRID DIMENSIONS FOR UNALIASED TRANSFORMS TO SPECTRAL:

    DIMENSION                    LINEAR              QUADRATIC
    -----------------------      ---------           -------------
    IMAX                         2*MAXWV+2           3*MAXWV/2*2+2
    JMAX (IDRT=4,IROMB=0)        1*MAXWV+1           3*MAXWV/2+1
    JMAX (IDRT=4,IROMB=1)        2*MAXWV+1           5*MAXWV/2+1
    JMAX (IDRT=0,IROMB=0)        2*MAXWV+3           3*MAXWV/2*2+3
    JMAX (IDRT=0,IROMB=1)        4*MAXWV+3           5*MAXWV/2*2+3
    JMAX (IDRT=256,IROMB=0)      2*MAXWV+1           3*MAXWV/2*2+1
    JMAX (IDRT=256,IROMB=1)      4*MAXWV+1           5*MAXWV/2*2+1
 
 


  
SPLIB.tar
  
Library contains routines to be
   be used for a variety of spectral transform functions. (Fortran90) 

   Date posted: 2/23/2007