sptgptd.f

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C> @file
C> @brief Transform spectral to station point gradients.
C>
C> ### Program History Log
C> Date | Programmer | Comments
C> -----|------------|---------
C> 96-02-29 | Iredell | Initial.
C> 1998-12-15 | Iredell | Openmp directives inserted.
C>
C> @author Iredell @date 96-02-29
 
C> This subprogram performs a spherical transform
c> from spectral coefficients of scalar fields
c> to specified sets of station point gradients on the globe.
C>
C> The wave-space can be either triangular or rhomboidal.
C>
C> The wave and point fields may have general indexing,
c> but each wave field is in sequential 'IBM order',
c> i.e. with zonal wavenumber as the slower index.
C>
C> The transforms are all multiprocessed over stations.
C>
C> Transform several fields at a time to improve vectorization.
C>
C> Subprogram can be called from a multiprocessing environment.
C>
C> @param IROMB spectral domain shape
c> (0 for triangular, 1 for rhomboidal)
C> @param MAXWV spectral truncation
C> @param KMAX number of fields to transform.
C> @param NMAX number of station points to return
C> @param KWSKIP skip number between wave fields
C> (defaults to (MAXWV+1)*((IROMB+1)*MAXWV+2) if KWSKIP=0)
C> @param KGSKIP skip number between station point sets
C> (defaults to NMAX if KGSKIP=0)
C> @param NRSKIP skip number between station lats and lons
C> (defaults to 1 if NRSKIP=0)
C> @param NGSKIP skip number between station points
c> (defaults to 1 if NGSKIP=0)
C> @param RLAT station latitudes in degrees
C> @param RLON station longitudes in degrees
C> @param WAVE wave fields
C> @param XP station point x-gradient sets
C> @param YP station point y-gradient sets
C>
C> @author Iredell @date 96-02-29
      SUBROUTINE sptgptd(IROMB,MAXWV,KMAX,NMAX,
     &                   KWSKIP,KGSKIP,NRSKIP,NGSKIP,
     &                   RLAT,RLON,WAVE,XP,YP)
 
      REAL RLAT(*),RLON(*),WAVE(*),XP(*),YP(*)
      REAL EPS((MAXWV+1)*((IROMB+1)*MAXWV+2)/2),EPSTOP(MAXWV+1)
      REAL ENN1((MAXWV+1)*((IROMB+1)*MAXWV+2)/2)
      REAL ELONN1((MAXWV+1)*((IROMB+1)*MAXWV+2)/2)
      REAL EON((MAXWV+1)*((IROMB+1)*MAXWV+2)/2),EONTOP(MAXWV+1)
      REAL WD((MAXWV+1)*((IROMB+1)*MAXWV+2)/2*2+1,KMAX)
      REAL WZ((MAXWV+1)*((IROMB+1)*MAXWV+2)/2*2+1,KMAX)
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C  CALCULATE PRELIMINARY CONSTANTS
      CALL spwget(iromb,maxwv,eps,epstop,enn1,elonn1,eon,eontop)
      mx=(maxwv+1)*((iromb+1)*maxwv+2)/2
      mdim=2*mx+1
      kw=kwskip
      IF(kw.EQ.0) kw=2*mx
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C  CALCULATE STATION FIELDS
C$OMP PARALLEL DO PRIVATE(KWS)
      DO k=1,kmax
        kws=(k-1)*kw
        CALL splaplac(iromb,maxwv,enn1,wave(kws+1),wd(1,k),1)
        wz(1:2*mx,k)=0.
      ENDDO
      CALL sptgptv(iromb,maxwv,kmax,nmax,mdim,kgskip,nrskip,ngskip,
     &             rlat,rlon,wd,wz,xp,yp)
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      END