sptran.f File Reference

Perform a scalar spherical transform. More...

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Functions/Subroutines
subroutine	sptran (IROMB, MAXWV, IDRT, IMAX, JMAX, KMAX, IPRIME, ISKIP, JNSKIP, JSSKIP, KWSKIP, KGSKIP, JBEG, JEND, JCPU, WAVE, GRIDN, GRIDS, IDIR)
	This subprogram performs a spherical transform between spectral coefficients of scalar quantities and fields on a global cylindrical grid. More...

Detailed Description

Perform a scalar spherical transform.

Program History Log

Date	Programmer	Comments
96-02-29	IREDELL	Initial
1998-12-15	IREDELL	Generic fft used, openmp directives inserted

Author

IREDELL

Date

96-02-29

Definition in file sptran.f.

Function/Subroutine Documentation

sptran()

subroutine sptran	(		IROMB,
			MAXWV,
			IDRT,
			IMAX,
			JMAX,
			KMAX,
			IPRIME,
			ISKIP,
			JNSKIP,
			JSSKIP,
			KWSKIP,
			KGSKIP,
			JBEG,
			JEND,
			JCPU,
		real, dimension(*)	WAVE,
		real, dimension(*)	GRIDN,
		real, dimension(*)	GRIDS,
			IDIR
	)

This subprogram performs a spherical transform between spectral coefficients of scalar quantities and fields on a global cylindrical 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 wave and grid fields may have general indexing, but each wave field is in sequential 'IBM order', i.e. with zonal wavenumber as the slower index.

Transforms are done in latitude pairs for efficiency; thus grid arrays for each hemisphere must be passed. If so requested, just a subset of the latitude pairs may be transformed in each invocation of the subprogram.

The transforms are all multiprocessed over latitude except the transform from Fourier to spectral is multiprocessed over zonal wavenumber to ensure reproducibility.

Transform several fields at a time to improve vectorization. Subprogram can be called from a multiprocessing environment.

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

Parameters

	IROMB	spectral domain shape (0 for triangular, 1 for rhomboidal)
	MAXWV	spectral truncation
	IDRT	grid identifier IDRT=4 for Gaussian grid, IDRT=0 for equally-spaced grid including poles, IDRT=256 for equally-spaced grid excluding poles
	IMAX	even number of longitudes.
	JMAX	number of latitudes.
	KMAX	number of fields to transform.
	IPRIME	longitude index for the prime meridian. (defaults to 1 if IPRIME=0)
	ISKIP	skip number between longitudes (defaults to 1 if ISKIP=0)
	JNSKIP	skip number between n.h. latitudes from north (defaults to imax if JNSKIP=0)
	JSSKIP	skip number between s.h. latitudes from south (defaults to -imax if JSSKIP=0)
	KWSKIP	skip number between wave fields (defaults to (MAXWV+1)*((IROMB+1)*MAXWV+2) IF KWSKIP=0)
	KGSKIP	skip number between grid fields (defaults to IMAX*JMAX IF KGSKIP=0)
	JBEG	latitude index (from pole) to begin transform (defaults to 1 if JBEG=0) (if JBEG=0 and IDIR<0, wave is zeroed before transform)
	JEND	latitude index (from pole) to end transform (defaults to (JMAX+1)/2 IF JEND=0)
	JCPU	number of cpus over which to multiprocess
[out]	WAVE	wave fields if IDIR>0
[out]	gridn	n.h. grid fields (starting at jbeg) if IDIR<0
[out]	grids	s.h. grid fields (starting at jbeg) if IDIR<0
	IDIR	transform flag (idir>0 for wave to grid, idir<0 for grid to wave)

Author

IREDELL

Date

96-02-29

Definition at line 84 of file sptran.f.

References ncpus(), and sptranf().

Referenced by sptrun(), sptrund(), sptrung(), sptrunl(), sptrunm(), sptruns(), and sptrunv().