W3FT39

The W3FT39 routine computes 2.5 x 2.5 N. HEMI. grid of
           145 x 37 points from spectral coefficients in a 
           Rhomboidal 30 resolution representing a vector field.

USAGE:  CALL W3FT39(VLN,GN,PLN,FL,WORK,TRIGS,RCOS)

   Input variables:
      VLN    ARG LIST  992 COMPLEX COEFF.
      PLN    ARG LIST  (32,31,37) REAL SPACE WITH LEGENDRE POLYNOMIALS
                       COMPUTED BY W3FA12.
      FL     ARG LIST  31 COMPLEX SPACE FOR FOURIER COEFF.
      WORK   ARG LIST  144 WORK SPACE FOR SUBR. W3FT12
      TRIGS  ARG LIST  216 PRECOMPUTED TRIG FUNCS. USED
                       IN W3FT12, COMPUTED BY W3FA13
      RCOS   ARG LIST  37 RECIPROCAL COSINE LATITUDES OF
                       2.5 X 2.5 GRID MUST BE COMPUTED BEFORE
                       FIRST CALL TO W3FT11 USING SR W3FA13.
 
    Output variables:
      GN     ARG LIST  (145,37) GRID VALUES.
                       5365 POINT GRID IS TYPE 29 OR 1D O.N. 84

REMARKS:
    W3FT09 WAS OPTIMIZED TO RUN IN A SMALL AMOUNT OF
    MEMORY, IT WAS NOT OPTIMIZED FOR SPEED, 70 PERCENT OF THE TIME WAS
    USED BY SUBROUTINE W3FA12 COMPUTING THE LEGENDRE POLYNOMIALS. SINCE
    THE LEGENDRE POLYNOMIALS ARE CONSTANT THEY NEED TO BE COMPUTED
    ONLY ONCE IN A PROGRAM. BY MOVING W3FA12 TO THE MAIN PROGRAM AND
    COMPUTING PLN AS A (32,31,37) ARRAY AND CHANGING THIS SUBROUTINE
    TO USE PLN AS A THREE DIMENSION ARRAY THE RUNNING TIME WAS CUT
    70 PERCENT. ADD FOLLOWING CODE TO MAIN PROGRAM TO COMPUTE EPS, PLN,
    TRIGS, AND RCOS ONE TIME IN PROGRAM.

 
W3lib.tar Library contains Fortran 90 decoder/encoder routines for GRIB edition 1. (Fortran90)
Date posted: 2/22/2007