W3FT21

The W3FT21 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 scalar field.

USAGE:  CALL W3FT21(FLN,GN,PLN,EPS,FL,WORK,TRIGS,L1,L2,I2)

   Input variables:
      FLN        961 COMPLEX COEFF.
      PLN        992 REAL SPACE FOR LEGENDRE POLYNOMIALS
      EPS        992 REAL SPACE FOR COEFFS. USED IN COMPUTING PLN.
      FL         31 COMPLEX SPACE FOR FOURIER COEFF.
      WORK       144 REAL WORK SPACE FOR SUBR. W3FT12
      TRIGS      216 PRECOMPUTED TRIG FUNCS,  USED
                 IN W3FT12, COMPUTED BY W3FA13
      L1         STARTING WAVE NUMBER
      L2         ENDING WAVE NUMBER
      I2         MODE OF SPECTRAL COEFFICIENTS
 
   Output variables:
      GN         (145,37) GRID VALUES.
                 5365 POINT GRID IS TYPE 29 OR 1D HEX O.N. 84

REMARKS:
        THIS SUBROUTINE WAS OPTIMIZED TO RUN IN A SMALL AMOUNT OF
        MEMORY, IT IS NOT OPTIMIZED FOR SPEED, 70 PERCENT OF THE TIME IS
        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 YOU CAN CUT THE RUNNING
        TIME 70 PERCENT.

 


  
W3lib.tar
  
Library contains Fortran 90 decoder/encoder
   routines for GRIB edition 1. (Fortran90) 

   Date posted: 2/22/2007