CALL SEQUENCE...
       grset  GG INPUT OUTPUT \ 
           [ -n   VAL1  -name VAL2  -plv  VAL3  -lon  VAL4  \ 
             -lat VAL5  -npg  VAL6  -a    VAL7  -b    VAL8  \ 
             -c   VAL9  -d    VAL10 -delt VAL11 -kind VAL12 \ 
             -t1  VAL13 VAL14 -lv1  VAL15 [ VAL16 [ VAL17 ] ] \ 
             -def [DEFLEVS][FREEFMT][LASTSTEP] ]
 
 
      DESCRIPTION...
       CGRSET   - CREATES A GAUSSIAN GRID FIELD FOR TESTING PURPOSES
 
 
      AUTHOR  - R.LAPRISE, CCC  MAY 11/83.
      LAST REVISION: $Header: Correction-au-mode-DEFLEVS-et-autres-trucs-divers @ 2019-04-15 09:48:36 -0400 (dugas) $
 
 
      PURPOSE - CREATES A FILE, GG, CONTAINING NSETS OF ILEV LEVELS OF GRID
                OF SIZE (ILG,ILAT). FIELDS ARE SET BY THIS EQUATION...
                GG(T,LON,LAT,P) =
                    A + B*P + (C+D*P)*(SIN(2PI*T/NSETS)+2.*SIN(LON))*COS(LAT)
                WHERE T   = 1,NSTEPS
                      LON = 1,ILG
                      LAT = 1,ILA
                      P   = LVL(1), ... , LVL(ILEV)
 
 
      OUTPUT FILE...
       GG = OUTPUT SETS OF MULTI OR SINGLE LEVEL GRIDS
 
 
      INPUT PARAMETERS...
 
       NSETS (n)   = NUMBER OF INDIVIDUAL TIMESTEPS (DEF=1).
       DELT        = TIME DELTA BETWEEN SAMPLES IN SECONDS (DEF=0).
                     THIS ARGUMENT IS ALWAYS LESS THAN 99999 AND CAN
                     ONLY BE SET VIA THE COMMAND LINEY.
       DATEO (t1/t2) = INITIAL TIME (DEF=19790101/00). THESE TWO NUMBERS
                     STAND FOR YYYYMMDD AND HHMMSS. AGAIN, THEY CAN
                     ONLY BE SET VIA THE COMMAND LINE.
       NAME        = NAME ASSIGNED TO THE SET LABEL (DEF='DATA').
       ILEV  (plv) = NUMBER OF PRESSURE LEVELS IN SETS (DEF=16;MAX=999)
                     IF ILEV IS NEGATIVE, EACH -ILEV LVL VALUES ARE READ WITH
                     A I10 FORMAT OR AN E10.0 IF ITS VALUE CONTAINS A DECIMAL
                     POINT.
       ILG   (lon) = NUMBER OF DISTINCT LONGITUDE POINTS (DEF=128).
       ILAT  (lat) = NUMBER OF GAUSSIAN LATITUDES POINTS (DEF=64).
       NPACK (npg) = PACKING DENSITY DESIRED. NEGATIVE PACKING SUPPORTED
                     AND THE DEFAULT IS NO PACKING (DEF=-32).
       A,B,C,D     = PARAMETERS USED TO CALCULATE VALUES ON THE GRID (DEF=1.0).
       KIND        = VERTICAL LEVEL TYPE. IT CAN ONLY BE USED WITH CMC/RPN STD
                     FILES AND THEN LV1 AND LV2 ARE ASSUMED TO CONTAIN DECODED
                     VALUES. FURTHERMORE, THIS PARAMETRE CAN ONLY BE SPECIFIED
                     IN COMMAND-LINE MODE. THE CURRENTLY SUPPORTED VALUES ARE:
                     'HAUTEUR'   , heights (m) with respect to sea level
                     'SIGMA'     , classical terrain following (0.0 -> 1.0)
                     'ETA'       , first version of the GEM ETA coordinate
                     'PRESSION'  , pressure (mb) (*** DEFAULT ***)
                     'ARBITRAIRE', arbitrary level (no units apply)
                     'HAUTEURS'  , heights (M) with respect to the surface
                     'HYBRIDE'   , hybrid GEM coordinate
                     'THETA'     , potential temperature coordinate
                     'GALCHEN'   , GalChen generalized coordinate
       LVL   (lv1) = ARRAY OF VERTICAL LEVELS TO BE USED IN IBUF(4) (DEF=500).
 
       Notes: 1) The first input line is NOT read if any command-line
                 parameters are passed.
              2) Furthermore, the second line will not be read either
                 if the -def command-line argument is specied by itself
                 or with the 'DEFLEVS' value, as this activates a default
                 level values processing mode. These defaults are then 
                 as specified in the example below and ILEV is also
                 reset to 16, for consistency.
              3) Specifying '-def FREEFMT' indicates that the output model
                 levels should read with a list-directed free format. This
                 is obviously not the default behaviour. Level values should
                 then only be separated by spaces or comas, and spread over
                 one or more lines. These numbers are then always assumed
                 to be the actual real model levels, and not their possibly
                 encoded integer values.
                 Turning on the "FREE_FORMAT_LEVEL_IO" environment
                 variable will also activate this behaviour.
              4) Specifying '-def LASTSTEP' indicates that only the last
                 timestep will be processed
              5) Finally, the -def level-related parameters will all
                 ignored if any level values are specified via the
                 '-lv1' parameter.
 
       READ( 5,5010 ) NSETS,NAME,ILEV,ILG,ILAT,NPACK,A,B,C,D
 
       IF (FREEFMT)      READ( 5,* )    (ETA(I),I=1,ABS(ILEV))
       IF (ILEV.GT.0)    READ( 5,5020 ) (LVL(I),I=1,ILEV)
       IF (ILEV.LT.0)    READ( 5,5030 ) (LVL(I),I=1,-ILEV)
 5010  FORMAT(10X,I5,1X,A4,4I5,4E10.0)
 5020  FORMAT(16I5)
 5030  FORMAT(8I10)
 
 
      EXAMPLE OF INPUT CARDS (with format 5020 & 5030)...
 
  GRSET      10 TEMP   16  100   50  -16      273.      -10.       10.        1.
   10   20   30   50   70  100  150  200  250  300  400  500  700  850  925 1000
 
         0123456789012345678901234567890123456789012345678901234567890
         1         2         3         4         5         6         7
 
   (THIS WILL PRODUCE 10 SETS OF 16 LEVEL 100X50 GRIDS WITH NAME 'TEMP')
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 ERROR ABORT READING INPUT CARD 1
        2 ERROR ABORT READING OUTPUT LEVELS
        3 UNSUPPORTED DEFAULT
        4 MORE THAN ONE LEVEL TYPE
        5 CODED LVL DATA IS NOT CONSISTENT WITH KIND
        6 UNRECOGNIZED -DEF ARGUMENT VALUE
        7 KIND MUST DE DEFINED WHEN REAL OUTPUT LEVELS ARE SPECIFIED