 
      CALL SEQUENCE...
       pgen  XIN POUT [LNSP] OUTPUT \ 
             [-kind VAL0 -a VAL1 -d VAL2 -i VAL3 -def [VAL4] ]
 
 
      DESCRIPTION...
       pgen   - CREATES A FILE WITH VALUES SET EQUAL TO PRESSURE LEVEL
 
 
      AUTHOR  - B.Dugas, NOV 29/83.
      LAST REVISION: $Header: /data/armnraid1/cvs/RMNLIB/utils/rdiag/lspgm/pgen.ptn,v 4.15 2012/05/17 21:12:51 dugas Exp $
 
 
      PURPOSE - GENERATES A FILE WHOSE VALUES ARE SET TO THE PRESSURE 
                LEVEL VALUE FOUND IN IBUF(4).
 
      NOTES     1) FOR SPECTRAL TYPE FILES, ONLY THE REAL PART OF
                   THE (0,0) COEFFICIENT RECORD VALUES IS SET.
                2) FOR CMPL TYPE FILES, ONLY THE REAL PART OF 
                   EACH WORD IS SET.
 
 
      INPUT FILE...
       XIN  = FILE CONTAINING RECORDS AT PRESSURE LEVEL(S), IT CAN BE
              OF TYPE SPECTRAL, ZONAL CROSS-SECTIONS, COMPLEX ARRAYS
              OR GAUSSIAN GRID(S).
       LNSP = (OPTIONAL) LOG OF SURFACE PRESSURE FIELD USED BY THE TERRAIN
              FOLLOWING COORDINATES TO DETERMINE THE LOCAL PRESSURE.
 
      OUTPUT FILE...
       POUT = FILE OF THE SAME TYPE AS XIN WITH THE VALUE(S) OF EACH RECORD
              SET EQUAL TO THE LOCAL PRESSURE VALUES (IN MB). THIS DATA IS
              FOUND IN IBUF(4) WHEN THE VERTICAL COORDINATE IS ITSELF
              PRESSURE. 
 
 
      COMMAND-LINE PARAMETERS...
 
       KIND      = INPUT VERTICAL COORDINATE: POSSIBLE OPTIONS ARE
                  'PRES'/'ETA' FOR PRESSURE/GCM-ETA AND 'GEM'/'GEM2'/
                  'GEM3' FOR DIFFERENT VERSIONS OF THE GEM COORDINATE.
       PTOIT (a) = PRESSURE (PA) AT THE LID OF MODEL. THE DEFAULT VALUE
                   IS 0.01 OTHERWISE. THIS VALUE IS ONLY REQUIRED WITH
                   THE CCCma GCM VERTICAL COORDINATES.
 
       The next two parametres are only used when COORD='GEM2' or 'GEM3'.
 
       PREF  (d) = REF PRESSURE (DEF 80000 PA).
       R     (i) = REFERENCE EXPONENT (DEF 1.0)
 
 
 
      NOTES: 1) THE PROGRAM REQUIRES THAT DATA TYPES BE EITHER OF 'GRID',
                'SUBA' OR 'ZONL' WHEN OPERATING WITH ANY OF THE TERRAIN
                FOLLOWING VERTICAL COORDINATES. THE OTHER TYPES OF DATA
                ARE ONLY SUPPORTED WITH PRESSURE VERTICAL COORDINATES.
             2) 'GEM' IS THE ORIGINAL GEM ETA COORDINATE, WHILE 'GEM2' IS
                THE FIRST GEM HYBRID COORDINATE AS IMPLEMENTED BY EDOUARD
                & GRAVEL IN GEM/DM V2.2.0. 'GEM3' IS THE NORMALIZED VERSION
                THAT WAS IMPLEMENTED IN THE V2.3.1 GEM/DM.
             3) THE DEFAULT VALUE OF COORD IS DETERMINED BY THE FILE TYPE
                AND THE PROGRAM WILL ALSO TRY TO DETERMINE IT BY THE
                (INTERNAL) CODING USED FOR THE COORDINATE ITSELF.
             4) Specifying "-def AABB" will force the attempt to read
                a text file called aabb.nml, containing a FORTRAN
                namelist AABB_NML, which in turns will hold two arrays,
                A and B such that the local pressure at level K, PL(K),
                can be calculated as "A(K)+B(K)*PS". This then by-passes
                all of the normal COORD-related calculations for PL(K).
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 UNABLE TO READ XIN
        2 MORE THAN ONE SIZE IN XIN
        3 UNKNOWN DATA TYPE
        4 ILLEGAL "KIND" VALUE
        5 LNSP FILE MISSING OR EMPTY
        6 LNSP AND XIN NOT THE SAME SIZE
        7 UNABLE TO CONTINUE (SEE NOTE 1)
        8 PROBLEM READING PARAMETRES
        9 UNSUPPORTED VERTICAL COORDINATE IN XIN
       10 KIND PARAMETRE AND XIN DATA MISMATCH
       11 UNABLE TO READ AABB NAMELIST
       12 LNSP DOES NOT CONTAIN LN(SURFACE PRESSURES) FOR EARTH
