CALL SEQUENCE...
       delhat  PSFIL DHFIL INPUT OUTPUT [ -plv VAL1 -def [DEFLEVS][FREEFMT] ]
 
 
      DESCRIPTION...
       delhat - COMPUTES THE FUNCION DELTA-HAT FOR ALL PRESSURE LEVELS
 
 
      AUTHOR  - J.D.Henderson, JUL 08/80.
      LAST REVISION: $Header: Correction-au-mode-DEFLEVS-et-autres-trucs-divers @ 2019-04-15 09:48:36 -0400 (dugas) $
 
 
      PURPOSE - COMPUTES THE FUNCTION DELTA-HAT FOR A FILE OF SURFACE 
                PRESSURE GRIDS (ONE SET FOR EACH PRESSURE GRID)
 
      NOTES   - 1) PRESSURE VALUES ARE READ FROM STDIN
                2) DELTA-HAT IS 1.0 ABOVE THE SURFACE AND 0.0 BELOW IT
                3) THE MAXIMUM NUMBER OF LEVELS IS SET TO 999
 
 
      INPUT FILE...
       PSFIL = INPUT SERIES OF SURFACE PRESSURE GRIDS (MB).
 
      OUTPUT FILE...
       DHFIL = DELTA-HAT AT REQUESTED PRESSURE LEVELS FOR EACH
               PRESSURE GRID IN PSFIL.
 
 
      INPUT PARAMETERS...
 
       NLEV (plv) = NUMBER OF REQUESTED PRESSURE LEVELS (DEF 16, MAX 999).
                    IF NLEV IS NEGATIVE, EACH -NLEV LEV VALUES ARE READ WITH
                    EITHER A I10 FORMAT OR AN E10.0 DEPENDING ON WETHER ANY
                    OF THESE VALUES CONTAINS A DECIMAL POINT. INTEGER VALUES
                    ARE THEN ASSUMED TO BE ENCODED (via LVCODE or CONVIP)
 
       LEV        = VALUES OF THE PRESSURE IN MILLIBARS AS CODED 
                    BY ROUTINE LVCODE. THE DEFAULTS ARE SPECIFIED
                    IN THE EXAMPLE BELOW.
 
       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 when
                 the "-def" (or "-def DEFLEVS") defaults processing
                 mode is requested. Any "-plv" value is also ignored.
              3) Specifying "-def FREEFMT" indicates that the output pressure
                 levels should read with a list-directed free format. This
                 is obviously not the default behaviour. Pressure 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 pressure values,
                 and not their possibly encoded integer values. Turning
                 on the "FREE_FORMAT_LEVEL_IO" environment variable will
                 also activate this behaviour.
 
       READ( 5,5010 )  NLEV
       IF (FREEFMT)      READ( 5,* )    ( PR(I),I=1,ABS(NPL))
       ELSEIF (NLEV > 0) READ( 5,5020 ) (LEV(I),I=1,    NPL)
       ELSEIF (NLEV < 0) READ( 5,5030 ) (LEV(I),I=1,   -NPL)
 5010  FORMAT(10X,I5)
 5020  FORMAT(16I5)
 5030  FORMAT(8E10.0)
 
 
      EXAMPLE OF INPUT CARDS (with format 5010 & 5020)...
 
    DELHAT   16
   10   20   30   50   70  100  150  200  250  300  400  500  700  850  925 1000
 
         01234567890123456789012345678901234567890123456789012345678901234567890
         1         2         3         4         5         6         7
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 TOO MANY OR NOT ENOUGH REQUIRED LEVELS
        2 PRESSURE LEVELS DO NOT VARY MONOTONICALLY
        3 PREMATURE EOF ON FILE PSFC
        4 ERROR READING FIRST LINE INPUT PARAMETERS
        5 ERROR READING SECOND LINE INPUT PARAMETERS
        6 LEV DOES NOT CONTAIN PRESSURE DATA
        7 UNRECOGNIZED -DEF ARGUMENT VALUE