CALL SEQUENCE...
       zoncov  GGIN1 GGIN2 ZXC OUTPUT [ -def ] [-lat VAL1 -name VAL2]
       zonvar  GGIN1 ZXV       OUTPUT [ -def ] [-lat VAL1]
 
 
      DESCRIPTION...
       zoncov - COMPUTES ZONAL COVARIANCES OF TWO GRID SETS
       zonvar - COMPUTES ZONAL VARIANCES OF A GRID SET 
  
 
      AUTHOR  - J.D.Henderson, NOV 5/80.
      LAST REVISION: $Header: /home/cvs/RMNLIB/utils/rdiag/lspgm/zoncov.ptn,v 4.17 2014/09/25 20:20:56 dugas Exp $
 
  
      PURPOSE - COMPUTES A SET OF CROSS-SECTIONS CONTAINING THE ZONAL 
                VARIANCE/COVARIANCE OF THE ONE OR TWO INPUT MULTI-LEVEL
                GRID FILES.
 
      NOTES   - 1) The grid files do not have to be pre-processed by
                   ZONDEV. ZONCOV/ZONVAR can remove the zonal means
                   from input files when the "-def" key is specified.
                2) By default, when GGIN1 and GGIN2 contain different
                   variables, the output variable name is set to "COV".
                   this behavior can be overwritten by using the "-name"
                   command-line parametre to specify an altername name.
                3) The maximum number of levels is 999.
                4) For complex fields, the following will be performed:
                >> ZONAVG( GGIN1 * COMPLEX CONJUGATE( GGIN2 ) ) << or
                >> ZONAVG( GGIN1 * COMPLEX CONJUGATE( GGIN1 ) ) <<,
                   depending on which of ZONCOV or ZONVAR was invoked.
  
 
      INPUT FILES...  
       GGIN1  = FIRST SET OF MULTI-LEVEL GRIDS. 
       GGIN2  = SECOND SET OF MULTI-LEVEL GRIDS. 
  
      OUTPUT FILE... 
       ZXC    = CORRESPONDING SERIES OF ZONAL COVARIANCES.
       ZXV    = CORRESPONDING SERIES OF ZONAL VARIANCES.
 
 
      MISSING VALUE TREATMENT IS SUPPORTED VIA EITHER THE "MISSING_VALUE"
      ENVIRONMENT VARIABLE OR THE "-mvalue" COMMAND-LINE ARGUMENT. PLEASE
      SEE THE R.DIAG WEB DOCUMENTAION FOR MORE DETAILS.
 
 
      (OPTIONAL) PARAMETRE (ONLY USED WITH GEM Z-TYPE INPUT GRIDS) ...
 
       LAT  = NUMBER OF LATITUDES IN THE OUTPUT ZONAL CROSS-SECTIONS.
              DEFAULTS TO THE MINIMUM OF THE TWO HORIZONTAL DIMENSIONS
              OF THE INPUT FIELDS.
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 PROBLEM WITH INPUT FILES
        2 FOUND INPUT TYPE OTHER THAN 'GRID' OR 'CMPL' IN FILE GGIN1
        3 PREMATURE EOF ON FILE GGIN1
        4 MORE THAN ONE SIZE IN FILE GGIN1
        5 MISSING RECORD IN FILE GGIN2
        6 CORRESPONDING RECORDS NOT THE SAME SIZE
        7 ERROR READING INPUT PARAMETRE
        8 OPERATING/INPUT MODE MITMATCH