CALL SEQUENCE...
       zonavg  GGIN ZMOUT OUTPUT       [ -lat VAL1 ]
       zonvavg UIN VIN ZU ZV OUTPUT    [ -lat VAL1 ]
       rzonavg GGIN D ZMOUT OUTPUT     [ -lat VAL1 ]
       rzonvavg UIN VIN D ZU ZV OUTPUT [ -lat VAL1 ]
 
      DESCRIPTION...
       zonavg   - COMPUTES MULTI-LEVEL ZONAL AVERAGE OF A SET OF GRIDS 
       zonvavg  - COMPUTES MULTI-LEVEL ZONAL AVERAGE OF A SET OF WINDS
       rzonavg  - COMPUTES MULTI-LEVEL representative ZONAL AVERAGE OF A SET OF GRIDS 
       rzonvavg - COMPUTES MULTI-LEVEL representative ZONAL AVERAGE OF A SET OF WINDS
  
 
      AUTHOR  - J.D.Henderson, FEB 18/80.
      LAST REVISION: $Header: /home/cvs/RMNLIB/utils/rdiag/lspgm/zonavg.ptn,v 4.17 2014/09/25 20:20:56 dugas Exp $
 
  
      PURPOSE - COMPUTES A VECTOR OF ZONAL MEANS FOR EACH GRID AND SAVES 
                THEM ON FILE ZMOUT. 
 
      NOTES:  1) EACH ZMOUT RECORD IS A VECTOR OF LATITUDINAL AVERAGES 
                 RUNNING SOUTH TO NORTH. MAXIMUM NUMBER OF LEVELS IS 999.
              2) zonvavg PERFORMS WIND ROTATIONS AS NEEDED. IF NO SUCH
                 OPERATION IS REQUIRED, ZONAVG CAN BE USED INSTEAD.
              3) FURTHERMORE, IF ggvecz HAS ALLREADY BEEN APPLIED TO THE
                 VECTOR COMPONENTS, zonvavg SHOULD **NOT** BE USED, AS
                 THE RESULT WILL BE IN ERROR. PLEASE USE zonavg IN
                 THOSE CIRCUMSTANCES.
              4) The representative zonavg RZ(X) of X is defined as
                 RZ(X) = Z(D*X) / Z(D),  IF Z(D).NE.0.,
                       = Z(X)         ,  IF Z(D).EQ.0.
                 where Z(X) is the usual zonal average.
 
  
      INPUT FILE (zonavg and rzonavg) ... 
       GGIN  = (REAL OR COMPLEX) GRIDS TO BE ZONALLY AVERAGED. 
 
      INPUT FILES (zonvavg and rzonvavg) ... 
       UIN   = REAL U WIND COMPONENT TO BE ZONALLY AVERAGED. 
       VIN   = REAL V WIND COMPONENT TO BE ZONALLY AVERAGED. 
  
      OUTPUT FILE (zonavg and rzonavg) ... 
       ZMOUT = ZONAL AVERAGES OF EACH GRID IN GGIN. 
 
      OUTPUT FILES (zonvavg and rzonvavg) ... 
       ZU    = ZONAL AVERAGES OF THE ZONAL WIND COMPONENTS.
       ZV    = ZONAL AVERAGES OF THE MERIDIONAL WIND COMPONENTS.
 
      AND (rzonavg and rzonvavg)...
       D     = REAL topographic MASK (FROM 0 BELOW GROUND TO 1 ABOVE)
 
 
      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. This option is
      exclusive to the representative zonal averages option.
 
 
      (OPTIONAL) PARAMETRE (ONLY 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 PROBLEMS READING GGIN OR UIN
        2 FOUND INPUT TYPE OTHER THAN 'GRID','SUBA' OR 'CMPL'
        3 PREMATURE EOF ON FILE GGIN
        4 MORE THAN ONE SIZE IN INPUT FILE
        5 ERROR READING INPUT PARAMETRE
        6 PROBLEMS READING VIN
        7 UIN AND VIN NOT THE SAME SIZE
        8 OPERATING/INPUT MODE MITMATCH
        9 PROBLEM READING DELTA FILE
       10 NO D "mask"PROCESSING WITH -mvalue