CALL SEQUENCE...
       zxpsi  ZXIN ZXOUT OUTPUT
 
 
      DESCRIPTION...
       zxpsi  - COMPUTES MERIDIONAL STREAM-FUNCTION FROM CROSS-SECTION.
 
 
      AUTHOR  - J.D.Henderson, NOV 1980.
      LAST REVISION: $Header: /home/cvs/RMNLIB/utils/rdiag/lspgm/zxpsi.ptn,v 4.15 2014/09/25 20:20:57 dugas Exp $
 
 
      PURPOSE - COMPUTES CROSS-SECTION OF MERIDIONAL STREAM FUNCTION FROM 
                CROSS-SECTIONS OF V WIND COMPONENT OR FIELDS OF  VERTICAL 
                MOTIONS.
 
 
      INPUT FILE... 
       ZXIN  = CONTAINS CROSS-SECTION DATA ON PRESSURE LEVELS
 
      OUTPUT FILE... 
       ZXOUT = THE MERIDIONAL STREAM FUNCTION CROSS-SECTIONS
 
 
      EXIT CONDITIONS...
        0 NO PROBLEMS
        1 ZXIN CONTAINS NON-ZONAL INPUT
        2 PREMATURE EOF ON ZXIN
        3 MORE THAN ONE SIZE
        4 UNABLE TO READ ZXIN
        5 LEVELS DO NOT VARY MONOTONICALLY
        6 ZXIN NOT ON PRESSURE LEVELS