!====================== include file "iounit.h" ========================

!     i/o units and related variables

!     taum1disk = disk pointer for tau-1 latitude rows
!     taudisk   = disk pointer for tau   latitude rows
!     taup1disk = disk pointer for tau+1 latitude rows
!     kflds     = disk unit used for two dimensional fields
!     latdisk   = disk units for latitude rows (alternately pointed to
!                by taum1disk, taudisk, and taup1disk)
!     wide_open_mw = logical to indicate that the MW is fully opened.
!              if .true. then jmw = jmt and there are no latitude rows
!              on disk. Instead, they are all in the MW.
!              if .false. then jmw < jmt and all latitude rows are on
!              disk so they must be transferred between the MW and disk.

!     iodoc  = unit for documentation
!     iostab = unit for stability testing
!     iotim  = unit for time means
!     iotim1 = scratch disk (SSD) unit for accumulating time means

!     for the following, a control # < 0 implies that unformatted data
!     will be written to a unit selected by the i/o manager "iomngr.F"
!     and given a hardwired name (grep getunit *.F to see names)
!     and formatted data (to stdout) will be written. if a # > 0 and
!      # <> stdout, only unformatted data will be written.

!     iotavg = control # for tracer averages
!     iotmb  = control # for writing tracer meridional budget.
!     iotrmb = control # for term balances for tracer and momentum
!     ioglen = control # for writing global energetics integrals
!     iovmsf = control # for writing meridional stream function
!     iogyre = control # for writing gyre transport.
!     ioprxz = control # for writing x-z sections from latitudes
!     ioext  = control # for writing external mode (stream function)
!     iodsp  = control # for writing diagnostic surface pressure
!     iotsi  = control # for writing time step integrals
!     ioxbt  = control # for writing time averaged xbt data
!     iozmbc = control # for writing zonal mean surf boundary conditions

!     iotext    = 120 character text string for describing the details
!                 of the next unformatted data record.
!     expnam    = 60 character text string for the experiment name
!     runstamp  = 120 character text string for the run stamp

!     when writing unformatted data records in MOM, each data record is
!     proceeded by a header record which was written as:
!     write(unit) stamp, iotext, expnam
!     where stamp is a 32 character specification of the model date &
!     time corresponding to the time step when the data was written and
!     iotext is a 120 character description of what is in the
!     data record and how it is to be read. expnam is a 60 character
!     experiment name which shows which experiment wrote the data.
!     this makes it easy to decipher any unformatted output from the
!     model by using a program similar to the following:

!      program decifr

!-----------------------------------------------------------------------
!      decipher an unformatted file from MOM by showing the header
!      records. the file needs to copied to file "fort.21"
!-----------------------------------------------------------------------

!      character*32 stamp
!      character*120 iotext
!      character*60 expnam

!      iounit = 21
!      rewind iounit
!      do n=1,100000

!        read the header record

!        read (iounit, end=110) stamp, iotext, expnam
!        write (*,'(1x,a32,1x,a80)') stamp, iotext

!        skip the data record

!        read (iounit)
!      enddo
!110   continue
!      write (*,*) " => end of file on fort.",iounit
!      stop
!      end

!     note: all unformatted diagnostic MOM data is handled this way.
!     to insure that data is read properly, verify that arrays are
!     dimensioned correctly by comparing the listed variables against
!     those in the *.h files. (grep -i -n "variable" *.h) Also, most
!     data from MOM is written IEEE 32bit so it is read directly by
!     most workstations. However, when trying to read these IEEE files
!     on the CRAY, they must be assigned IEEE before being read.
!     Some diagnostic data is averaged over time before being written.
!     In these cases, the time "stamp" refers to the last time step
!     at the end of the averaging period. An averaging interval is
!     also written as part of the data. Averaging periods = zero
!     indicate instantaneous data.

      character iotext*120, expnam*60, runstamp*120
      common /iounit_c/ iotext, expnam, runstamp

      integer taum1disk, taudisk, taup1disk, latdisk, kflds
      integer iodoc, iostab, iotavg, iotmb, iotrmb, iotim, iotim1
      integer ioglen, iovmsf, iogyre, ioprxz, ioext, iodsp
      integer iotsi, iozmbc, ioxbt

      common /iounit_i/ taum1disk, taudisk, taup1disk, latdisk(2), kflds
      common /iounit_i/ iodoc, iostab, iotavg, iotmb, iotrmb, iotim
      common /iounit_i/ iotim1, ioglen, iovmsf, iogyre, ioprxz, ioext
      common /iounit_i/ iodsp, iotsi, iozmbc, ioxbt

      logical wide_open_mw
      common /iounit_l/ wide_open_mw