MODULE step
   !!======================================================================
   !!                       ***  MODULE step  ***
   !! Time-stepping    : manager of the ocean, tracer and ice time stepping
   !!                    version for standalone surface scheme
   !!======================================================================
   !! History :  OPA  !  1991-03  (G. Madec)  Original code
   !!             -   !  1991-11  (G. Madec)
   !!             -   !  1992-06  (M. Imbard)  add a first output record
   !!             -   !  1996-04  (G. Madec)  introduction of dynspg
   !!             -   !  1996-04  (M.A. Foujols)  introduction of passive tracer
   !!            8.0  !  1997-06  (G. Madec)  new architecture of call
   !!            8.2  !  1997-06  (G. Madec, M. Imbard, G. Roullet)  free surface
   !!             -   !  1999-02  (G. Madec, N. Grima)  hpg implicit
   !!             -   !  2000-07  (J-M Molines, M. Imbard)  Open Bondary Conditions
   !!   NEMO     1.0  !  2002-06  (G. Madec)  free form, suppress macro-tasking
   !!             -   !  2004-08  (C. Talandier) New trends organization
   !!             -   !  2005-01  (C. Ethe) Add the KPP closure scheme
   !!             -   !  2005-11  (G. Madec)  Reorganisation of tra and dyn calls
   !!             -   !  2006-01  (L. Debreu, C. Mazauric)  Agrif implementation
   !!             -   !  2006-07  (S. Masson)  restart using iom
   !!            3.2  !  2009-02  (G. Madec, R. Benshila)  reintroduicing z*-coordinate
   !!             -   !  2009-06  (S. Masson, G. Madec)  TKE restart compatible with key_cpl
   !!            3.3  !  2010-05  (K. Mogensen, A. Weaver, M. Martin, D. Lea) Assimilation interface
   !!             -   !  2010-10  (C. Ethe, G. Madec) reorganisation of initialisation phase + merge TRC-TRA
   !!            3.4  !  2011-04  (G. Madec, C. Ethe) Merge of dtatem and dtasal
   !!            3.5  !  2012-03  (S. Alderson)
   !!----------------------------------------------------------------------

   !!----------------------------------------------------------------------
   !!   stp             : OPA system time-stepping
   !!----------------------------------------------------------------------
   USE oce              ! ocean dynamics and tracers variables
   USE dom_oce          ! ocean space and time domain variables 
   USE in_out_manager   ! I/O manager
   USE iom              !
   USE lbclnk

   USE daymod           ! calendar                         (day     routine)

   USE sbcmod           ! surface boundary condition       (sbc     routine)
   USE sbcrnf           ! surface boundary condition: runoff variables

   USE eosbn2           ! equation of state                (eos_bn2 routine)

   USE diawri           ! Standard run outputs             (dia_wri routine)
   USE stpctl           ! time stepping control            (stp_ctl routine)
   USE prtctl           ! Print control                    (prt_ctl routine)

   USE timing           ! Timing            

   IMPLICIT NONE
   PRIVATE

   PUBLIC   stp   ! called by opa.F90

   !! * Substitutions
#  include "domzgr_substitute.h90"
#  include "zdfddm_substitute.h90"
   !!----------------------------------------------------------------------
   !! NEMO/OPA 3.3 , NEMO Consortium (2010)
   !! $Id: step.F90 3294 2012-01-28 16:44:18Z rblod $
   !! Software governed by the CeCILL licence     (NEMOGCM/NEMO_CeCILL.txt)
   !!----------------------------------------------------------------------
CONTAINS

#if defined key_agrif
   SUBROUTINE stp( )
      INTEGER             ::   kstp   ! ocean time-step index
#else
   SUBROUTINE stp( kstp )
      INTEGER, INTENT(in) ::   kstp   ! ocean time-step index
#endif
      !!----------------------------------------------------------------------
      !!                     ***  ROUTINE stp  ***
      !!                      
      !! ** Purpose : - Time stepping of OPA (momentum and active tracer eqs.)
      !!              - Time stepping of LIM (dynamic and thermodynamic eqs.)
      !!              - Tme stepping  of TRC (passive tracer eqs.)
      !! 
      !! ** Method  : -1- Update forcings and data  
      !!              -2- Update ocean physics 
      !!              -3- Compute the t and s trends 
      !!              -4- Update t and s 
      !!              -5- Compute the momentum trends
      !!              -6- Update the horizontal velocity
      !!              -7- Compute the diagnostics variables (rd,N2, div,cur,w)
      !!              -8- Outputs and diagnostics
      !!----------------------------------------------------------------------
      INTEGER ::   jk       ! dummy loop indice
      INTEGER ::   indic    ! error indicator if < 0
      !! ---------------------------------------------------------------------

#if defined key_agrif
      kstp = nit000 + Agrif_Nb_Step()
# if defined key_iomput
      IF( Agrif_Nbstepint() == 0 )   CALL iom_swap
# endif   
#endif   
                             indic = 0                    ! reset to no error condition
      IF( kstp /= nit000 )   CALL day( kstp )             ! Calendar (day was already called at nit000 in day_init)
                             CALL iom_setkt( kstp )       ! say to iom that we are at time step kstp

                             CALL sbc    ( kstp )         ! Sea Boundary Condition (including sea-ice)

                             CALL dia_wri( kstp )         ! ocean model: outputs

                             indic = 0
                             CALL stp_ctl( kstp, indic )
      IF( indic < 0      )   THEN
                             CALL ctl_stop( 'step: indic < 0' )
                             CALL dia_wri_state( 'output.abort', kstp )
      ENDIF
      !
      IF( nn_timing == 1 .AND.  kstp == nit000  )   CALL timing_reset
      !
   END SUBROUTINE stp

   !!======================================================================
END MODULE step