i4dvar_roms.h

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      MODULE roms_kernel_mod
!
!git $Id$
!================================================== Hernan G. Arango ===
!  Copyright (c) 2002-2025 The ROMS Group            Andrew M. Moore   !
!    Licensed under a MIT/X style license                              !
!    See License_ROMS.md                                               !
!=======================================================================
!                                                                      !
!  ROMS Strong Constraint 4-Dimensional Variational Data Assimilation  !
!              Driver, Incremental Approach (I4D-Var)                  !
!                                                                      !
!  This driver is used for the primal formulation (model space) strong !
!  constraint, incremental 4D-Var where the only errors considered are !
!  those for the observations. The model is assumed to be perfect.     !
!                                                                      !
!  The routines in this driver control the initialization,  time-      !
!  stepping, and finalization of ROMS  model following ESMF/NUOPC      !
!  conventions:                                                        !
!                                                                      !
!     ROMS_initialize                                                  !
!     ROMS_run                                                         !
!     ROMS_finalize                                                    !
!                                                                      !
!  References:                                                         !
!                                                                      !
!    Moore, A.M., H.G. Arango, G. Broquet, B.S. Powell, A.T. Weaver,   !
!      and J. Zavala-Garay, 2011: The Regional Ocean Modeling System   !
!      (ROMS)  4-dimensional variational data assimilations systems,   !
!      Part I - System overview and formulation, Prog. Oceanogr., 91,  !
!      34-49, doi:10.1016/j.pocean.2011.05.004.                        !
!                                                                      !
!    Moore, A.M., H.G. Arango, G. Broquet, C. Edward, M. Veneziani,    !
!      B. Powell, D. Foley, J.D. Doyle, D. Costa, and P. Robinson,     !
!      2011: The Regional Ocean Modeling System (ROMS) 4-dimensional   !
!      variational data assimilations systems, Part II - Performance   !
!      and application to the California Current System, Prog.         !
!      Oceanogr., 91, 50-73, doi:10.1016/j.pocean.2011.05.003.         !
!                                                                      !
!=======================================================================
!
      USE mod_param
      USE mod_parallel
      USE mod_arrays
      USE mod_fourdvar
      USE mod_iounits
      USE mod_ncparam
      USE mod_scalars
      USE mod_stepping
!
      USE i4dvar_mod
!
      USE close_io_mod,      ONLY : close_inp, close_out
      USE def_dai_mod,       ONLY : def_dai
      USE inp_par_mod,       ONLY : inp_par
#ifdef MCT_LIB
# ifdef ATM_COUPLING
      USE mct_coupler_mod,   ONLY : initialize_ocn2atm_coupling
# endif
# ifdef WAV_COUPLING
      USE mct_coupler_mod,   ONLY : initialize_ocn2wav_coupling
# endif
#endif
      USE stats_modobs_mod,  ONLY : stats_modobs
      USE stdout_mod,        ONLY : set_stdoutunit, stdout_unit
      USE strings_mod,       ONLY : founderror
      USE wrt_dai_mod,       ONLY : wrt_dai
      USE wrt_rst_mod,       ONLY : wrt_rst
!
      implicit none
!
      PUBLIC  :: roms_initialize
      PUBLIC  :: roms_run
      PUBLIC  :: roms_finalize
!
      CONTAINS
!
      SUBROUTINE roms_initialize (first, mpiCOMM)
!
!=======================================================================
!                                                                      !
!  This routine allocates and initializes ROMS state variables and     !
!  and internal parameters. It reads standard input parameters.        !
!                                                                      !
!=======================================================================
!
!  Imported variable declarations.
!
      logical, intent(inout) :: first
!
      integer, intent(in), optional :: mpiCOMM
!
!  Local variable declarations.
!
      logical :: allocate_vars = .true.
!
#ifdef DISTRIBUTE
      integer :: MyError, MySize
#endif
      integer :: chunk_size, ng, thread
#ifdef _OPENMP
      integer :: my_threadnum
#endif
!
      character (len=*), parameter :: MyFile =                          &
     &  __FILE__//", ROMS_initialize"
 
#ifdef DISTRIBUTE
!
!-----------------------------------------------------------------------
!  Set distribute-memory (mpi) world communictor.
!-----------------------------------------------------------------------
!
      IF (PRESENT(mpicomm)) THEN
        ocn_comm_world=mpicomm
      ELSE
        ocn_comm_world=mpi_comm_world
      END IF
      CALL mpi_comm_rank (ocn_comm_world, myrank, myerror)
      CALL mpi_comm_size (ocn_comm_world, mysize, myerror)
#endif
!
!-----------------------------------------------------------------------
!  On first pass, initialize model parameters a variables for all
!  nested/composed grids.  Notice that the logical switch "first"
!  is used to allow multiple calls to this routine during ensemble
!  configurations.
!-----------------------------------------------------------------------
!
      IF (first) THEN
        first=.false.
!
!  Initialize parallel control switches. These scalars switches are
!  independent from standard input parameters.
!
        CALL initialize_parallel
!
!  Set the ROMS standard output unit to write verbose execution info.
!  Notice that the default standard out unit in Fortran is 6.
!
!  In some applications like coupling or disjointed mpi-communications,
!  it is advantageous to write standard output to a specific filename
!  instead of the default Fortran standard output unit 6. If that is
!  the case, it opens such formatted file for writing.
!
        IF (set_stdoutunit) THEN
          stdout=stdout_unit(master)
          set_stdoutunit=.false.
        END IF
!
!  Read in model tunable parameters from standard input. Allocate and
!  initialize variables in several modules after the number of nested
!  grids and dimension parameters are known.
!
        CALL inp_par (inlm)
        IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
!
!  Initialize counters. The 'Nrun' counter will be recomputed in the
!  RBL4D-Var phases to process the obervation operator correctly.
!
        nrun=1                ! run counter
        erstr=1               ! ensemble start counter
        erend=nouter          ! ensemble end counter
!
!  Set domain decomposition tile partition range.  This range is
!  computed only once since the "first_tile" and "last_tile" values
!  are private for each parallel thread/node.
!
#if defined _OPENMP
        mythread=my_threadnum()
#elif defined DISTRIBUTE
        mythread=myrank
#else
        mythread=0
#endif
        DO ng=1,ngrids
          chunk_size=(ntilex(ng)*ntilee(ng)+numthreads-1)/numthreads
          first_tile(ng)=mythread*chunk_size
          last_tile(ng)=first_tile(ng)+chunk_size-1
        END DO
!
!  Initialize internal wall clocks. Notice that the timings does not
!  includes processing standard input because several parameters are
!  needed to allocate clock variables.
!
        IF (master) THEN
          WRITE (stdout,10)
 10       FORMAT (/,' Process Information:',/)
        END IF
!
        DO ng=1,ngrids
          DO thread=thread_range
            CALL wclock_on (ng, inlm, 0, __line__, myfile)
          END DO
        END DO
!
!  Allocate and initialize modules variables.
!
        CALL roms_allocate_arrays (allocate_vars)
        CALL roms_initialize_arrays
        IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
 
      END IF
 
#if defined MCT_LIB && (defined ATM_COUPLING || defined WAV_COUPLING)
!
!-----------------------------------------------------------------------
!  Initialize coupling streams between model(s).
!-----------------------------------------------------------------------
!
      DO ng=1,ngrids
# ifdef ATM_COUPLING
        CALL initialize_ocn2atm_coupling (ng, myrank)
# endif
# ifdef WAV_COUPLING
        CALL initialize_ocn2wav_coupling (ng, myrank)
# endif
      END DO
#endif
!
!-----------------------------------------------------------------------
!  Set application grid, metrics, and associated variables. Then,
!  proccess background prior error covariance standard deviations
!  and normalization coefficients.
!-----------------------------------------------------------------------
!
      lgetstd=.true.
      lgetnrm=.true.
 
      DO ng=1,ngrids
#ifdef STD_MODEL
        ldefstd(ng)=.true.
        lwrtstd(ng)=.true.
#else
        lreadstd(ng)=.true.
#endif
        CALL prior_error (ng)
        IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
        setgridconfig(ng)=.false.
      END DO
!
      RETURN
      END SUBROUTINE roms_initialize
!
      SUBROUTINE roms_run (RunInterval)
!
!=======================================================================
!                                                                      !
!  This routine runs the incremental, strong constraint I4D-Var data   !
!  assimilation algorithm. It time-steps ROMS nonlinear, tangent       !
!  linear, and adjoint kernels.                                        !
!                                                                      !
!  On Input:                                                           !
!                                                                      !
!     RunInterval     Execution time stepping window (seconds)         !
!                                                                      !
!=======================================================================
!
!  Imported variable declarations
!
      real(dp), intent(in) :: RunInterval
!
!  Local variable declarations.
!
      integer :: my_outer, ng
!
      character (len=*), parameter :: MyFile =                          &
     &  __FILE__//", ROMS_run"
!
!=======================================================================
!  Run I4D-Var algorithm (primal formulation).
!=======================================================================
!
!  Initialize relevant parameters.
!
      DO ng=1,ngrids
#if defined ADJUST_BOUNDARY || defined ADJUST_STFLUX || \
    defined adjust_wstress
        lfinp(ng)=1         ! forcing index for input
        lfout(ng)=1         ! forcing index for output history files
#endif
#ifdef ADJUST_BOUNDARY
        lbinp(ng)=1         ! boundary index for input
        lbout(ng)=1         ! boundary index for output history files
#endif
        lold(ng)=1          ! old minimization time index
        lnew(ng)=2          ! new minimization time index
      END DO
!
!  Start outer loop iterations.
!
      outer_loop : DO my_outer=1,nouter
        outer=my_outer
        inner=0
!
!  Compute nonlinear background state trajectory, Xb(t)|n-1. Interpolate
!  the background at the observation locations, and compute the quality
!  control accept/reject flag, ObsScale. The background state is used
!  to linearize the tangent linear and adjoint models during the
!  minimization.
!
        CALL background (my_outer, runinterval)
        IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
!
!  Compute 4D-Var data assimilation increment, dXa, by iterating over
!  the inner loops, and minimizing the cost function.
!
        CALL increment (my_outer, runinterval)
        IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
!
!  Compute 4D-Var data assimilation analysis, Xa = Xb + dXa.  Set
!  nonlinear model initial conditions for next outer loop.
!
        CALL analysis (my_outer, runinterval)
        IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
 
      END DO outer_loop
!
!  Initialize the nonlinear model with the estimated 4D-Var state and
!  interpolate the solution at observation locations for posterior
!  analysis.
!
      CALL posterior_analysis (runinterval)
      IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
!
      RETURN
      END SUBROUTINE roms_run
!
      SUBROUTINE roms_finalize
!
!=======================================================================
!                                                                      !
!  This routine terminates ROMS I4D-Var execution.                     !
!                                                                      !
!=======================================================================
!
!  Local variable declarations.
!
      integer :: Fcount, ng, thread
!
      character (len=*), parameter :: MyFile =                          &
     &  __FILE__//", ROMS_finalize"
!
!-----------------------------------------------------------------------
!  Write out 4D-Var analysis fields that used as initial conditions for
!  the next data assimilation cycle.
!-----------------------------------------------------------------------
!
      IF (exit_flag.eq.noerror) THEN
        DO ng=1,ngrids
          ldefdai(ng)=.true.
          CALL def_dai (ng)
          IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
!
#ifdef DISTRIBUTE
          CALL wrt_dai (ng, myrank)
#else
          CALL wrt_dai (ng, -1)
#endif
          IF (founderror(exit_flag, noerror, __line__, myfile)) RETURN
        END DO
      END IF
!
!-----------------------------------------------------------------------
!  Compute and report model-observation comparison statistics.
!-----------------------------------------------------------------------
!
      IF (exit_flag.eq.noerror) THEN
        DO ng=1,ngrids
#ifdef DISTRIBUTE
        CALL stats_modobs (ng, myrank)
#else
        CALL stats_modobs (ng, -1)
#endif
        END DO
      END IF
!
!-----------------------------------------------------------------------
!  If blowing-up, save latest model state into RESTART NetCDF file.
!-----------------------------------------------------------------------
!
!  If cycling restart records, write solution into record 3.
!
      IF (exit_flag.eq.1) THEN
        DO ng=1,ngrids
          IF (lwrtrst(ng)) THEN
            IF (master) WRITE (stdout,10)
 10         FORMAT (/,' Blowing-up: Saving latest model state into ',   &
     &                ' RESTART file',/)
            fcount=rst(ng)%load
            IF (lcyclerst(ng).and.(rst(ng)%Nrec(fcount).ge.2)) THEN
              rst(ng)%Rindex=2
              lcyclerst(ng)=.false.
            END IF
            blowup=exit_flag
            exit_flag=noerror
#ifdef DISTRIBUTE
            CALL wrt_rst (ng, myrank)
#else
            CALL wrt_rst (ng, -1)
#endif
          END IF
        END DO
      END IF
!
!-----------------------------------------------------------------------
!  Stop model and time profiling clocks, report memory requirements,
!  and close output NetCDF files.
!-----------------------------------------------------------------------
!
!  Stop time clocks.
!
      IF (master) THEN
        WRITE (stdout,20)
 20     FORMAT (/,'Elapsed wall CPU time for each process (seconds):',/)
      END IF
!
      DO ng=1,ngrids
        DO thread=thread_range
          CALL wclock_off (ng, inlm, 0, __line__, myfile)
        END DO
      END DO
!
!  Report dynamic memory and automatic memory requirements.
!
      CALL memory
!
!  Close IO files.
!
      DO ng=1,ngrids
        CALL close_inp (ng, inlm)
      END DO
      CALL close_out
!
      RETURN
      END SUBROUTINE roms_finalize
!
      END MODULE roms_kernel_mod