C $Header: /home/ubuntu/mnt/e9_copy/MITgcm_contrib/ksnow/press_release/code/pressure_release_theta.F,v 1.4 2017/04/07 13:49:05 dgoldberg Exp $
C $Name:  $

#include "PACKAGES_CONFIG.h"
#include "CPP_OPTIONS.h"

CBOP
      SUBROUTINE PRESSURE_RELEASE_THETA( 
     U                       gT_arr,
     I                       iMin,iMax,jMin,jMax, k, bi,bj,
     I                       myTime, myIter, myThid )
C     *============================================================*
C     | SUBROUTINE PRESSURE_RELEASE_THETA
C     | o Transport theta with darcy flux
C     *============================================================*
      IMPLICIT NONE

C     === Global variables ===
#include "SIZE.h"
#include "EEPARAMS.h"
#include "PARAMS.h"
#include "GRID.h"
#include "DYNVARS.h"
#include "SURFACE.h"
#include "FFIELDS.h"

C     === Routine arguments ===
C     myThid -  Number of this instance 

      _RL     gT_arr(1-OLx:sNx+OLx,1-OLy:sNy+OLy)
      INTEGER k,bi,bj
      INTEGER iMin,iMax,jMin,jMax
      _RL     myTime
      INTEGER myIter
      INTEGER myThid

CEndOfInterface

#ifdef ALLOW_PRESSURE_RELEASE_CODE
C     === Local Variables ===
      INTEGER i,j,k_e,k_ce,k_s,k_cs,k_w,k_cw,k_n,k_cn
      _RL     T_trans_west,T_trans_east,T_trans_south,T_trans_north

      DO j=jMin+1,jMax-1
        DO i=iMin+1,iMax-1

        T_trans_west = 0.0 
        T_trans_north = 0.0
        T_trans_east = 0.0 
        T_trans_south = 0.0

C calculate the k cells the tracers are transferred between in north,
C south east and west cells.
C Need to find if adjacent cells are deeper or shallower
          IF (kLowC(i,j,bi,bj) .GE. kLowC(i+1,j,bi,bj)) THEN
             k_e = kLowC(i+1,j,bi,bj)
             k_ce = kSurfC(i,j,bi,bj)
          ELSE
             k_e = kSurfC(i+1,j,bi,bj)
             k_ce = kLowC(i,j,bi,bj)
          ENDIF

          IF (kLowC(i,j,bi,bj) .GE. kLowC(i-1,j,bi,bj)) THEN
             k_w = kLowC(i-1,j,bi,bj)
             k_cw = kSurfC(i,j,bi,bj)
          ELSE
             k_w = kSurfC(i-1,j,bi,bj)
             k_cw = kLowC(i,j,bi,bj)
          ENDIF

          IF (kLowC(i,j,bi,bj) .GE. kLowC(i,j+1,bi,bj)) THEN
             k_n = kLowC(i,j+1,bi,bj)
             k_cn = kSurfC(i,j,bi,bj)
          ELSE
             k_n = kSurfC(i,j+1,bi,bj)
             k_cn = kLowC(i,j,bi,bj)
          ENDIF

          IF (kLowC(i,j,bi,bj) .GE. kLowC(i,j-1,bi,bj)) THEN
             k_s = kLowC(i,j-1,bi,bj)
             k_cs = kSurfC(i,j,bi,bj)
          ELSE
             k_s = kSurfC(i,j-1,bi,bj)
             k_cs = kLowC(i,j,bi,bj)
          ENDIF

C calculate the net tracer flux through north, south east and west
C faces.


          IF (k .EQ. k_cw) THEN
           if (k_cw.gt.0 .and. k_w.gt.0) then
            T_trans_west =0.5 _d 0  * 
     &                  ( pReleaseTransX(i,j,bi,bj) *
     &                  (theta(i-1,j,k_w,bi,bj)+theta(i,j,k_cw,bi,bj))
     &                   +abs(pReleaseTransX(i,j,bi,bj)) * 
     &                  (theta(i-1,j,k_w,bi,bj)-theta(i,j,k_cw,bi,bj)))
     &                  *recip_rA(i,j,bi,bj)
     &                  *recip_deepFac2C(k_cw)*recip_rhoFacC(k_cw)
     &                  *recip_drF(k_cw)*_recip_hFacC(i,j,k_cw,bi,bj)
           endif
          ENDIF
          IF (k .EQ. k_ce) THEN
           if (k_ce.gt.0 .and. k_e.gt.0) then
            T_trans_east =0.5 _d 0  *
     &                  ( pReleaseTransX(i+1,j,bi,bj) *
     &                  (theta(i,j,k_ce,bi,bj)+theta(i+1,j,k_e,bi,bj))
     &                   +abs(pReleaseTransX(i+1,j,bi,bj)) *
     &                  (theta(i,j,k_ce,bi,bj)-theta(i+1,j,k_e,bi,bj)))
     &                  *recip_rA(i,j,bi,bj)
     &                  *recip_deepFac2C(k_ce)*recip_rhoFacC(k_ce)
     &                  *recip_drF(k_ce)*_recip_hFacC(i,j,k_ce,bi,bj)
           endif
          ENDIF
          IF (k .EQ. k_cs) THEN
           if (k_cs.gt.0 .and. k_s.gt.0) then
            T_trans_south =0.5 _d 0  *
     &                  ( pReleaseTransY(i,j,bi,bj) *
     &                  (theta(i,j-1,k_s,bi,bj)+theta(i,j,k_cs,bi,bj))
     &                   +abs(pReleaseTransY(i,j,bi,bj)) *
     &                  (theta(i,j-1,k_s,bi,bj)-theta(i,j,k_cs,bi,bj)))
     &                  *recip_rA(i,j,bi,bj)
     &                  *recip_deepFac2C(k_cs)*recip_rhoFacC(k_cs)
     &                  *recip_drF(k_cs)*_recip_hFacC(i,j,k_cs,bi,bj)
           endif
          ENDIF
          IF (k .EQ. k_cn) THEN
           if (k_cn.gt.0 .and. k_n.gt.0) then
            T_trans_north =0.5 _d 0  *
     &                  ( pReleaseTransY(i,j+1,bi,bj) *
     &                  (theta(i,j,k_cn,bi,bj)+theta(i,j+1,k_n,bi,bj))
     &                   +abs(pReleaseTransY(i,j+1,bi,bj)) *
     &                  (theta(i,j,k_cn,bi,bj)-theta(i,j+1,k_n,bi,bj)))
     &                  *recip_rA(i,j,bi,bj)
     &                  *recip_deepFac2C(k_cn)*recip_rhoFacC(k_cn)
     &                  *recip_drF(k_cn)*_recip_hFacC(i,j,k_cn,bi,bj)
           endif
          ENDIF


!          IF (k .EQ. k_cw) THEN
!           if (k_w.gt.0 .and. k_cw.gt.0) then
!            T_trans_west =pReleaseTransX(i,j,bi,bj)*
!     &                  (theta(i-1,j,k_w,bi,bj) -theta(i,j,k_cw,bi,bj))
C     &                  *rhoFacC(k)*mass2rUnit
C     &                  *_dyG(i,j,bi,bj)*recip_rA(i,j,bi,bj)*
!     &                  *recip_dxG(i,j,bi,bj)
!     &                  *recip_drF(k_cw)*_recip_hFacC(i,j,k_cw,bi,bj)
!           endif
!          ENDIF 
!          IF (k .EQ. k_ce) THEN
!           if (k_e.gt.0 .and. k_ce.gt.0) then
!            T_trans_east =pReleaseTransX(i+1,j,bi,bj)*
!     &                  (theta(i,j,k_ce,bi,bj) -theta(i+1,j,k_e,bi,bj))
!     &                  *recip_dxG(i,j,bi,bj)
!     &                  *recip_drF(k_ce)*_recip_hFacC(i,j,k_ce,bi,bj)
!           endif
!          ENDIF
!          IF (k .EQ. k_cs) THEN
!           if (k_s.gt.0 .and. k_cs.gt.0) then
!            T_trans_south =pReleaseTransY(i,j,bi,bj)*
!     &                  (theta(i,j-1,k_s,bi,bj) -theta(i,j,k_cs,bi,bj))
!     &                  *recip_dyG(i,j,bi,bj)
!     &                  *recip_drF(k_cs)*_recip_hFacC(i,j,k_cs,bi,bj)
!           endif
!          ENDIF
!          IF (k .EQ. k_cn) THEN
!           if (k_n.gt.0 .and. k_cn.gt.0) then
!            T_trans_north =pReleaseTransY(i,j+1,bi,bj)*
!     &                  (theta(i,j,k_cn,bi,bj) -theta(i,j+1,k_n,bi,bj))
!     &                  *recip_dyG(i,j,bi,bj)
!     &                  *recip_drF(k_cn)*_recip_hFacC(i,j,k_cn,bi,bj)
!           endif
!          ENDIF

C Add to get total tracer tendency.
          gT_arr(i,j) = gT_arr(i,j) + T_trans_west - T_trans_east
     &                 + T_trans_south - T_trans_north       

         ENDDO
       ENDDO

#endif /* ALLOW_PRESSURE_RELEASE_CODE */

      RETURN
      END