--- MITgcm/pkg/mom_vecinv/mom_vi_u_coriolis.F	2001/09/05 17:46:03	1.3
+++ MITgcm/pkg/mom_vecinv/mom_vi_u_coriolis.F	2003/08/03 02:49:35	1.4
@@ -1,18 +1,18 @@
-C $Header: /home/ubuntu/mnt/e9_copy/MITgcm/pkg/mom_vecinv/mom_vi_u_coriolis.F,v 1.3 2001/09/05 17:46:03 heimbach Exp $
+C $Header: /home/ubuntu/mnt/e9_copy/MITgcm/pkg/mom_vecinv/mom_vi_u_coriolis.F,v 1.4 2003/08/03 02:49:35 jmc Exp $
 C $Name:  $
 
 #include "CPP_OPTIONS.h"
 
       SUBROUTINE MOM_VI_U_CORIOLIS( 
-     I        bi,bj,K,
-     I        vFld,omega3,r_hFacZ,
+     I        bi,bj,k,
+     I        vFld,omega3,hFacZ,r_hFacZ,
      O        uCoriolisTerm,
      I        myThid)
       IMPLICIT NONE
-C     /==========================================================\
-C     | S/R MOM_VI_U_CORIOLIS                                    |
-C     |==========================================================|
-C     \==========================================================/
+C     *==========================================================*
+C     | S/R MOM_VI_U_CORIOLIS
+C     | o Calculate meridional flux of vorticity at U point
+C     *==========================================================*
 
 C     == Global variables ==
 #include "SIZE.h"
@@ -24,26 +24,29 @@
       INTEGER bi,bj,K
       _RL vFld(1-OLx:sNx+OLx,1-OLy:sNy+OLy)
       _RL omega3(1-OLx:sNx+OLx,1-OLy:sNy+OLy)
+      _RS hFacZ (1-OLx:sNx+OLx,1-OLy:sNy+OLy)
       _RS r_hFacZ(1-OLx:sNx+OLx,1-OLy:sNy+OLy)
       _RL uCoriolisTerm(1-OLx:sNx+OLx,1-OLy:sNy+OLy)
       INTEGER myThid
 
 C     == Local variables ==
+      LOGICAL upwindVort3, use_original_hFac
       INTEGER I,J
       _RL vBarXY,vort3u
-      LOGICAL upwindVort3
-
-      upwindVort3=.FALSE.
-
-       DO J=1-Oly,sNy+Oly-1
-        DO I=2-Olx,sNx+Olx
+      _RS epsil
+      PARAMETER ( upwindVort3      =.FALSE. )
+      PARAMETER ( use_original_hFac=.FALSE. )
+
+      epsil = 1. _d -9 
+
+      DO J=1-Oly,sNy+Oly-1
+       DO I=2-Olx,sNx+Olx
+        IF ( use_original_hFac ) THEN
          vBarXY=0.25*(
      &       vFld( i , j )*dxG( i , j ,bi,bj)*hFacS( i , j ,k,bi,bj)
      &      +vFld( i ,j+1)*dxG( i ,j+1,bi,bj)*hFacS( i ,j+1,k,bi,bj)
      &      +vFld(i-1, j )*dxG(i-1, j ,bi,bj)*hFacS(i-1, j ,k,bi,bj)
      &      +vFld(i-1,j+1)*dxG(i-1,j+1,bi,bj)*hFacS(i-1,j+1,k,bi,bj))
-c        vBarXY=0.25*(vFld( i ,j)+vFld( i ,j+1)
-c    &               +vFld(i-1,j)+vFld(i-1,j+1))
          IF (upwindVort3) THEN
           IF (vBarXY.GT.0.) THEN
            vort3u=omega3(I,J)*r_hFacZ(i,j)
@@ -51,12 +54,30 @@
            vort3u=omega3(I,J+1)*r_hFacZ(i,j+1)
           ENDIF
          ELSE
-          vort3u=0.5*(omega3(i,j)*r_hFacZ(i,j)
-     &               +omega3(i,j+1)*r_hFacZ(i,j+1))
+           vort3u=0.5*(omega3(i,j)*r_hFacZ(i,j)
+     &                +omega3(i,j+1)*r_hFacZ(i,j+1))
          ENDIF
-         uCoriolisTerm(i,j)=
-     &   +vort3u*vBarXY*recip_dxc(i,j,bi,bj)
-     &   *_maskW(I,J,K,bi,bj)
+        ELSE
+c--      test a different formulation (relatively to hFac)
+         vBarXY=0.5*(
+     &       vFld( i , j )*dxG( i , j ,bi,bj)*hFacZ(i,j)
+     &      +vFld(i-1, j )*dxG(i-1, j ,bi,bj)*hFacZ(i,j)
+     &      +vFld( i ,j+1)*dxG( i ,j+1,bi,bj)*hFacZ(i,j+1)
+     &      +vFld(i-1,j+1)*dxG(i-1,j+1,bi,bj)*hFacZ(i,j+1)
+     &              )/MAX( epsil, hFacZ(i,j)+hFacZ(i,j+1) ) 
+         IF (upwindVort3) THEN
+          IF (vBarXY.GT.0.) THEN
+           vort3u=omega3(i,j)
+          ELSE
+           vort3u=omega3(i,j+1)
+          ENDIF
+         ELSE
+           vort3u=0.5*(omega3(i,j)+omega3(i,j+1)) 
+         ENDIF
+        ENDIF
+
+        uCoriolisTerm(i,j)=
+     &   +vort3u*vBarXY*recip_dxC(i,j,bi,bj)*_maskW(i,j,k,bi,bj) 
 cph *note* put these comments after end of continued line
 cph        to ensure TAMC compatibility
 C high order vorticity advection term
@@ -70,8 +91,8 @@
 c    &          fCori(I-1,J,bi,bj)*vBarY(I-1,J,K,bi,bj)  )
 C original form of Coriolis term (copied from calc_mom_rhs)
 c    &   +0.5*(fCori(i,j,bi,bj)+fCori(i-1,j,bi,bj))*vBarXY
-        ENDDO
        ENDDO
+      ENDDO
 
       RETURN
       END