C $Header: /u/gcmpack/MITgcm/model/src/calc_grid_angles.F,v 1.2 2013/02/17 02:29:52 jmc Exp $ C $Name: $ #include "CPP_OPTIONS.h" C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| CBOP C !ROUTINE: CALC_GRID_ANGLES C !INTERFACE: SUBROUTINE CALC_GRID_ANGLES( skipCalcAngleC, myThid ) C !DESCRIPTION: \bv C *===================================================================* C | SUBROUTINE CALC_GRID_ANGLES C | o calculate the angle between geographical north and model grid C | north, assuming that yG holds the geographical coordinates C *===================================================================* C \ev C !USES: IMPLICIT NONE C === Global variables === #include "SIZE.h" #include "EEPARAMS.h" #include "PARAMS.h" #include "GRID.h" C !INPUT/OUTPUT PARAMETERS: C == Routine arguments == C skipCalcAngleC :: skip setting of grid-angle at cell-center location C myThid :: my Thread Id Number LOGICAL skipCalcAngleC INTEGER myThid CEOP C !LOCAL VARIABLES: C == Local variables == C bi,bj :: Tile indices C i, j :: Loop counters INTEGER bi, bj INTEGER i, j C pseudo velocities _RL uPseudo(1-OLx:sNx+OLx,1-OLy:sNy+OLy) _RL vPseudo(1-OLx:sNx+OLx,1-OLy:sNy+OLy) _RL uC, vC, uNorm, tmpVal CEOP C- For each tile ... DO bj = myByLo(myThid), myByHi(myThid) DO bi = myBxLo(myThid), myBxHi(myThid) C- compute pseudo velocities from stream function psi = -yG*deg2rad, C that is, zonal flow DO j = 1-OLy,sNy+OLy-1 DO i = 1-OLx,sNx+OLx IF ( _dyG(i,j,bi,bj).GT.0. ) THEN uPseudo(i,j) = & - ( yG(i,j,bi,bj) - yG(i,j+1,bi,bj) )*deg2rad & / _dyG(i,j,bi,bj) ELSE uPseudo(i,j) = 0. ENDIF u2zonDir(i,j,bi,bj) = rSphere*uPseudo(i,j) ENDDO ENDDO DO j = 1-OLy,sNy+OLy DO i = 1-OLx,sNx+OLx-1 IF ( _dxG(i,j,bi,bj).GT.0. ) THEN vPseudo(i,j) = & + ( yG(i,j,bi,bj) - yG(i+1,j,bi,bj) )*deg2rad & / _dxG(i,j,bi,bj) ELSE vPseudo(i,j) = 0. ENDIF v2zonDir(i,j,bi,bj) = rSphere*vPseudo(i,j) ENDDO ENDDO IF ( .NOT.skipCalcAngleC ) THEN DO j = 1-OLy,sNy+OLy-1 DO i = 1-OLx,sNx+OLx-1 uC = 0.5*(uPseudo(i,j) + uPseudo(i+1,j)) vC = 0.5*(vPseudo(i,j) + vPseudo(i,j+1)) uNorm = SQRT(uC*uC+vC*vC) IF ( uNorm .NE. 0. _d 0 ) uNorm = 1. _d 0/uNorm angleCosC(i,j,bi,bj) = uC*uNorm angleSinC(i,j,bi,bj) = -vC*uNorm ENDDO ENDDO ENDIF C- To check angular momentum conservation, use an alternative definition C of grid-angles cosine (@ U pt) & sine (@ V pt) (consistent with C stream-function of solid-body velocity field). DO j = 1-OLy,sNy+OLy-1 DO i = 1-OLx,sNx+OLx C- Note: most natural way would be to divide by dyG (as below); but scaling by C dxC/rAw ensures that u2zonDir is exactly =1 with current Lat-Lon grid c tmpVal = _dyG(i,j,bi,bj) * COS( deg2rad* tmpVal = _rAw(i,j,bi,bj) * COS( deg2rad* & ( yG(i,j,bi,bj) + yG(i,j+1,bi,bj) )*halfRL ) IF ( tmpVal.GT.0. ) THEN u2zonDir(i,j,bi,bj) = rSphere & *( SIN( yG(i,j+1,bi,bj)*deg2rad ) & - SIN( yG(i, j, bi,bj)*deg2rad ) & )* _dxC(i,j,bi,bj)/tmpVal c & )/tmpVal ELSE u2zonDir(i,j,bi,bj) = 1. ENDIF ENDDO ENDDO DO j = 1-OLy,sNy+OLy DO i = 1-OLx,sNx+OLx-1 C- Note: most natural way would be to divide by dxG (as below); for symetry C reason with u2zonDir expression, we use instead dyC/rAs scaling factor c tmpVal = _dxG(i,j,bi,bj) * COS( deg2rad* tmpVal = _rAs(i,j,bi,bj) * COS( deg2rad* & ( yG(i,j,bi,bj) + yG(i+1,j,bi,bj) )*halfRL ) IF ( tmpVal.GT.0. ) THEN v2zonDir(i,j,bi,bj) = -rSphere & *( SIN( yG(i+1,j,bi,bj)*deg2rad ) & - SIN( yG(i,j,bi,bj)*deg2rad ) & )* _dyC(i,j,bi,bj)/tmpVal c & )/tmpVal ELSE v2zonDir(i,j,bi,bj) = 0. ENDIF ENDDO ENDDO C- bi,bj-loops ENDDO ENDDO RETURN END