C $Header: /u/gcmpack/MITgcm/pkg/generic_advdiff/gad_del2.F,v 1.5 2006/12/05 22:20:06 jmc Exp $ C $Name: $ #include "GAD_OPTIONS.h" CBOP C !ROUTINE: GAD_DEL2 C !INTERFACE: ========================================================== SUBROUTINE GAD_DEL2( I bi,bj,k, I dTdx,dTdy, O del2, I myThid ) C !DESCRIPTION: C Calculates the horizontal Laplacian of a tracer: C \begin{equation*} C \nabla^2 \theta = \partial_{xx} \theta + \partial_{yy} \theta C \end{equation*} C !USES: =============================================================== IMPLICIT NONE #include "SIZE.h" #include "GRID.h" C !INPUT PARAMETERS: =================================================== C bi,bj :: tile indices C k :: vertical level C dTx :: zonal tracer gradient C dTy :: meridional tracer gradient C myThid :: thread number INTEGER bi,bj,k _RL dTdx(1-OLx:sNx+OLx,1-OLy:sNy+OLy) _RL dTdy(1-OLx:sNx+OLx,1-OLy:sNy+OLy) INTEGER myThid C !OUTPUT PARAMETERS: ================================================== C del2 :: Laplacian of tracer _RL del2(1-OLx:sNx+OLx,1-OLy:sNy+OLy) C !LOCAL VARIABLES: ==================================================== C i,j :: loop indices INTEGER i,j CEOP C-- Initialise to zero. DO j=1-Oly,sNy+Oly DO i=1-Olx,sNx+Olx del2(i,j)= 0. _d 0 ENDDO ENDDO C Difference of zonal fluxes & meridional fluxes C and divide by grid-cell volume DO j=1-Oly,sNy+Oly-1 DO i=1-Olx,sNx+Olx-1 del2(i,j)=recip_rA(i,j,bi,bj)*recip_deepFac2C(k) & *recip_drF(k)*_recip_hFacC(i,j,k,bi,bj) & *( ( dTdx(i+1,j)-dTdx(i,j) ) & +( dTdy(i,j+1)-dTdy(i,j) ) & ) ENDDO ENDDO RETURN END