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C $Header: /u/gcmpack/MITgcm/pkg/generic_advdiff/gad_dst2u1_adv_x.F,v 1.6 2006/12/05 22:21:50 jmc Exp $ |
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C $Name: $ |
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#include "GAD_OPTIONS.h" |
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CBOP |
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C !ROUTINE: GAD_DST2U1_ADV_X |
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C !INTERFACE: ========================================================== |
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1.3 |
SUBROUTINE GAD_DST2U1_ADV_X( |
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jmc |
1.7 |
I bi,bj,k, advectionScheme, calcCFL, |
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jmc |
1.4 |
I deltaTloc, uTrans, uFld, |
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jmc |
1.1 |
I tracer, |
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O uT, |
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I myThid ) |
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C !DESCRIPTION: |
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C Calculates the area integrated zonal flux due to advection |
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jmc |
1.3 |
C of a tracer using second-order Direct Space and Time (DST-2) |
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jmc |
1.1 |
C interpolation (=Lax-Wendroff) or simple 1rst order upwind scheme. |
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C !USES: =============================================================== |
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IMPLICIT NONE |
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#include "SIZE.h" |
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#include "GRID.h" |
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#include "GAD.h" |
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C !INPUT PARAMETERS: =================================================== |
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C bi,bj :: tile indices |
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C k :: vertical level |
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1.3 |
C advectionScheme :: advection scheme to use: either 2nd Order DST |
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1.1 |
C or 1rst Order Upwind |
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1.7 |
C calcCFL :: =T: calculate CFL number ; =F: take uFld as CFL |
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C deltaTloc :: local time-step (s) |
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1.1 |
C uTrans :: zonal volume transport |
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1.7 |
C uFld :: zonal flow / CFL number |
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1.1 |
C tracer :: tracer field |
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C myThid :: thread number |
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INTEGER bi,bj,k |
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INTEGER advectionScheme |
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1.7 |
LOGICAL calcCFL |
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1.1 |
_RL deltaTloc |
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_RL uTrans(1-OLx:sNx+OLx,1-OLy:sNy+OLy) |
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1.4 |
_RL uFld (1-OLx:sNx+OLx,1-OLy:sNy+OLy) |
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1.1 |
_RL tracer(1-OLx:sNx+OLx,1-OLy:sNy+OLy) |
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INTEGER myThid |
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C !OUTPUT PARAMETERS: ================================================== |
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C uT :: zonal advective flux |
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_RL uT (1-OLx:sNx+OLx,1-OLy:sNy+OLy) |
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C !LOCAL VARIABLES: ==================================================== |
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C i,j :: loop indices |
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C rLimit :: centered (vs upwind) fraction |
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C uCFL :: Courant-Friedrich-Levy number |
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INTEGER i,j |
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1.7 |
_RL uCFL, xLimit, uAbs |
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1.1 |
CEOP |
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xLimit = 0. _d 0 |
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IF ( advectionScheme.EQ.ENUM_DST2 ) xLimit = 1. _d 0 |
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DO j=1-Oly,sNy+Oly |
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uT(1-Olx,j)=0. |
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DO i=1-Olx+1,sNx+Olx |
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uCFL = uFld(i,j) |
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IF ( calcCFL ) uCFL = ABS( uFld(i,j)*deltaTloc |
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& *recip_dxC(i,j,bi,bj)*recip_deepFacC(k) ) |
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c uT(i,j) = |
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c & uTrans(i,j)*(tracer(i-1,j)+tracer(i,j))*0.5 _d 0 |
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c & + ( 1. _d 0 - xLimit*(1. _d 0 - uCFL) )*ABS(uTrans(i,j)) |
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c & *(tracer(i-1,j)-tracer(i,j))*0.5 _d 0 |
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C-- above formulation produces large truncation error when: |
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C 1rst.O upWind and u > 0 & |tracer(i-1,j)| << |tracer(i,j)| |
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C or u < 0 & |tracer(i-1,j)| >> |tracer(i,j)| |
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C-- change to a more robust expression: |
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uAbs = ABS(uTrans(i,j)) |
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& *( 1. _d 0 - xLimit*(1. _d 0 - uCFL) ) |
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uT(i,j) = ( uTrans(i,j)+uAbs )* 0.5 _d 0 * tracer(i-1,j) |
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& + ( uTrans(i,j)-uAbs )* 0.5 _d 0 * tracer(i,j) |
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1.1 |
ENDDO |
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ENDDO |
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RETURN |
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END |
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