/[MITgcm]/MITgcm/pkg/generic_advdiff/gad_dst2u1_adv_r.F
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revision 1.1 by jmc, Sat Oct 22 19:56:32 2005 UTC revision 1.2 by jmc, Mon Jun 12 16:06:28 2006 UTC
# Line 7  CBOP Line 7  CBOP
7  C !ROUTINE: GAD_DST2U1_ADV_R  C !ROUTINE: GAD_DST2U1_ADV_R
8    
9  C !INTERFACE: ==========================================================  C !INTERFACE: ==========================================================
10        SUBROUTINE GAD_DST2U1_ADV_R(        SUBROUTINE GAD_DST2U1_ADV_R(
11       I           bi,bj,k, advectionScheme,       I           bi,bj,k, advectionScheme,
12       I           deltaTloc, rTrans, wVel,       I           deltaTloc, rTrans, wVel,
13       I           tracer,       I           tracer,
# Line 16  C !INTERFACE: ========================== Line 16  C !INTERFACE: ==========================
16    
17  C !DESCRIPTION:  C !DESCRIPTION:
18  C  Calculates the area integrated vertical flux due to advection  C  Calculates the area integrated vertical flux due to advection
19  C  of a tracer using second-order Direct Space and Time (DST-2)  C  of a tracer using second-order Direct Space and Time (DST-2)
20  C  interpolation (=Lax-Wendroff) or simple 1rst order upwind scheme.  C  interpolation (=Lax-Wendroff) or simple 1rst order upwind scheme.
21    
22  C !USES: ===============================================================  C !USES: ===============================================================
# Line 54  C  rLimit            :: centered (vs upw Line 54  C  rLimit            :: centered (vs upw
54  C  wFld              :: velocity, vertical component  C  wFld              :: velocity, vertical component
55  C  wCFL              :: Courant-Friedrich-Levy number  C  wCFL              :: Courant-Friedrich-Levy number
56        INTEGER i,j,km1        INTEGER i,j,km1
57        _RL wFld, wCFL, rLimit        _RL wFld, wCFL, rLimit, wAbs
58  CEOP  CEOP
59    
60        rLimit = 0. _d 0        rLimit = 0. _d 0
# Line 76  c        wFld = wVel(i,j,k,bi,bj) Line 76  c        wFld = wVel(i,j,k,bi,bj)
76           wFld = rTrans(i,j)*recip_rA(i,j,bi,bj)           wFld = rTrans(i,j)*recip_rA(i,j,bi,bj)
77           wCFL = ABS(wFld*deltaTloc*recip_drC(k))           wCFL = ABS(wFld*deltaTloc*recip_drC(k))
78    
79           wT(i,j) = maskC(i,j,kM1,bi,bj)*(  c        wT(i,j) = maskC(i,j,km1,bi,bj)*(
80       &     rTrans(i,j)*(Tracer(i,j,km1)+Tracer(i,j,k))*0.5 _d 0  c    &     rTrans(i,j)*(tracer(i,j,km1)+tracer(i,j,k))*0.5 _d 0
81       &   + ( 1. _d 0 - rLimit*(1. _d 0 - wCFL) )*ABS(rTrans(i,j))  c    &   + ( 1. _d 0 - rLimit*(1. _d 0 - wCFL) )*ABS(rTrans(i,j))
82       &                *(tracer(i,j,km1)-tracer(i,j,k))*0.5 _d 0*rkSign  c    &                *(tracer(i,j,km1)-tracer(i,j,k))*0.5 _d 0*rkSign
83    c    &                                  )
84    C-- above formulation produces large truncation error when:
85    C    1rst.O upWind and   w*rkSign > 0 & |tracer(k-1)| << |tracer(k)|
86    C                   or   w*rkSign < 0 & |tracer(k-1)| >> |tracer(k)|
87    C-- change to a more robust expression:
88             wAbs = ABS(rTrans(i,j))*rkSign
89         &       *( 1. _d 0 - rLimit*(1. _d 0 - wCFL) )
90             wT(i,j) = maskC(i,j,km1,bi,bj)*(
91         &             ( rTrans(i,j)+wAbs )* 0.5 _d 0 * tracer(i,j,km1)
92         &           + ( rTrans(i,j)-wAbs )* 0.5 _d 0 * tracer(i,j,k)
93       &                                  )       &                                  )
94          ENDDO          ENDDO
95         ENDDO         ENDDO
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