/[MITgcm]/MITgcm/pkg/generic_advdiff/gad_dst2u1_adv_y.F
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revision 1.2 by heimbach, Wed Jun 7 01:55:14 2006 UTC revision 1.3 by jmc, Mon Jun 12 16:06:28 2006 UTC
# Line 7  CBOP Line 7  CBOP
7  C !ROUTINE: GAD_DST2U1_ADV_Y  C !ROUTINE: GAD_DST2U1_ADV_Y
8    
9  C !INTERFACE: ==========================================================  C !INTERFACE: ==========================================================
10        SUBROUTINE GAD_DST2U1_ADV_Y(        SUBROUTINE GAD_DST2U1_ADV_Y(
11       I           bi,bj,k, advectionScheme, deltaTloc,       I           bi,bj,k, advectionScheme, deltaTloc,
12       I           vTrans, vVel,       I           vTrans, vVel,
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 meridional flux due to advection  C  Calculates the area integrated meridional 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 51  C  yLimit            :: centered (vs upw Line 51  C  yLimit            :: centered (vs upw
51  C  vFld              :: velocity [m/s], meridional component  C  vFld              :: velocity [m/s], meridional component
52  C  vCFL              :: Courant-Friedrich-Levy number  C  vCFL              :: Courant-Friedrich-Levy number
53        INTEGER i,j        INTEGER i,j
54        _RL vFld, vCFL, yLimit        _RL vFld, vCFL, yLimit, vAbs
55  CEOP  CEOP
56    
57        yLimit = 0. _d 0        yLimit = 0. _d 0
# Line 68  c       vFld = vVel(i,j,k,bi,bj) Line 68  c       vFld = vVel(i,j,k,bi,bj)
68       &        *recip_drF(k)*_recip_hFacS(i,j,k,bi,bj)       &        *recip_drF(k)*_recip_hFacS(i,j,k,bi,bj)
69          vCFL = ABS(vFld*deltaTloc*recip_dyC(i,j,bi,bj))          vCFL = ABS(vFld*deltaTloc*recip_dyC(i,j,bi,bj))
70    
71          vT(i,j) =  c       vT(i,j) =
72       &     vTrans(i,j)*(Tracer(i,j-1)+Tracer(i,j))*0.5 _d 0  c    &     vTrans(i,j)*(tracer(i,j-1)+tracer(i,j))*0.5 _d 0
73       &   + ( 1. _d 0 - yLimit*(1. _d 0 - vCFL) )*ABS(vTrans(i,j))  c    &   + ( 1. _d 0 - yLimit*(1. _d 0 - vCFL) )*ABS(vTrans(i,j))
74       &                *(tracer(i,j-1)-tracer(i,j))*0.5 _d 0  c    &                *(tracer(i,j-1)-tracer(i,j))*0.5 _d 0
75    C-- above formulation produces large truncation error when:
76    C    1rst.O upWind and   v > 0 & |tracer(i,j-1)| << |tracer(i,j)|
77    C                   or   v < 0 & |tracer(i,j-1)| >> |tracer(i,j)|
78    C-- change to a more robust expression:
79            vAbs = ABS(vTrans(i,j))
80         &       *( 1. _d 0 - yLimit*(1. _d 0 - vCFL) )
81            vT(i,j) = ( vTrans(i,j)+vAbs )* 0.5 _d 0 * tracer(i,j-1)
82         &          + ( vTrans(i,j)-vAbs )* 0.5 _d 0 * tracer(i,j)
83    
84         ENDDO         ENDDO
85        ENDDO        ENDDO
86    
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