/[MITgcm]/MITgcm/pkg/generic_advdiff/gad_dst2u1_adv_x.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 16:06:27 2006 UTC
# Line 7  CBOP Line 7  CBOP
7  C !ROUTINE: GAD_DST2U1_ADV_X  C !ROUTINE: GAD_DST2U1_ADV_X
8    
9  C !INTERFACE: ==========================================================  C !INTERFACE: ==========================================================
10        SUBROUTINE GAD_DST2U1_ADV_X(        SUBROUTINE GAD_DST2U1_ADV_X(
11       I           bi,bj,k, advectionScheme,       I           bi,bj,k, advectionScheme,
12       I           deltaTloc, uTrans, uVel,       I           deltaTloc, uTrans, uVel,
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 zonal flux due to advection  C  Calculates the area integrated zonal 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 28  C !USES: =============================== Line 28  C !USES: ===============================
28  C !INPUT PARAMETERS: ===================================================  C !INPUT PARAMETERS: ===================================================
29  C  bi,bj             :: tile indices  C  bi,bj             :: tile indices
30  C  k                 :: vertical level  C  k                 :: vertical level
31  C  advectionScheme   :: advection scheme to use: either 2nd Order DST  C  advectionScheme   :: advection scheme to use: either 2nd Order DST
32  C                                                or 1rst Order Upwind  C                                                or 1rst Order Upwind
33  C  uTrans            :: zonal volume transport  C  uTrans            :: zonal volume transport
34  C  uVel              :: zonal flow  C  uVel              :: zonal flow
# Line 52  C  rLimit            :: centered (vs upw Line 52  C  rLimit            :: centered (vs upw
52  C  uFld              :: velocity [m/s], zonal component  C  uFld              :: velocity [m/s], zonal component
53  C  uCFL              :: Courant-Friedrich-Levy number  C  uCFL              :: Courant-Friedrich-Levy number
54        INTEGER i,j        INTEGER i,j
55        _RL uFld, uCFL, xLimit        _RL uFld, uCFL, xLimit, uAbs
56  CEOP  CEOP
57    
58        xLimit = 0. _d 0        xLimit = 0. _d 0
# Line 67  c       uFld = uVel(i,j,k,bi,bj) Line 67  c       uFld = uVel(i,j,k,bi,bj)
67       &        *recip_drF(k)*_recip_hFacW(i,j,k,bi,bj)       &        *recip_drF(k)*_recip_hFacW(i,j,k,bi,bj)
68          uCFL = ABS(uFld*deltaTloc*recip_dxC(i,j,bi,bj))          uCFL = ABS(uFld*deltaTloc*recip_dxC(i,j,bi,bj))
69    
70          uT(i,j) =  c       uT(i,j) =
71       &     uTrans(i,j)*(Tracer(i-1,j)+Tracer(i,j))*0.5 _d 0  c    &     uTrans(i,j)*(tracer(i-1,j)+tracer(i,j))*0.5 _d 0
72       &   + ( 1. _d 0 - xLimit*(1. _d 0 - uCFL) )*ABS(uTrans(i,j))  c    &   + ( 1. _d 0 - xLimit*(1. _d 0 - uCFL) )*ABS(uTrans(i,j))
73       &                *(tracer(i-1,j)-tracer(i,j))*0.5 _d 0  c    &                *(tracer(i-1,j)-tracer(i,j))*0.5 _d 0
74    C-- above formulation produces large truncation error when:
75    C    1rst.O upWind and   u > 0 & |tracer(i-1,j)| << |tracer(i,j)|
76    C                   or   u < 0 & |tracer(i-1,j)| >> |tracer(i,j)|
77    C-- change to a more robust expression:
78            uAbs = ABS(uTrans(i,j))
79         &       *( 1. _d 0 - xLimit*(1. _d 0 - uCFL) )
80            uT(i,j) = ( uTrans(i,j)+uAbs )* 0.5 _d 0 * tracer(i-1,j)
81         &          + ( uTrans(i,j)-uAbs )* 0.5 _d 0 * tracer(i,j)
82         ENDDO         ENDDO
83        ENDDO        ENDDO
84    
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