/[MITgcm]/MITgcm/pkg/generic_advdiff/gad_advection.F
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revision 1.3 by adcroft, Mon Sep 17 19:48:04 2001 UTC revision 1.4 by adcroft, Wed Sep 19 20:45:09 2001 UTC
# Line 1  Line 1 
1  C $Header$  C $Header$
2  C $Name$  C $Name$
3    
4    CBOI
5    C !TITLE: pkg/generic\_advdiff
6    C !AUTHORS: adcroft@mit.edu
7    C !INTRODUCTION:
8    C \section{Generica Advection Diffusion Package}
9    C
10    C Package "generic\_advdiff" provides a common set of routines for calculating
11    C advective/diffusive fluxes for tracers (cell centered quantities on a C-grid).
12    C
13    C Many different advection schemes are available: the standard centered
14    C second order, centered fourth order and upwind biased third order schemes
15    C are known as linear methods and require some stable time-stepping method
16    C such as Adams-Bashforth. Alternatives such as flux-limited schemes are
17    C stable in the forward sense and are best combined with the multi-dimensional
18    C method provided in gad\_advection.
19    C
20    C There are two high-level routines:
21    C  \begin{itemize}
22    C  \item{GAD\_CALC\_RHS} calculates all fluxes at time level "n" and is used
23    C  for the standard linear schemes. This must be used in conjuction with
24    C  Adams-Bashforth time-stepping. Diffusive and parameterized fluxes are
25    C  always calculated here.
26    C  \item{GAD\_ADVECTION} calculates just the advective fluxes using the
27    C  non-linear schemes and can not be used in conjuction with Adams-Bashforth
28    C  time-stepping.
29    C  \end{itemize}
30    CEOI
31    
32  #include "GAD_OPTIONS.h"  #include "GAD_OPTIONS.h"
33    
34    CBOP
35    C !ROUTINE: GAD_ADVECTION
36    
37    C !INTERFACE: ==========================================================
38        SUBROUTINE GAD_ADVECTION(bi,bj,advectionScheme,tracerIdentity,        SUBROUTINE GAD_ADVECTION(bi,bj,advectionScheme,tracerIdentity,
39       U                         Tracer,Gtracer,       U                         Tracer,Gtracer,
40       I                         myTime,myIter,myThid)       I                         myTime,myIter,myThid)
 C     /==========================================================\  
 C     | SUBROUTINE GAD_ADVECTION                                 |  
 C     | o Solves the pure advection tracer equation.             |  
 C     |==========================================================|  
 C     \==========================================================/  
       IMPLICIT NONE  
41    
42  C     == Global variables ===  C !DESCRIPTION:
43    C Calculates the tendancy of a tracer due to advection.
44    C It uses the multi-dimensional method given in \ref{sect:multiDimAdvection}
45    C and can only be used for the non-linear advection schemes such as the
46    C direct-space-time method and flux-limiters.
47    C
48    C The algorithm is as follows:
49    C \begin{itemize}
50    C \item{$\theta^{(n+1/3)} = \theta^{(n)}
51    C      - \Delta t \partial_x (u\theta) + \theta \partial_x u$}
52    C \item{$\theta^{(n+2/3)} = \theta^{(n+1/3)}
53    C      - \Delta t \partial_y (v\theta) + \theta \partial_y v$}
54    C \item{$\theta^{(n+3/3)} = \theta^{(n+2/3)}
55    C      - \Delta t \partial_r (w\theta) + \theta \partial_r w$}
56    C \item{$G_\theta = ( \theta^{(n+3/3)} - \theta^{(n)} )/\Delta t$}
57    C \end{itemize}
58    C
59    C The tendancy (output) is over-written by this routine.
60    
61    C !USES: ===============================================================
62          IMPLICIT NONE
63  #include "SIZE.h"  #include "SIZE.h"
64  #include "EEPARAMS.h"  #include "EEPARAMS.h"
65  #include "PARAMS.h"  #include "PARAMS.h"
# Line 21  C     == Global variables === Line 67  C     == Global variables ===
67  #include "GRID.h"  #include "GRID.h"
68  #include "GAD.h"  #include "GAD.h"
69    
70  C     == Routine arguments ==  C !INPUT PARAMETERS: ===================================================
71    C  bi,bj                :: tile indices
72    C  advectionScheme      :: advection scheme to use
73    C  tracerIdentity       :: identifier for the tracer (required only for OBCS)
74    C  Tracer               :: tracer field
75    C  myTime               :: current time
76    C  myIter               :: iteration number
77    C  myThid               :: thread number
78        INTEGER bi,bj        INTEGER bi,bj
79        INTEGER advectionScheme        INTEGER advectionScheme
80        INTEGER tracerIdentity        INTEGER tracerIdentity
       _RL Tracer(1-Olx:sNx+Olx,1-Oly:sNy+Oly,Nr,nSx,nSy)  
81        _RL Gtracer(1-Olx:sNx+Olx,1-Oly:sNy+Oly,Nr,nSx,nSy)        _RL Gtracer(1-Olx:sNx+Olx,1-Oly:sNy+Oly,Nr,nSx,nSy)
82        _RL myTime        _RL myTime
83        INTEGER myIter        INTEGER myIter
84        INTEGER myThid        INTEGER myThid
85    
86  C     == Local variables  C !OUTPUT PARAMETERS: ==================================================
87    C  gTracer              :: tendancy array
88          _RL Tracer(1-Olx:sNx+Olx,1-Oly:sNy+Oly,Nr,nSx,nSy)
89    
90    C !LOCAL VARIABLES: ====================================================
91    C  maskUp               :: 2-D array for mask at W points
92    C  iMin,iMax,jMin,jMax  :: loop range for called routines
93    C  i,j,k                :: loop indices
94    C  kup                  :: index into 2 1/2D array, toggles between 1 and 2
95    C  kdown                :: index into 2 1/2D array, toggles between 2 and 1
96    C  kp1                  :: =k+1 for k<Nr, =Nr for k=Nr
97    C  xA,yA                :: areas of X and Y face of tracer cells
98    C  uTrans,vTrans,rTrans :: 2-D arrays of volume transports at U,V and W points
99    C  af                   :: 2-D array for horizontal advective flux
100    C  fVerT                :: 2 1/2D arrays for vertical advective flux
101    C  localTij             :: 2-D array used as temporary local copy of tracer fld
102    C  localTijk            :: 3-D array used as temporary local copy of tracer fld
103    C  kp1Msk               :: flag (0,1) to act as over-riding mask for W levels
104    C  calc_fluxes_X        :: logical to indicate to calculate fluxes in X dir
105    C  calc_fluxes_Y        :: logical to indicate to calculate fluxes in Y dir
106    C  nipass               :: number of passes to make in multi-dimensional method
107    C  ipass                :: number of the current pass being made
108        _RS maskUp  (1-OLx:sNx+OLx,1-OLy:sNy+OLy)        _RS maskUp  (1-OLx:sNx+OLx,1-OLy:sNy+OLy)
109        INTEGER iMin,iMax,jMin,jMax        INTEGER iMin,iMax,jMin,jMax
110        INTEGER i,j,k,kup,kDown,kp1        INTEGER i,j,k,kup,kDown,kp1
# Line 47  C     == Local variables Line 120  C     == Local variables
120        _RL kp1Msk        _RL kp1Msk
121        LOGICAL calc_fluxes_X,calc_fluxes_Y        LOGICAL calc_fluxes_X,calc_fluxes_Y
122        INTEGER nipass,ipass        INTEGER nipass,ipass
123    CEOP
124    
125  C--   Set up work arrays with valid (i.e. not NaN) values  C--   Set up work arrays with valid (i.e. not NaN) values
126  C     These inital values do not alter the numerical results. They  C     These inital values do not alter the numerical results. They
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