Next: 2.10.7 Topography: partially filled
Up: 2.10 Spatial discretization of
Previous: 2.10.5 Horizontal grid
Contents
Figure 2.10:
Two versions of the vertical grid. a) The cell centered
approach where the interface depths are specified and the tracer
points centered in between the interfaces. b) The interface centered
approach where tracer levels are specified and the w-interfaces are
centered in between.
a)
|
b)
|
|
As for the horizontal grid, we use the suffixes ``c'' and ``f'' to
indicates faces and centers. Fig. 2.10a shows the default
vertical grid used by the model.
is the difference in
(vertical coordinate) between the faces (i.e.
where the minus sign appears due to the convention that the
surface layer has index .).
The vertical grid is calculated in subroutine INI_VERTICAL_GRID and specified via the vector DELR in
namelist PARM04. The units of ``r'' are either meters or Pascals
depending on the isomorphism being used which in turn is dependent
only on the choice of equation of state.
There are alternative namelist vectors DELZ and DELP which
dictate whether z- or
p- coordinates are to be used but we intend to
phase this out since they are redundant.
The reciprocals
and
are
pre-calculated (also in subroutine INI_VERTICAL_GRID). All
vertical grid descriptors are stored in common blocks in GRID.h.
The above grid (Fig. 2.10a) is known as the cell centered
approach because the tracer points are at cell centers; the cell
centers are mid-way between the cell interfaces.
This discretization is selected when the thickness of the
levels are provided (delR, parameter file data,
namelist PARM04)
An alternative, the vertex or interface centered approach, is shown in
Fig. 2.10b. Here, the interior interfaces are positioned
mid-way between the tracer nodes (no longer cell centers). This
approach is formally more accurate for evaluation of hydrostatic
pressure and vertical advection but historically the cell centered
approach has been used. An alternative form of subroutine INI_VERTICAL_GRID is used to select the interface centered approach
This form requires to specify vertical distances delRc
(parameter file data, namelist PARM04, e.g.
verification/ideal_2D_oce/input/data)
corresponding to surface to center, center to center, and center to
bottom distances.
Next: 2.10.7 Topography: partially filled
Up: 2.10 Spatial discretization of
Previous: 2.10.5 Horizontal grid
Contents
mitgcm-support@dev.mitgcm.org
Copyright © 2002
Massachusetts Institute of Technology |
|
|