3.15.4 Code Configuration

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Next: 3.16 Customizing MITgcm Up: 3.15 Centennial Time Scale Previous: 3.15.3 Discrete Numerical Configuration Contents

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3.15.4 Code Configuration

The model configuration for this experiment resides under the directory verification/exp1/. The experiment files

input/data
input/data.pkg
input/eedata,
input/windx.sin_y,
input/topog.box,
code/CPP_EEOPTIONS.h
code/CPP_OPTIONS.h,
code/SIZE.h.

contain the code customizations and parameter settings for this experiments. Below we describe the customizations to these files associated with this experiment.

3.15.4.1 File input/data

This file, reproduced completely below, specifies the main parameters for the experiment. The parameters that are significant for this configuration are

Line 4,
```
 tRef=20.,10.,8.,6.,
```
this line sets the initial and reference values of potential temperature at each model level in units of C. The entries are ordered from surface to depth. For each depth level the initial and reference profiles will be uniform in and .
$\fbox{ \begin{minipage}{5.0in} {\it S/R INI\_THETA}({\it ini\_theta.F}) \end{minipage}}$
Line 6,
```
 viscAz=1.E-2,
```
this line sets the vertical Laplacian dissipation coefficient to . Boundary conditions for this operator are specified later. This variable is copied into model general vertical coordinate variable viscAr.
$\fbox{ \begin{minipage}{5.0in} {\it S/R CALC\_DIFFUSIVITY}({\it calc\_diffusivity.F}) \end{minipage}}$
Line 7,
```
viscAh=4.E2,
```
this line sets the horizontal Laplacian frictional dissipation coefficient to . Boundary conditions for this operator are specified later.
Lines 8,
```
no_slip_sides=.FALSE.
```
this line selects a free-slip lateral boundary condition for the horizontal Laplacian friction operator e.g. =0 along boundaries in and =0 along boundaries in .
Lines 9,
```
no_slip_bottom=.TRUE.
```
this line selects a no-slip boundary condition for bottom boundary condition in the vertical Laplacian friction operator e.g. at , where is the local depth of the domain.
Line 10,
```
diffKhT=4.E2,
```
this line sets the horizontal diffusion coefficient for temperature to . The boundary condition on this operator is at all boundaries.
Line 11,
```
diffKzT=1.E-2,
```
this line sets the vertical diffusion coefficient for temperature to . The boundary condition on this operator is = 0 on all boundaries.
Line 13,
```
tAlpha=2.E-4,
```
This line sets the thermal expansion coefficient for the fluid to
$\fbox{ \begin{minipage}{5.0in} {\it S/R FIND\_RHO}({\it find\_rho.F}) \end{minipage} }$
Line 18,
```
eosType='LINEAR'
```
This line selects the linear form of the equation of state.
$\fbox{ \begin{minipage}{5.0in} {\it S/R FIND\_RHO}({\it find\_rho.F}) \end{minipage} }$
Line 40,
```
usingSphericalPolarGrid=.TRUE.,
```
This line requests that the simulation be performed in a spherical polar coordinate system. It affects the interpretation of grid input parameters, for example delX and delY and causes the grid generation routines to initialize an internal grid based on spherical polar geometry.
$\fbox{ \begin{minipage}{5.0in} {\it S/R INI\_SPEHRICAL\_POLAR\_GRID}({\it ini\_spherical\_polar\_grid.F}) \end{minipage} }$
Line 41,
```
phiMin=0.,
```
This line sets the southern boundary of the modeled domain to latitude. This value affects both the generation of the locally orthogonal grid that the model uses internally and affects the initialization of the coriolis force. Note - it is not required to set a longitude boundary, since the absolute longitude does not alter the kernel equation discretisation.
Line 42,
```
delX=60*1.,
```
This line sets the horizontal grid spacing between each y-coordinate line in the discrete grid to in longitude.
Line 43,
```
delY=60*1.,
```
This line sets the horizontal grid spacing between each y-coordinate line in the discrete grid to in latitude.
Line 44,
```
delZ=500.,500.,500.,500.,
```
This line sets the vertical grid spacing between each z-coordinate line in the discrete grid to , so that the total model depth is . The variable delZ is copied into the internal model coordinate variable delR
$\fbox{ \begin{minipage}{5.0in} {\it S/R INI\_VERTICAL\_GRID}({\it ini\_vertical\_grid.F}) \end{minipage} }$
Line 47,
```
bathyFile='topog.box'
```
This line specifies the name of the file from which the domain bathymetry is read. This file is a two-dimensional () map of depths. This file is assumed to contain 64-bit binary numbers giving the depth of the model at each grid cell, ordered with the x coordinate varying fastest. The points are ordered from low coordinate to high coordinate for both axes. The units and orientation of the depths in this file are the same as used in the MITgcm code. In this experiment, a depth of indicates a solid wall and a depth of indicates open ocean. The matlab program input/gendata.m shows an example of how to generate a bathymetry file.
Line 50,
```
zonalWindFile='windx.sin_y'
```
This line specifies the name of the file from which the x-direction surface wind stress is read. This file is also a two-dimensional () map and is enumerated and formatted in the same manner as the bathymetry file. The matlab program input/gendata.m includes example code to generate a valid zonalWindFile file.

other lines in the file input/data are standard values that are described in the MITgcm Getting Started and MITgcm Parameters notes.

3.15.4.2 File input/data.pkg

This file uses standard default values and does not contain customizations for this experiment.

3.15.4.3 File input/eedata

This file uses standard default values and does not contain customizations for this experiment.

3.15.4.4 File input/windx.sin_y

The input/windx.sin_y file specifies a two-dimensional () map of wind stress , $\tau_{x}$ , values. The units used are $Nm^{-2}$ . Although $\tau_{x}$ is only a function of n in this experiment this file must still define a complete two-dimensional map in order to be compatible with the standard code for loading forcing fields in MITgcm. The included matlab program input/gendata.m gives a complete code for creating the input/windx.sin_y file.

3.15.4.5 File input/topog.box

The input/topog.box file specifies a two-dimensional () map of depth values. For this experiment values are either or $-2000\,{\rm m}$ , corresponding respectively to a wall or to deep ocean. The file contains a raw binary stream of data that is enumerated in the same way as standard MITgcm two-dimensional, horizontal arrays. The included matlab program input/gendata.m gives a complete code for creating the input/topog.box file.

3.15.4.6 File code/SIZE.h

Two lines are customized in this file for the current experiment

Line 39,
```
 sNx=60,
```
this line sets the lateral domain extent in grid points for the axis aligned with the x-coordinate.
Line 40,
```
 sNy=60,
```
this line sets the lateral domain extent in grid points for the axis aligned with the y-coordinate.
Line 49,
```
 Nr=4,
```
this line sets the vertical domain extent in grid points.

3.15.4.7 File code/CPP_OPTIONS.h

This file uses standard default values and does not contain customizations for this experiment.

3.15.4.8 File code/CPP_EEOPTIONS.h

This file uses standard default values and does not contain customizations for this experiment.

3.15.4.9 Other Files

Other files relevant to this experiment are

model/src/ini_cori.F. This file initializes the model coriolis variables fCorU.
model/src/ini_spherical_polar_grid.F
model/src/ini_parms.F,
input/windx.sin_y,

contain the code customizations and parameter settings for this experiments. Below we describe the customizations to these files associated with this experiment.

Next: 3.16 Customizing MITgcm Up: 3.15 Centennial Time Scale Previous: 3.15.3 Discrete Numerical Configuration Contents

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