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t:units = "seconds since 2000-01-01 00:00:00 +08" ;
t:coordinate_type = "time" ;
double x_centre(j_centre, i_centre) ;
x_centre:long_name = "Longitude at cell centre" ;
x_centre:coordinate_type = "longitude" ;
x_centre:units = "degrees_east" ;
x_centre:projection = "geographic" ;
double y_centre(j_centre, i_centre) ;
y_centre:long_name = "Latitude at cell centre" ;
y_centre:coordinate_type = "latitude" ;
y_centre:units = "degrees_north" ;
y_centre:projection = "geographic" ;
}
4.10.22 Mixing coefficient boundary conditions
Open boundary conditions can be imposed on the vertical mixing coefficients Vz and Kz. The
same boundary conditions applicable to tracers may also be applied to Vz and Kz with the
exception of FILEIN and CUSTOM. If the boundary condition type for mixing coefficients is
unspecified then the default condition of NOTHIN is imposed, which assigns the mixing values
on the open boundaries via selected mixing scheme computations. Since these computations
usually involve vertical velocity shear and density gradients on the open boundary, all of
which use values derived from other open boundary conditions, it is possible that error is
introduced into vertical mixing coefficients on the open boundary in this case. The velocity
computations interior to the open boundary use the vertical viscosity on the open boundary
hence it is possible for this error to propagate into the domain. Under these circumstances it
is preferable to specify the mixing coefficients on the boundary via an open boundary
condition.
4.10.23 Split conditions for tracers
A NOGRAD boundary condition may be applied above a certain depth for tracers and a
FILEIN or CUSTOM condition below this depth. This is invoked by setting:
BOUNDARY0.BCOND_TRA<n>
BOUNDARY0.TRPC_TRA<n>
FILEIN|NOGRAD
-50
(or CUSTOM|NOGRAD)
Where <n> is the tracer number and in this case the depth above which the NOGRAD
condition is applied is 50m. The depths should always be entered as a negative number.
4.10.24 Constant boundary bathymetry
Bathymetry may be specified as constant adjacent to an open boundary via;
BOUNDARY0.BATHY_CON
n # Specify bathymetry constant for n cells
# into the model interior.
This is performed by finding the bathymetry n cells into the interior and setting the bathymetry
th
th
at all cells between the boundary and this n cell equal to this n cell bathymetry value. Note
that the input file must be re-created when the bathymetry is altered using this option.
Additionally, the boundary zone may be smoothed using:
20/08/2015
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Version: 1.00