18.7 Summary of options for topography

The following is a list of options used within the topography module. They are in no particular order.

•  topog_diagnostic. Saves out topography and related fields in NetCDF or IEEE format for analysis.

•  drive_topog. To execute module topog in a stand alone mode rather from within a model execution.

•  scripps_kmt. Builds a field from Scripps 1 degree topography data.

•  etopo_kmt. Builds a field from Etopo 1/12 degree topography data.

•  smooth_topo. Smooths the interpolated topography from Etopo 1/12 degree or Scripps 1 degree datasets to help eliminate the Killworth Instability (Section 18.5). Such smoothing is also useful for removing grid scale power in the topography field. Note, however, that option  smooth_topo will not allow for grid points to be deepened. To allow deepening, one must also turn on option  smooth_topo_allow_deepening.

•  smooth_topo_allow_deepening. When enabled with  smooth_topo, this option will smooth the topography and will allow for this smoothing to deepen grid cells. The topography from both  smooth_topo and  smooth_topo_allow_deepening is somewhat smoother than the topography using only  smooth_topo. It should be noted that if using Levitus initial conditions, the values used in the deepened grid points will need to be computed through an extrapolation procedure described in Section 28.1.4. Errors can arise from this extrapolation and so one should be aware of this issue when using the deepening option.
•  smooth_topog_after_user_changes. This option is useful for those cases in which the researcher changes the land mask by adding or removing land points, but still wants to maintain a smooth topography to avoid numerical problems.

•  rectangular_box. Builds a field for a flat bottomed rectangular box.

•  idealized_kmt. Builds a field based on a highly idealized (not very accurate) geometry. Topography is un-realistic. It is useful for porting MOM to various architectures without having to worry about datasets. It can be easily modified for other idealized studies.

•  gaussian_kmt. Builds the based on a gaussian bump on a sloping ocean floor in a rectangular domain. It is highly portable and can be easily modified for other idealized studies.

•  flat_bottom. Resets the bottom within the ocean to the deepest level regardless of which method was used to construct the field.

•  partial_cell. Allows bottom cells to be of variable thickness within the same vertical level.

•  bbl_ag. Allows for a bottom boundary layer.

•  rough_mixing. Calculates the bottom roughness by examining the curvature of the Etopo 1/12 degree dataset. If option etopo_kmt is not used, then the roughness is set to zero.

•  read_unformatted_kmt. Imports from older kmt.dta files saved without format control.

•  read_my_kmt. Imports from file kmt.dta under format control.

•  write_my_kmt. Exports fo file kmt.dta under format control.

•  read_my_roughness. Imports a roughness field from file rough.dta (unformatted).

•  write_my_roughness. Exports a roughness field from file rough.dta (unformatted).

•  solid_walls. Land boundaries along the northern, southern, eastern, and western limits of the domain.

•  cyclic. Land boundaries along the northern and southern limits of the domain. However, what flows out of the eastern boundary enters through the western boundary and visa versa.

•  fill_shallow. Fills ocean cells with land where the bottom is less than the specified minimum number of vertical levels.

•  round_shallow. Where the bottom is less than the specified minimum number of vertical levels, the bottom is rounded to either zero depth or the minimum number of vertical levels.

•  deepen_shallow. Where the bottom is less than the specified minimum number of vertical levels, the bottom is deepened to the minimum number of vertical levels.

•  fill_isolated_cells. Fills one cell wide potholes and trenches with land.

•  fill_isolated_dont_change_landmask does not allow the land/sea mask to change when filling isolated cells.

•  skip_island_map. To eliminate land mass map indicating island perimeters.

•  skip_perimeter_details. To eliminate listing the land mass perimeter points.

•  skip_kmt_map. To eliminate printing the map of kmt.

•  skip_translation_details. Interpolating data near the prime meridian is a problem for the interpolation routines because the longitude is not monotonic. Basically, it is difficult for the interpolation routines to decide in general if an error was made in specifying longitudes or not. So the topography data is translated in longitude to move the prime meridian so that longitudes defining real data are monotonic within the model domain. Normally, the original and translated longitudes are printed out. Use this option to eliminate the printing.

  

Figure: a) A portion of the kmt field indicating ocean and land areas with potential problems. b) Topography along the slice indicated in a)