NOCS ORCA1 home page

The NOCS ORCA1 home page

Editing the Model Bathymetry

Ensuring that key straits, sills and ridges are present in the model requires a certain amount of hand-editing. A graphical editor is the least tedious way of doing this and, fortunately, previous modelling projects at NOCS had programs which could be adapted for use with NEMO grids.

The ncterraform f90 program allows mouse-based editing of bathymetric values at the gridcell level. It has all the windowing, zoom and pan operations required to operate on large datasets. In a previous manifestation, the program was used to handcraft the OCCAM 1/12° global bathymetry. It does, however, use the UNIRAS graphics libraries which are not widely available so its use in the wider NEMO community may be limited.

A good example of an area often needing attention in coarse models is the Denmark Strait/Faroe Bank Channel region of the North Atlantic. The following image shows the potential temperature in the region at 880m after a 6 month test integration with the edited bathymetry:

Clearly, both the Denmark Strait overflow (which is closed at this depth but has been set to a realistic depth) and the Faroe Bank channel (which has been manually opened to its correct depth) are allowing the cold dense waters of the GIN sea to enter the North Atlantic.

A more complete description of the key topographic changes will be produced in due course. The released version is currently being tested in a fully configured ORCA1-LIM model forced with 6 hourly, NCAR-CORE atmospheric fields. A 6 model-month integration has not revealed any problems but a longer run is required before a full assessment can be made of the oceanic transports in the current model. The surface speed field from the end of the test run is shown on the "selected results" page (under NOCS specifics).