The Scottish Shelf Model. Part 1: Shelf-Wide Domain

6 Summary and Conclusions

This report describes the process of setting up the Scottish Shelf Waters FVCOM model from the assembling of data sets, through development of a stable grid, implementation of forcing (tidal, meteorological and river discharge), calibration and validation. The calibration period was March - June 2009 inclusive, while the validation has been carried out over the period May 2008 - March 2009.

The model grid has been set up to provide at least 1km resolution around the Scottish coast. The model extends over the whole NW European continental shelf and into the North Atlantic in order to properly represent the tidal regime.

It was found necessary to use the HEATING_CALCULATED option rather than HEATING_ON, within the FVCOM model, in order to get a reasonable evolution of the SST. The sources of met forcing data have been explored, including which variables to download from the Met Office Unified Model output and ERA40/ ERA-Interim reanalysis datasets.

The model has then been used to assess the tidal energy resource and, using climatological forcing, the monthly mean circulation pattern. These results have been assessed qualitatively against previously published work and found to be in good agreement.

The most difficult part of the model implementation was to develop a stable grid. In the end, by trial and error and also advice from various sources, including Prof Chen, via CH2M Hill, it was found that the model was sensitive to the connectivity of the mesh (no more than 8 elements must be connected to a single node), steep gradients in bathymetry and issues related to the river forcing. Some smoothing of bathymetry was necessary, near the shelf edge and the Norwegian Trench. At river nodes it was necessary to ensure that the depth was at least 5m in order to ensure that the river inflow could be accepted and propagated into the main body of the model grid.

The model was calibrated by adjusting the number of vertical layers, the bottom friction and the turbulent closure scheme. Validation was carried out by comparison with water surface elevation data, from coastal and offshore tide gauges, current meter data and CTD profiles.