Relation to WAM, WAVEWATCH III and others

The basic scientific philosophy of SWAN is identical to that of WAM (Cycle 3 and 4). SWAN is a third-generation wave model and it uses the same formulations for the source terms (although SWAN uses the adapted code for the DIA technique). On the other hand, SWAN contains some additional formulations primarily for shallow water. Moreover, the numerical techniques are very different. WAVEWATCH III not only uses different numerical techniques but also different formulations for the wind input and the whitecapping.


This close similarity can be exploited in the sense that

• scientific findings with one model can be shared with the others and
• SWAN can be readily nested in WAM and WAVEWATCH III (the formulations of WAVEWATCH III have not yet been implemented in SWAN).

When SWAN is nested in WAM or WAVEWATCH III, it must be noted that the boundary conditions for SWAN provided by WAM or WAVEWATCH III may not be model consistent even if the same physics are used. The potential reasons are manifold such as differences in numerical techniques employed and implementation for the geographic area (spatial and spectral resolutions, coefficients, etc.). Generally, the deep water boundary of the SWAN nest must be located in WAM or WAVEWATCH III where shallow water effects do not dominate (to avoid too large discontinuities between the two models). Also, the spatial and spectral resolutions should not differ more than a factor two or three. If a finer resolution is required, a second or third nesting may be needed.