The Momentum Flux Balance at the Sea Surface

Today, secondand third-generation wave models are used for many applications around the world. From the design of coastal structures to proper regional sediment management and from estimates of mixing in the upper ocean to the efficient the routing of ships across oceans, the accuracy of these models has critical importance. However, following the development of the WAM model in the mid to late 1980’s, there has been little effort focused directly on wave model development. Instead, most research in this area has involved re-calibrating various source terms to obtain better fits to observations (satellite and in situ). Two likely reasons for the lack of focus in this area are 1) the general acceptance outside of the wave community that the WAM model physics provided a good “detailed -balance” description of the wave generation process and 2) wave researchers cannot agree on necessary modifications to the WAM physics. The purpose of this paper is to revisit the general framework of the physics of wave generation and attempt to formulate a concept for wave generation that seems to “fit” some important constraints implicit in observations over a wide range of generation scales (time and space). Toward this end, data from three very different sites will be used: 1. Lake George – a small, shallow site located in Southeast Australia (Figure 1); 2. FRF Gage #630 – a coastal site located in the Atlantic Ocean in a depth of about 18 meters of water approximately 5 km off the coast of Duck, North Carolina (Figure 2); and 3. NDBC Buoy 46035 – an open-ocean site located in deep-water in the Bering Sea (Figure 3).