3.3.2. Event II

The event II in DF2 (0.2–0.3 Hz) band occurs on days 2014/327, 328, and 329, and arrives at the stations in south section before north section as indicated by the curved red arrow in Figure 4d. This sequence can be explained by the ocean wave interactions associated with the continental slope (Figure 4c).

On day 327, the wave energy in frequency band of 0.1–0.2 Hz is relatively higher on lower Blake Plateau (water depth 200–2000 m) and many great circles of the stations in the south section intersect on the edge of this area. The PSD levels at the stations in the south section are roughly proportional to their distances to lower Blake Plateau. Then on day 328 the wave front moves north along the continental slope to south of Cape Hatteras while the wave energy increases to the highest. The great circles of almost all stations in south section intersect in this area, and the PSD levels at these stations increase significantly. On day 329, the wave front moves further north to the area between Georges Bank and Cape Hatteras where the strike of the continental slope turns almost 90◦ , causing the significant increase of wave energy in this area. The great circles at the stations in north section do not intersect in the open ocean where the wave energy is higher, but on the continental slope segments south of Georges Bank and north of Cape Hatteras. The PSD levels at the stations to the north increase but not as significantly as at the southern stations on day 328. The great circles at the southern stations still intersect at the continental slope between Cape Hatteras and Blake Plateau but not as concentrated as on day 328.
