南海內潮之傳播與演化(I)

Large-scale internal waves, such as internal tidal waves, internal solitons, are energetic and
ubiquitous physical processes in the northern South China Sea (NSCS) basin. In the NSCS, the
surface signatures of internal solitons, with lateral scale spanning hundreds of kilometers, could
be seen from satellite imageries quite often. These signals correspond usually to bands of rips,
with width of 1-2 kilometers, on the surface. When a ship passes through such a rip band, one
may encounter choppy seas full of rolling waters, and the rip bands are seemingly endless,
originating from one horizon and extending to the other. According to previous observations,
we anticipate that these rip bands are surface signatures of internal solitons, whose ancestors are
internal tidal waves generated along the Batan island chain, east of Luzon Strait. The
flow-topography interaction mechanism, i.e. tidal currents pushing stratified waters flowing
through the saddle shaped sill topography in between islands, could interpret the generation of
internal tidal waves well. The latter then propagate into the NSCS and evolve into internal
solitons along their way to the western NSCS basin, in which they are dissipated and eliminated
finally. The evolution process of internal tidal waves and its possible relationship with the
NSCS circulations are interesting and important topics to the regional oceanography. During the
past year we have established the real-time remote-sensing technology by using a marine-Radar,
which is the first step of the future field works for the present project. Additionally, we have
done some theoretical works. The mechanism developed could interpret qualitatively the
occurrence of a clockwise eddy found on the continental shelf during the ASIAEX experiment.