A TWO-DIMENSIONAL VORTICITY MODEL OF INTERNAL TIDES GENERATED ON THE CONTINENTAL SHELF/SLOPE

A two-dimensional spectral-difference mode (with vorticity and density equations) of internal tides isdeveloped for studying the genration and propagration of internal tides generated at the continentalshelf/slope. In general, internal tides propagate seaward in deep sea regions and shoreward on the shelf,and are dissipated rapidly. When the Vaisala frequency decreases vertically, waves may be mostly limited to thecontinental slope region. in deep sea region, motions may have either boam-like structure or modal structure,depending on the stratification strerigth and structure, whereas a modal structure may always exist onthe shelf. Waves show strong bottom intensification on the slope when strong stratification exists on thebottom. The barotropic tidal advection may affed the temporal character of internal tides at thecontinental slope, shelf break and shelf regions. but may have little influence on the energy density and energy flux of internal tides. ln the case of strong stratification, waverforms

A two-dimensional spectral-difference model (with vorticity and density equations) of internal tides is developed for studying the generation and propagation of internal tides generated at the continental shelf/slope. In general, internal tides propagate seaward in deep sea regions and shoreward on the shelf, and are dissipated rapidly. When the Vaisala frequency decreases vertically, waves may be mostly limited to the continental slope region. In deep sea region, motions may have either beam-like structure or modal structure, depending on the stratification strength and structure, whereas a modal structure may always exist on the shelf. Waves show strong bottom intensification on the slope when strong stratification exists on the bottom. The barotropic tidal advection may affect the temporal character of internal tides at the continental slope, shelf break and shelf regions, but may have little influence on the energy density and energy flux of internal tides. In the case of strong stratification, waveforms of internal tides on the continental slope, shelf break and shelf may be deformed by the barotropic tidal advection, and sometimes intermittency appears. Waves depend considerably on the relative slopeδ = α/C (where a denotes topography slope and C is the characteristic slope) and the e-fold scale b of the Vaisala frequency. As in Craig (1987a), the deep sea energy flux F1 and on-shelf flux F2also vary exponentially, but our exponents are different from his in the subcritical case, and may have complicated dependence on δin the supercritical case. For subcritical topography, F2 increases linearly with b but F1 remains nearly constant. For supercritical topography, F, increases linearly with b and F2 varies complicatedly. For special values of b, waves may have strong bottom intensification because of the self-closing of ray on the bottom of the slope.There is qualitative agreement between model results and field data on the East China Sea.