STATISTICAL AND DYNAMIC ANALYSIS OF INTERNAL WAVES ON THE CONTINENTAL-SHELF OF THE MIDDLE ATLANTIC BIGHT FROM SPACE-SHUTTLE PHOTOGRAPHS

By interpreting two space shuttle photographs taken with a Linhof came ra on June 8, 1991, a total of 34 internal soliton packets on the cont inental shelf of the Middle Atlantic Bight are recognized. The interna l soliton field has a three-level structure: packet groups with averag e wavelength of 17.5 km, packets with average wavelength of 7.9 km, an d solitons with average wavelength of 0.6 km. Using the finite-depth t heory we derive that the maximum amplitude of solitons is 5.6 m, the p hase speed is 0.42 m/s, and the period is 23.8 min. The frequency dist ribution of solitons is triple-peaked at 1.9 x 10(-4) Hz, 3.0 X 10(-4) , and 6.9 x 10(-4) Hz. Substituting statistical results of number of s olitons in a packet into the fission law, we find that the upper and t he lower edges of the shelf break are the primary and the secondary ge neration sources of internal solitons, respectively. This reveals that the sharp change in the bottom topography is a key condition for the soliton fission or disintegration. Calculations show that the group pe riod of solitons is 12.5 hours coinciding with that of local semidiurn al tides. This fact confirms that the tides are a dominant generation force for internal solitons on the continental shelf.