perturbation in the thermocline (solitary internal wave of mode 2) is formed on the
western (leeward) side of the sill when the directions of the tidal current and the
quasi-constant flow coincide. At the moment of weakening of the tidal current
directed to the west, the solitary wave disturbance begins to move to the east
towards the quasistationary mean flow. It moves to the shallow part of the sill,
where it transforms and decays into a train of short internal waves resembling
solitons. Then, the short-period internal waves remain within the bank and eventually collapse here failing to overcome a sufficiently strong counterflow.
Thus, in the central part of the ridge we detected intense internal waves: a single
perturbation of the second mode in the form of a hydraulic internal jump formed by
the current behind the underwater sill and the region above the sill occupied by
short internal soliton-like waves. The process of transformation of a solitary disturbance propagating over a shallow bank during the ebb phase was investigated
with its decay into the soliton-like waves. We emphasize especially that the short
internal waves generated by a solitary wave also retained the features of belonging
to the oscillations of the second mode. It should also be noted that these facts
represented the first observation of the internal hydraulic jump of the second mode
in the ocean.
Mode 2 Waves in the Luzon Strait
Over the past 15 years, regular studies of internal waves in the South China Sea,
which is the World Ocean region with the largest internal waves (height more than
100 m) have been carried out [6, 7]. These studies revealed frequent occurrence of
Fig. 3 Temperature section (isotherms) of a solitary disturbance of mode 2 (C) and a region of
short-period waves (B), measured by “yo-yo” soundings during the drift above the sill
214
A. N. Serebryany
western (leeward) side of the sill when the directions of the tidal current and the
quasi-constant flow coincide. At the moment of weakening of the tidal current
directed to the west, the solitary wave disturbance begins to move to the east
towards the quasistationary mean flow. It moves to the shallow part of the sill,
where it transforms and decays into a train of short internal waves resembling
solitons. Then, the short-period internal waves remain within the bank and eventually collapse here failing to overcome a sufficiently strong counterflow.
Thus, in the central part of the ridge we detected intense internal waves: a single
perturbation of the second mode in the form of a hydraulic internal jump formed by
the current behind the underwater sill and the region above the sill occupied by
short internal soliton-like waves. The process of transformation of a solitary disturbance propagating over a shallow bank during the ebb phase was investigated
with its decay into the soliton-like waves. We emphasize especially that the short
internal waves generated by a solitary wave also retained the features of belonging
to the oscillations of the second mode. It should also be noted that these facts
represented the first observation of the internal hydraulic jump of the second mode
in the ocean.
Mode 2 Waves in the Luzon Strait
Over the past 15 years, regular studies of internal waves in the South China Sea,
which is the World Ocean region with the largest internal waves (height more than
100 m) have been carried out [6, 7]. These studies revealed frequent occurrence of
Fig. 3 Temperature section (isotherms) of a solitary disturbance of mode 2 (C) and a region of
short-period waves (B), measured by “yo-yo” soundings during the drift above the sill
214
A. N. Serebryany