On the effect of subinertial phenomena on the internal lee waves generation in the Strait of Gibraltar

The generation of internal lee waves (ILW) in the Strait of Gibraltar takes place in the main sill where the tidal flow interacts with a submarine obstacle. The tidal flow is perturbed by subinertial phenomena of different nature summarized in the subinertial currents that can inhibit the ILW generation. The authors present an attempt to randomize the problem by the introduction of a Gaussian noise in the Taylor-Goldstein equation. The random number sets are generated from the statistical distribution of the previously isolated random part of the subinertial currents from experimental data taken in the area during the Gibraltar Experiment 94-96. The effect of the noise is translated into a continuous spreading of the spectrum around the solution of the noise-free problem. A stability analysis is carried out in order to determine the single neutral modes of oscillations and the phase space is divided onto regions of stability and instability as a function of the inflowing subinertial current. The methodology and results could be useful for the design and timing of oceanographic surveys in straits where the ILWs occur.