Short large-amplitude internal waves have been investigated in the Strait of Gibraltar. A buoy system consisting basically of a moored thermistor chain has been developed to get a detailed picture of the wave trains and preceding internal fronts. The buoy system is briefly described. The recordings reveal that the internal (boundary) waves form definite wave trains consisting of 5-8 cycles, preceded by internal fronts. Amplitudes of the waves vary between a few metres and 40 m; the periods vary between 6 min and 20 min. Two categories of wave trains can roughly be distinguished. The first one shows a maximum amplitude at the onset of the oscillations being then followed by a relatively smooth decay of the amplitude, the frequency remaining almost constant. The second one is characterized by growing amplitudes and increasing frequency during the course of the oscillations, leading to an abrupt decay of the oscillations after the maximum amplitude has been reached. © 1969.
