engleski

Wind-induced internal wave dynamics near the Adriatic shelf break

Current and temperature measurements from a thermistor chain and current meter mooring were analysed to describe the near-surface internal wave field close to the middle Adriatic shelf break. Wind speed and direction from the nearby meteorological station Lastovo were analysed too. being a possible internal waves generating force. Spectral properties of currents and temperatures in the surface mixed and thermocline layers indicate strong deviations from the Garrett and Munk (Geophysical Fluid Dynamics 2 (1972) 225 Journal of Geophysical Research 80 (1975) 291) deep ocean internal wave models. The frequency spectra were dominated by three energetic bands: at 0.060 cph (near-inertial frequency), 0.080 cph (M, tidal frequency) and between 3 and 4 cph. Near-inertial and high-frequency (3-4 cph) internal waves were generated by wind and or surface wind waves. The frequency band 3-4 cph of high-frequency energetic waves does not correspond to the local Brunt-Vaisala frequency (30 cph), but to the thickest constant N layer below the thermocline-Sabinin (Izvestiya Academy of Sciences, USSR, Atmospheric and Oceanic Physics, English Edition 2 (1966) 872) "resonance layer". Near-inertial oscillations represented a major contribution to the horizontal kinetic energy accounting for about 25% (10%) of the total surface (bottom) current variances. Vertically, the clockwise current vector rotations in the surface layer are out of phase by 180 degrees compared with those below the thermocline. The level of surface near-inertial spectral peak was very high compared to the Garrett-Munk level. because of the proximity of wind generating force, while its bandwidth was typical for mid-latitudes.

internal waves; inertial oscillations; resonant frequency; wind wave generation; Croatia; Adriatic Sea

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