Inertial – period oscillations in the North Adriatic

(in Croatian)

Abstract

Since 1978, Hydrographic Institute of the Yugoslav Navy has organised continous meteorological and oceanographic measurements at the oil-driling platform “Panon”. The existence of inertial-period oscillations was observed only in summer season when sub-tropical high pressure disappears and cyclonic disturbances travel towards the Adriatic Sea. Inertial oscillations are unbalanced motions in stratified sea. They are generated by the temporal variations of the wind and occur outside the coastal boundary layer during geostrophic adjustment process. In this paper inertial oscillations were examined in August, 1985, when the platform “Panon” was located in the North Adriatic. Current data were subjected to the rotary spectral analysis. The most prominent peaks are centred at the local inertial frequency in the clockwise part of the spectrum at three depths. The inertial peak in the surface layer was almost one order of magnitude larger than the peaks at 25 and 63 meters depth. The 180° phase-lag between the surface and deeper layers was observed. Zero-crossing was probably in the termocline. During the outset of the stormy wind, mean hourly current speed reached value of about 60 cm s^-1.