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Field Phase of the East Adriatic Coastal Experiment Completed

East Adriatic Coastal Experiment concentrated on the current inflowing to the Adriatic along the east coast. Previous measurements have indicated that the current is best developed during the winter, that in the Middle Adriatic it usually has a core positioned close to the coast, and that further north it is laterally more uniform in speed. Preliminary modeling has suggested that the core is generated by the Middle Adriatic river inputs and surface buoyancy loss related to the winter evaporation and cooling events, with the maximum disappearing in the North Adriatic where the east coast river inputs are weak. The experiment was carried out between November 2002 and June 2003 with the aim of supplementing early measurements and testing existing interpretations. Meteorological (solar and net radiation, air temperature, humidity, precipitation, air pressure, wind speed and direction) and oceanographic (sea temperature) data were collected at station Veli Rat. CTD profiling was done at a network of 21 stations off Veli Rat on seven occasions. Currents were measured at two stations in the network using barny-mounted ADCPs. The data are still undergoing a detailed quality check, but some preliminary results are already emerging. Basic statistical analysis of meteorological data reveals that February 2003 was exceptionally cold and dry and that the spring 2003 was considerably warmer and drier than usual. The sea responded promptly to these weather conditions. The winter cooling resulted in lower-than-average temperatures, which persisted in the intermediate and bottom layers throughout the spring season. Surface temperatures gradually became greater than long-term averages, due to intensive spring heating. Salinities were close to the averages during winter, but surpassed them - without any sign of haline stratification - during spring, reflecting anomalously dry atmospheric conditions, which were accompanied by weak river inflows. Monthly means computed from current data show that the onshore ADCP station was positioned closer to the core of the inflowing current than the offshore station. The current was almost uniform along the vertical. Month-to-month variability of the current did not follow expected pattern: either this was an anomaly due to atypical meteorological and hydrological conditions or the classical notions on the seasonal variability are wrong. The current data allow some higher-frequency phenomena to be studied as well. Harmonic analysis reveals that tidal currents are almost linearly polarized in the area and that they are aligned with the coast. Bottom friction manifests itself in the classical Sverdrup veering at semidiurnal periods and a different behaviour at diurnal periods. The spectra computed from detided currents show at the offshore station maxima at the period somewhat exceeding 17.2 h, which is the local inertial period. Probably, the mismatch is due to interaction of internal Poincare waves with currents inflowing along the east Adriatic coast. There is another maximum on both stations at about 21 h, obviously related to the fundamental Adriatic seiche. Finally, there is an increase of energy towards the greatest periods in all the spectra computed. A part of it should be attributed to the wind-driven currents. More puzzling is variability at periods exceeding 10 days. It has been repeatedly observed in the Adriatic, but is still lacking a proper interpretation.

Meteorological conditions; CTD; currents; Adriatic

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