FORCED AND FREE RESPONSE OF THE ADRIATIC SEA-LEVEL

The aim of this paper is to improve the knowledge of the variations of the sea level in the Adriatic Sea in the domains of forced and free o scillations. For this purpose, one-year long-time series of data colle cted at nine tide gauge stations placed on the eastern shoreline have been collected and processed by spectral analysis. The harmonic consti tuents have been calculated too. Semidiurnal and diurnal tides have go t larger variations of amplitude on the islands than on the coast. The response of the sea level in the domain of synoptic and planetary for mations is quite synchronous in the whole Adriatic for periods longer than 3.5 days, with a gap around 9.5 days. These formations excite the sea level first in the North Adriatic, and then, secondly in the Midd le and South Adriatic. The seiches occurred at already known periods o f 22-23, 10.8 and 7.5-8 hours, and at a new one of about 4 hours. 4 ho ur seiche occurs in the region inside the Middle Adriatic islands, and it is predominantly influenced by the Sirocco wind forcing.