An analysis of the Adriatic storm surge of 1 December 2008

Extremely high sea levels, known as acqua alta, occasionally occur in the Adriatic in late autumn and winter, causing floods along the northern coastline and significant damage — especially in Venice. An exceptionally strong event of this kind was observed on 1 December 2008 when high sea level flooded a number of cities. During this event the oldest Croatian tide gauge station, Bakar, recorded the highest sea level, 121 cm, in its operating history (since 1929). In order to examine this particular event, we have analyzed time series of sea level, air pressure and wind recorded at stations along both sides of the Adriatic. Harmonic analysis was performed on the sea-level records to remove the tidal signal. The data were low-pass, band-pass and high-pass filtered in order to determine the low-frequency variability, the Adriatic-wide seiche and the local seiche activity, respectively. It turned out that the event was the result of superposition of several phenomena: storm surge caused by synoptic atmospheric systems, tide, basin-wide seiche, sea-level rise due to a low-frequency atmospheric disturbance and the local seiche. The present analysis may serve as an example of a possible contribution to the NVO AdriaMeteo project.