Storm surges and meteotsunamis of the Adriatic Sea: interplay and quantification of hazard level

Sea level time series of up to 19 years length, recorded with one-minute sampling interval at 18 tide gauges, evenly distributed along the eastern and western coast of the Adriatic Sea, were analysed in an attempt to quantify hazard related to the Adriatic Sea level extremes.  Prior to analysis, quality control and pre-processing were done: all unphysical spikes and outliers were removed; shorter gaps were interpolated, and time series were de-tided.

For each tide gauge, two types of sea level extremes were defined and extracted from residual time series: (1) extremes related to storm surges, i.e. extremes that dominate the total residual signal; (2) extremes related to meteotsunamis, i.e. extremes that dominate the high-frequency signal (T < 2 h). The two types of extremes were analysed in detail and following conclusions were reached: (1) on average, extremes related to storm surges are stronger than those related to meteotsunamis; (2) nonetheless, there are stations at which two types of extremes are of almost comparable strength (e.g. Vela Luka, Stari Grad); (3) high-frequency oscillations can contribute significantly (up to 30% of residual signal) to the storm surge related extremes  at most areas; (4) extremes related to storm surges mostly happen from October to January while the second type of extremes happen more throughout the year, with peak appearances of the strongest ones from May to September. 

Conclusively, for both types of episodes, it has been shown that the high-frequency signal contributes significantly to total extremes and that analysis of sea level time series sampled at a one-minute time interval is a prerequisite for proper analysis of hazards related to sea level extremes.