Northern Adriatic meteorological tsunamis: Observations, link to the atmosphere, and predictability

Abstract

A total of 16 events of tsunami‐like sea level oscillations are documented in the northern Adriatic between 1955 and 2010. These oscillations, recorded at the long‐term operating Rovinj tide gauge, are characterized by wave heights of up to 60 cm, periods of 20 to 150 min, and duration of 1 to 48 h. The sea level oscillations are found to be coincident with pronounced atmospheric pressure disturbances characterized by a 2–4 hPa air pressure change over 10 min. Convective activity is recognized as the most likely source of atmospheric pressure disturbances. Analysis of propagation speed and direction of the atmospheric pressure disturbances indicates that the sea level oscillations were generated and enhanced via the Proudman resonance over a wide and shallow northern Adriatic shelf. Typical conditions under which pronounced air pressure disturbances occur include an air pressure surface minimum centered over the northern Adriatic, a temperature front at a height of approximately 850 hPa, and a strong southwesterly jet stream with wind speeds reaching 20–30 m/s at a height of approximately 500 hPa over the northern Adriatic. Based on these parameters, a possibility for forecasting tsunami‐like sea level oscillations from synoptic conditions is discussed. It appears that under favorable synoptic conditions sea level oscillations are more likely to occur than to not. However, no reliable conclusion on strength of an event can be reached from synoptic conditions only.