Meteotsunami waves in Ilyichevsk port June 2014

The time series of changes in the level on the tide gauge tape in the port of Ilyichevsk (Sukhoi Liman) is a superposition of seiche oscillations, a long-period trend and directly meteotsunami waves.

A 232-minute record was analyzed. Digitization was performed with a one-minute discreteness. Low-frequency oscillations were successively removed during filtering. As a result, a wave packet of four waves is clearly visible on the resulting graph. Visual observers on the beach recorded only one wave in the case of the Odessa tsunami. Other conditions may have been in effect in the Sukhoi Liman: the morphometric characteristics and the location of the tide gauge directly in the estuary itself suggest that this is already a "port" case for meteotsunami waves.

The second distinctive feature of the sea level fluctuations during the passage of meteotsunami waves is the constant and clear presence of short-period waves (period of about 8 minutes and amplitude of up to 6 cm). It should be noted that such fluctuations were not recorded on seiche oscillations before the arrival of meteotsunami waves.

A qualitatively similar structure of oscillations was recorded in the port of Rovinj (Croatia) according to I. Vilibich and J. Šepić. A possible mechanism for the appearance of high-frequency wave "ripples" on long waves of meteotsunami may be nonlinear interactions of the wave packet with seiche movements with weak hydrodynamic instability of the oscillatory system.