Features of Meteotsunami at the Capes of the Kuril Islands Urup and Kunashir

Purpose. The aim of the present work is to study the features of the sea level oscillations with the periods characteristic of tsunami waves nearby the capes of Urup and Kunashir islands using in situ observations, to determine the range of the Froude number values which meteorological tsunami are generated at, and to scrutinize resonance features of the water areas for defining possibility of meteotsunami amplification. Methods and Results. The time series of the waves obtained in the Institute of Marine Geology and Geophysics, Far East Branch of Russian Academy of Sciences in 2008 and 2009 by the instruments installed in the coastal area of the capes Castricum, Van der Lind and Lovtsova at the southern Kuril Islands - Kunashir and Urup, as well as the synoptic maps provided by the Sakhalin Hydrometeorological Service of Federal Service of Russia for Hydrometeorology and Environmental Monitoring were used. To assess potential danger of the meteorological tsunami, considered were the resonance features of the water areas where the instruments were installed. It was shown that passage of the atmospheric disturbance along the Kuril Islands was accompanied by generation of the sea level anomalous oscillations just in the places where the wave recorders were installed. According to the criterion calculated by the root-mean-square background level, the observed event could be identified as a meteorological tsunami. The range of the Froude numbers was determined; it showed that moving at the velocity within the above-mentioned range, the atmospheric disturbance under consideration could generate meteorological tsunami in the coastal zone of the islands. It was revealed that the q - factor of the resonance system was the highest in Cape Lovtsova: in case of arrival of the waves, the oscillations of which were close to the resonance system eigen oscillation, the amplification factor could reach 19.1. Conclusions. Arrival of the sea waves of considerable amplitude whose oscillation is close to the resonance system eigen oscillation, can be followed by generation of dangerous waves. At that, if the Froude number value is close to 1, the sea waves, according to the mechanism described by Proudman, can be continuously pumped with atmospheric energy. As a result, the forced sea wave becomes significantly amplified and dangerous.