Physical Oceanography (Aug 2020)
Seiсhes Excited by the Atmospheric Disturbances within the Range of the Meteotsunami Periods nearby the Southern Part of the Sakhalin Island
Abstract
Purpose. The aim of the paper is to study four synoptic situations, in which the seiches energy increase was observed in the coastal zone of the southern part of the Sakhalin Island, and to consider their possible meteorological origin. Methods and Results. Records of the waves obtained in the Institute of Marine Geology and Geophysics in 2008 using both the instruments installed in eight points in the coastal zone of the southern part of the Sakhalin Island, and the synoptic maps provided by the Sakhalin Hydrometeorological Service Department, were used. For all the observation points, four synoptic situations characterized by increase of the seiches energy within the meteotsunami existence range were considered. It is shown that the amplitudes of the main part of the observed waves exceed the criterion equal to 4 xrms. Therefore the events under consideration can be related to meteotsunami; at that, their energy is distributed almost all over the whole range of tsunami waves. When meteotsunami is absent, energy of the sea level oscillations in the range 4–120 min is reduced by an order. Since fluctuations are observed in the coastal zone possessing the resonant properties, arrival of meteotsunamis to these areas eventually results in exciting the seiches which are recorded. It is shown that in the coastal zone, cold fronts generate meteotsunamis, which, in their turn, give rise to seiches. Conclusions. The conditions for generating sea waves by the atmospheric disturbances within the range of the tsunami periods 2–120 minutes are described. It is found that movement of an extended cold front in the east-south direction leads to generation of the large-amplitude seiches in the region of the southern part of the Sakhalin Island, just where all the settlements are located. At a synoptic situation when two cold fronts are moving over the island, generation of high-amplitude seiches is possible in the places, near which a cold front is passing.
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