Probabilistic Characteristics of Intensive Short-Period Internal Waves in the Sea of Japan

Abstract

Purpose. The paper is aimed at studying the regional features of the internal waves’ field in the Sea of Japan (the Peter the Great Bay) based on the field data, namely, determination of the internal waves’ statistical characteristics that can be used to predict possibility of generating the waves of extreme amplitudes. Methods and Results. The records of water temperature variability in the Peter the Great Bay (the depth at the point of measurements is 42 m) obtained for October 11 – 20, 2011 were used as the initial data. Sampling frequency of the records was 1 s that permitted to analyze the shape of the short-period internal waves. The data on the salinity vertical distribution near the measurement point was also used. The law of the power density spectrum decay (as applied to the studied record) is well described by the Garrett – Munk model for the Sea of Japan zone being under consideration. The calculated temporal series of density were applied for obtaining the basic statistical characteristics including the statistical moments. Besides, empirical distribution for such parameters as the wave heights, periods and steepness and the wave slope amplitude was approximated by the log-normal distribution law and analyzed. The expected wave heights were forecasted using the Poisson statistics. Conclusions. It is shown that the probabilistic characteristics of the internal waves are described well by the log-normal distribution. Based on repeatability of the internal waves’ heights, probability of appearance of intensive disturbances is estimated. It is shown that within 10 days, occurrence of a short-period wave with the height not less than 7 m is guaranteed at the observation point at the 42 m depth. Keywords intensive internal waves, in situ data, probabilistic characteristics of extreme waves, shelf, Sea of Japan.