Features of Formation of the Cyclone Wakes (Fluctuations in Seawater Temperature) in the Area of Cape Svobodny, the Southeastern Part of the Sakhalin Island

Abstract

Purpose. The purpose of this work is to study the particulars of the formation of cyclone wakes after the regular passage of cyclones over the area of the wave measurements, and to estimate the internal wave parameters along the track according to the field observations. Methods and Results. The analysis of data from the field observations of sea waves and water temperature is presented. The measurements were carried out by a ARW-K14 device (autonomous recorder of the waves and water temperature) in the area of the Cape Svobodny on the southeastern coast of the Sakhalin Island at a depth about 8 m. The recorded time series of the sea level and temperature fluctuations, lasting about one and a half months, were subjected to spectral analysis using specialized Kyma spectral analysis software. Dominant temperature fluctuations reaching 8.5 °C with a 13.1 h period were detected in the upper mixed layer of the ocean. These fluctuations were identified as the cyclone wakes in the stage of their relaxation. Taking into account the synoptic circumstances that existed during the passage of several cyclones and the associated storms in the observation area, the authors investigated the presence or absence of a trace. Conclusions. It is shown that if the next storm arrives earlier than 10 days after the previous one, the trace may be shorter or even absent due to active water mixing in the upper mixed layer of the ocean. For the data obtained, the value of the coefficient ∈ in the expression ω = (1 + ∈ ) f, which connects the dominant frequency ω of internal waves, i.e. almost inertial oscillations in the trace of each typhoon, with the inertial frequency f (the Coriolis parameter determined by the geographical latitude of the water area where the waves propagate), is close to the value proposed in the paper by E. Kunze. Using a formula due to J. F. Price, the characteristic horizontal lengths of internal waves in the direction of movement inside the wakes of cyclones moving at a speed 15–35 knots are determined. These lengths range from 304.6 to 1066.1 km.

Keywords

• cyclone
• internal waves
• cyclone wake
• seawater temperature fluctuations
• upper mixed layer