VARIABILITY OF THE SOUND FIELD IN THE PRESENCE OF INTERNAL KELVIN WAVES IN A STRATIFIED LAKE

The spatiotemporal variability of low-and mid-frequency sound field in the presence of internal Kelvin waves (IKWs) was studied in Lake Kinneret (Israel). Experimental measurements of the sound field were carried out using a vertical line array (VLA) consisting of ten hydrophones with 3 m spacing. The VLA was deployed in the deepest (37 m) part of the lake. Signals were transmitted from the source deployed at peripheral lake location at the distance of 5.5 km from the VLA at 5-m depth. Chirp signals (300 – 2000 Hz) were transmitted with 5 sec intervals during >24 hours (the period of the IKWs). IKWs were registered using three thermistor chains (TCs) positioned along the northwest transect at 10-m, 20-m and 37-m station depths. This setting allowed us to characterize the variations of thermal structure and the corresponding sound speed profile along the transect. The vertical structure of sound field obtained with the VLA shows correlation with temporal variability due to IKWs. The modeling of sound propagation was done using Parabolic Equation (PE) method, taking into account the parameters of bottom, lake bathymetry and variation of water temperature. The PE results showed close agreement with experimental measurements. [This work was supported by Israel Science Foundation, grant 565/15].