Preliminary study on effects of typhoon Usagi on underwater sound propagation

Argo floats and multi-satellite data were used to analyze the effects of typhoon Usagi (2013) on underwater sound propagation in the Eastern Luzon Strait. Results showed that (1) when Usagi passed by, the sea surface temperature (SST) in the surrounding areas significantly decreased by ~ 2°C on average and the significant wave height (SWH) increased obviously. The right region of the typhoon track was more influenced, and the mixed-layer depth increased from 25 to 75 m. (2) At source depth (SD) = 10 m and source frequency (SF) = 1000 Hz, Usagi had a great effect on sound propagation whether the receiver depth (RD) was 10 or 200 m. At RD = 10 m, a dual-channel composed of surface sound channel and convergence zone channel appeared, and the transmission loss (TL) in shadow zones was reduced by ~20 dB during the passage of Usagi. At RD = 200 m, the acoustic energy in shadow zones was 10-15 dB higher than before Usagi passed. (3) At SD = 200 m and SF = 1000 Hz, Usagi had a great effect on sound propagation at RD = 10 m, and the acoustic energy in the shadow zone was ~ 10 dB higher than before Usagi passed. At RD = 200 m, Usagi generally had no effect on sound propagation. (4) At SD = 10 m and SF = 100 Hz or at SD = 200 m and SF = 100 Hz, Usagi had little effect on underwater sound propagation whether RD was 10 or 200 m.