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Internal solitary waves(ISWs) are frequently observed in the area between Dongsha Island(DI) and Taiwan Island. However, there have been few in-situ observations southwest of DI. To improve our knowledge of ISWs in this area, we observed the ISWs over the continental shelf(115.4°E, 20.3°N) from Aug. 29 to Oct. 10, 2011 with temperature sensors and an acoustic Doppler current profiler(ADCP). The observations showed that the a fully developed ISW produced a current whose maximum westward velocity was 0.92 m/s and maximum northward velocity was 0.47 m/s. During the 41-day observation period the ISWs appeared for three periods with about 7-day gaps between each period. During each day, two types of ISWs were observed. The first type of wave arrived regularly diurnally at the same time each day, with a similar pattern to that of the type- a wave identified by Ramp et al.(2004). The second type arrived about 12 h after the first type and was delayed about 1 hour each day; this wave type was related to the type- b wave. Thus, our observations confirmed that both type- a and type- b waves can reach the area southwest of the DI. Moreover, the waves observed by the mooring propagated toward the directions of 270°–315° clockwise from true north, indicating obvious refraction from uneven topography around DI.
Internal, solitary waves (ISWs) are frequently observed in the area between Dongsha Island (DI) and Taiwan Island. However, there have been few in situ situations southwest of DI. To improve our knowledge of ISWs in this area, we observed the ISWs over the continental shelf (115.4 ° E, 20.3 ° N) from Aug. 29 to October 10, 2011 with temperature sensors and an acoustic Doppler current profiler (ADCP). The observations showed that the a fully developed ISW produced a current where maximum westward velocity was 0.92 m / s and maximum northward velocity was 0.47 m / s. During the 41-day observation period the ISWs were observed for three periods with about 7-day gaps between each period. During each day, two types of ISWs were observed The first type of wave arrival regularly diurnally at the same time each day, with a similar pattern to that of the type-a wave identified by Ramp et al. (2004). The second type arrived about 12 h after the first type and was delayed about 1 hour each day; this wave type wa Thus, our observations confirmed that both type-a and type-b waves can reach the area southwest of the DI. Moreover, the waves observed by the mooring propagated toward the directions of 270 ° -315 ° clockwise from true north, indicating obvious refraction from uneven topography around DI.