Fast Internal Waves from Luzon Strait
Cho-Teng Liu(1) , Ming-Kuang Hsu(2) , and Antony Liu(3)
National Taiwan University,
#1, Section 4, Roosevelt Road,
ROC 106, Taipei,
(2) Northern Taiwan Institute of Science and Technolog, 2, Xue Yuan Rd, 112 ROC, Taipei, Taiwan
(3) NASA/GSFC, Ocean Sciences Branch, Greenbelt, MD 20771, United States
Non-linear internal waves (NLIWs) have been observed in most oceans. Their propagation speeds are mostly below 2.5 m/s and they slow down when they shoal on the continental shelf. The propagation speed of NLIW depends on both the stratification and the amplitude of internal waves. Studies have shown that Luzon Strait is a region where M2 tide converts its energy into internal tide that propagates westward into the South China Sea. Becase of the large amplitude of tidal current across Luzon Strait and the deep submarine ridge, the internal tide energizes the water column deeper than 1500 m with maximal amplitude over 140 m in the thermocline. The deep penetration of internal tide results the internal tide propagating at the speed of first model which is nearly 2.7 m/s. In May 2005, we were successful in finding and tracking NLIWs from Luzon Strait. But, no data are sufficient to find the exact location of the source region of these NLIWs. The field observation of NLIWs from Luzon included two T-chains hanging over from two fishing boats that are 105 km apart. The data show that the propagation speed NLIW from Luzon is about 2.9 m/s. The satellite images from Radarsat and Modis verified this fast speed of NLIWs. We expect that the wide-swath Envisat SAR images will provide us better satellite images during May experiment of 2006. It in turn permits us to pinpoint the source region of these NLIWs in Luzon Strait.