Typhoon-induced strong surface flows in the Taiwan strait and pacific |
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Authors: | Yu-Chia Chang Ruo-Shan Tseng Luca R Centurioni |
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Institution: | (1) Department of Earth Sciences, National Taiwan Normal University, 88, Section 4 Ting-Chou Road, Taipei, 11677, Taiwan;(2) International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI, USA; |
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Abstract: | Surface Velocity Program drifters drogued at 15 m depth were deployed in the Taiwan Strait (TS) and Luzon Strait in 2005 and
2006. Several drifters in the TS and the Pacific were fortuitously overrun by the typhoon Hai-Tang (July 2005) and Shan-Shan
(September 2006), respectively. The drifter and QuikSCAT wind data clearly demonstrate that the surface current over the TS
and the Pacific can change dramatically for a period of about two days due to the strong winds of a typhoon during its passage.
Our results show that the area of storm-affected surface currents is considerably smaller for a weaker typhoon (category 2
Shan-Shan), about 300∼400 km in radius, than for a stronger typhoon (category 5 Hai-Tang), about 800 km in radius. The maximum
observed current speed in the TS was 1.7 ms−1 (or 2.2 ms−1 in net speed change) under the influence of Hai-Tang, and 2 ms−1 in the Pacific under the influence of Shan-Shan. Drifter observations revealed the unusual phenomenon of flow reversal in
the surface layer of TS and the Kuroshio induced by the typhoon passage. The effect of a typhoon on surface flows is amplified
by the long, narrow geometry of the TS. Surface currents generated by wind forcing along the passage of a traveling typhoon
can be explained by the Ekman drift. |
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