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Observation of Tropical Cyclone‐Induced Shallow Water Currents in Taiwan Strait
Author(s) -
Shen Junqiang,
Qiu Yun,
Zhang Shanwu,
Kuang Fangfang
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc012737
Subject(s) - barotropic fluid , baroclinity , geology , inertial wave , waves and shallow water , mooring , water column , current (fluid) , tropical cyclone , internal wave , climatology , geophysics , oceanography , atmospheric sciences , wave propagation , physics , longitudinal wave , mechanical wave , quantum mechanics
The data from three stations equipped with Acoustic Doppler Current Profilers (ADCPs) deployed in the shallow water of the Taiwan Strait (TWS) were used to study the shallow coastal ocean response to five quasi‐continuous tropical cyclone (TC) events in the late summer 2006. We revealed that, in the forced stage, when the large and strong TC (Bilis) transited, the geostrophic currents were formed which dominated the whole event, while the strong but relatively small one (Saomai) or the weak one (Bopha) primarily leaded to the generation of Ekman currents. In the relaxation stage, the barotropic subinertial waves and/or the baroclinic near‐inertial oscillations (NIOs) were triggered. Typically, during the transit of the Saomai, subinertial waves were induced which demonstrated a period of 2.8–4.1 days and a mean alongshore phase velocity of 14.9 ± 3.2 m/s in the form of free‐barotropic continental shelf waves. However, the NIOs are only notable in the area in which the water column is stably stratified and also where the wind stress is dominated by the clockwise component and accompanied by high‐frequency (near‐inertial) variations. We also demonstrated that, due to the damping effects, the nonlinear wave‐wave interaction (e.g., between NIO and semidiurnal tide in our case), together with the well‐known bottom friction, led to the rapid decay of the observed TC‐induced near‐inertial currents, giving a typical e ‐folding time scale of 1–3 inertial periods. Moreover, such nonlinear wave‐wave interaction was even found to play a major role during the spring tide in TWS.