Response of Coastal Water in the Taiwan Strait to Typhoon Nesat of 2017

The oceanic response of the Taiwan Strait (TWS) to Typhoon Nesat (2017) was investigated using a fully coupled atmosphere-ocean-wave model (COAWST) verified by observations. Ocean currents in the TWS changed drastically in response to significant wind variation during the typhoon. The response of ocean currents was characterised by a flow pattern generally consistent with the Ekman boundary layer theory, with north-eastward volume transport being significantly modified by the storm. Model results also reveal that the western TWS experienced the maximum generated storm surge, whereas the east side experienced only moderate storm surge. Heat budget analysis indicated that surface heat flux, vertical diffusion, and total advection all contributed to changes in water temperature in the upper 30 m with advection primarily affecting lower depths during the storm. Momentum balance analysis shows that along-shore volume acceleration was largely determined by a combined effect of surface wind stress and bottom stress. Cross-shore directional terms of pressure gradient and Coriolis acceleration were dominant throughout the model run, indicating that the effect of the storm on geostrophic balance was small. This work provides a detailed analysis of TWS water response to typhoon passage across the strait, which will aid in regional disaster management.

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ENSO effect on the sea surface wind and sea surface temperature in the Taiwan Strait

Geophysical Research Letters ◽

10.1029/2004gl020303 ◽

2004 ◽

Vol 31 (13) ◽

pp. n/a-n/a ◽

Cited By ~ 23

Author(s):

Nan-Jung Kuo ◽

Chung-Ru Ho

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

Surface Wind ◽

Taiwan Strait ◽

Sea Surface ◽

Sea Surface Wind ◽

The Taiwan Strait

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An Oceanic Current against the Wind: How Does Taiwan Island Steer Warm Water into the East China Sea?

Journal of Physical Oceanography ◽

10.1175/jpo3134.1 ◽

2007 ◽

Vol 37 (10) ◽

pp. 2563-2569 ◽

Cited By ~ 45

Author(s):

Jiayan Yang

Keyword(s):

Pressure Gradient ◽

Wind Stress ◽

Pressure Difference ◽

East Coast ◽

Taiwan Strait ◽

Momentum Balance ◽

Western Boundary ◽

Current Layer ◽

The Taiwan Strait ◽

The Kuroshio

Abstract Along the Taiwan Strait (<100 m in depth) a northeastward flow persists in all seasons despite the annually averaged wind stress that is strongly southwestward. The forcing mechanism of this countercurrent is examined by using a simple ocean model. The results from a suite of experiments demonstrate that it is the Kuroshio that plays the deciding role for setting the flow direction along the Taiwan Strait. The momentum balance along the strait is mainly between the wind stress, friction, and pressure gradient. Since both wind stress and friction act against the northward flow, it is most likely the pressure gradient that forces the northward flow, as noted in some previous studies. What remains unknown is why there is a considerable pressure difference between the southern and northern strait. The Kuroshio flows along the east coast of Taiwan, and thus the western boundary current layer dynamics applies there. Integrating the momentum equation along Taiwan’s east coast shows that there must be a pressure difference between the southern and the northern tip of Taiwan to counter a considerable friction exerted by the mighty Kuroshio. This same pressure difference is also felt on the other side of the island where it forces the northward flow through Taiwan Strait. The model shows that the local wind stress acts to dampen this northward flow. This mechanism can be illustrated by an integral constraint for flow around an island.

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Effects of wave-current interaction on storm surge in the Taiwan Strait: Insights from Typhoon Morakot

Continental Shelf Research ◽

10.1016/j.csr.2017.08.009 ◽

2017 ◽

Vol 146 ◽

pp. 47-57 ◽

Cited By ~ 15

Author(s):

Xiaolong Yu ◽

Weiran Pan ◽

Xiangjing Zheng ◽

Shenjie Zhou ◽

Xiaoqin Tao

Keyword(s):

Storm Surge ◽

Taiwan Strait ◽

Typhoon Morakot ◽

Current Interaction ◽

The Taiwan Strait

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THE NUMERICAL SIMULATION OF STORM-SURGE AND COASTAL INUNDATION OF 2007 TYPHOON SEPAT

Coastal Engineering Proceedings ◽

10.9753/icce.v32.currents.16 ◽

2011 ◽

Vol 1 (32) ◽

pp. 16

Author(s):

Yu-Hsien Lin ◽

Hwung-Hweng Hwung ◽

Ming-Chung Fang ◽

Ray-Yeng Yang

Keyword(s):

Storm Surge ◽

Atmospheric Pressure ◽

Wind Waves ◽

Taiwan Strait ◽

Negative Contribution ◽

Coastal Inundation ◽

Simulation Results ◽

Central Taiwan ◽

The Taiwan Strait ◽

Typhoon Event

A comprehensive numerical model for simulating storm surge has been aimed at the middle-east Taiwan Strait, in which contains the Penghu Channel (PHC) and Changyun Rise (CYR). The simulation results can be used to understand the direct impact of storm surge on the interest area during typhoon invades. The case in this study is Typhoon SEPAT, which passed through central Taiwan in 2007. The transport characteristics through the Taiwan Strait under the influence of Typhoon SEPAT were analyzed using both field observations and numerical simulations during the typhoon period. The results show that storm surge did not respond to the southerly winds but the northerly winds, in contrast to the wind waves. According to the influence of dynamical forces on the storm surge in the Taiwan Strait, the atmospheric pressure gradient is found to be the dominant force of the coastal inundation during the typhoon event. By comparing with the numerical experiment, the Coriolis force is found to have a negative contribution to the storm surge generation in the Taiwan Strait.

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Tide-Surge-Wave Interaction in the Taiwan Strait during Typhoons Soudelor (2015) and Dujuan (2015)

Applied Sciences ◽

10.3390/app10207382 ◽

2020 ◽

Vol 10 (20) ◽

pp. 7382

Author(s):

Li Zhang ◽

Shaoping Shang ◽

Feng Zhang ◽

Yanshuang Xie

Keyword(s):

Water Level ◽

Storm Surge ◽

Taiwan Strait ◽

Storm Tide ◽

Tidal Period ◽

Resonant Coupling ◽

Wave Setup ◽

Water Level Rise ◽

Astronomical Tide ◽

The Taiwan Strait

Typhoons Soudelor (2015) and Dujuan (2015) were two of the strongest storms to affect the Taiwan Strait in 2015. This study investigated the response of the waters on the western bank of the Taiwan Strait to the passage of Soudelor and Dujuan. This included an investigation of the resonant coupling between the tide and storm surge, typhoon wave variation caused by the storm tide, and wave-induced water level rise. Analyses conducted using numerical model simulations and observations from tidal stations and buoys, obtained during the passage of both Soudelor and Dujuan, revealed that resonant coupling between the astronomical tide and storm surge in the Taiwan Strait was prominent, which resulted in tidal period oscillation on the storm surge and reduced tidal range. The tide wave arrived earlier than the predicted astronomical tide because of the existence of the storm surge, which was attributable to acceleration of the tidal wave caused by the water level rise. Wave height observations showed that the storm tide predominantly affected the waves, which resulted in wave heights that oscillated within the tidal period. Numerical experiments indicated that both the current and the water level affected wave height. Waves were affected mainly by the current in the middle of the Taiwan Strait, but mostly by water level when the water level was comparable with water depth. Wave setup simulations revealed that wave setup also oscillated within the tidal period, and that local bathymetry was the most important influencing factor of wave setup distribution.

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Influence of Local Dynamical Air–Sea Feedback Process on the Hawaiian Lee Countercurrent

Journal of Climate ◽

10.1175/jcli-d-12-00586.1 ◽

2013 ◽

Vol 26 (18) ◽

pp. 7267-7279 ◽

Cited By ~ 6

Author(s):

Hideharu Sasaki ◽

Bunmei Taguchi ◽

Nobumasa Komori ◽

Yukio Masumoto

Keyword(s):

Wind Stress ◽

General Circulation ◽

Heat Budget ◽

Surface Wind ◽

Sea Surface ◽

Wind Stress Curl ◽

The West ◽

Speed Increase ◽

Budget Analysis ◽

Hawaiian Lee Countercurrent

Abstract Local air–sea interactions over the high sea surface temperature (SST) band along the Hawaiian Lee Countercurrent (HLCC) are examined with a focus on dynamical feedback of SST-induced wind stress to the ocean using the atmosphere–ocean coupled general circulation model (CGCM). A pair of ensemble CGCM simulations are compared to extract the air–sea interactions associated with HLCC: the control simulations and other simulations, the latter purposely eliminating influences of the high SST band on the sea surface flux computations in the CGCM. The comparison reveals that oceanic response to surface wind convergence and positive wind stress curl induced by the high SST band increases (decreases) the HLCC speed in the southern (northern) flank of the HLCC. The HLCC speed changes are driven by the Ekman suction associated with positive wind stress curl over the warm HLCC via the thermal wind balance. The HLCC speed increase is more significant than its decrease. This dynamical feedback is likely to be important to sustain the extension of the HLCC far to the west. The heat budget analysis confirms that advection of warm water from the west associated with this significant current speed increase plays a role in the southward shift of the HLCC axis. The dynamical feedback with the HLCC speed increase can potentially amplify the seasonal and interannual variations of HLCC.

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Wintertime Supercell Thunderstorms in a Subtropical Environment: Numerical Simulation

Monthly Weather Review ◽

10.1175/2008mwr2616.1 ◽

2009 ◽

Vol 137 (7) ◽

pp. 2175-2202 ◽

Cited By ~ 7

Author(s):

Chung-Chieh Wang ◽

George Tai-Jen Chen ◽

Shan-Chien Yang ◽

Kazuhisa Tsuboki

Keyword(s):

Taiwan Strait ◽

Vertical Shear ◽

Diagnostic Study ◽

Grid Spacing ◽

Thermodynamic Structure ◽

Low Level ◽

Budget Analysis ◽

The Taiwan Strait ◽

The Right ◽

Subtropical Environment

Following an earlier diagnostic study, the present paper performs numerical simulations of the rare wintertime supercell storms during 19–20 December 2002 in a subtropical environment near Taiwan. Using Japan Meteorology Agency (JMA) 20-km analyses and horizontal grid spacing of 1.5 and 0.5 km, the Cloud-Resolving Storm Simulator (CReSS) of Nagoya University successfully reproduced the three major storms at the correct time and location, but the southern storm decayed too early over the Taiwan Strait. The two experiments produce similar overall results, suggesting that the 1.5-km grid spacing is sufficient even for storm dynamics. Model results are further used to examine the storm structure, kinematics, splitting process, and the variation in the mesoscale environment. Over the Taiwan Strait, the strong surface northeasterly flow enhanced low-level vertical shear and helped the storms evolve into isolated supercells. Consistent with previous studies, the vorticity budget analysis indicates that midlevel updraft rotation arose mainly from the tilting effect, and was reinforced by vertical stretching at the supercell stage. As the ultimate source of vorticity generation, the horizontal vorticity (vertical shear) was altered by the baroclinic (solenoidal) effect around the warm-core updraft, as well as the tilting of vertical vorticity onto, and rotation of vortex tubes in the x–y plane, forming a counterclockwise pattern that pointed generally northward (westward) at the right (left) flanks of the updraft. In both runs, model storms travel about 15°–20° to the left of the actual storms, and they are found to be quite sensitive to the detailed low-level thermodynamic structure of the postfrontal atmosphere and the intensity of the storms themselves, in particular whether or not the existing instability can be released by forced uplift at the gust front. In this regard, the finer 0.5-km grid did produce stronger storms that maintained longer across the strait. The disagreement in propagation direction between the model and real storms is partially attributed to the differences in environment, while the remaining part is most likely due to differences not reflected in gridded analyses. Since the conditions (in both the model and real atmosphere) over the Taiwan Strait are not uniform and depend on many detailed factors, it is anticipated that a successful simulation that agrees with the observation in all aspects over data-sparse regions like this one will remain a challenging task in the foreseeable future.

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Effects of Wave–Current Interaction on the Eastern China Coastal Waters during Super Typhoon Lekima (2019)

Journal of Physical Oceanography ◽

10.1175/jpo-d-20-0224.1 ◽

2021 ◽

Vol 51 (5) ◽

pp. 1611-1636

Author(s):

Renhao Wu ◽

Shimei Wu ◽

Tianhua Chen ◽

Qinghua Yang ◽

Bo Han ◽

...

Keyword(s):

Storm Surge ◽

Wind Stress ◽

Coastal Waters ◽

Wave Breaking ◽

Water Levels ◽

Ocean Currents ◽

Momentum Balance ◽

Gradient Force ◽

Super Typhoon ◽

Current Interaction

AbstractLekima was a devastating super typhoon hitting China in 2019. Here, we use a high-resolution wave–current coupling model to investigate the impacts of wave–current interaction during Lekima on wave height, storm surge, ocean currents, and momentum balance. The model results were in good agreement with observations. It was found that, in the open waters, the strong currents generated by the typhoon winds reduced the typhoon-induced maximum significant wave heights (MSWHs) by 6%–15%. The baroclinicity of seawater also slightly reduced the MSWHs by approximately 3%. In the coastal waters, the MSWHs were increased by 6%–15% when feedbacks from water levels were considered. The typhoon-induced highest storm surge occurred in the coastal waters right of the typhoon’s landing position. The nonconservative wave forces contributed by approximately 0.1–0.4 m to the most severe storm surge (3 m), with this effect being most prominent in coastal waters. The baroclinicity of seawater generally increased the storm surge but had little influence on very shallow waters. Tides tend to exacerbate storm surge in most nearshore waters, except in a small bay. Waves generally increased the velocity of offshore ocean currents via the wave-breaking-induced acceleration. A cross-shore momentum balance analysis shows that when the typhoon was near the shore, the dominant terms in the momentum equation were the horizontal pressure gradient force and the surface wind stress, and the contribution of wave breaking had similar pattern to that of the wind stress but a lower magnitude. Our findings have significant implications for the numerical modeling of typhoons and the prediction of their impacts in the coastal environment.

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