Abstract
Typhoon-induced strong winds can dramatically change the oceanic environment, occasionally resulting in sudden stratification changes. In July 2015, two consecutive typhoons, Chanhom and Nangka, passed over the Yellow and East/Japan Seas within a week. Remarkable temperature variations were observed near the southeastern coast of Korea, caused by typhoon-induced upwelling and downwelling events, which altered the energy of semidiurnal internal tides. During the typhoon-induced downwelling event, the energy of semidiurnal internal tides near the southeastern coast of Korea varied independently from the barotropic tidal forcing. Data-assimilated numerical simulation results reveal that the pycnocline, which is typically tilted toward the coast, enables the semidiurnal internal tidal energy to propagate toward shallow regions after being generated off the coast. Meanwhile, the downwelling event deepens the pycnocline near the coast and reflects and concentrates the semidiurnal internal tide energy near the bottom off the coast. A simple mechanism using the ratio between the wave characteristic slope and the bottom slope is proposed to explain the observed variations of semidiurnal internal tide energy near the coast. This paper demonstrates a case study showing that typhoon passage can modify the energetics of internal tides, which has the potential to cause unusual short-term coastal environmental changes.
Highlights
The southeastern coast of Korea is well known for its frequent upwelling events that occasionally last longer than a week during summer months
Considering the southeastern coast of Korea, typhoons passing over the Yellow Sea can create an eastward Ekman transport and typhoons passing over the East/Japan Sea can create a westward Ekman transport, inducing coastal upwelling and downwelling processes, respectively [4,5]
In July 2015, coastal upwelling and downwelling events caused by two typhoons occurred along the southeastern coast of the Korean Peninsula
Summary
The southeastern coast of Korea is well known for its frequent upwelling events that occasionally last longer than a week during summer months. Showed that the generation and propagation of semidiurnal internal tides at the southwestern corner of the East/Japan Sea changed based on the background current and stratification conditions. Korea Strait propagates near the southeastern coast by using the Regional Oceanic Modeling System They showed that background stratification changes could modify the internal wave field. Showed mately 5 days, which was recorded near the southeastern coast of Korea using an ocean that the generation and propagation of semidiurnal internal tides at the southwestern buoy measuring temperatures at three depths (Figure 1c). (ADCP) was deployed at a site close to the ocean buoy (Figure 1c) for approximately half a typhoon-induced changes in the stratification and the associated variation in semidiurnal month in July 2015, which overlapped with the period of the two typhoons. Dynamical explanations for the variation in semidiurnal internal tides are presented
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